[Show abstract][Hide abstract] ABSTRACT: The benefit provided by chickpea ( Cicer arietinum L.) to the following durum wheat [ Triticum turgidum L. subsp. durum (Desf.) Husn.] crop is smaller than that provided by pea ( Pisum sativum L.) in the Great Plains of America. Rotation crops and the specific cropping practices associated with them may impact soil fungal communities, which in turn could affect the productivity of subsequent crops. Two separate field experiments were carried out to test the effect of pea and chickpea crops and of foliar fungicide use in chickpea on the community of fungi hosted in the roots of a subsequent durum wheat crop. The fungal communities in the healthy and diseased roots of durum wheat at maturity were characterized using plate culture and PCR-based identification. The effect of cropping practices on root-associated fungal communities depended on root type and varied with year. Functionally important fungal taxa were affected by specific cropping practices. Endophytic fungal antagonists were less abundant after chickpea than after pea and after fungicide-treated chickpea than after untreated chickpea. The chickpea cultivar CDC Vanguard increased the abundance of highly virulent pathogens in durum wheat roots in comparison with the chickpea cultivar CDC Luna and pea. We conclude that the negative impact of chickpea on durum wheat yield could be due in part to an increase in fungal pathogens resulting from the suppression of endophytic fungal antagonists by chickpea.
[Show abstract][Hide abstract] ABSTRACT: Agriculture consumes more than two thirds of the total freshwater of the planet. This issue causes substantial conflict in freshwater allocation between agriculture and other economic sectors. Regulated deficit irrigation (RDI) is key technology because it helps to improve water use efficiency. Nonetheless, there is a lack of understanding of the mechanisms with which plants respond to RDI. In particular, little is known about how RDI might increase crop production while reducing the amount of irrigation water in real-world agriculture. In this review, we found that RDI is largely implemented through three approaches: (1) growth stage-based deficit irrigation, (2) partial root-zone irrigation, and (3) subsurface dripper irrigation. Among these, partial root-zone irrigation is the most popular and effective because many field crops and some woody crops can save irrigation water up to 20 to 30 % without or with a minimal impact on crop yield. Improved water use efficiency with RDI is mainly due to the following: (1) enhanced guard cell signal transduction network that decreases transpiration water loss, (2) optimized stomatal control that improves the photosynthesis to transpiration ratio, and (3) decreased evaporative surface areas with partial root-zone irrigation that reduces soil evaporation. The mechanisms involved in the plant response to RDI-induced water stress include the morphological traits, e.g., increased root to shoot ratio and improved nutrient uptake and recovery; physiological traits, e.g., stomatal closure, decreased leaf respiration, and maintained photosynthesis; and biochemical traits, e.g., increased signaling molecules and enhanced antioxidation enzymatic activity.
Full-text · Article · Mar 2016 · Agronomy for Sustainable Development
[Show abstract][Hide abstract] ABSTRACT: In arid and populated areas or countries, water shortage and heavy carbon emissions are threatening agricultural sustainability with food security severely, and becoming a major issue. It is unclear whether improved farming systems can be developed to tackle those issues through a sustainable agriculture. Here three farming practices that have proven to be essential and successful, which were: (a) crop intensification through strip intercropping, (b) water harvesting through conservation tillage; and (c) carbon sequestration through improved crop residue management options, were integrated in one cropping system. We hypothesize that the integrated system allows the increase of crop yields with improved water use efficiency, while reducing carbon emissions from farming. The hypothesis was tested in field experiments at Hexi Corridor (37°96'N, 102°64'E) in northwest China. We found that the integrated system increased soil moisture (mm) by 7.4% before sowing, 10.3% during the wheat-maize co-growth period, 8.3% after wheat harvest, and 9.2% after maize harvest, compared to the conventional sole cropping systems. The wheat/maize intercrops increased net primary production by 68% and net ecosystem production by 72%; and when combined with straw mulching on the soil surface, it decreased carbon emissions by 16%, compared to the monoculture maize without mulch. The wheat/maize intercrops used more water but increased grain yields by 142% over the monoculture wheat and by 23% over the monoculture maize, thus, enhancing water use efficiency by an average of 26%. We conclude that integrating strip intercropping, conservation tillage as well as straw mulching in one cropping system can significantly boost crop yields, improve the use efficiency of the limited water resources in arid areas, while, lowering the carbon emissions from farming. The integrated system may be considered in the development of strategies for alleviating food security issues currently experienced in the environment-damaged and water-shortage areas.
