No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Effect of industrial hemp (Cannabis sativa L) planting density on weed suppression, crop growth, physiological responses, and fibre yield in the subtropics
Abstract
Population density of industrial hemp (Cannabis sativa L.) in the field influences crop growth habit, fibre yield and quality. Therefore, optimization of plant population density is required to control growth and
... Increasing density from 100 to 200 plants/m 2 reduced weed biomass from 23.2 g/m 2 to 6.5 g/m 2 . At 300 and 400 plants/m 2 , weed biomass further decreased to 2.6 g/m 2 and 1.5 g/m 2 , respectively (Hall et al., 2014), indicating a non-linear relationship between density and weed suppression. Sufficient plant density eliminates the need for herbicides (Prade 2011;Reeves 2013). ...
... Tailoring seeding rates to specific purposes is crucial. Insufficient sowing reduces yield, product quality, and increases weed competition, while excessive density leads to self-thinning and growth limitations in later stages (Hall et al., 2014). Hemp variety, growing season, soil type, and agronomic practices also influence the optimal density. ...
... Hemp's rapid growth and efficient resource utilization make it highly competitive against weeds. Its vigorous growth following emergence enables it to overshadow and outcompete weeds for sunlight, water, and nutrients (Hall et al., 2014;Kousta et al. 2023;Lotz et al. 1991;Thompson et al. 1998). A study highlighted hemp's adaptability to diverse climates and its ability to thrive in low-nitrogen soils, make hemp particularly suitable for low-input agricultural systems (Zatta et al. 2012). ...
Industrial hemp has experienced a resurgence in global cultivation due to its diverse applications in textiles, food, bioplastics, biofuels, and environmental benefits such as phytoremediation and carbon sequestration. However, optimizing hemp production remains challenging, particularly in weed management, where limited approved herbicides and varying regional weed pressures pose significant obstacles. Weed dynamics across different regions highlight the prevalence of problematic species like Chenopodium album and Amaranthus spp. While hemp’s rapid canopy closure and high planting densities can reduce herbicide dependence, early-season weed competition can significantly impact crop establishment and yield. This review explores the current state of weed management in hemp cultivation, highlighting cultural, mechanical, and chemical strategies. Additionally, it evaluates the efficacy and phytotoxicity of pre- and post-emergent herbicides. Recent trials indicate that pre-emergent pendimethalin is consistently safe across multiple studies, while post-emergent grass herbicides like quizalofop, clethodim, and fluazifop provide effective control with minimal crop injury. For broadleaf control, clopyralid and bromoxynil show relative safety, though varietal responses vary. The limited availability of registered herbicides underscores the need for continued research and regulatory advancements. The review identifies critical knowledge gaps, including limited understanding of variety-specific herbicide tolerance and regional weed dynamics. Current research priorities include systematic herbicide screening across varieties and regions, optimizing cultural practices, and developing herbicide-tolerant cultivars. By integrating these strategies, hemp can fulfil its potential as a sustainable and profitable crop, contributing to environmentally friendly agricultural systems. This review provides a foundation for future research and policy decisions to optimize weed management in hemp production.
... The stem width of hemp is an essential quality factor for fiber hemp production because the stem is suitable for textile production depending on the width. Hall et al. [52] assumes that finer stems provide higher quality for application in the textile industry. The measurements show that there is no statistically significant difference in stem width between fertilization with 40 (0.74 mm) and 120 kg N (0.69 mm). ...
... This is because stem yield tends to stabilize regardless of row width. Low stand density can delay plant canopy development [100] and increase weed occurrence [52], both of which result in yield reduction [52,100]. At high stand density, more and taller stems are present in the plant population, but more self-thinning occurs due to interplant competition [85,101], as described earlier in this study. ...
... This is because stem yield tends to stabilize regardless of row width. Low stand density can delay plant canopy development [100] and increase weed occurrence [52], both of which result in yield reduction [52,100]. At high stand density, more and taller stems are present in the plant population, but more self-thinning occurs due to interplant competition [85,101], as described earlier in this study. ...
Shallow arable soils (<35 cm depth) are classified as marginal for common agriculture but may still support biomass production from industrial crops like fiber hemp, which has a low indirect land-use change risk. However, little is known about hemp’s performance under such conditions. Therefore, this study investigated the biomass yield and quality of fiber hemp and other crops on a shallow (<35 cm), stony (>15% stone content), and clay-rich (>50% clay content) soil at 800 m above sea level in Southwest Germany (2018–2021). A randomized field trial tested different row widths and nitrogen (N) fertilization levels to assess low-input options for the given type of marginal land. Across years and row widths, hemp achieved average grain dry matter (DM) yields of 1.3 Mg/ha at a fertilization rate of 40 kg N/ha and 1.6 Mg/ha at 120 kg N/ha (with on average 30.9 ± 1.4% crude fat content across treatments). The average stem DM yields accounted for 5.11 Mg/ha (40 kg N/ha) and 6.08 Mg/ha (120 kg N/ha), respectively. Reduced N fertilization (40 kg/ha) lowered DM yields by up to 16% compared to full fertilization (120 kg/ha), but the effect was not significant and weaker at wider row spacing (45 cm). Additionally, maize reached acceptable DM yields (>17 Mg/ha). These findings suggest that shallow soils classified as marginal require reassessment, as they may offer viable opportunities for sustainable industrial hemp cultivation and contribute to a bio-based economy.
... Another significant challenge to hemp production is planting density. It can affect the growth pattern, and quantity and quality of fibers produced (Hall et al., 2014a). Low plant density may lead to poor production quality (Ranalli, 1999), increased weed competition (Mosjidis & Wehtje, 2011;Vera et al., 2006), and harvesting challenges due to thicker stems. ...
... Compared to fiber crops planted at higher densities, low seeding density for a grain crop promotes branching, shorter plant height, and heavier individual plant weight. The former encourages taller, lighter, and less branched individual plants (Hall et al., 2014a). Erect plants with minimal branching ease harvesting for fiber, enhancing fiber quality (Hall et al., 2014a). ...
... The former encourages taller, lighter, and less branched individual plants (Hall et al., 2014a). Erect plants with minimal branching ease harvesting for fiber, enhancing fiber quality (Hall et al., 2014a). Secondary fibers (hurd) are smaller and shorter than primary fibers (bast) due to thick lignified cell walls, with the latter being preferable for textile use due to these qualities (Stevens, 2010). ...
Industrial hemp (Cannabis sativa L.) exhibits growth potential in water‐limited regions due to its deep roots and drought tolerance. However, limited knowledge exists about its agronomic production in semiarid West Texas. A 2‐year (2022–2023) field experiment evaluated the effect of planting dates (P1: April 19, P2: May 10, and P3: June 6) and seeding densities (SD1: 84500 seeds ha⁻¹, SD2: 1,408,000 seeds ha⁻¹, and SD3: 1,972,000 seeds ha⁻¹) on the growth, physiology, and yield of hemp in a split‐plot block design. In both years, P3 reduced photosynthesis but increased transpiration compared to earlier plantings. In 2022, SD1 increased transpiration during the vegetative stage; however, no significant difference was observed during 2023. Photosynthesis remained consistent among densities throughout both years. In 2022, P2 accumulated 15%, 24%, 33%, and 43% greater plant height, biomass, bast fiber, and hurd fiber, respectively, but 45% lower grain yield than P3. In 2023, P1 and P2, on average, produced 32%, 175%, 149%, and 243% greater height, biomass, bast fiber, and hurd fiber than P3, respectively, while P2 accumulated 36% higher grain yield than P1 and 94% than P3. In 2022, SD3 had the highest bast, while hurd yield did not differ among densities. During 2023, SD3 produced the greatest bast and hurd fiber and significantly greater grain yield than SD1, with no variation with SD2. In conclusion, these findings suggest that early planting at higher seeding density can maximize resource use efficiency and production in West Texas. This makes them a viable strategy for sustainable hemp production under water‐limited conditions.
... The wide array of potential applications of hemp, arising from the plasticity of its raw products, is one of the main drivers of its recent rebirth, as testified by the increase in acreage observed, for example, in Europe, where it passed from 9400 ha to 34,970 ha from 1994 to 2019 (Eurostat 2021), or in Canada, where hemp cultivation peaked in 2017 with over 60,000 ha (Aubin et al. 2015;Cherney and Small 2016;Moran 2015). The resurgence of this crop also finds its source in several agronomic characteristics, such as its capacity to efficiently insert itself in a rotation system (Gorchs et al. 2017;van der Werf 2002), its ability to suppress weeds (Hall et al. 2014a;van der Werf et al. 1995a;van der Werf et al. 1995b), its ability to structure and enrich the soil (Amaducci et al. 2008a;Robson et al. 2002; Zegada-Lizarazu and Monti 2011), its relatively low input requirements in terms of nitrogen and phytosanitary products (van der Werf 2004) and the biomass yields it can achieve, with more than 20 t ha À1 of dry stem reported in a Lithuanian environment (Tang et al. 2016). In addition to the plasticity of its raw products and its agronomic potential, hemp is also adapted to various environments, rendering its cultivation possible throughout an extensive range of latitudes and climates. ...
... Hemp's fast canopy closure and increase in height in the first phases of its growth suppress weed growth and break the reproductive cycle, meaning that in autumn, the successive crop will be less prone to face strong weed competition for resources. However, this weed suppressing capacity depends on the density at which hemp is sown; higher sowing densities lead to faster canopy closure and higher height increments in the first phase of hemp growth due to the shade avoidance syndrome (Hall et al. 2014a). ...
... The optimal sowing densities vary depending on the researched fibre quality and depending on the targeted fiber production. Targeted plant densities at emergence as high as 200-750 plants m À2 (Dempsey 1975) or 300-500 plants m À2 (Hall et al. 2014a) were reported as the optimum plant densities for producing high-quality fibre. Contrary to this, the Italian traditional hemp cultivation for textile fibre production is performed by sowing at relatively lower densities of 90-100 plants m À2 (Venturi and Amaducci 1999). ...
Hemp is a crop that in recent years has received renewed attention and been cultivated in numerous countries after having been abandoned by many during the twentieth century. This ‘rebirth’ is due to numerous factors: its favorable agronomical characteristics, its image of being a sustainable crop, and the plasticity of the products it can provide. However, due to its absence for a long time, there is a lack of expert knowledge on cultivating hemp. There is a lack of scientific knowledge regarding the specificities of its biology, and the strong interaction between genotype and environment remains a limiting factor of hemp cultivation, affecting both the yield and quality of the biomass produced. In this chapter, we have discussed the ins and outs of the cultivation of hemp through a scientific prism to address the principal factors, environmental and genotypic, that drive the agronomical characteristics of a hemp crop. Thereafter, we have focussed on the best crop management practices for optimizing hemp cultivation in terms of yield and quality parameters of the different fractions of the biomass that hemp can provide.KeywordsAgronomyCrop managementCultivationEcophysiologyIndustrial hemp
... Similarly, seeding density of hemp in the field can influence both the quantity and quality of fibers produced (Hall et al., 2014). Excessively dense planting results in self-thinning (Ranalli, 1999), and resource competition for light, which may negatively impact plant function and production (Jarecki and Bobrecka-Jamro, 2011). ...
... This extension in P2-22 allowed the continued resource channeling toward vegetative development. While in P3-22, reduced vegetative growth due to short days and an early seasonal shift to flowering decreases yield (Cosentino et al., 2012;Hall et al., 2014). Several researchers observed lower hemp yields with short time intervals between emergence and flowering (Cromack, 1998;Sankari, 2000;Struik et al., 2000). ...
... This crop's many advantageous agronomic characteristics, including its capacity to compete with weeds [16], its ability to successfully enter a crop rotation system [17], its relatively low input requirements for nitrogen and plant protection products (insecticides, fungicides, herbicides, etc.), and its capacity to produce biomass yields of over 20 t ha −1 of dry shoots [18], are the reasons for the renewed interest. ...
... The plant density set in this study was 120 plants per square meter, a level that the literature suggests can help suppress weed growth [16]. Furthermore, this density is considered optimal based on previous research [33][34][35], as it can lead to increased yields of both dry and fresh above-ground biomass. ...
Hemp is a multipurpose crop that produces high amounts of lignocellulosic biomass. There are few studies dealing with hemp’s biomass production (lignocellulosic and fiber) under cropping strategies such as irrigation and nitrogen fertilizer. Therefore, the aim of the current study was to assess the effect of irrigation and N-fertilization on the lignocellulosic biomass of one of the most well-known industrial hemp (Cannabis sativa L.) varieties worldwide (Felina 32) under a typical Mediterranean climate. For the purposes of this study, a field experiment was conducted in central Greece (Thessaly region) over the cultivating years 2022 and 2023. We determined the produced biomass dry yield and the dry biomass yield vs. N-uptake relation, as well as quality characteristics for hemp (cv. Felina 32) under three irrigation (I1: 33%, I2: 66%, and I3: 100% ETo) and three N-fertilization levels (N1: 0, N2: 70, and N3: 140 kg ha⁻¹). A significant difference in the dry biomass yield was found, ranging between 10–11.2 t ha⁻¹ using I2 and/or I3 irrigation levels and remaining at 8.6 t ha⁻¹ with lower irrigation (I1). In terms of fertilization factor, it appeared that in samplings where statistically significant changes were observed, all degrees of fertilization differed from one another, with the N3 treatment exhibiting the highest production (11.4 t ha⁻¹). The average protein content varied between 10% in 2023 and 14% in 2023. A linear biomass yield–nutrient uptake relationship was found with high R², pointing to a nitrogen use efficiency of 55.15 kg kg⁻¹. Thus, it would seem that nitrogen fertilization and irrigation are both crucial factors of industrial hemp cultivation, helping to raise the crop’s overall yield of lignocellulosic biomass. The introduction of hemp into land-use systems necessitates thorough evaluation, as hemp shows considerable potential as a crop that can yield substantial quantities of above-ground biomass (lignocellulosic: stems and fibers). This is especially true in regions where irrigation is possible, and the application of nitrogen fertilizers can further enhance these yields.
