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Recent recommendations advocating the use of cover crop mixtures instead of single-species in semi-arid environments require rigorous scientific studies. One of those stated benefits is greatly reduced water use by cover crops grown in mixtures. The objectives of this study were to characterize soil water extraction patterns and determine water use of cover crops grown in single-species plantings and in a 10-species mixture and to compare cover crop water use to evaporative water loss from no-till fallow. The study was conducted at Akron, CO, and Sidney, NE, during the 2012 and 2013 growing seasons on silt loam soils. At each location there were a dryland treatment and an irrigated treatment. Soil water contents were measured by neutron scattering and time-domain reflectometry at six depths (0.0–1.8 m, Akron) or four or five depths (to 1.2 m or 1.5 m, Sidney). There were no consistent significant differences in soil water contents or growing season crop water use with the single-species plantings compared with the 10-species mixture. Cover crop water use (216 mm) averaged 1.78 times greater than evaporative water loss (122 mm) from the no-till fallow treatment with proso millet (Panicum miliaceum L.) residue. There appears to be no evidence from data collected in this semi-arid environment, even when irrigated to simulate higher rainfall environments, to support the conclusion that cover crops grown in multi-species mixtures use water differently than single species-plantings of cover crops.
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... This improves water infiltration and moisture retention, inhibiting surface runoff, reducing soil degradation, slow nutrient release and delivering them to the rhizosphere of the plant, which ultimately improves resource efficiency [218,238,[240][241][242][243]. Many authors have reported the beneficial effect of legume CCs on increasing soil moisture [195,244,245]. This effect is likely to result from improving the soil's structural features, which increase the infiltration rate and reduce soil water evaporation [246,247]. ...
... aestivum) is decisive in terms of water availability in soil, apart from environmental conditions. Nielsen et al. [245] demonstrated that in a semi-arid environment, CCs use limited water reserves in the soil, which may also affect the availability of water for the successive crop cultivation and, consequently, its yield. Under these environmental conditions, the cultivation of mixed-species CCs is also unjustified as they use a similar amount of water as single-species CC cultivations. ...
Book
Analysis of weed infestation of selected fields of grain (winter wheat, spring wheat, spring triticale) was conducted between 2013 and 2016 in five commercial farms in south-eastern Poland (49◦52’ N, 21◦46’ E) based on a quantitative and qualitative (quadrat) method and an agro-phytosociological method. The quadrat analysis was conducted prior to weeding procedures, and the agro-phytosociological analysis by grain harvest. The biodiversity of weed communities was measured with the Shannon and Simpson indices. The degree of weed infestation of grain species was significantly differentiated by weeding procedures carried out by farmers. The highest share of weeds in grain crops included dicot weeds (80.6–86.4% of all species, depending on location), and the remaining weed groups were a much smaller issue. The greatest weed infestation was found in spring triticale, and the smallest in winter wheat. The highest Shannon biodiversity index was recorded in the field of triticale, and the lowest in the field of winter wheat. The Simpson index points to the greatest biodiversity in fields of triticale and the smallest in fields of spring wheat. The conducted research will help categorize segetal flora characteristics for a given crop, determine its quantity and species composition, and evaluate biodiversity of weeds in fields of grain.
... Cover crops can have complicated effects on groundwater recharge. First, by covering the soil, they can increase transpiration and reduce evaporation (Qi and Helmers 2010;Nielsen et al. 2015;Tribouillois et al. 2016). Second, they can increase water infiltration and reduce runoff (Snapp et al. 2005;Blanco-Canqui et al. 2015;Yu et al. 2016). ...