No preview · Article · Mar 2016 · European Journal of Agronomy
[Show abstract][Hide abstract] ABSTRACT: Agriculture in rainfed dry areas is often challenged by inadequate water and nutrient supplies. Summerfallowing has been used to conserve rainwater and promote the release of nitrogen via the N mineralization of soil organic matter. However, summerfallowing leaves land without any crops planted for one entire growing season, creating lost production opportunity. Additionally, summerfallowing has serious environmental consequences. It is unknown whether alternative systems can be developed to retain the beneficial features of summerfallowing with little or no environmental impact. Here, we show that diversifying cropping systems with pulse crops can enhance soil water conservation, improve soil N availability, and increase system productivity. A 3-yr cropping sequence study, repeated for five cycles in Saskatchewan from 2005 to 2011, shows that both pulse-and summerfallow-based systems enhances soil N availability, but the pulse system employs biological fixation of atmospheric N 2, whereas the summerfallow-system relies on miningâ ™ soil N with depleting soil organic matter. In a 3-yr cropping cycle, the pulse system increased total grain production by 35.5%, improved protein yield by 50.9%, and enhanced fertilizer-N use efficiency by 33.0% over the summerfallow system. Diversifying cropping systems with pulses can serve as an effective alternative to summerfallowing in rainfed dry areas.
[Show abstract][Hide abstract] ABSTRACT: Inclusion of legumes in crop rotations is a sustainable approach to reducing nitrogen (N) fertilizer requirements and increasing subsequent crop yields. However, the magnitude of the benefit will depend on the specific legume, the subsequent crop and site-specific conditions. This study compared the effects of preceding legumes and non-legumes on yields and economic optimum N rates (EONR) in a Hard Red Spring wheat (Triticum aestivum L.)–hybrid canola (Brassica napus L.) cropping sequence. Field pea (Pisum sativum L.), lentil (Lens culinaris Medik), faba bean (Vicia faba L.; faba bean-seed), canola and wheat grown for grain, and faba bean grown as green manure (faba bean-GRM) were the preceding crops and were direct-seeded at six locations in western Canada in 2010. Wheat was seeded in 2011 and canola in 2012, with N fertilizer applied at 0, 30, 60, 90 and 120 kg N ha−1 in each year. Averaged across preceding crops, N application increased crop yields at all sites. Wheat grain yield was greater, with a corresponding lower EONR, following legumes than non-legumes due in part to increased N availability. Greater non-N benefits to wheat following legumes than non-legumes were also evident at all but one site, with non-N benefits being lowest for preceding wheat. While preceding legumes had no effect on canola seed yield across sites, EONR for canola were >50% lower for legume-wheat than non-legume-wheat rotations. Among the legumes, growing faba bean-GRM, field pea and lentil were most likely to increase crop yields and reduce EONR as compared to faba bean-seed. Overall, growing legumes for seed before a wheat–canola cropping sequence in conventional cereal cropping systems can increase crop yields, reduce EONR and improve the long-term sustainability of cereal cropping systems.