... After emergence, in each plot, we recorded plant density. Plant density is related to the ability to suppress weeds [4,33] and to other plant structural characteristics related to hemp products; e.g., despite contrasting weeds efficiently, a high plant density can reduce plant height, stem diameter, and plant total biomass. Plant density was calculated by counting all the plants in 1 m 2 at 60 days after sowing. ...
... CS cultivar was late flowering, had the lowest plant density, and produced tall plants. This is in agreement with previous studies which reported that late flowering and low plant density maximize stem size [33,34]. Low density and plant height suggest that CS could be more sensitive to weed invasion and lodging compared to the other cultivars [4,53,76], while leaf traits, which indicated a predisposition toward a fast growth and acquisitive strategy, suggest that this cultivar could be suitable for cultivation in unstable environments [40]. ...
Agricultural diversification and high-quality products deriving from sustainable crops such as hemp can represent a solution to revitalize marginal areas and reverse land abandonment. This study aimed at comparing four different hemp cultivars (Carmagnola Selezionata, “CS”; Futura 75, “FUT”; Felina 32, “FEL”; Secuieni Jubileu, “JUB”) to provide information to select the best suited cultivar for cultivation in mountain marginal areas and for specific end-use applications. Hemp cultivars were cultivated in a single experimental field to compare their ecological and agronomic behavior (duration of life cycle phases, plant size and biomass allocation, and plant resource-use strategies). Through metabolomic analysis of both vegetative and reproductive parts of the plants we tested the presence of substances of nutraceutical interest and traced seed nutritional profile. The four cultivars had different ecological and agronomic behavior, and nutritional profile. We found several compounds with potential pharmaceutical and nutraceutical values in all parts of the plant (leaves, inflorescences, and stems). JUB resulted the most suitable for seed production while CS showed the highest content of bioactive compounds in flowers and leaves. FUT, showed the best suitability for multi-purpose cultivation, while FEL seemed to be not appropriate for the cultivation in mountain area. The multi-disciplinary approach we adopted was effective in distinguish across hemp cultivars and provided information to farmers for the selection of the best hemp cultivar to select. Hemp had a high potential for cultivation in marginal lands, demonstrating to be an economic resource due to its multi-purpose use and to the possibility to generate high-added values products. Our results could serve as a stimulus for the reintroduction of this culture in the study area and in other similar environments.
... At a sowing amount of 20 kg ha -1 , the hemp plants were shorter but more branchy. The effect of density on the growth of hemp was studied in more detail by Hall et al. (2014). It was not only the sowing density was analyzed, but also other factors influencing the yield of plants were scrutinized, e.g. the content of minerals in the soil, temperature and precipitation during the growing season. ...
... It was necessary to use weed control with a power harrow. In the study of Hall (2014), a lower level of weed infestation was noted on plantations with a larger density. This difference results from the adopted density levels, as in the aforementioned studies the plant density was assumed to be from 100 to 400 plants m -2 . ...
... ), Hall et.al., [7]. Fast growing dense jute canopy (200-348/m 2 ) at 25 days after sowing with mean height of 29 cm, reduces the light penetration at its canopy base by 90-95 per cent and dominated all C4 weeds and eliminated weeding in jute. ...
... Most of the remaining weeds remain stunted (Photo 4) and similar results have been reported by Hall et al., [7], Auskalniene et al., [9], Marin and Weiner [10], Ghorai et al., [8] in other field crops like hemp, corn, wheat and jute. Proper agronomic management practices of high density broadcast mustard sowing with particular reference to seed rate, date of sowing, uniform sowing, irrigation, and fertiliser application in mustard will eliminate the weeding problem in it and eliminate herbicide or manual weeding in mustard and produce good crop with smothered and scanty weeds at harvest (Photo 4). ...
Manual weed control in mustard is very expensive because of its high labour requirement i.e., 150-250 labourers/ha. Chemical weed control again imposes environmental hazards. Mechanical weed control in mustard is not still that popular till date. Due to severe weed competition, the yield reduction in Indian mustard may go as high as 70 per cent. Thus weed control in zero till mustard using its high-density sowing (HDS) was studied in different farmers’ field, at ICAR-CRIJAF, in North 24 PGS and Purulia, from 2018-2022. Fast growing and high- density uniform mustard canopy (100-200 m2) developed at early stages hinders sunlight penetration (up to 99.98 per cent) below its canopy (at 35- 40 days), leading to scanty and under developed growth of different composite weed species at harvest, those germinate or grow below mustard canopy. Weed population below mustard canopy was reduced by 92 to 97 per cent at mustard harvest. It was only 10-80/m2 at harvest over 350-1000/m2 in weedy situation at initial germination. The reduction of dicot weed biomass below matured mustard at harvest was 81-99 percent (5-150g/ m2) percent over weedy plots (500-800/ m2). Reduction of effective flowers/pods of different weeds under matured mustard canopy were up to 99.5 percent. Proper agronomic management practices of HDS mustard e.g., seed rate, date of sowing, uniformity of sowing, irrigation and fertiliser application will eliminate the herbicide application or manual weeding in mustard. Nearly 80 percent mustard plants remain active at harvest. It saves 150-250 labours /ha depending on weed species and its density of germination. Mustard grain yield ranged from 15-30 q/ha depending on management and varieties used. This weed smothering merit of mustard can be used for eco friendly weed control in other wide spaced field/horticultural crops using its dwarf variety (Toria).
... Its weed suppression potential is well suited to crop rotation. Hemp oil and crop residues can be used in organic farming as eco-friendly organic insecticides and pesticides [17,18]. Amaducci et al. [19] found that due to the variation in root morphology under different growth conditions, hemp could play an important role in sustainable cropping systems. ...
... A plant density of 120 plants m −2 gave maximum fiber yield. Garcia-Tejero et al. [85] reported that in southwest Spain, high density (9777 plants ha −1 ) and low density (5866 plants ha − A detailed study was conducted to understand the effect of plant density on weed suppression, crop growth, physiological responses, and fiber yield in a subtropical site (Bundaberg) in Queensland, Australia [17]. This study used an improved subtropical fiber and grain hemp variety with low THC to identify the suitable plant density after thinning (100,200,300, and 400 plants m −2 ) with two sowing dates, 1 and 15 October 2010. ...
Hemp (Cannabis sativa L. ssp. sativa) has a long history of domestication due to its versatile use. Recently, different sectors in the economy are investigating hemp cultivation to increase agronomic production and to limit delta-9-tetrahydrocannabinol (THC). Despite the rapid growth of hemp literature in recent years, it is still uncertain whether the knowledge gained from higher latitude regions is applicable to low latitude and tropical regions where hemp has not been grown traditionally. This review provides a comprehensive and updated survey of hemp agronomy, focusing on environmental and management factors influencing the growth and yield of hemp, methods of cannabinoids detection and quantification, and hemp breeding. This review suggests that some previous claims about hemp as a low input crop may not hold true in low-latitude regions. Additional research strategies, such as the integration of experimentation and modeling efforts, are encouraged to hasten new discoveries. Furthermore, to effectively increase the outputs of value products (cannabinoids, seeds, fiber and biomass, etc.) while limiting the THC level, new collaborations between hemp agronomists and economists may streamline the production process by increasing the efficiency of the total production system of hemp as a multifaceted crop.
... Increase of plant density from 100 to 200 plants/ m 2 markedly reduced weed weight from 23.2 to 6.5 g/m 2 . Further reductions in weed weights in hemp field were observed at 300 plants/m 2 (2.6 g/ m 2 ) and 400 plants/m 2 (1.5 g/m 2 ) Hall et al (2014). Preliminary information showed that high density broadcast jute sowing (6.75-7.5 kg/ha) coupled with improved agronomic practices, with an initial population of 268/m 2 at 25 days after sowing, can effectively smother weeds in jute field by restricting sunlight entry (>95%) below its canopy, un affecting its fibre production (38.37 q/ha) which saved 89-145 mandays /ha ( Ghorai and Roy, 2020). ...
... Rest 95 per cent area do not require any weeding and thinning which die or decomposes below the jute canopy due to internal competition (Ghorai and Roy, 2020). Reductions in weed weights in hemp field were observed at 300 plants m 2 (2.6 g/m 2 ) and 400 plants/m 2 (1.5 g/m 2 ), Hall et al (2014. A plant density of 1,11,111 plants/ha in normal planting (60 cm x 15 cm) produced significantly more kapas yield (3.134 t/ha), reduced weed dry matter with higher weed control efficiency (61.88 % as against high plant density of 1, 11,111 plants/ha paired row planting and 1,48,148 plants/ha), Madavi et al (2017). ...
Jute being a C3 crop, cannot compete with the C4 weeds at its early stage and requires about 40 per cent of total cost of cultivation in weeding process alone. Scarcity of farm labours during weeding, spiraling labour cost, slow mechanization in jute and environment concern of herbicides encouraged us to smother weeds in jute field by its high density sowing. Experiments were thus conducted for three years at ICAR-CRIJAF, Barrackpore focusing smothering of composite weeds in jute field by its high density broadcast
sowing (HDS, seed rate @ 6.0 kg/ha) and was compared with other weed management treatments. From the experiments it was found that fast growing dense jute canopy (200-348/m2) at 25 days after sowing with mean height of 29 cm, reduces the light penetration at its canopy base by 90-95 per cent and dominated all C4 weeds. It reduced the grass, broadleaf, sedges weed population and weed bio mass by 70, 98.5, 64.5 and 91.65 per cent, respectively over manual weeding twice. Remaining weeds were rudimentary, incapable of producing seeds and decomposed before jute harvest. Only 6.3 to 7.64 lakhs jute/ha i.e., 16 to 23.5 per cent of total initial population could be harvested at maturity, 125 to135 DAS. This high density jute sowing eliminated weeding and thinning processes, saved 102 man days/ha over conventional manual weeding, produced 3.82 t fibre/ha and was cheaper by Rs. 25,500/ha. Weed smothering by intercropping green gram with jute (1:1) was also found economic, produced 0.5-1.0 t pulse grain/ha along with 2.7-2.9 t jute fibre and 1.7 to 2 t nitrogen rich (2.35%) pulse waste/ha. Pre-emergence herbicides Pretilachlor 50 EC and Ipfencarbazone 22.8 per cent SC were found effective for weed control in jute. Spraying of Pretilachlor 50 EC @ 0.9 l a.i/ha on paira crop, immediately after rice harvest was found effective for weed control in paira crop. Thus, weed smothering by high density broadcast jute sowing will eliminate dependence on manual weeding, herbicides, and mechanical weeding and make jute farming sustainable.
... Increase of plant density from 100 to 200 plants/ m 2 markedly reduced weed weight from 23.2 to 6.5 g/m 2 . Further reductions in weed weights in hemp field were observed at 300 plants/m 2 (2.6 g/ m 2 ) and 400 plants/m 2 (1.5 g/m 2 ) Hall et al (2014). Preliminary information showed that high density broadcast jute sowing (6.75-7.5 kg/ha) coupled with improved agronomic practices, with an initial population of 268/m 2 at 25 days after sowing, can effectively smother weeds in jute field by restricting sunlight entry (>95%) below its canopy, un affecting its fibre production (38.37 q/ha) which saved 89-145 mandays /ha ( Ghorai and Roy, 2020). ...
... Rest 95 per cent area do not require any weeding and thinning which die or decomposes below the jute canopy due to internal competition (Ghorai and Roy, 2020). Reductions in weed weights in hemp field were observed at 300 plants m 2 (2.6 g/m 2 ) and 400 plants/m 2 (1.5 g/m 2 ), Hall et al (2014. A plant density of 1,11,111 plants/ha in normal planting (60 cm x 15 cm) produced significantly more kapas yield (3.134 t/ha), reduced weed dry matter with higher weed control efficiency (61.88 % as against high plant density of 1, 11,111 plants/ha paired row planting and 1,48,148 plants/ha), Madavi et al (2017). ...
... Increase of plant density from 100 to 200 plants/ m 2 markedly reduced weed weight from 23.2 to 6.5 g/m 2 . Further reductions in weed weights in hemp field were observed at 300 plants/m 2 (2.6 g/ m 2 ) and 400 plants/m 2 (1.5 g/m 2 ) Hall et al (2014). Preliminary information showed that high density broadcast jute sowing (6.75-7.5 kg/ha) coupled with improved agronomic practices, with an initial population of 268/m 2 at 25 days after sowing, can effectively smother weeds in jute field by restricting sunlight entry (>95%) below its canopy, un affecting its fibre production (38.37 q/ha) which saved 89-145 mandays /ha ( Ghorai and Roy, 2020). ...