Article
Some European countries are exploring the idea of replacing dedicated crops with energy cover crops for biogas production. Indeed, energy cover crops can generate consequential biomass without competing with food crops for land use. However, the potential benefits and impacts of this choice are not fully understood. Here, we review what is known about the consequences of energy cover crop usage by examining management regimes and digestate use, including impacts on the environment and cropping system performance. First, compared to cover crops, energy cover crops are intensively managed to produce more biomass (< 5 t DM/ha vs. up to 16 t DM/ha). Second, nitrogen is conserved during anaerobic digestion and is more readily available to crops in digestate than in cover crops residues. However, ammonia is lost via volatilization, which could reduce nitrogen use efficiency, depending on the storage conditions and application method. Third, 43–80% of the crops’ initial carbon is transformed into biogas. That said, levels of soil carbon storage may nonetheless resemble those obtained with cover crops left behind because carbon is stabilized during anaerobic digestion and the energy cover crops’ roots and stubble are left behind in the soil. Fourth, energy cover crops can act as multiservice cover crops, reducing nitrate leaching, improving soil microbial activity, and enhancing soil physical properties during the fallow period. Fifth, energy cover crop usage can have certain disservices, such as soil compaction, the need for additional inputs (e.g., irrigation, fertilization, pesticides), reduced groundwater recharge, and reduced following crop yield. In summary, expanding the usage of energy cover crops for biogas production does not seem to be an environmental threat. However, care must be taken to avoid the intensification of irrigation and lengthening growing periods to boost biomass, which could reduce food production.
... CC may provide the most benefits from a CC than a single species CC (Chapagain et al., 2020). Other studies, on the other hand, reported no advantage of CC mixtures compared with single species (DeLaune et al., 2020;Holman et al., 2018;Nielsen et al., 2015). Holman et al. (2018) concluded that CC species with low seed cost and greater forage accumulation are more profitable in the semiarid Great Plains. ...
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Replacing long fallow periods with dual‐purpose forage cover crops increases productivity and profitability of dryland crop rotations. However, little information is available on specific forage cover crops mixtures that optimizes productivity, nutritive value, and profitability. The objective of this research was to quantify forage productivity, nutritive value, and profitability of spring‐planted single or mixed species cover crops in a winter wheat (Triticum aestivum L.)–grain sorghum [Sorghum bicolor (L.) Moench]–fallow (WSF) crop rotation. This study was conducted from 2015 to 2017 at the Kansas State University Hearting Beason Ranch near Brownell, KS. The experimental design was a split‐plot randomized complete block with four replications. The main plots were three crop phases of the WSF rotation (wheat–sorghum–fallow, sorghum–fallow–wheat, and fallow–wheat–sorghum), and subplots were five spring‐planted cover crop treatments: (a) spring oat (Avena sativa L.), (b) spring triticale [×Triticosecale Wittm. ex A. Camus (Secale × Triticum)], (c) oat and triticale mixture (OT, two‐species mixture), (d) oat, triticale, and pea (Pisum sativum L.) (OTP, three‐species mixture), and (e) oat, triticale, pea, radish (Raphanus sativus L.), turnips (Brassica campestris L.), and buckwheat (Fagopyrum esculentum Moench) (six‐species mixture). Results showed that cover crop forage accumulation was 33–35% greater in sole triticale and OT mixture compared with sole spring oat or cocktail treatments. Multispecies mixtures, cocktail and OTP cover crops, had significantly greater available energy, digestibility, and dry matter intake based on measured crude protein, acid and netural detergent fiber, and in vitro dry matter digestibility compared with single species (oat or triticale). Net return was US$100 ha–1 greater for the OT treatment compared with the multispecies mixtures. We concluded that greater productivity and net return, along with adequate nutritive value, from sole triticale and OT mixture made them better dual‐purpose forage cover crop alternatives. Productivity was 33–35% greater with sole triticale and oat–triticale mixture than with sole spring oat or cocktail. Multispecies mixtures had greater nutritive value compared with single species (oat or triticale). Net return was $100 ha−1 more for the oat–triticale compared with multispecies mixtures. Greater productivity, net return, and adequate nutritive value make triticale and oat–triticale mixture better cover crops.
... This region has a semi-arid climate, with an average annual precipitation of 420 mm, and average monthly temperatures of 23 • C in July and − 5 • C in the January. The soil used in this experiment is classified as a Weld silt loam (Nielsen et al., 2015). ...