Full-text · Article · Aug 2015 · Field Crops Research
[Show abstract][Hide abstract] ABSTRACT: Frequent application of foliar fungicide is essential for chickpea production due to the susceptibility of this plant to ascochyta blight. Chlorothalonil, pyraclostrobin, and boscalid are commonly used to control the disease in Saskatchewan. While fungicides are meant to target specific fungal pathogens, they may impact non-target organisms and alter soil microbial community structure. The effects of the typical 5-time foliar fungicide application program to chickpea CDC Vanguard on the fungal communities associated with seminal and adventitious roots of the following durum wheat crop were studied in a 2 yr field experiment. Root fungal communities were characterized through analysis of the ITS1 region of root metagenomic DNA at the genus level. One hundred and seven fungal genera were detected in durum wheat roots. Fusarium was predominant in both years. A three-way interaction of fungicide application, root type and year on fungal community structure was detected. Unlike Fusarium, the relative abundances of the genera Olpidium, Alternaria, and Cryptococcus were greater in 2010, a very wet year. Fungicide application to chickpea increased the relative abundance of Fusarium in the seminal roots of a subsequent durum crop in 2009, but did not affect the relative abundance of Fusarium in 2010. We could not detect a significant impact of fungicide application to chickpea on durum wheat yield in the subsequent year. The effect of changes in root fungal communities on durum wheat grain yield is discussed.
[Show abstract][Hide abstract] ABSTRACT: Soil N fertilization stimulates the activity of the soil bacterial species specialized in performing the different steps of the denitrification processes. Different responses of these bacterial denitrifiers to soil N management could alter the efficiency of reduction of the greenhouse gas N2O into N2 gas in cultivated fields. We used next generation sequencing to show how raising the soil N fertility of Canadian canola fields differentially modifies the diversity and composition of nitrite reductase (nirK and nirS) and nitrous oxide reductase (nosZ) gene-carrying denitrifying bacterial communities, based on a randomized complete blocks field experiment. Raising soil N levels increased up to 60% the ratio of the nirK to nirS genes, the two nitrite reductase coding genes, in the Brown soil and up to 300% in the Black soil, but this ratio was unaffected in the Dark Brown soil. Raising soil N levels also increased the diversity of the bacteria carrying the nitrite reductase gene nirK (Simpson index, P = 0.0417 and Shannon index, 0.0181), and changed the proportions of the six dominant phyla hosting nirK, nirS, and nosZ gene-carrying bacteria. The level of soil copper (Cu) and the abundance of nirK gene, which codes for a Cu-dependent nitrite reductase, were positively related in the Brown (P = 0.0060, R2 = 0.48) and Dark Brown (0.0199, R2 = 0.59) soils, but not in the Black soil. The level of total diversity of the denitrifying communities tended to remain constant as N fertilization induced shifts in the composition of these denitrifying communities. Together, our results indicate that higher N fertilizer rate increases the potential risk of nitrous oxide (N2O) emission from canola fields by promoting the proliferation of the mostly adaptive N2O-producing over the less adaptive N2O-reducing bacterial community.
No preview · Article · May 2015 · Applied Soil Ecology
[Show abstract][Hide abstract] ABSTRACT: Family farms in populated countries must produce sufficient quantities of food to meet the ever-growing population needs. It is unknown whether innovated farming systems can alleviate this issue. Here, we carried out field experiments in arid northwest China from 2009 to 2012 to determine the response of water use, grain yield, and water use efficiency. We integrated crop intensification via relay-planting and straw mulching in the same system. Straw mulching included stubble standing, straw covering, or straw incorporation to the soil. Results show that wheat and maize relay-planting with straw mulching increased yields by up to 153 % versus mono-planting of maize and wheat. Straw covering approached the highest yield. Relay-planting with stubble standing or straw covering decreased water consumption by 4.6 %. The integrated systems increased water use efficiency by up to 46 % compared to conventional mono-planting maize and wheat.