... Rest 95 per cent area do not require any weeding and thinning which die or decomposes below the jute canopy due to internal competition (Ghorai and Roy, 2020). Reductions in weed weights in hemp field were observed at 300 plants m 2 (2.6 g/m 2 ) and 400 plants/m 2 (1.5 g/m 2 ), Hall et al (2014. A plant density of 1,11,111 plants/ha in normal planting (60 cm x 15 cm) produced significantly more kapas yield (3.134 t/ha), reduced weed dry matter with higher weed control efficiency (61.88 % as against high plant density of 1, 11,111 plants/ha paired row planting and 1,48,148 plants/ha), Madavi et al (2017). ...
The study was conducted in the Thiruvananthapuram and Pathanamthitta districts of Kerala to
study the adoption behaviour of awardee farmers. Altogether, 70 awardee farmers, 35 each from
the two districts constituted the sample. A list of farming practices in coconut, rice, banana and
vegetables were selected from package of practices recommendations of Kerala Agricultural
University (KAU, 2016) to study the adoption behaviour of awardee farmers. The statements on
recommended practices were administered to awardee farmers and it was measured as no
adoption, partial adoption, full adoption and modified adoption. The results showed that majority
of the awardee farmers belonged to the medium to the high category of adoption behaviour.
Profile characteristics like farming experience, decision making ability, dealing with failure,
creativity, credit orientation and training acquired had a significant relationship with adoption
behaviour.
Key Words: Awardee farmers, Adoption behaviour, Package of practices recommendations,
decision making ability, dealing with failure, creativity, credit orientation.
... Increase of plant density from 100 to 200 plants/ m 2 markedly reduced weed weight from 23.2 to 6.5 g/m 2 . Further reductions in weed weights in hemp field were observed at 300 plants/m 2 (2.6 g/ m 2 ) and 400 plants/m 2 (1.5 g/m 2 ) Hall et al (2014). Preliminary information showed that high density broadcast jute sowing (6.75-7.5 kg/ha) coupled with improved agronomic practices, with an initial population of 268/m 2 at 25 days after sowing, can effectively smother weeds in jute field by restricting sunlight entry (>95%) below its canopy, un affecting its fibre production (38.37 q/ha) which saved 89-145 mandays /ha ( Ghorai and Roy, 2020). ...
... Rest 95 per cent area do not require any weeding and thinning which die or decomposes below the jute canopy due to internal competition (Ghorai and Roy, 2020). Reductions in weed weights in hemp field were observed at 300 plants m 2 (2.6 g/m 2 ) and 400 plants/m 2 (1.5 g/m 2 ), Hall et al (2014. A plant density of 1,11,111 plants/ha in normal planting (60 cm x 15 cm) produced significantly more kapas yield (3.134 t/ha), reduced weed dry matter with higher weed control efficiency (61.88 % as against high plant density of 1, 11,111 plants/ha paired row planting and 1,48,148 plants/ha), Madavi et al (2017). ...
... Increase of plant density from 100 to 200 plants/ m 2 markedly reduced weed weight from 23.2 to 6.5 g/m 2 . Further reductions in weed weights in hemp field were observed at 300 plants/m 2 (2.6 g/ m 2 ) and 400 plants/m 2 (1.5 g/m 2 ) Hall et al (2014). Preliminary information showed that high density broadcast jute sowing (6.75-7.5 kg/ha) coupled with improved agronomic practices, with an initial population of 268/m 2 at 25 days after sowing, can effectively smother weeds in jute field by restricting sunlight entry (>95%) below its canopy, un affecting its fibre production (38.37 q/ha) which saved 89-145 mandays /ha ( Ghorai and Roy, 2020). ...
... Rest 95 per cent area do not require any weeding and thinning which die or decomposes below the jute canopy due to internal competition (Ghorai and Roy, 2020). Reductions in weed weights in hemp field were observed at 300 plants m 2 (2.6 g/m 2 ) and 400 plants/m 2 (1.5 g/m 2 ), Hall et al (2014. A plant density of 1,11,111 plants/ha in normal planting (60 cm x 15 cm) produced significantly more kapas yield (3.134 t/ha), reduced weed dry matter with higher weed control efficiency (61.88 % as against high plant density of 1, 11,111 plants/ha paired row planting and 1,48,148 plants/ha), Madavi et al (2017). ...
Journal of Krishi Vigyan is regularly published by the Society of Krishi Vigyan and its NAAS rating is 4.55 w.e.f. 1/1/2021. All scientists related to agriculture and allied fields are requested to kindly see this journal and comment.
... Increase of plant density from 100 to 200 plants m-2 markedly reduced weed weight from 23.2 to 6.5 g m-2. Further reductions in weed weights in hemp field were observed at 300 plants m-2 (2.6 g m-2) and 400 plants m-2 (1.5 g m-2), Hall et al., (2014). ...
... HDS, reduced the weed dry weight to 2.6 g/m2 at 41 DAS. Reductions in weed weights in hemp field were observed at 300 plants m-2 (2.6 g m-2) and 400 plants m-2 (1.5 g m-2), Hall et al., (2014). ...
Jute being a C3 crop, it cannot compete with the C4 weeds at its early stage and about 40 per cent of total cost of cultivation of jute goes in weeding process alone. Upsurge of new weed flora, labour scarcity, herbicidal resistance and its environmental concern and slow mechanization urged us to control weeds in jute field by its smothering effect. Experiments were conducted at ICAR-CRIJAF, Barrackpore, WB in 2018-19, 2019-20 & 2020-21 with jute (cv. NJ-7010) by its high density broadcast sowing (seed rate @ 6.0 to 7.5 kg/ha). Irrigation, fertiliser and pesticides requirements were standardised for this purpose. Only 45 cm wide strip (5% of total area) around the jute field was manually weeded to prevent seed formation of weeds in boarder areas. The dense jute canopy (200-348 /m2) of 29 cm mean height at 25-DAS reduced the incident light at jute base by 90-95 per cent and dominated all C4 weeds. In this 1st year it reduced the grass, broadleaf, sedges weed population (max 52/ m2) and weed bio mass by 98, 98.5, 64.5 and 91.65 per cent respectively over manual weeding twice. Next year at 25 DAS it reduced the grass sedges weed population by 70, and 62% respectively over initial status. In third year most of the grass (507/m2), broadleaved (504/m2) and sedges (52/m2) were smothered by its cover crop effect at early stage (25 DAS). Remaining weeds were rudimentary, incapable of producing seeds. In consecutive three years out, of 20.7 lakh (40 DAS), 26.8 (25 DAS), 34.8 l lakh jute plants/ha (15 DAS), only 3.3, 6.3 and 7.64 lakhs jute plants/ha i.e., 16, 23.5 and 22 % of total initial population were found effective and harvested (125 to135 DAS). The improved experiment of 2nd and 3rd year produced 3.837 & 3.798 t fibre/ha respectively which were at par with manual weeding, chemical herbicide and mechanical weed control process. It eliminated weeding and thinning processes and consumed only 195 and 276 man days/ha from sowing to fibre extraction over conventional method (340 to 365 man days/ha). It saved 89-145 man days/ha (Rs.22500 to 36250/ha). Mesta (Hibiscus cannabinus) also showed similar response as smother crop (2018-19). Pretilachlor 50 EC @ 0.9 l a.i/ha (POE, 7 days) was found effective for weed control in zero till piara crop. Weed smothering by intercropping green garm with jute (1:1)/mixed cropping were also found economic, produced 0.8-1.0 t pulse grain/ha along with 2.7-2.9 t jute fibre and 1.7 to 2 tonnes nutrogen rich (2.35%) pulse waste per ha.. Pre emergence herbicide Pretilachlor 50 EC and Ipfencarbazone 22.8 %SC were found effective for jute. This weed smothering merit of jute can be used for reducing weed seeds in seed bank growing in repeated flushes, it can also be used as cover crops for different crops which will seqester a lot of carbon to soil also. Weed smothering by high density broadcast jute sowing will eliminate dependence on herbicides, mechanical and manual weeding and make jute farming more remunerative and sustainable in nature.
... Several studies have assessed the suitability of older hemp varieties for production in temperate environments (e.g., Europe and North America) (Campbell et al., 2019;Cosentino et al., 2012;Small and Marcus, 2003;Tang et al., 2016), but agronomic and chemical data are scarce for tropical and subtropical environments. There appears to be a lack of varieties that suit those climates (Hall et al., 2014a;Sengloung et al., 2009). Research on cultivars that have low variability in terms of growth and biomass, seed quality and cannabinoids, is required to expand this emerging industry (Amaducci et al., 2015;Tang et al., 2016). ...
... Only a few studies have investigated growing hemp in low latitude regions. Sengloung et al. (2009) showed that to maximise hemp stem development in North Thailand (latitude: 18 • North), sowing has to be carried out before July; others (Hall et al., 2014a(Hall et al., , 2014b stated that their tested variety showed inadequate phenological development and yields due to tropical environment conditions, unless grown over 13 h and 40 m daylength. Given the scarcity of information regarding the responses of hemp to nutrition, daylength and temperature under tropical conditions, the following questions were asked in the current study: a) do different tropical daylengths and temperatures affect the growth and time to flowering of temperate and tropical varieties of hemp? ...
Hemp (Cannabis sativa L.) has regained worldwide interest as a crop across temperate and subtropical regions. However, there is a paucity of information about the responses of hemp to environmental conditions and interactions between genotype and environment. This study compared the growth responses of a temperate hemp variety (Morphet Late) and three tropical/subtropical varieties (ECO-GH15, ECO-MC16 and ECO-YP16) to tropical daylengths (11.5 h and 12.5 h), temperatures and varying nitrogen (0, 50, 100, 150 kg ha⁻¹ of N) rates. Three experiments under controlled environmental conditions were conducted to test the growth, and cannabinoid production responses to N. Analysis of phenological data revealed significantly different responses between varieties in terms of days to emergence, time to flowering, growth patterns and final biomass showing predominant responses to daylength or temperature depending on the variety. Two tropical/subtropical varieties (ECO-GH15, ECO-MC16) responded similarly under all conditions; the other (ECO-YP16) showed a marked response to temperature rather than daylength, although all varieties had a strong biomass response to N increase. For all varieties, except the temperate variety, the concentration of Δ⁹-tetrahydrocannabinol (THC), cannabidiol (CBD), and some minor cannabinoids were significantly increased by a one-hour daylength increase. This study highlights the importance of temperature, daylength, and nitrogen for growth, time to flowering, and cannabinoid concentrations of different hemp varieties grown under tropical conditions and shows the importance of selecting low THC varieties for production in tropical/subtropical environments.
... The chlorophyll content remained consistent from planting to harvest across all treatments, with a slight increase in the middle growth stages. Bhattarai and Midmore (2014) also found no difference in chlorophyll content in industrial hemp at four different planting densities. The lack of variation in chlorophyll content across treatments could be due to the enriched status of soil nutrients and the genetic characteristics of the cultivars. ...
There is rising interest in the United States for industrial hemp (Cannabis sativa L.) cultivation as a new cash crop after the recent reversal of its production ban. Due to limited research during its long prohibition, little information is available regarding its optimal cropping system and crop management practices. Hence, the study was conducted to identify the optimal plant spacing for two cannabidiol (CBD)‐dominant industrial hemp cultivars (BaOX and Wife) in Florida. Three plant spacing treatments, that is, 61 cm (24 in.), 91 cm (36 in.), and 122 cm (48 in.), were used with a common row spacing of 1.52 m. Plant height, chlorophyll content using soil plant analysis development 502, and canopy cover using Canopeo were recorded every 2‐weeks interval throughout the crop growing season. The final biomass yield, CBD, and delta‐9‐tetrahydrocannabinol (THC) yield were also recorded. The results showed no significant differences between the cultivars in biomass, CBD yield, and plant growth and physiological parameters in most of the observations. Plant height and chlorophyll content were mostly unaffected by spacing. Canopy cover was higher during most of the growing season at lower spacing. Dry biomass yield per plant was higher with wider spacing, but there was no significant difference in total biomass yield per unit area. Wider spacing (91 and 122 cm) also resulted in higher CBD and THC yield in one of the tested cultivars (BaOX). The results suggest that wider plant spacing in industrial hemp could help maximize CBD production in Florida and other regions with similar environmental conditions.
... Many different recommendations for fiber seeding rates exist, with most findings supporting a range from 45 to 90 kg ha −1 (58-115 plants m −2 ) (Amaducci et al., 2012;Koma & Bamka et al., 2022;Roseberg et al., 2019). Other research has found very high-density planting (300-500 plants m −2 ) ensures high fiber quality and suppresses weeds (Hall et al., 2014). High density planting of fiber hemp is meant to ensure tall, slender stalks that increase the bast to hurd ratio ( Figure 1). ...