Article
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The adoption of conservation agriculture has gained considerable attention due to growing interest in managing soil biological diversity and overall soil health. However, there is limited understanding of how practices such as conservation tillage and residue retention affect soil biota across different spatial scales and are associated with alterations to other soil properties. In this study, we examined changes in soil physicochemical properties, soil macrofauna, and microbial communities at two soil depths (0–10 cm, and 10–20 cm) in a 6-year field experiment manipulating tillage and maize residue management. The following treatments were included in the experiment: no-till with residue retention; no-till with residue harvest; conventional tillage with residue retention; and conventional tillage with residue harvest. Macrofauna taxa were identified and estimated visually, while bacterial and fungal communities were identified and analyzed using high throughput sequencing and multivariate statistics including non-metric dimensional scaling and indicator species analysis. Soil physicochemical properties measured include soil carbon and nitrogen, soil moisture, permanganate oxidizable carbon, available soil phosphate, pH, electrical conductivity and aggregate stability. Residue retention increased macrofauna abundance and diversity across soil depths and tillage treatments. Fungal diversity was also highest under residue retention in the topsoil (0–10 cm), while bacterial diversity was generally higher under conventional tillage. Residue retention was the main driver of macrofauna and microbial community composition, while an interaction between tillage and residue management indicated that the effect of tillage on microbial communities was most pronounced when residues were retained. Soil carbon and nitrogen, aggregate stability, permanganate oxidizable carbon, soil moisture content, available soil phosphate and soil electrical conductivity were all enhanced under residue retention in the topsoil. Indicator species analysis suggested that macrofauna taxa belonging to Annelida, Aranaea and Chilopoda together with bacterial phyla Fibrobacteres and fungal phyla Rozellomycota were indicators for no-till combined with residue retention, while Coleoptera, Spirochaetae and Basidiomycota were indicators for conventional tillage with residue retention. Multivariate analyses suggested that total macrofauna abundance, soil carbon and pH were strongly associated with bacterial and fungal community composition in the topsoil layer. Co-inertia analysis indicated significant covariation between soil physicochemical, macrofauna, bacterial and fungal datasets, suggesting a strong association between different soil parameters and cascading effects of management on multiple soil properties. Our findings demonstrate that residue retention enhances soil biological, physical and chemical properties and that communities of soil macro- and microorganisms tend to respond in similar ways to these management interventions.
... Consistent with previous research in semi-arid environments (e.g., Holman et al., 2018;Mitchell et al., 2015;Nielsen et al., 2015), we did not find a significant difference in soil water use by mixtures compared to monocultures. However, the relative soil water recharge post-termination varied with cover crop type and year. ...
Article
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Conventional dryland cropping systems rely upon frequent and lengthy fallow periods to conserve soil water and mineral nitrogen to stabilize crop production. However, this is associated with depletion of soil organic matter and decreased fallow efficiency. Intensifying cropping systems by planting cover crops has been touted as a means to stem soil organic matter loss and improve fallow efficiency. We investigated whether the manipulation of cover crop functional trait diversity and sowing proportions (utilizing Poaceae, Fabaceae, and Brassicaceae) could provide complementary functions that improve soil water and mineral N management during fallow. Grass-legume mixtures represented the best compromise between biomass production (> 4000 kg DM ha − 1), N retention (142 kg N ha − 1), N supply via biological N fixation (35 kg N ha − 1) and maintained an additional 70 mm of water at the end of fallow period. Regardless of functional trait type, cover crops increased N retention but maintained similar soil mineral N content at the end of fallow period. However, soil water effects were functional trait-specific, and there were significant soil water deficits with brassica-dominated cover crops. Soil water accumulation post cover crop termination was significantly higher in cover crops compared with conventional fallows, but the overall fallow efficiency was higher in the conventional fallow. This study demonstrates that cover crops are not universally beneficial, and careful selection of cover crop functional traits in mixtures could enhance fallow soil water and N management in semi-arid subtropical drylands.