No preview · Article · Apr 2015 · Agronomy for Sustainable Development
[Show abstract][Hide abstract] ABSTRACT: Canola (Brassica napus L.) production has been steadily increasing in western Canada. Here we determine the effect of canola rotation frequency on canola seed yield, quality and associated pest species. From 2008 to 2013, direct-seeded experiments involving continuous canola and all rotation phases of wheat (Triticum aestivum L.) and canola or field pea (Pisum sativum L.), barley (Hordeum vulgare L.) and canola were conducted at five western Canada locations. Fertilizers, herbicides, and insecticides were applied as required for optimal production of all crops. Canola rotation frequency did not influence canola oil or protein concentration or the level of major (composition > 1%) seed oil fatty acids. High canola yields were associated with sites that experienced cooler temperatures with adequate and relatively uniform precipitation events. For each annual increase in the number of crops between canola, canola yield increased from 0.20 to 0.36 Mg ha-1. Although total weed density was not strongly associated with canola yield, decreased blackleg disease and root maggot damage were associated with greater canola yields as rotational diversity increased. Long-term sustainable canola production will increase with cropping system diversity.
Full-text · Article · Jan 2015 · Canadian Journal of Plant Science
[Show abstract][Hide abstract] ABSTRACT: Water scarcity, water pollution, and water-related waste threaten humanity globally,
largely due to the limited supply of freshwater on the planet, the unbalanced
distribution of water resources, and the excessive consumption of water from the
growing population and its economic development. China is facing severe water
shortages; the northern part of the country has an average freshwater availability
of 760 cubic meter per capita per year, 25% below the internationally accepted
threshold for water scarcity. Agriculture in northwest China relies on annual precipitation
of 50–500 mm, 70% of which occurs from July to September, and annual
evaporation from 1500 to 2600 mm. In the Hexi Corridor regions where annual precipitation
is below 150 mm, farming largely depends on irrigation with water from
Qilian Mountain snowmelt. However, permanent snow on the mountain has moved
upwards at a rate of 0.2–1.0 m annually, and groundwater in the valley has declined
at a rate of 0.5–1.8 m year−1. Consequently, some natural oases, along the old Silk
Road, have shrunk or disappeared and wells have dried up. At the meantime, some
farms use irrigation water at a rate as high as 11,000 m3 ha−1, much greater than
crop water requirements for high yield. In recent years, many innovative research
projects have dealt with the water issue in arid and semiarid northwestern China.
In this chapter, we summarize some key water-saving technologies developed from
some of these recently completed research projects, and discuss integrated and
innovative approaches for the development of water-saving agricultural systems.
Our goal is to encourage the use of innovative water-saving technologies to reduce
agricultural water use, increase crop water-use efficiency, and improve agricultural
Full-text · Article · Dec 2014 · Advances in Agronomy
[Show abstract][Hide abstract] ABSTRACT: Synergistic regulation on water competition and compensation is critical to effective use of water for sustainable intercropping systems in arid areas. Field experiment was carried out in 2009, 2010, and 2011 in Hexi Corridor, northwest China. Two late-sown crops [maize (Zea mays) and soybean (Glycine max)] intercropping with three early-sown crops [pea (Pisum sativum), rape (Brassia campestris), and wheat (Triticum aestivum)] were designed in comparison with the respective sole crops. Differences in soil water (soil water of late-sown crops minus that of early-sown crops in intercropping) were found to be mostly positive during the co-growth period which changed to negative during the fallow period of early-sown crops. Absolute values of the difference between wheat and maize strips both in co-growth and fallow period were the greatest among treatments, followed by maize–pea intercropping, while they were lowest in soybean–wheat intercropping in 2009 and 2010 and in maize–rape intercropping in 2011. In the co-growth period, the mean soil water competition for wheat strips in maize–wheat intercropping across 3 years was 71 mm, while it was 16 mm and 27 mm, respectively, for maize–rape and maize–pea intercropping. Sole wheat recharged the greatest amount of soil water from wheat harvest to maize harvest. In each year, intercropped wheat, rape, and pea recharged 24–76, 42–67, and 32–49 mm soil water, respectively. It was concluded that the methodology to calculate soil water competition and compensation was a very useful tool for evaluating the amount of soil water movement in intercropping systems.
[Show abstract][Hide abstract] ABSTRACT: Surface-placed residue increased the near soil surface moisture and reduced root heat stress. The improved micro environment resulted in greater root length for wheat (Triticum aestivum L.) and canola (Brassica napus) and 34, 8 and 8% higher yield, 7, 52 and 20% more straw and 7, 5, and 7.5 cm taller than the non-residue check for wheat, canola and dry pea (Pisum sativum), respectively.