Hemp (Cannabis sativa L.) is a dioecious, diploid (2n = 2x = 20), photoperiod‐sensitive crop cultivated worldwide for a variety of uses, including food, feed, medicine, and fiber. Hemp is parsed into different market types, including fiber, grain, dual purpose, and high cannabinoid production. Planting densities for the different market types varies greatly, with fiber production systems planted at a much higher density than those for cannabinoid production. Current recommendations for fiber seeding rates range between 45 and 67 kg per hectare (kg ha⁻¹), with other recommendations reaching 90 kg ha⁻¹. However, few studies have been conducted to determine optimal planting density while considering fiber quality, yield, and input cost. In this study, we used four different planting densities (221 plants m⁻², 111 plants m⁻², 74 plants m⁻² and 55 plants m⁻²) in a replicated greenhouse trial to study their effect on plant height, stem diameter, and branching. Planting density significantly affected each trait, with a seeding density of 221 plants m⁻² producing the thinnest, shortest, and least branched plants. All stem traits were positively correlated with plant height, and stem diameter was the most correlated. A planting density of 111 plants m⁻² reduced branching but still produced long, thin stems, translating into a high bast fiber yield while reducing seed input costs and competition between plants.
... Some residues from hemp processing can be valorized as botanical insecticides, miticides, or repellents, being integrated into ecological pest management programs (Adesina et al., 2020;Benelli et al., 2018). Hemp oil and plant residues can be used as natural insecticides and pesticides in organic agriculture (Hall et al., 2014;Benelli et al., 2018). Hemp also produces essential oils with insect-repellent properties and antifungal effects (Kurczyński and Wcisło, 2024). ...
This review explores the multiple directions of industrial hemp (Cannabis sativa L.) utilization at a global level, highlighting the importance of this crop as a renewable, sustainable, and environmentally friendly resource. While hemp has traditionally been employed for the production of fibers, seeds, and medicinal products, recent studies have expanded its applications into innovative fields such as eco-friendly construction materials (e.g., hempcrete and composite materials), automotive and aerospace industries, cosmetics, biofuels, and others. The remarkable properties of hemp, including low density, superior mechanical strength, carbon sequestration capability, and moisture regulation, help reduce energy consumption and enhance the performance of construction materials, thereby providing competitive advantages in sustainability-oriented sectors. Moreover, hemp extracts and oils, rich in bioactive compounds (essential fatty acids, vitamins, antioxidants, and cannabinoids), have demonstrated therapeutic potential, reinforcing the role of hemp in the development of food, cosmetic, and pharmaceutical products. Additionally, hemp significantly contributes to phytoremediation by absorbing heavy metals and contaminants from the soil, and hemp fibers stand out for their durability and resistance, being valued in the textile industry for their ecological characteristics and superior performance. Industrial hemp stands out for its high versatility, and its valuable properties along with its favorable environmental impact, support its integration into a wide range of sectors, opening promising perspectives for a more sustainable and environmentally responsible future.
... The variations in height and diameter mostly depend on sowing density, irrigation, and cultivar type (Burczyk et al. 2009). In lower sowing densities, hemp will branch out and increase its diameter and panicle density (Bhattarai, Jack Hall and Midmore 2014;Horne 2020). High planting densities cause plants to grow taller and more slenderer with smaller diameters (Burczyk et al. 2009). ...
The production of industrial hemp (Cannabis sativa L.) has expanded recently in the US. Limited agronomic knowledge and supply chain issues, however, stemming from a long-standing cultivation ban, pose a barrier to continued market expansion of hemp, which leads to the import of most hemp products. This review examines the most recent cultivation methods, fertilizer and nutrient requirements, soil management practices, environmental parameters, and post-harvest processing methods, particularly in the context of environmental benefits such as soil phytoremediation and CO2 sequestration. Details of the valorization of hemp biomass into sustainable products, such as fibers, papers, packaging, textiles, biocomposites, biofuels, biochar, and bioplastics, along with current limitations and scope for improvements, are explored. Finally, an overall summary of the life cycle and techno-economic analysis aimed at optimizing their environmental performance and economic feasibility are discussed with a focus on intersection with the growing circular economy paradigm.
... While corn and soybeans have a variety of established management practices, and often rely on herbicide applications, weed suppression may be an increasing issue in fiber hemp production, as producers cannot apply post-emergence herbicides to hemp (Flessner et al., 2020). Gaps in fiber hemp production research have been addressed by multiple authors (Bhattarai et al., 2014;Sandler & Gibson, 2019), who noted that in order to push fiber hemp into commercial-scale production like other commodity crops, weed management would have to be researched and resolved. The rapid growth pattern of fiber hemp and the development of its canopy have the ability to suppress weed growth and germination, but studies on specific weed biomass and species are lacking (Adesina et al., 2020;Sandler & Gibson, 2019). ...
With the lack of herbicides approved for use in industrial hemp (Cannabis sativa L.) production, it is important to determine which cultural practices can be utilized to manage weeds. With the general quick growth and dense stand to shade soil surface, hemp produced for fiber, when established early, has the potential to compete with weed populations and prevent weed proliferation. The objectives of this study were to evaluate how a planting date continuum of fiber hemp impacted weed pressure under two growing scenarios, continuous hemp and weed competition or early season weed removal, to inform future research and provide production guidance to hemp producers. Pre‐plant tillage and herbicide applications to establish fiber hemp in the present study resulted in plots that were generally weed‐free. Data collected on weed biomass and species present supported that planting and harvest dates did not significantly impact weed pressure, and that weeds present were also biologically insignificant relative to the fresh fiber hemp yield measured. When planting fiber hemp, producers should focus on proper field location and preparation, timely planting, and correct seeding rates to mitigate weed pressures in the interim to post‐emergence herbicide approvals.
... Seasonal weed emergence from the seed bank may vary from 0.1% to 30% (Forcella, 1992). Weeds have been reported to decrease yields in industrial hemp (Hall et al., 2014;Jankauskiene et al., 2014) and other row crops such as cotton (Nalini et al., 2015), corn (Zea mays L.; Soltani et al., 2016), wheat (Triticum aestivum L.; Flessner et al., 2021), soybean (Glycine max L.; Bensch et al., 2003), and sesame (Sesamum indicum L.; Rose et al., 2023). ...
Industrial hemp is receiving attention for its numerous benefits, particularly in the fiber industry. Weed competition is a primary concern for hemp cultivation, causing reduced yields and inferior‐quality fiber. However, little is known about herbicide application in hemp since a limited range of herbicides are available for hemp production. During 2023, this study evaluated the effect of different post‐emergence herbicides applied at early and late growth stages to optimize weed suppression and minimize crop injury in hemp under semiarid conditions. A randomized complete block design was used with six herbicide treatments, including early post (2 weeks after planting [WAP]) and late post (5 WAP) emergence applications of S‐metolachlor, clopyralid, and ethalfluralin. Hemp plant stand showed no significant difference among treatments. Early post herbicide application reduced 86% of weed biomass compared to untreated control at 7 WAP. By 10 WAP, weed biomass became comparable across treatments. At harvest, untreated control recorded comparatively higher weed biomass than early post treatments and late post ethalfluralin. Plant height remained nonsignificant among treatments until 10 WAP. At harvest, control showed no variation with late post treatments but recorded an average of 63% lower plant height than early post applications. Hemp biomass was insignificantly affected by treatments at 10 WAP. However, on average, early post S‐metolachlor and ethalfluralin applications demonstrated potential as effective herbicides, yielding four‐folds greater hemp biomass than untreated control at harvest. In conclusion, early post S‐metolachlor and ethalfluralin are promising tools for weed control, enhancing crop competitiveness and yield in hemp cultivation.
... This is consistent with studies reporting that NDVI was best suited for estimating aboveground biomass of wheat under different N fertilizer rates (Erdle et al. 2011;Geipel et al. 2016;Viña and Gitelson 2005), although an obvious operational preference would be a model that performs effectively across years instead of a model adapted for each year. These results indicate that plant identification, selection, and quantification from aerial imaging is a viable tool for determining hemp growth and production with the important consideration of specific site and year (Daughtry and Walthall 1998;Hall et al. 2014) (Fig. 1B). The observations from our study are well associated with changes in plant performance due to fertilizer application that can be further inferred from an assessment with aerial imaging. ...
The recent introduction of hemp (Cannabis sativa L., <0.3% D 9-tetrahydrocannabinol) to the United States has been met with a limited understanding of cultivation practices and environmental monitoring techniques. Aerial imaging can contribute to site-specific management and improve hemp production by monitoring crop growth and health in response to agricultural inputs. Drone-based spectral imaging was deployed with the objective of identifying a spectral signature for floral hemp variety 'Wife'; detecting differences in plant size, yield, and spectral reflectance in response to nitrogen (N) fertilizer application rates; and assessing field-level variation in crop health and yield observable by aerial imaging to advance hemp management decisions. We conducted an in-field N experiment to test the effects of six N application rates (0, 56, 112, 168, 224, and 280 kg·ha 21) on the high-cannabinoid flower variety 'Wife' from 2020 to 2022. A quad-copter with a multispectral sensor collected images from an altitude of 61 m between final fertilization and harvest. Each plant canopy was defined in the image and evaluated for size and reflectance as Normalized Difference Vegetation Index (NDVI) and Green Normalized Difference Vegetation Index (GNDVI). The N application rate of 224 kg·ha 21 N resulted in significant increase in hemp biomass from 112 and 56 kg·ha 21 , whereas significant increases in floral yield and canopy area were observed just at 112 and 56 kg·ha 21 N. The N application rate of 224 kg·ha 21 N produced significantly greater NDVI values compared with those of the application rate of 112 kg·ha 21 N, whereas GNDVI was significantly greater at 224 kg·ha 21 N when compared with N rates less than 168 kg·ha 21 N. Canopy area and plant indices consistently showed strong positive linear correlation with aboveground biomass. This study revealed that drone-based aerial imaging can be an effective tool for monitoring crop growth and health while informing N management decisions in hemp cropping systems.
... The noticed decrease in weed density as the population of I. hirsuta increased may be attributed to rise in inter-specific competition for light and other resources (Hall et al., 2014). For effective weed suppression, planting I. hirsuta at 50 2 plants/m may be the best growing density. ...
A field experiment was conducted at the Crop Garden, Department of Crop Protection and Environmental Biology, University of Ibadan, Nigeria to investigate the effect of planting density on the performance of Indigofera hirsuta and its ability to suppress weeds. Seeds sown at 1 cm soil depth were spaced at 20 cm inter-row 2 and varying intra-row spacings: 10, 20, 40, 80 and 160 cm to have densities 50, 25, 12.5, 6.25 and 3.13 plants/m2 , which are equivalent to 500,000, 250,000, 125,000, 62,500 and 31,250 plants/ha, respectively. Plots where I. hirsuta were not planted served as control. The experiment was conducted in two trials in a randomised complete block design replicated three times with the five densities and control randomly allocated to plots in each block. The plant height (PH) in cm, stem diameter (SD) in cm, shoot dry weight (SDW) in kg and weed dry weight in kg were measured at 14 weeks after planting and the treatments compared using one-way ANOVA. The PH of I. hirsuta at density 50 plants/m (105.0 – first trial and 107.0 – second trial) were significantly higher than the 2 heights recorded in other test densities. The SD and SDW at density 3.13 plants/m (0.97 cm and 0.38 kg – first trial; 0.93 cm and 0.38 kg – second trial) were significantly higher than the SD and SDW recorded in other test 2 densities. The weed dry weight on 50 plants/m plot (0.55 kg and 0.59 kg in the first and second trial, respectively) was significantly lower than those on the other plots. Indigofera hirsuta proved effective in 2 suppressing other weeds, which increased with increasing density (WCE = 23.37 and 22.51% at 3.13 plants/m ; 2 70.11 and 69.11 at 50 plants/m in the first and second trial, respectively). The weed suppressive ability of Indigofera hirsuta is attributed to competition for light due to its rapid growth and spreading habit.
... Within each block, three rows were arranged for each plot (population), each extending 10 m in length, and with a row spacing of 60 cm and plant spacing of 90 cm, with a total of 10 plants planted across each row. A drip irrigation system was implemented, and plants were grown in soil amended with compost and fertilized with a balanced, water-soluble fertilizer (N, P, K) [72]. All plants were grown under natural light conditions from April to September 2019. ...
Background
Future breeding and selection of Cannabis sativa L. for both drug production and industrial purposes require a source of germplasm with wide genetic variation, such as that found in wild relatives and progenitors of highly cultivated plants. Limited directional selection and breeding have occurred in this crop, especially informed by molecular markers.
Results
This study investigated the population genomics of a natural cannabis collection comprising male and female individuals from various climatic zones in Iran. Using Genotyping-By-Sequencing (GBS), we sequenced 228 individuals from 35 populations. The data obtained enabled an association analysis, linking genotypes with key phenotypes such as inflorescence characteristics, flowering time, plant morphology, tetrahydrocannabinol (THC) and cannabidiol (CBD) content, and sex. We detected approximately 23,266 significant high-quality Single Nucleotide Polymorphisms (SNPs), establishing associations between markers and traits. The population structure analysis revealed that Iranian cannabis plants fall into five distinct groups. Additionally, a comparison with global data suggested that the Iranian populations is distinctive and generally closer to marijuana than to hemp, with some populations showing a closer affinity to hemp. The GWAS identified novel genetic loci associated with sex, yield, and chemotype traits in cannabis, which had not been previously reported.