... Sufficient soil water storage during the sowing period is crucial to establish the crop canopy well in the water stress environment [13,33]. The amount and distribution of rainfall and the water depletion due to the growth of the preceding crop have an obvious impact on the soil water condition at the sowing stage [34,35]. Norwood [36] has reported that significant effects of preceding crops on dryland winter wheat were caused by different soil water storage at the sowing stage of wheat. ...
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Integrating a forage crop into the fallow (F) of the peanut (Arachis hypogaea L.) (P) mono-cropping system is a practical approach to provide forage yield and increase the resource use efficiency. However, little information about the comprehensive assessment of water utilization and economic benefits in the crop–livestock system exists for the North China Plain (NCP). This study aims to identify the crop rotation for optimizing water management and enhance economic benefit. The field experiment was performed over three years (2011–2014) to assess production, water utilization, and economic benefits when inserting forage triticale (X Triticosecale Wittmack) (T) into the peanut mono-cropping system. Results showed that replacing the fallow F-P cropping system with forage triticale provided a substantial amount of forage (the average of 9.8 t ha−1 per year) and enhanced the average system productivity by 85.1%. Cultivation of forage triticale during the fallow period decreased the subsequent peanut pod yield by 8.3% due to a 19.3% decline in soil water storage capacity during the sowing stage of peanut. Replacing fallow with forage triticale increased the system net income by 1016.2 US$ ha−1 and the water use efficiency (WUE) by 30.0%, while not affecting the economic efficiency of water use (EEWU), and thus can be recommended as a better option for maintaining relatively high system production, economic benefit, and WUE in NCP.
... According to Sharma et al. (2018), cover crops contribute to reducing water evaporation from the soil thereby preserving soil moisture for the following crop. Though this has been observed in some environments (Basche et al., 2018), under water-limited conditions without irrigation, cover crops have frequently been found to limit soil moisture for subsequent crops (Nielsen et al., 2015(Nielsen et al., , 2020. ...
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Grasses as well as leguminous and non-leguminous broadleaves are the major categories of commonly grown cover crops worldwide. This review focuses on the contribution of cover crops to soil properties. The review first considers the single and mixed cover crops and shows that grass species are desirable for their decay and ability to provide substantial soil cover, broadleaf species are used for their quick decomposition and capacity of releasing residues into the soil, while the leguminous species are used for their ability to fix atmospheric nitrogen. Secondly, the impacts of cover crops on soil health are reviewed. Integrating cover crops into conventional cropping systems may reduce soil bulk density, improve soil structure and hydraulic properties to facilitate increased water infiltration and storage. Crop residue additions from cover crops may enhance soil organic C and N accretion as well as increase availability of P, K, Ca, Fe and Mg in some soil types under certain climatic conditions. Further, cover crops may provide a better condition for microbial activity, abundance, and diversity. Finally, the review shows that through proper management, cover crops may be utilized as an essential component of soil conservation practices for enhanced soil health. Still, further investigation is necessary to determine cover crop effects in additional cropping systems and climatic zones as well as the long-term effects of cover crops on soil properties, subsequent crop yield, and overall cropping system profitability. This review is an important source of information for crop growers, crop management institutions, universities, and crop consultants for sustainable agricultural production.
... In our study, CC biomass was not the only driver of weed suppression contrary to what is commonly affirmed (Bybee-Finley et al., 2017;MacLaren et al., 2019;Florence and McGuire, 2020). However, we did not relate greater weed suppression observed in 8-species non-legume CC mixtures to a better use of water, as observed by (Nielsen et al., 2015), nor nitrogen, but to species characteristics such as rapid growth rate (Tribouillois et al., 2015) and early soil coverage (Brennan and Smith, 2005). When composing CC mixtures, attention should be paid to species characteristics and their response to contrasted levels of water and nitrogen availability. ...