Conclusion
The study's findings highlight the distinct genetic structure of Iranian Cannabis populations. The identification of novel genetic loci associated with important traits suggests potential targets for future breeding programs. This research underscores the value of the Iranian cannabis germplasm as a resource for breeding and selection efforts aimed at improving Cannabis for various uses.
... Plant density in hemp affects yield and yield criteria by enabling the plant to benefit from light, water and nutrients effectively (Westerhuis, 2016;Tang et al., 2017;Yazici et al., 2020). Studies on the effect of plant density on fiber and seed yield in hemp have been conducted on a large scale such as 90 (Ranalli, 1999), 150-225 (Townshend & Boleyn, 2008) and 300 plants/m 2 (Hall et al., 2014). However, even if the sowing is done at a level to obtain the appropriate plant density, the chance of obtaining the desired quality fiber and seed decreases if uniform germination does not occur due to environmental or seed-borne factors. ...
Seed maturation in hemp is not homogeneous, and the harvest is done when the seeds are 70-80% mature. This study was carried out to determine the germination and emergence performance of hemp (Cannabis sativa L.) seeds at different maturation stages. Mature, semi-mature and immature seeds were used as material in the study. The study was carried out as two separate experiments, germination and emergence. The germination test was carried out in petri dishes and the emergence test in viols. Both experiments were carried out according to the randomized complete block design with 3 replications. Germination rate (%), shoot and root length (mm), shoot and root fresh weight (mg plant-1) and shoot and root dry weight (mg plant-1) parameters were investigated in the germination study. In the emergence study, the emergence rate (%), seedling and root length (mm), seedling and root fresh weight (mg plant-1), and seedling and root dry weight (mg plant-1) values were examined. In the germination study, semi-mature seeds germinated but did not develop. Therefore, no data could be obtained from other parameters except germination rate. In germination study, germination rate varied between 6.67 and 84.67%, shoot length 27.2-38 mm, root length 39.4-50.8 mm, shoot fresh weight 30.66-49.89 mg plant-1, root fresh weight 4.32-7.69 mg plant-1, shoot dry weight 3.25-7.99 mg plant-1, root dry weight 0.68-2.03 mg plant-1. In the emergence study, emergence rate ranged between 5.18-82.69%, shoot length 68-136.4 mm, root length 37.4-69.6 mm, shoot fresh weight 60.33-154.80 mg plant-1, root fresh weight 27.30-46.73 mg plant-1, shoot dry weight 3.97-10.24 mg plant-1, root dry weight 2.61-5.43 mg plant-1. In both experiments, the highest values obtained from all the examined traits were obtained from mature seeds. In both studies, the highest values were obtained from mature seeds for all traits examined. Semi-mature and immature seeds gave similar results in terms of the traits examined.
... Finola was first included in the official list of plant varieties in Finland in 2003 and is on the list of industrial hemp in the European Union [4]. The seeds of the hemp variety Finola have a high oil and protein content and are a dioecious plant according to their flowering time. ...
Industrial hemp (Cannabis sativa L.) is a multi-purpose crop grown for its fibres, seeds and oil obtained from its seed. Finola hemp variety is a dioecious plant according to its flowering state, and its seeds have high protein and oil content and low THC content, making them preferred for use. This study was conducted to determine the effects of some herbicides on the Finola hemp variety. The trial was carried out in the trial area of Yozgat Bozok University in the form of pot and field studies. In the trial, the phytotoxic effects of herbicides on Finola variety hemp, plant height, technical stem length, stem diameter, biomass yield, dry stem yield, and fibre yield were examined. As a result of the experiment, the highest phytotoxicity was obtained from the application of bentazone (%75.52). The highest plant height (88.91 cm), technical stem length (660.25 cm), stem diameter (6.69 mm), biomass yield (1479.1 kg ha–1)$, dry stem yield (378.6 kg ha–1), and fibre yield (427.1 kg ha–1) were obtained in the weed-free control plots. The lowest plant height was obtained from the weedy control (34.12 cm), the lowest technical stem length was from the bromoxynil application (20.85 cm), the lowest stem diameter was from the bromoxynil application (3.87 mm), the lowest biomass yield was from the bromoxynil application (352.0 kg ha–1), the lowest dry stem yield (136.0 kg ha–1), and the lowest fibre yield were obtained from bentazone application (129.0 kg ha–1).
... Darby et al. (2018) found that their thickest stem diameters came from their least dense stands. Hall et al. (2014) also reported that they saw a significant inverse relationship between plant density and stem diameter. Taken together, these correlations highlight phenotypic plasticity in fiber hemp and suggest a need to fine-tune planting densities to produce stems with the desired morphology for their end-use application. ...
Field trials were conducted in 2021 and 2022 to evaluate the effects of planting date (mid‐March, mid‐April, and mid‐May) on 11 fiber hemp (Cannabis sativa L. <0.3% total tetrahydrocannabinol) varieties. Trials were conducted in Goldsboro, Kinston, and Salisbury, NC. Each location followed a split‐plot randomized complete block design with at least three blocks where planting date was the main‐plot and variety the sub‐plot. Varieties investigated originated from China and Australia (2021 only). Data collection included flowering time, end of season stand counts, stem height, diameter, and final retted dry straw yield. We found differences among the varieties investigated in both years; however, no distinct trend was observed across years. All varieties investigated flowered at the end of August and beginning of September, allowing for a long growing season and ability to produce abundant biomass. In general, the Chinese genetics yielded higher stem biomass compared to previously reported European genetics. Stem thickness was >7.5 mm, which is generally considered the maximum width for textile‐grade fiber production. To achieve thinner stems from the varieties investigated, harvesting prior to male‐flower initiation may be required. The crop experienced temperatures below freezing in both years with no signs of damage. Taken together, farmers seeking to plant fiber hemp in North Carolina have a wide planting window from mid‐March to mid‐May using these Chinese varieties.
... The larger the spacing the larger stem thickness whereas the lowest stem thickness was observed as the density of population increases. Stem thickness showed inverse relationship with sowing density (Amaducci 2008;Hall et al. 2014). Another report by Van der Werf (1996) indicates that increasing plant density results in thinner stemmed plants. ...
Haricot bean (phaseolus vulgaris L.) is among the five pulse crops predominantly grown in Ethiopia. The experiment was conducted to determine the effect of plant density on yield components of haricot bean in randomized complete block design with three replications. The Data collected for Plant height, Number of branches per plant, Number of leaves per plant and Stem thickness were analyzed using analysis of variance (ANOVA). The analysis of variance showed significantly (p≤0.05) different for number of branches per plant, number of leaves per plant and stem thickness whereas non significant (p≥0.05) different for plant height. The second plot with below the recommended density or twelve (12) plants per plot was contain large stem thickness, shorter plant height, more broad and dark green leaf as compared to treatment one and three whereas the third plot with above the recommended density or sixty (60) plant per plot was contain small stem thickness, longer plant height, small leaf number and medium number of branches as compared to others.
... In addition to agriculture, it has many agro-industrial applications in the field of construction, textiles, bio-composites, paper, automotive, biofuel, functional foods, biodiesel, cosmetics, personal care products, and pharmaceutical products [7] . It can serve as a natural insect repellent [8] , a weed retardant [9,10] , and a pathogen inhibitor [11] . It can reduce greenhouse gas emissions by binding approximately 2.5 tons of CO 2 per ha [12] . ...
Industrial hemp (Cannabis sativa L.) is a water-efficient crop that could fit in the declining water situation of West Texas. However, being a new crop, there is a lack of knowledge about hemp cultivation practices. Therefore, multiple experiments were conducted at Quaker Research Farm of Texas Tech University to (1) evaluate the biomass productivity potential of several imported hemp cultivars under different planting dates in field conditions, and (2) test the seed germination capacity of hemp cultivars in a range of temperatures using a growth chamber. In the field, the highest biomass yield was recorded for Jinma in 2020, which was almost 180% higher than the average biomass of two other cultivars. In 2021, early planting observed higher plant biomass, plant height, and irrigation water use efficiency compared to late planting. The highest biomass was recorded for Jinma, followed by Yuma, Eletta Campana, and Fibranova in 2021. Jinma and Yuma resulted in high Tetrahydrocannabinol content at harvesting. In the growth chamber study, percentage germination remained similar from 10 to 30 °C, but it decreased by 28% at 35 °C compared to 30 °C. The speed of germination was higher at 30 °C compared to other temperatures. The mean germination time was recorded the highest at 10−15 °C, and in Jinma among cultivars. Results indicate that Eletta campana with early planting could be more productive in West Texas. Overall, hemp germination was more sensitive to high temperatures compared to low temperatures.
... Several studies on stem diameter report that maturation is a significant factor in increasing hemp stem diameter (in different subspecies or cultivars). The findings of this study corroborated those of previous studies (Hall et al., 2014;Yazici et al., 2020) in that stem thickness had a positive relationship with the N application rate and harvesting stage. In contrast, Höppner and Menge-Hartmann (2007) discovered no statistically significant relationship between stem diameter and harvesting stage. ...
Hemp (Cannabis sativa L.) is one of the world's oldest and most diversely cultivated plants, but legal constraints and a lack of agronomic rules have curtailed its production. This study aimed to determine the optimum nitrogen (N) application rate and harvesting stage for hemp yield in terms of seed, fiber, and stem. Treatments included (1) five nitrogen application rates (control [N0], 60 kg ha⁻¹ [N60], 120 kg ha⁻¹ [N120], 180 kg ha⁻¹ [N180], and 240 kg ha⁻¹ [N240]) and (2) three harvesting stages: before flowering (HS1), during flowering (HS2), and at the end of flowering (HS3). A 2‐year field experiment was conducted with three replicates. Harvest stages were randomly distributed over N rates in both years. The following agronomic parameters were evaluated: plant height, stem diameter (lower, middle, upper), number of leaves/plant, leaflet width, leaflet length, dry stem yield, fiber yield, and seed yield. The highest stem yield and fiber yield were obtained in the 240 kg ha⁻¹ N treatment, and also the highest fiber (bast) yield and dry stem (hurd fiber) were obtained flowering and at the end of the flowering stages, respectively. When nitrogen application rate was increased from 0 to 240 kg ha⁻¹, plant height, stem, and fiber yields increased by 48%, 65% and 57%, respectively. Agronomic parameters increased significantly (p < 0.01) when the harvesting time was moved from “before flowering” to “at the end of flowering.”
... It is estimated that biological progress is mainly related to increasing the productivity of plants; therefore, there is a need to select appropriate cultivars and optimise the most important agrotechnical factors. High seed yield, as well as hemp biomass, depends on sowing density and harvesting date, but fertilisation, especially with nitrogen (N), is a key factor (Amaducci et al. 2002, Bennett et al. 2006, Hall et al. 2014. Tang et al. (2017) found that an application rate of 60 kg N/ha was sufficient due to hemp's highly efficient use of soil nitrogen. ...
... The length of the inflorescence is followed by the length of the first branch, which is 15-20 cm in the densest treatment and 50-55 cm in N/20 and P/20 treatments (data not shown). A significant influence of hemp crop density on several phenological traits, yield and weed suppression is reported by Hall et al. (2014). The yield of the stem in the experiment varied between 7.5 and 14.0 tons per hectare (Tab. ...
One-year experiments conducted with one hemp variety were established to determinate the cultivation practices (growth density and pinching) which could be used to optimize the technological process of hemp varieties production for different purposes. The results showed that reduced crop density and pinching result in development of shorter plants. In denser non-pinched crops, the stem is over 180 cm high, while the plants start branching in the upper 1/4-1/5 part. In the non-pinched treatment with a larger area available for individual plants, as well as in the pinched treatments, more productive branches of less thickness develop in the lower parts. The non-pinched treatments generally produce higher stem and fiber yields, which increase when crop density is reduced. The obtained results can serve as a basis for determining certain treatments during the evaluation of production technology for different varieties of hemp intended for specific purposes.
... Significant at *: P≤0.05; **: P≤0.01; ns: Non-significant In accordance with our findings, many researchers reported that when the number of plants per unit area decrease, MST of the plants increase. Namely, there is an inverse relationship between plant density and MST trait [33,34,35,36]. ...
This study was conducted to determine the effect of different row spacings (RS) and seeding rates (SR) on the forage yield and related traits of forage pea (Pisum sativum ssp. arvense L.). The field experiments of the research were established according to the Split Plots in Randomized Complete Block Design with three replications under the rainfed conditions of Bismil, district of Diyarbakır province, Turkey, during two consecutive growing seasons (2019-20 and 2020-21). In the experiments, four row spacings, placed in the main plots, and four seeding rates, placed in the sub-plots, were tested, thus sixteen combination treatments were studied. Due to the great climatic variation between the growing seasons, statistically highly significant (P < 0.01) differences were detected between the growing seasons in terms of all the investigated traits. And the means of the results determined in rainy growing season (2019-20) were found to be higher than those obtained in the dry growing season (2020-21) in terms of all of the investigated traits. Additionally, the means of the investigated traits changed among the row spacing and seeding rate treatments as follows; days to 50% flowering 137.3-144.0 days, natural plant height 53.33-81.00 cm, main stem height 74.50-148.80 cm, main stem numbers per plant 1.12-2.16 stems plant-1 , main stem thickness 3.42-5.56 mm, fresh forage yield 10.15-45.57 t ha-1 and dry forage yield 2.65-9.87 t ha-1. By considering all the means of the investigated traits in the two growing seasons, the biplot analysis results revealed that the investigated traits were divided into three groups, and fresh forage and dry forage yield traits took part in the same group. In terms of the two forage yield traits, 20 cm row spacing and 100 seeds m-2 treatment was found as the best combination treatment. Hence, when forage yield of forage pea is targeted, that treatment should be preferred.
... It is estimated that biological progress is mainly related to increasing the productivity of plants; therefore, there is a need to select appropriate cultivars and optimise the most important agrotechnical factors. High seed yield, as well as hemp biomass, depends on sowing density and harvesting date, but fertilisation, especially with nitrogen (N), is a key factor (Amaducci et al. 2002, Bennett et al. 2006, Hall et al. 2014. Tang et al. (2017) found that an application rate of 60 kg N/ha was sufficient due to hemp's highly efficient use of soil nitrogen. ...
The aim of the experiments was to determine the effect of sowing density and nitrogen fertilisation on the cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) yields in selected cultivars of fibre hemp. A three-factor field experiment was conducted in 2014–2016. Factor A: cultivar (Futura 75, KC Dora and Tygra), factor B: sowing density (60 and 180 seeds/m2) and factor C: nitrogen fertilisation (0, 30, 60 and 90 kg/ha). The CBD yield ranged from 10.52 g/m2 in cv. Tygra to 10.99 g/m2 in cv. KC Dora. Among the examined cultivars, the highest yield of Δ9-THC in cv. KC Dora was observed. Sowing density did not modify the CBD yield, but increasing the density from 60 to
180 seeds/m2 caused an increase in the yield of Δ9-THC in cvs. KC Dora and Tygra. Nitrogen fertilisation significantly influenced the yields of CBD and Δ9-THC. In both cases, yield increased until the rate of 60 kg N/ha.
... Plant cultivation density is also an important factor affecting fiber yield and quality [17,18]. Hall et al. [19] reported that hemp planted at a high density encourages taller heights and restricts side branching, both positively affecting the fiber quality. Opposite to the aforementioned report, Campiglia et al. [20] reported that a higher plant density results in shorter plant heights as the hemp plants tended to reach the reproductive stage earlier. ...
The study was aimed at determining the most suitable irrigation schedule program for hemp grown for fibers by using evaporation from the free water surface (Eo), measured by a Class A pan and related crop plant coefficient (Kc). The experiment, carried out in Vojvodina, a northern part of the Republic of Serbia, included three irrigation regimes: I1, I2, and I3 corresponding, respectively, to daily evaporation from an open water surface (Eo), two interrow spacings: RS1 (12.5 cm) and RS2 (25 cm), and topped (T) and not topped (NT) variants. The Kc values used for the calculation of daily evapotranspiration (ETd) were 0.42 for April and May and 1.00 (I1), 0.80 (I2), and 0.60 (I3) from June to the harvest. In addition, the nonirrigated (Io) control variant was also included in the trial. The dioecious fiber hemp variety Marina was used for the trials. Irrigation was carried out by a drip irrigation system and was scheduled based on the water budget method. It started when readily available water (RAW) in the soil layer of 0.4 m was completely depleted by the plants. In the first year of the study, irrigation did not influence the yield of hemp fiber, but in the second one, the best result was achieved for the irrigation variant I1. Interrow spacing did not have a statistically significant effect on both the hemp fiber yield and the quality. The topping of plants significantly decreased the yield of hemp, and it is not recommended when the hemp is cultivated for fibers. The quality of the hemp fibers was not influenced by irrigation, inter-row spacing, and topping. The rate of hemp evapotranspiration was in an interval of 312 mm (ETa) to 520 mm (ETm). The highest values of IWUE and ETWUE in both years and the bark yield in the first year were detected for the I3 irrigation variant, which suggested that the crop plant coefficient (Kc) of 0.6 could be recommended for the correction of Eo values in the calculation of the daily evapotranspiration of hemp (ETd) from June to August. The yield response factor (Ky) with values of 0.22 and 0.60 for the total growing season reveals that, in rainy years, hemp for fiber production could be grown without irrigation in the temperate climate of the Vojvodina region. However, such years are rare. Without doubt, irrigation of fiber hemp is recommended in the mentioned region in order to obtain high yields of good quality product.
... Membrane leakage and osmotic potential were generally higher and lower, respectively, in upper leaves of the higher density plants, presenting a negative effect of high density on the physiological state (Figure 7). It should be noted that very high plant densities (>20 plants/m 2 ) reduced cannabis hemp-type plant height as was described previously (Amaducci et al., 2002;Bhattarai and Midmore, 2014). However, since industrial fiber-hemp morphology differs from drug-type medical cannabis, and the growth patterns were bred for different production goals, developmental and physiological responses are expected to differ. ...
A major challenge for utilizing cannabis for modern medicine is the spatial variability of cannabinoids in the plant, which entail differences in medical potency. Since secondary metabolism is affected by environmental conditions, a key trigger for the variability in secondary metabolites throughout the plant is variation in local micro-climates. We have, therefore, hypothesized that plant density, which is well-known to alter micro-climate in the canopy, affects spatial standardization, and concentrations of cannabinoids in cannabis plants. Canopy density is affected by shoot architecture and by plant spacing, and we have therefore evaluated the interplay between plant architecture and plant density on the standardization of the cannabinoid profile in the plant. Four plant architecture modulation treatments were employed on a drug-type medicinal cannabis cultivar, under a density of 1 or 2 plants/m². The plants were cultivated in a naturally lit greenhouse with photoperiodic light supplementation. Analysis of cannabinoid concentrations at five locations throughout the plant was used to evaluate treatment effects on chemical uniformity. The results revealed an effect of plant density on cannabinoid standardization, as well as an interaction between plant density and plant architecture on the standardization of cannabinoids, thus supporting the hypothesis. Increasing planting density from 1 to 2 plants/m² reduced inflorescence yield/plant, but increased yield quantity per area by 28–44% in most plant architecture treatments. The chemical response to plant density and architecture modulation was cannabinoid-specific. Concentrations of cannabinoids in axillary inflorescences from the bottom of the plants were up to 90% lower than in the apical inflorescence at the top of the plant, considerably reducing plant uniformity. Concentrations of all detected cannabinoids in these inflorescences were lower at the higher density plants; however, cannabinoid yield per cultivation area was not affected by neither architecture nor density treatments. Cannabigerolic acid (CBGA) was the cannabinoid least affected by spatial location in the plant. The morpho-physiological response of the plants to high density involved enhanced leaf drying at the bottom of the plants, increased plant elongation, and reduced cannabinoid concentrations, suggesting an involvement of chronic light deprivation at the bottom of the plants. Therefore, most importantly, under high density growth, architectural modulating treatments that facilitate increased light penetration to the bottom of the plant such as “Defoliation”, or that eliminated inflorescences development at the bottom of the plant such as removal of branches from the lower parts of the plant, increased chemical standardization. This study revealed the importance of plant density and architecture for chemical quality and standardization in drug-type medical cannabis.
... The xylem/cortex value in transverse sections of both positions 1 and 2 hemp stems was not statistically significant (p ¼ 0.7). This value may vary depending on the nutrient supply of plants, seeding rate, light conditions, hormonal regulations within plants, etc. (Amaducci et al., 2005;Hall et al., 2014). The microscopic images of transverse sections of positions 1 and 2 hemp stems, respectively, are provided in the Mendeley Data repository: Figures S2 and S3. ...
Industrial hemp (Cannabis sativa L.) is identified as a leading fibre crop and there is increasing interest in C. sativa fibre due to its new range of industrial applications. However, the complexity of hemp germplasm resulted in insufficient information on the effect of genotypes on fibre quality and quantity. In this study, 16 fibre and non-fibre type hemp genotypes were evaluated to compare the morpho-anatomical differences of stems and physico-mechanical fibre properties under three retting methods and to understand the effect of stem colour on the properties of hemp fibres. Morphological markers were scored and stem anatomy was examined using live and herbarium collections. Stems were retted using chemical, enzymatic, and microbiological methods. The resulting fibres were tested for tensile strength, moisture retention, colour, bast and hurd dry weights. Hemp genotypes showed morphological variations that affect fibre processing and a unique pattern of fibre wedges in cross-sections of the basal internode. Fibre yield, tensile strength, colour, and moisture retention significantly varied among the genotypes. The hemp collection used in this study formed three clusters in principal component analysis and traits such as internodal length, node number, hurd yield, and tensile strength highly contributed to the total variability. Additionally, non-fibre type hemp genotypes that showed important fibre properties were identified. The hemp genotypes that were selected based on our approaches can be tailored towards the specificities of the end-usage of choice. Our methods will enable the exploration of hemp genetic diversity pertaining to fibre properties and contribute to the preliminary identification of genotypes as a supplement to genetic analyses.
... While in our study oilseed radish was not necessarily among the crops with the greatest spring RGR it was among the top three for greatest leaf area and the greatest % ground cover throughout the growing season demonstrating that the weed suppressive abilities of oilseed radish are due to aboveground light competition. Hemp has also been known to have weed suppressive properties due to its rapid and tall growth [99]. Here we also found hemp var. ...
Non-marketable crops are increasingly being used as a tool to promote agroecosystem services and sustainable agriculture. Nevertheless, crops vary greatly in the traits by which they capture resources and influence the local ecosystem. Here we report on the traits and associated soil microbial communities that relate to aboveground biomass production, nutrient capture, weed suppression, erosion control and building particulate organic matter of 22 different full-season cover crops. All agroecosystem services were positively correlated with maximum canopy height and leaf area. Rooting density was positively associated with indices of bacterial diversity. While some legumes produced the greatest standing N and P in aboveground biomass, they were also poor at capturing soil nitrate and promoted high levels of potential plant fungal pathogens. Conversely, Brassicaceae crops had the lowest levels of potential plant fungal pathogens, but also suppressed saprophytic fungi and rhizobia. Thus, not all crops are equal in their ability to promote all agroecosystem services, and while some crops may be ideal for promoting a specific agroecosystem service, this could result in a trade-off with another. Nonetheless, our study demonstrates that plant functional traits are informative for the selection of crops for promoting agroecosystem services.
Çalışmada bor noksan alanlarda yetiştirilen endüstriyel kenevirin (Cannabis sativa L, cv: Vezir) bor uygulamasına tepkisini ortaya koymak ve bor uygulamasının endüstriyel kenevirin gelişimi ve lif verimi üzerine etkilerini belirlemek amaçlanmıştır. Endüstriyel kenevir bitkisi ile yürütülen tarla denemesi Kastamonu ili, Taşköprü ilçesi Kızılcaörhen Köyü sınırları içerisinde 23.04.2023 tarihinde tesadüf blokları deneme desenine göre üç tekerrürlü olacak şekilde üretici tarlasında (41.51126 K, 34.02726 D, yükseklik 708m) kurularak yürütülmüştür. Denemede topraklara bor 0, 0.2 mg B kg-1 ve 0.4 mg B kg-1 olacak şekilde % 20.8 bor içeren Etidot-67 (Disodyum oktaborat tetrahidrat, Na3B8O13.4H2O) gübresinden uygulanmış ve çözelti formundaki borlu gübreler homojen bir şekilde toprak yüzeyine püskürtülmüş ve ayrıca çapa kullanılarak toprakla iyice karıştırılmıştır. Toprak analiz sonuçları göre ekimle birlikte 8 kg N da-1, 8 kg P2O5 da-1 ve 8 kg K2O da-1 15-15-15 gübresinden, üst gübreleme olarak ise bitkiler yaklaşık 30 cm boya ulaştığında 20.05.2023 tarihinde 4 kg N da-1 üre gübresinden uygulanmıştır. Hasat sonrası elde edilen bitkilerde yapılan ölçüm ve analizler sonucunda, Endüstriyel kenevir bitkisinde yaş ve kuru ağırlık ile bitki boyu ve teknik sap uzunluğu uygulanan bora bağlı olarak artmış ve borlu gübrelemenin bu parametreler üzerine etkili olduğu belirlenmiştir. Kontrol uygulamasına 0.4 mg B kg-1 uygulandığında yaş ağırlık miktarında % 28.8, kuru ağırlık miktarında % 27.2, lif veriminde % 73.5 ve lif randımanında ise % 41.2 oranında artış olmuştur. Kontrole göre 0.4 mg B kg-1 bor uygulandığında bitki boyu % 20.7 ve teknik sap uzunluğu % 24.4 oranında artmıştır. Bor uygulanmadığında endüstriyel kenevir bitkisi yaprağında ve lifinde bor konsantrasyonu kritik konsantrasyonun (< 20 mg B kg-1) altında olduğu belirlenirken 0.4 mg B kg-1 uygulandığında yaprakta ve lifte bor konsantrasyonu artmış ve endüstriyel kenevir bitkisi yaprağında belirlenen bor noksanlığı bor uygulaması ile normal düzeye çıkmış ve genç yapraklarda görülen bor noksanlık belirtileri ortadan kalkmıştır.