Article
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Cover crop (CC) mixtures appear as a promising agroecological tool for weed management. Although CC supress weed growth by competing for resources, their suppressive effect under contrasting levels of soil resource availability remains poorly documented. A two field:year experiment was conducted to investigate the weed suppressive effect of four CC mixtures. They were composed of 2 or 8 species including or not legume species and compared to a bare soil control. The experiment included two levels of irrigation and nitrogen fertilisation at CC sowing. The objectives were to assess (i) weed and CC aboveground biomass response to CC mixtures and resource availability, (ii) the weed suppressive effect of CC mixtures across a gradient of CC biomass and (iii) weed community response to CC mixtures and resource availability. CC and weed biomass were mainly influenced by interactions between CC mixtures and fertilisation and between CC mixtures and irrigation, with contrasted effects between field:years. Nitrogen fertilisation increased biomass of non-legume based CC mixtures but this only resulted into a further reduction of weed biomass of little biological relevance. Legume-based CC mixtures suppressed weeds to a greater extent without nitrogen fertilisation in year 2 but not in year 1, possibly due to contrasted initial soil nitrogen availability (lower in year 2). Weed biomass generally benefited more from irrigation than CC mixtures. Among the 33 weed species recorded, weed communities in each plot were dominated by wheat volunteers, Geranium dissectum, Veronica persica and Echinochloa crus-galli, whose biomass varied depending on the interaction between year, CC mixture and resource availability. Our results revealed that competitive outcomes between CC mixtures and weed species were driven by a complex interaction between resource availability and species traits. Further experiments focusing on plant traits should improve our understanding of weed:CC competitive outcomes under various levels of resource availability.
... This region experiences a semi-arid climate with mean annual rainfall of 420 mm and mean monthly temperatures ranging from 23 °C in the summer to −5 °C in the winter. Soils at the field site are classified as Weld silt loam (fine, smectitic, mesic Aridic Argiustolls; Nielsen et al., 2015). ...
... However, these observations were made in more humid environments than the semi-arid central Great Plains. Previous studies with CCs in the semi-arid Great Plains concluded diverse mixtures of grass, legume, and other broadleaf species often yield the same or less than the most productive grass monocultures (Nielsen et al., 2015a(Nielsen et al., , 2015bCalderón et al., 2016). These authors further observed CC mixtures to have similar water use and effects on soil microbial properties as monocultures. ...
Article
Replacing summer-fallow by growing cover crops (CC) in semi-arid regions might provide several soil health benefits. This study examined the effects of long-term CC management in place of fallow on soil properties in a no-till (NT) winter wheat (Triticum aestivum L.)-grain sorghum (Sorghum bicolor Moench)-fallow (WSF) cropping system. Fallow replacement treatments were spring-planted and included peas (Pisum sativum L.) for grain as well as one-, three-, and six-species CC mixtures compared with summer-fallow. Half of each CC treatment was harvested for forage and the other half remained standing after termination. Soil organic carbon (SOC) stocks within the 0- to 15-cm soil depth increased by 0.14 Mg ha⁻¹ yr⁻¹ for each Mg ha⁻¹ CC residue added from 2008 to 2012 and were unaffected by CC diversity. However, SOC stocks were not different than fallow in 2018 likely because CC residue inputs declined due to a succession of drought years. Residue contribution from grain sorghum in the WSF rotation best predicted SOC in 2018 compared to 2012. Soil aggregation was greater with CCs compared to peas or fallow and was unaffected by CC diversity. Mean weight diameter (MWD) of water stable aggregates in 2018 was greater with standing CCs (1.11 mm) compared to peas (0.77 mm) but was similar to fallow (0.84 mm). The MWD of dry aggregates with standing (3.55 mm) and hayed (3.62 mm) CCs were greater compared to fallow (2.75 mm). Our findings suggest simple CC mixtures and CCs managed for hay provide similar soil benefits as diverse CC mixtures or CCs left standing in this semi-arid environment.