Industrial hemp (Cannabis sativa L.) production is expanding in the United States, generating sustained interest in this multipurpose crop, though the optimal agronomic conditions (e.g., row spacing, planting density, and nutrient management) for maximizing fiber yield remain unclear in many regions. Key factors like row spacing not only affect resource utilization but also play a crucial role in weed suppression, especially in regenerative organic systems. This research at the Rodale Institute, Kutztown, PA, examined the effects of row spacing (19 cm narrow vs. 38 cm wide) and fertilization treatments (control, blood meal containing 12% N at 112 kg ha⁻¹ and 224 kg ha⁻¹, and compost at 60 t ha⁻¹) on yield and chemical composition of industrial hemp seed (cultivar: Canda) over two growing seasons (2019 and 2020). The narrow row spacing increased plant and stalk density, boosting bast fiber yield, while wider spacing promoted weed biomass due to reduced crop competition. Higher temperatures in the late growing season in 2020 led to 3.5 times increase in biomass yield and improved grain protein content. Principal component analysis indicated that compost influenced nutrient availability and heavy metal uptake more strongly than row spacing or blood meal treatments. Blood meal had limited effects, likely due to insufficient application rates, but showed promise for minimizing heavy metal uptake compared to compost. Optimal crop performance depends on the interaction between climatic conditions and agronomic practices. Selecting appropriate row spacing and nutrient sources is essential for enhancing hemp production while reducing input costs and minimizing environmental impact.
Future breeding and selection of Cannabis sativa L. for drug production and industrial purposes require a source of germplasm with wide genetic variation, such as that found in wild relatives and progenitors of highly cultivated plants. Limited directional selection and breeding have occurred in this crop, especially informed by molecular markers. Here, we investigated the population genomics of a natural cannabis collection of male and female individuals from differing climatic zones in Iran. Using Genotyping-By-Sequencing (GBS), we sequenced 228 genotypes from 35 populations. The results obtained from GBS were used to perform association analysis identifying links between genotype and important phenotypes, including inflorescence characteristics, flowering time, plant morphology, tetrahydrocannabinol (THC) content, cannabidiol (CBD) content and sex. Approximately 23,266 significant SNPs of high quality were detected to establish associations between markers and traits, and population structure showed that Iranian cannabis plants fall into five groups. A comparison of Iranian samples from this study to global data suggests that the Iranian population is distinctive and, in general, is closer to marijuana than to hemp, although some populations in this collection are closer to hemp. The GWAS results showed that novel genetic loci, not previously identified, contribute to sex, yield and chemotype traits in cannabis and are worthy of further study.
It has been proven that irrigation is an important factor climatically
oriented agrarian sector of the economy and adaptation to dry weather
conditions, as evidenced by scientific research and the growing number
publications over the past 20 years related to the development of irrigation.
The factors determining the state of irrigated soils in the zone were analyzed
Forest Steppe and Steppe. It has been established that the quality of irrigation water is one of the
dominant factors, which determines agrogenic changes in soil condition indicators and
the level of its fertility under long-term irrigation.
The industrial hemp market is rapidly expanding, and best crop practices need to be assessed. This study aimed to determine the effect of fertilization and weed management on hemp crops and weed flora during the 2019 and 2020 growing seasons. Field experiments were laid out in a split–split plot design with three replicates: two hemp cultivars as main plots, three fertilization treatments as sub-plots, and three sub-sub-plots (weedy, weed-free, and herbicide application). For the computation of crop traits, 10 plants were randomly selected by each plot. Weed species were collected by quadrate for density and biomass weight determination. Increased fertilization rate positively affected plant height and dry biomass, while no impact was recorded on yield and yield components. The density and biomass of nitrophilous weeds were enhanced by fertilization, negatively affecting hemp growth. Marked differences were recorded on the competitive ability of cultivars since “Fedora 17” decreased the weed studied traits better than “Uso 31”. Herbicide application decreased the biomass of annual and perennial weeds by 38% and 13%, respectively, while it caused a reduction in hemp growth and yield of “Uso 31” plants. Further research should be conducted to address hemp yield losses under different cultural practices and weed control systems.
The research was carried out at the Upytė Experimental Station of the Lithuanian Research Centre for Agriculture and Forestry in 2015–2016. The effect of sowing rate (50, 75, 100 kg ha–1) and fertilization rate (N0P0K0; N45P45K45; N45P45K45 + N34.4; N45P45K45 + N68.8) on the weeds suppression in the crop of hemp cultivars ‘Uso 31’ and ‘Felina 32’ was evaluated. It was found that in the crop of both investigated cultivars the least amount of declined weeds was when growing hemps without fertilizers. A positive, strong, moderately strong and statistically significant correlation (P < 0.05) was identified between the fertilization rate and the amount of declined weeds. Increasing the sowing rate of the investigated hemp cultivars resulted in an increase of the amount of weeds declined during vegetation. A positive, strong, moderately strong and statistically significant correlation (P < 0.05) was obtained between the sowing rate and the amount of declined weeds during vegetation, except cultivar ‘Uso 31’ under meteorological conditions favourable for hemp growing.
Background
Industrial hemp (Cannabis sativa L.) is rated among the important green fibers and density significantly alters the fiber and seed production. However, optimum planting density is unknown for different cultivars available in Turkey.
Methods
This study determined the effects of four plant densities (i.e., 100, 150, 200, and 250 plants m⁻²) on yield and quality traits of local ‘Narlısaray’ population and ‘Futura 75’ industrial hemp cultivar.
Results
Planting density significantly altered the yield and fiber production. The ‘Narlısaray’ population recorded higher values for plant height, technical stem length, stem diameter, biomass yield, dry stem weight, and fiber yield. In contrast, seed yield, fiber rate, and oil rate were higher in ‘Futura 75’ cultivar. According to the average data of two years, plant height varied from 183.1 to 202.4 cm, technical stem length ranged from 130.8 to 151.3 cm, stem diameter 7.2-10.2 mm, fresh biomass 16400.3-22790.3 kg ha⁻¹, stem dry weight 6730.8-9290.8 kg ha⁻¹, fiber yield 1820.9-2610.9 kg ha⁻¹, seed yield was 820.8-940.8 kh da⁻¹, fiber ratio 27.7-30.3 %, and oil ratio was 28.5-31.1%.
Conclusion
The two-season average evaluation showed that the most appropriate planting density was 150 plant m⁻² of hemp under ecological conditions of Yozgat province, Turkey.
Cannabis (Cannabis sativa L) is cultivated commercially in various parts of the world, predominantly for its medicinal properties (medicinal-type) and as a source of fibre and oilseed (fibre-type). The plant is known to contain over 567 chemical compounds out of which about one hundred chemicals belong to the highly valued unique class of Cannabinoids. At present, more than 25,000 Cannabis-based products worth 344 billion US 27,000 annually to import Cannabis for medicinal preparations. Cannabis is well- known for its wide range of environmental adaptation, higher nutrient and water use efficiency, low dependency on external inputs such as fertilizers and pesticides, high economic return for a unit area of land, and ability to cultivate both in indoors and outdoors. Considering the genetic resources and inherent knowledge, along with favourable climatic conditions available in the dry zone, suggest that Cannabis is an ideal crop, which could assure higher economic benefits under low inputs. While serving as a venture of foreign earnings, local cultivation would halt the country’s dependency on importation of Cannabis-based raw materials. However, legalization and cultivation should be rigorously monitored by an authorized body to ensure that the production meets the health regulations and utilized accordingly.
This paper reports on a 3-year agronomic study into fibre hemp (Cannabis sativa L.) conducted in Tasmania, Australia. The performance of selected hemp cultivars, and the responses to sowing date and plant density were investigated as part of a broad feasibility study to assess the potential of fibre hemp and flax (Linum usitatissimum L.) as sources of fibre for the Australian newsprint industry.
Trials were conducted at separate sites in north-west and south-east Tasmania. Nine cultivars from the Ukraine, Hungary and France were examined in 2 separate trials. The Hungarian cultivars, Kompolti and Unico B, and the French cultivar Futura 77 had the highest single plot dry stem yields (up to 1500 g/m ² ) and bark proportions (up to 40%). All the cultivars flowered toward the end of January, suggesting that the growing season in Tasmania could accommodate much later flowering and potentially higher yielding genotypes. Levels of the psychoactive agent, delta-9-tetrahydrocannabinol were consistently below the legal maximum of 0.35% (dry weight basis).
Three sowing date trials were conducted across 2 seasons incorporating dates between mid September and mid November and a single autumn planting at the end of May. Interactions with cultivar and planting density were also considered. Stem and bark yield declined with delays in sowing after early–mid October in response to a decline in calendar days and thermal time from sowing to flowering. The response was most pronounced in sowings of Kompolti, which flowered within a short period and differed more substantially in durations to flowering. Earlier sowings were limited by premature flowering in response to shorter daylengths and by poor drainage at one of the 2 trial sites. The success of early sowings in Tasmania would appear to depend on finding cultivars less sensitive tophotoperiod, and cultivation on well drained sites.
A further trial was conducted to investigate the influence of plant density on hemp yields. Treatments included densities from 50 to 300 plants/m ² . Plant density declined with crop growth across all treatments and was most pronounced for populations of 200 and 300 plants/m ² . Final harvest stem yield responded in a parabolic manner to plant density, with maximum yields at about 110 plants/m ² . Differences in the percentage of the long, high quality bark fibre at final harvest were generally small and not significant. However, regression analysis of the response of bark percentage suggested a linear decline with increasing initial density.
Research and development of an innovative production system for hemp (Cannabis sativa L.) fibre for textile use requires the integration of multidisciplinary knowledge from cultivation technique to realization of end products. Research was carried out to study the effect of the agronomic factors cultivation year (2003–2004), genotype (Futura 75 and Tiborszallasi), plant population (120, 240 and 360plantsm−2) and harvesting time (beginning and full flowering) on fibre yield and quality in the whole hemp stem, and in the basal and apical stem portions separately. The study of separate stem portions was done to determine the effect on fibre quality of an innovative harvesting and processing system in which hemp stems are cut in two portions of approximately 1m at harvest to enable processing on modern flax scutching lines.Stem and fibre yield were affected by most of the agronomic factors. The extreme drought experienced in the first year reduced stem and fibre yield, but stems had higher percentage of fibre (16.5%), that were finer (22.9μm) and with a higher degree of maturity (73.6%) in 2003 than in 2004 (respectively 16.0%; 24.5μm; 55.8%). Between the two genotypes under trial the monoecious Futura 75 largely out yielded the dioecious Tiborszallasi in both years. The latter however had finer primary fibres and less secondary ones. In both genotypes primary fibres maturity and quantity of secondary fibres increased at later harvest.Plant population affected stem biometrics and fibre characteristics, with finer fibres and less secondary growth at higher stands.It can be concluded that cultivation technique can be exploited in order to maximize the quality and yield of stems destined for the innovative harvesting and processing system herein described.
Hemp grown for textile applications must be sown at high densities (60–80 kg/ha) and harvested early to obtain fiber of high quality, and the interest in cultivating industrial hemp used for non-textile applications is growing. Broadening the use of hemp as a raw material for specific industrial products and obtaining maximum yields calls for revision of current sowing densities and harvest dates. Therefore, two experiments (A + B) have been carried out in 2004–2006 at the INF Experimental Farm in Pętkowo, Poland, near Środa Wielkopolska. In experiment A, four sowing densities of hemp grown for biomass, straw, panicles, and seed were tested (30, 40, 50, 60 kg/ha). In experiment B, lower sowing densities were compared for hemp grown for seed, panicles, and straw (5, 10, 15, 20 kg/ha). In both experiments, plants were harvested at three periods: beginning of panicle forming, full bloom, and full seed maturity. Panicles were harvested for essential oils. Results of field and laboratory testing confirmed a hypothesis that maximum yields of biomass, straw, cellulose, and fiber can be obtained at lower sowing densities (30 kg/ha) harvested at full bloom. When growing hemp for seed or panicles, the highest yields were obtained when hemp was sown at 10–20 kg/ha and harvested at full maturity of panicles. Following the results of the study, the norms for sowing hemp for non-textile applications used in agricultural practices require verification to increase yields of raw materials from 1 ha and to improve competitiveness of industrial products.
Fibre hemp may yield up to 25 t above ground dry matter per hectare (20 t stem dry matter ha−1) which may contain as much as 12 t ha−1 cellulose, depending on environmental conditions and agronomy. Its performance is affected by the onset of flowering and seed development. Effects of cultivar and management on yield and quality were tested at three contrasting sites in Italy, the Netherlands and the UK in three years, making use of standardised protocols for experimental design and research methodology. Highest yields (up to 22.5 t dry matter ha−1) were obtained in Italy when later cultivars were used. Attainable yields proved slightly lower in the Netherlands and much lower in the UK. The quality of the cellulose was relatively stable over the growing season, but lignification may proceed rapidly some time after flowering. Crop development was very rapid and crops maintained green leaf area for a long time, thus radiation interception was considerable. The radiation use efficiency changed during development. It was lower after flowering (about 1.0 g MJ−1 PAR) than before (about 2.2 g MJ−1 PAR). Growing earlier cultivars to obtain some seed set advanced the reduction in radiation use efficiency. Nitrogen proved to affect yield only slightly. A relatively small amount of fertiliser will be adequate to cover the crop’s needs. Plant density declined during growth in a site-specific manner when it was high initially. Very low plant densities may not show this self-thinning but reduced yield and (especially) quality. Final plant densities were proven to depend more on initial plant stands than expected from literature. This was true at all three contrasting sites and in the different years. Nitrogen and plant density hardly interacted within one site. Results suggest that hemp can yield large quantities of useful cellulose when ecologically adapted cultivars are sown in proper plant densities. The cultivation is environmentally friendly with little harmful accumulation or emission of chemical inputs. More research on ideotyping is required and breeding efforts should be broadened.