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Producers wishing to diversify crop production systems from the traditional winter wheat (Triticum aestivum L.)-fallow system of the central Great Plains need information regarding the impact of sunflower (Helianthus annuus L.) on subsequent winter wheat and proso millet (Panicum miliaceum L.) yields. This study was conducted to quantify winter wheat and proso millet yield reductions due to the lower available soil water that exists when sunflower is the prior crop in rotation. Eight crop rotations-including combinations of winter wheat (W), proso millet (M), corn (Zea mays L.) (C), sunflower (Sun), and fallow (F) - were established in 1990 and evaluated for yield, available soil water at planting, and crop water use in 1995, 1996, and 1997 . The experiment was conducted at Akron, CO, on a Weld silt loam (fine, smectitic, mesic Aridic Paleustoll). Available soil water at wheat and millet planting was lower where sunflower had been the previous crop than where sunflower was not the previous crop. In dry years, rotations with sunflower as the previous crop had lower wheat and millet water use than other rotations, but averaged over 3 yr, there was no effect of sunflower on wheat or millet water use. Average wheat yield in a W-Sun-F rotation was about 30% lower than wheat yield from W-C-Sun-F, W-M-Sun-F, W-C-F, and W-F. Average millet yield in a M-Sun rotation was 43% lower than millet yield from M-W-C. Wheat yield declined by 178.5 lb/acre (3 bu/acre) for each inch decline in available soil water at planting. Millet yield declined by 295.6 lb/acre for each inch decline in available soil water at planting. In making the decision to include sunflower in crop rotations, producers will have to consider impact on subsequent crop yields, as well as costs of production, market value of crop, impact on pest problems, and total productivity of all crops in the rotation.
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Crop residues have value when left in the field and also when removed from the field and sold as a commodity. Reducing soil water evaporation (E) is one of the benefits of leaving crop residues in place. E was measured beneath a corn canopy at the soil suface with nearly full coverage by corn stover or standing wheat stubble. E was also measured from a soil surface that was partially covered with corn stover without crop shading. E was measured with mini-lysimeters that were 300 mm in diameter and 140 mm deep. Surface coverage and amount of dry matter of crop residues influenced E. E was reduced nearly 50% compared with bare soil E when corn stover and wheat stubble nearly covered the surface under a corn canopy during the growing season. Partial surface coverage, from 25% to 75%, with corn stover caused small reductions in E compared with bare soil when there was no crop canopy. Full surface coverage reduced energy limited E 50% to 65% compared with E from bare soil with no shading. No-till management, using crop residues to significantly reduce E, required soil surfaces to be nearly covered. Economic benefits of crop residues for E suppression during the growing season can be as much as $365 ha -1. © 2009 American Society of Agricultural and Biological Engineers.
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The integration of cover crops into cropping systems brings costs and benefits, both internal and external to the farm. Benefits include promoting pest-suppression, soil and water quality, nutrient cycling efficiency, and cash crop productivity. Costs of adopting cover crops include increased direct costs, potentially reduced income if cover crops interfere with other attractive crops, slow soil warming, difficulties in predicting N mineralization, and production expenses. Cover crop benefits tend to be higher in irrigated systems. The literature is reviewed here along with Michigan farmer experience to evaluate promising cover crop species for four niches: Northern winter (USDA Hardiness Zones 5-6), Northern summer (Zones 5-6), Southern winter (Zones 7-8), and Southern summer (Zones 7-8). Warm season C4 grasses are outstanding performers for summer niches (6-9 Mg ha-1), and rye (Secale cereale L.) is the most promising for winter niches (0.8-6 Mg ha -1) across all hardiness zones reviewed. Legume-cereal mixtures such as sudangrass (Sorghum Sudanese L.)-cowpea (Vigna unguiculata L.) and wheat (Triticum aestivum L.)-red clover (Trifolium pretense L.) are the most effective means to produce substantial amounts (28 Mg ha-1) of mixed quality residues. Legume covers are slow growers and expensive to establish. At the same time, legumes fix N, produce high quality but limited amounts (0.5-4 Mg ha -1) of residues, and enhance beneficial insect habitat. Brassica species produce glucosinolate-containing residues (2-6 Mg ha-1) and suppress plant-parasitic nematodes and soil-borne disease. Legume cover crops are the most reliable means to enhance cash crop yields compared with fallows or other cover crop species. However, farmer goals and circumstances must be considered. If soil pests are a major yield limiting factor in cash crop production, then use of brassica cover crops should be considered. Cereal cover crops produce the largest amount of biomass and should be considered when the goal is to rapidly build soil organic matter. Legume-cereal or brassica-cereal mixtures show promise over a wide range of niches.
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Winter wheat (Triticum aestivum L.) is the foundation of dryland cropping systems in the Central Great Plains. The objective of this study was to quantify the effects of four short-season spring-planted crops used to replace summer fallow on the subsequent winter wheat crop. Wheat was seeded into four crop stubbles [spring triticale (xTriticosecale Wittmack), dry pea (Pisum sativum L.), foxtail millet (Setaria italica L. Beauv.), and proso millet (Panicum miliaceum L.)] at sites near Akron, CO, and Sidney, NE, in the fall of 2004 and 2005. These summer fallow replacement crops were planted into silt loam soils at three different soil water levels at planting (low, medium, and high). Winter wheat water use was 3.6 cm greater, and grain yield was 662 kg ha-1 greater in the high water treatment compared with the low water treatment averaged across all sites and years. Winter wheat used an average of 4.3 cm more water following early planted summer crops (triticale and dry pea) than after late planted summer crops (foxtail and proso millet), but this increased water use did not consistently translate into increased grain yield as a result of terminal drought at Sidney in 2006. The high water treatment always had a positive net return. The high cost of pea seed ($3.30 kg-1, USD) strongly reduced profitability. The flexible summer fallow cropping system appears to be most applicable when using short-duration summer annual forage crops such as triticale and foxtail millet.
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Growing a legume cover crop in place of fallow in a winter wheat (Triticum aestivum L.)-fallow system can provide protection against erosion while adding N to the soil. However, water use by legumes may reduce subsequent wheat yield. This study was conducted to quantify the effect of varying legume termination dates on available soil water content at wheat planting and subsequent wheat yield in the central Great Plains. Four legumes Austrian winter pea, Pisum sativum L. subsp. sativum var. arvense (L.) Poir.; spring field pea, P. sativum L.; black lentil, Lens culinaris Medikus; hairy vetch, Vicia villosa Roth.) were grown at Akron, CO, as spring crops from 1994 to 1999. Legumes were planted in early April and terminated at 2-wk intervals (four termination dates), generally starting in early June. Wheat was planted in September in the terminated legume plots, and yields were compared with wheat yields from conventional till wheat-fallow. Generally there were no significant differences in available soil water at wheat planting due to legume type. Soil water at wheat planting was reduced by 55 mm when legumes were terminated early and by 104 mm when legumes were terminated late, compared with soil water in fallowed plots that were conventionally tilled. Average wheat yield was linearly correlated with average available soil water at wheat planting, with the relationship varying from year to year depending on evaporative demand and precipitation in April, May, and June. The cost in water use by legumes and subsequent decrease in wheat yield may be too great to justify use of legumes as fallow cover crops in wheat-fallow systems in semiarid environments.
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Plants may be getting a little help with their tolerance of drought and heat.
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Subsoiling to alleviate compacted soil zones and planting cover crops to conserve soil water are accepted practices, but information regarding potential interactions between the two is limited. This study was designed to assess the effects of subsoiling and cover-crop management on soil water availability and corn (Zea mays L.) grain yield on Coastal Plain soils known to be responsive to in-row subsoiling. The experiment was conducted on a Norfolk loamy sand in 1985 and a Norfolk sand in 1986, both in the family of fine-loamy, siliceous, thermic Typic Kandiudults. Factors evaluated were subsoiling, cover crop (fallow or crimson clover [Trifolium incarnatum L.]), primary tillage (chisel plow or no-tillage) within fallow, and top-growth removal of crimson clover. Compared with fallow treatments, crimson clover depleted soil water in the surface 15 cm before corn planting by 28% in 1985 and 55% in 1986. Corn grain yield was reduced in the presence of crimson clover by 0.5 Mg ha-1 in 1985 and 0.9 Mg ha-1 in 1986. In 1985 only, grain yield reduction in the presence of crimson clover was entirely overcome by subsoiling. Averaged across cover crop and primary tillage factors, subsoiling increased grain yields by 25% (1.3 Mg ha-1) in 1985 and 86% (1.9 Mg ha-1) in 1986. Increased yields due to subsoiling were attributed to greater use of subsoil water by the corn crop. These results suggest that cover-crop desiccation should occur 7 to 10 d prior to corn planting to minimize the effects of soil water depletion under dry, early-spring conditions. Additionally, in-row subsoiling should be used on similar Coastal Plain soils responsive to deep tillage, irrespective of cover-crop use.