Temperature and photoperiod can be used to simulate post-emergent hemp (Cannabis sativa L.) phenology. With reference to hemp in Italy, our main objective was to model field crops grown under a range of temperature and day length regimes. Dates of emergence and 50% of flowering were collected at Cadriano (Bologna) from serially sown field experiments (1996–1999, 2003–2005) on five cultivars: Carmagnola (late maturity), Felina 34 (medium maturity), Fibranova (late maturity), Futura (medium-late maturity), and Tiborszallasi (medium-late maturity). The database of phenological records was segregated into calibration and validation subsets. A phenology model was developed which utilises the beta function for response to hourly air temperature, and a switch-off function for response to day length. The life cycle of hemp from emergence to 50% of flowering was defined in terms of physiological development days (chronological days at the optimum photoperiod and temperature) and considered in three phases: juvenile phase (BVP), photo-sensitive phase (PIP), flower development phase (FDP). Critical temperatures (Tb, base; To, optimum, Tc, ceiling), which did not vary widely across phases and cultivars, were estimated as common values: Tb = 1.9 °C for BVP and 11.3 °C for the other phases, To = 26.4 °C and Tc = 40.0 °C for all phases. Other parameters, i.e. day length of half-maximum development rate at PIP, and physiological development days for FDP, were also estimated as common values for all cultivars. Different genotypes were mainly characterised for the sensitivity to photoperiod (shape parameter n) and BVP length. With n ∼ 50, Felina 34 and Futura are regarded as low sensitive cultivars. Tiborszallasi was estimated as the highest sensitive cultivar (n close to 70), whereas Carmagnola and Fibranova showed an intermediate sensitivity (n ∼ 62). Felina 34 also differentiated for its relatively short BVP length at optimum conditions, i.e. ∼13 days; duration of about 20 days was the estimate for the other cultivars.Model performance against calibration dataset was good (percent relative root mean square in the range ∼6–20%), and comparison against independent data also confirmed the general applicability of this model. Owing to the importance of flowering date in hemp management techniques, these results can be used in decision support for hemp production though further evaluation of the model under a variety of latitudes is required.
The transition to flowering in plants is regulated by environmental factors such as temperature and light. Plants grown under dense canopies or at high density perceive a decrease in the ratio of red to far-red incoming light. This change in light quality serves as a warning of competition, triggering a series of responses known collectively as the 'shade-avoidance syndrome'. During shade avoidance, stems elongate at the expense of leaf expansion, and flowering is accelerated. Of the five phytochromes-a family of red/far-red light photoreceptors-in Arabidopsis, phytochrome B (phyB) has the most significant role in shade-avoidance responses, but the mechanisms by which phyB regulates flowering in response to altered ratios of red to far-red light are largely unknown. Here we identify PFT1 (PHYTOCHROME AND FLOWERING TIME 1), a nuclear protein that acts in a phyB pathway and induces flowering in response to suboptimal light conditions. PFT1 functions downstream of phyB to regulate the expression of FLOWERING LOCUS T (FT), providing evidence for the existence of a light-quality pathway that regulates flowering time in plants.
Fibre hemp (Cannabis sativa L.) may be an alternative to wood as a raw material for pulp and paper production. Research was done to assess the potential productivity of fibre hemp and to identify constraints to that productivity. Growth analyses were done on hemp crops in three consecutive years, using several cultivars and seeding rates. In 1987 the crops suffered severely from fungal diseases ; stem dry matter yields were 9.4 t ha−1. In 1988 and 1989 fungicides were applied and stem dry matter yields were respectively 11.9 t ha−1 and 13.6 t ha−1. The number of living plants m−2 ranged from 86 to 823 at emergence, depending on treatment, and from 38 to 102 at final harvest. Increased seeding rates led to earlier canopy closure and higher initial biomass production, but more plants died during the growing season and the stem yield at final harvest was not affected by seeding rate. Average radiation-use efficiency (RUE; above-ground accumulated dry matter divided by intercepted photosynthetically active radiation) for the entire growing season under favourable growing conditions was 1.9 g MJ−1, which is low compared to other C3 crops. Leaf photosynthesis rates at saturating light intensities, however, were high: 30 kg CO2ha−1 h−1. The light extinction coefficient of hemp canopies was high (0.96), and may have reduced canopy photosynthesis rate and RUE. The high lignin content of the stems, and the high fat and protein content in the seed, also reduced RUE. Furthermore, dry matter invested in the tap root and in shed dead leaves was ignored. The RUE was also underestimated because an appreciable proportion of the biomass of plants that died during the growing season could not be collected. More research is needed to optimize cultural practices in fibre hemp.
Shorter photoperiod cause early flowering, restricting yields in Industrial hemp (Cannabis sativa L.). Trials were conducted under different light regimes under the protected structure in Bundaberg, QLD, Australia. Little difference was observed in plant maturity when photoperiod was at or below 13 h 40 min but was significantly delayed when photoperiods exceeded 14 h 40 min. Plant heights at harvest increased significantly with extended light. Plant heights at harvest were 1,188 mm and 1,161 mm for natural light treatments, 1,286 mm in treatment 3 (13 h and 40 min light period) and 1,395 mm in treatment 4 (14 h and 40 min). Stem thickness increased, whereas stem and root yields at final harvest were greater with extended photoperiod. A parallel field trial as separate experiment was also planted at the same location over five consecutive dates (PD1- September 15, October 25, November 25, December 16, and January 23), which showed that November 25 as an optimum timing as evidenced by highest plant height and dry matter yield compared to other planting dates. Results from these trials clearly indicated that day length must exceed at least 13 h and 40 min during the growing season to produce high yielding hemp for the tested variety.
Hemp in the Northern hemisphere is planted in April–May under long-day conditions to prevent precocious flowering. In Queensland, Australia, where premature flowering is inevitable, it may be necessary to plant hemp closer to the summer solstice to optimize solar radiation and longer day-length. However, high temperature at that time may limit growth of hemp in the Burnett/Wide Bay region, Queensland, Australia. Field experiment where day length did not exceed 13 h and 40 min, we evaluated effect of five spring/summer sowing times on flowering time, plant growth and yield. Of the five planting dates (15 Sept–PD1, 25 Oct–PD2, 25 Nov–PD3, 16 Dec–PD4, and 23 Jan–PD5), (PD3) stood out as the optimal time of planting. Planting date 3 was significantly later to develop male buds and the first open male flowers. Plant height at harvest was the highest for PD3 (999 mm) compared to all other planting dates. Planting date 3 also yielded highest dry matter (7.8 t ha−1). Yields were well below what would be considered viable in Europe for fiber hemp, but the results of the experiment may be used to indicate potential of seed hemp crop for QLD.
In the second paper in this series factorial combinations of two short rotation coppice (SRC) willow varieties (S. viminalis cv. Jorunn and dasyclados) and five planting densities (10,000–111,000 ) were compared at a site in Cambridgshire, UK. Frequent measurements of above-ground and below-ground biomass accumulation (AGBA and BGBA), canopy radiation interception (I), green leaf area index (GLAI), radiation use efficiency (RUE), and attenuation coefficient (k) were made in 1997, 1998 and 1999 in order to explain density, variety and harvest interval related yield effects.
Hemp (Cannabis sativa L.) is a dioecious annual that commences its reproductive cycle when photoperiods are shorter than a critical length. Photoperiod-sensitive varieties grown in low latitudes with short-day lengths tend to produce early flowering, short plants affecting the yield and quality of the fiber. The photoperiodic sensitivity of the crop could be controlled by the activation or deactivation of genes triggered by the change in light duration perceived by photoreceptive pigments. The sexual dimorphism of Cannabis is genetically determined by the XY chromosomal mechanism although sexual morphology is primarily a result of endogenous plant growth regulator levels that fluctuate in response to environmental variables. Occurrence of occasional hermaphroditic flowers and monoecious plants are probably the result of these fluctuations. Understanding the mechanisms of photoperiodicity and sexual inheritance contributes to advances in breeding and crop management that may underpin the expansion of the commercial cultivation of the crop in nontraditional agroecological domains.
Sunn hemp is a tropical, herbaceous annual legume that has potential as a cover crop during the summer in temperate climates. Due to the recent increased interest in sunn hemp breeding and seed production for temperate climates, there is a need for weed control in sunn hemp production. No herbicide product currently on the market specifically identifies sunn hemp as a tolerant crop. The aims of this research were 1) to evaluate herbicides with the intent of identifying a herbicide program that can assure near weed free sunn hemp intended for seed harvest and 2) to demonstrate and quantify sunn hemp-weed suppression. Pre-emergence applied treatments consisted of pendimethalin alone, imazethapyr alone, and pendimethalin plus imazethapyr. Pendimethalin alone provided consistent effective weed control and maximum sunn hemp biomass, but when yellow nutsedge was present, imazethapyr was required for effective control and greater sunn hemp biomass. The combination of pendimethalin and imazethapyr was detrimental to sunn hemp biomass yield. Results also established that sunn hemp is tolerant of 2,4-DB applied post-emergence, but was not necessary for weed control in these studies because of the lack of broadleaf weed pressure. In a separate study with variable sunn hemp densities, weed biomass reductions of ≥50% were obtained with sunn hemp densities of only 20 to 50 plants m−2. This degree of weed suppression obtained from relatively modest sunn hemp densities is likely indicative of the ability of sunn hemp to grow faster and taller than other plants.
A field trial was conducted at the University of Wales Bangor Research Centre, Gwynedd using five varieties of hemp, sown at two seed rates: 150 and 300 seeds m−2 to determine the optimum time to cut hemp to maximise fibre yield and quality. Three cutting times were imposed from mid-August to mid-September, corresponding to start of flowering, mid-point of flowering and end of flowering, and following dew-retting in the field fibre from the stems was extracted to determine fibre yield and quality.A wide variation was found in fibre yields between the five varieties, although the first cut in mid-August resulted in the highest yields in all varieties except for Beniko. A decline in fibre yield was recorded from the first to the third cut and it is suggested that this is a result of lignification of the fibres occurring after mid-August. The importance of cutting hemp early in autumn to avoid lignification of the fibres is discussed, and it is suggested that varieties with reduced or delayed onset of lignification are important in the prevailing colder, wetter climates of the more northerly latitudes.The higher seed rate led to better weed suppression and higher fibre yields in all varieties. The monoecious varieties performed better than the dioecious and hybrid varieties in the northern climate where the trial was conducted. It is suggested that further research is required to develop a more accurate method of monitoring retting in the field.
To ascertain the reasons for the high plant mortality in fibre-hemp (Cannabis sativa L.) crops in the Netherlands changes in biomass yield, plant mortality and plant morphology were investigated in a hemp cultivar grown at initial densities of 10, 30, 90 and 270 plants m−2. At 90 plants m−2 this cultivar was compared with a high bast-fibre cultivar and a late-flowering cultivar. Rate of canopy establishment and early growth rate increased with increasing plant density. At 90 and 270 plants m−2, plants died as a result of self-thinning. Self-thinning was associated with a reduced crop growth rate. In self-thinning stands, dry biomass (B, g m−2) was related to density of surviving plants (D, m−2) as log B = 3.81 − 0.304 log D. At the same crop growth rate, the rate at which plants died from self-thinning was higher in hemp than in other herbaceous dicots. The proportion of stem in the total dry matter increased with increasing plant density. Stem yield was maximum at 90 plants m−2. Stem quality improved with increasing density as the bark content in the stem increased, but self-thinning reduced the bark content in the stem. Optimum plant density was close to that resulting after self-thinning. In hemp the relationship between yield and optimum plant density is approximated by the equation of its self-thinning line. The late-flowering cultivar yielded more than the other two cultivars because it grew faster during the latter part of the growing season.
Industrial hemp variety and seeding rate trial
- Anonymous
Anonymous. Industrial hemp variety and seeding rate trial 2009.
Optimisation of nitrogen fertilisation and seed density in hemp crop
- P Bassetti
- M Mediavilla
- V Scheid-Slembrouck L
Bassetti P, koneman M, Mediavilla V and Scheid-slembrouck L.
Optimisation of nitrogen fertilisation and seed density in hemp crop.
Agraforschung. 1998; 5:241-244. | Article
The cultivation of hemp: botany, varieties, cultivation and harvesting. Sebastopol, Hemptech. California. 186. | Book 7. BOM 2012. Climate statistics for Australian location
- I Bocsa
- M Karus
Bocsa I and Karus M. The cultivation of hemp: botany, varieties,
cultivation and harvesting. Sebastopol, Hemptech. California. 186. |
Book
7. BOM 2012. Climate statistics for Australian location-Bundaberg.1998.