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Rotation of corn (Zea mays L.) with soybean [Glycine max (L.) Merr.] provides certain economic and environmental advantages over monoculture corn. Low soybean residue production and persistence, however, promote potentially excessive soil erosion following soybean harvest. An irrigated field experiment was conducted in eastern Nebraska for 4 yr (1990-1993) under various tillage treatments and N rates to evaluate the effects of a winter rye (Secale cereale L.) cover crop following soybean on (i) rye dry matter yield, (ii) surface residue cover for erosion protection, and (iii) corn establishment and production. The soil was a Sharpsburg silty clay loam (fine, montmorillonitic, mesic Typic Argiudolls). Treatments were (i) no-tillage and disk tillage; (ii) corn following soybean with a winter rye cover crop (CBR), corn following soybean without rye (CB) and corn following corn (CC); and (iii) 0, 50, 100, 150, and 300 kg N ha-1 (applied to corn). Rye aboveground dry matter yield, surface residue cover, and corn yield parameters were estimated. Rye dry matter yield ranged from 0.25 to 2.9 Mg ha-1 and was influenced by tillage, N rate, and weather conditions in different years. During the years of high rye dry matter yield. presence of rye in the corn-soybean system gave approximately 16% additional surface residue cover prior to planting through cultivation, compared with soybean residue alone. Surface cover by rye and soybean residues in CBR was equivalent to corn residue in CC under both disk and no-till management. In 1 of the 3 yr, corn plant population and grain yield were reduced following rye (CBR) compared with the no rye system (CB), possibly due to apparent allelopathic effects related to the age of rye. No significant difference in N response was observed between CBR and CB corn yields. In general, rotation of corn with soybean (with and without rye) resulted in an increase of approximately 27% in corn grain yield and N uptake over continuous corn. During the years of high rye dry matter production, rye accumulated approximately 45 kg N ha-1 through aboveground dry matter. Overall, including a winter rye cover crop in the corn-soybean rotation system was beneficial.
Article
Previous studies have demonstrated benefits of individual cover crop species, but the value of diverse cover crop mixtures has received less attention. Th e objectives of this research were to determine the effects of spring-sown cover crop mixture diversity and mechanical cover crop termination method on cover crop and/or cash crop productivity, soil moisture and N, and profitability in an organic cropping system. An experiment was conducted between 2009 and 2011 near Mead, NE, where mixtures of two (2CC), four (4CC), six (6CC), and eight (8CC) cover crop species, or a summer annual weed mixture were included in a sunflower-soybean-corn rotation. Cover crops were terminated in late May using a field disk or sweep plow undercutter. Undercutting cover crops increased soil NO3-N (0-20 cm) by 1.0 and 1.8 mg NO3-N kg(-1) relative to disk incorporation in 2010 and 2011, respectively. Cover crop mixtures oft en reduced soil moisture (0-8 cm) before main crop planting, though cover crop termination with the undercutter increased soil moisture content by as much as 0.024 cm(3) cm(-3) compared to termination with the disk during early main crop growth. Crop yields were not influenced by cover crop mixture, but termination with the undercutter increased corn and soybean yield by as much as 1.40 and 0.88 Mg ha(-1), respectively. Despite differences in productivity between spring cover crop mixtures and weed communities, crop yield was not different among these treatments; thus, profitability of the weed mixture-undercutter treatment combination was greatest due to reduced input costs.