No preview · Article · Nov 2014 · Canadian Journal of Plant Science
[Show abstract][Hide abstract] ABSTRACT: Wheat is one of the world's most favoured food sources, reaching millions of people on a daily basis. However, its production has climatic consequences. Fuel, inorganic fertilizers and pesticides used in wheat production emit greenhouse gases that can contribute negatively to climate change. It is unknown whether adopting alternative farming practices will increase crop yield while reducing carbon emissions. Here we quantify the carbon footprint of alternative wheat production systems suited to semiarid environments. We find that integrating improved farming practices (that is, fertilizing crops based on soil tests, reducing summerfallow frequencies and rotating cereals with grain legumes) lowers wheat carbon footprint effectively, averaging -256 kg CO2 eq ha(-1) per year. For each kg of wheat grain produced, a net 0.027-0.377 kg CO2 eq is sequestered into the soil. With the suite of improved farming practices, wheat takes up more CO2 from the atmosphere than is actually emitted during its production.
Full-text · Article · Nov 2014 · Nature Communications
[Show abstract][Hide abstract] ABSTRACT: Soil microorganisms mediate many important biological processes for sustainable agriculture. However, correlations between soil microbial properties and crop productivity cannot always be demonstrated. We collected soil microbial data from a canola (Brassica napus L.) study that was conducted at seven sites on the Canadian prairies about agricultural practices focused on increasing canola yields. The treatments consisted of two canola seeding rates (75 or 150 seeds m−2), two nitrogen rates (1× and 1.5× soil test recommendation) and three nitrogen form–fungicide (prothioconazole) combinations (uncoated urea, no fungicide; uncoated urea + fungicide; and 50% polymer-coated urea + fungicide) in a 2 × 2 × 3 factorial arrangement. Microbial biomass C (MBC), β-glucosidase enzyme activity and functional bacterial diversity (based on C substrate utilization patterns) were determined in canola rhizosphere and in bulk soil and related to canola yields. The effects of seeding rate, nitrogen (N) rate and N form on soil microbial biomass, enzyme activity or bacterial functional diversity were usually not statistically significant. In the few cases where significance occurred, doubling the seeding rate from 75 to 150 seeds m−2 usually increased these microbial properties in canola rhizosphere or bulk soil. Increasing N rate to 1.5× the recommended rate had mostly positive effects in canola rhizosphere and negative effects in bulk soil. The effects of N form (including addition of fungicide) were inconsistent. Soil MBC and β-glucosidase enzyme activity correlated positively with canola grain yield at the five sites where yields were <4000 kg ha−1 (r = 0.51** to 0.76**), but no or weak negative correlations were observed at the two sites with yields >4000 kg ha−1. The functional diversity of soil bacteria was not or was weakly negatively correlated with grain yields. Some of these relationships appeared to be influenced by canola root maggot damage because root damage was usually negatively correlated with the soil microbial characteristics, but the correlations were too weak to be relevant. These results suggest underground feedback interactions between crops and soil microbes, i.e., crop/soil management practices that enhance crop growth also enhance soil microbial communities and their activities, and vice versa.
Full-text · Article · Nov 2014 · European Journal of Agronomy
[Show abstract][Hide abstract] ABSTRACT: The rising cost of N in western Canada has created interest in alternative sources of N fertilizer. Legumes have the ability to fix N supply for subsequent crops, but knowledge of the effects of legumes on subsequent canola or barley is limited. A multi-location study was conducted from 2009 to 2011 in western Canada to evaluate the economic effects of various preceding crops (P) and N rate on subsequent canola and barley in a P-canola-barley rotation. Six preceding crops (field pea, lentil, faba bean, canola, wheat, and green manure [GRM] legume [faba bean]) were grown in factorial combination with five N rates (0, 30, 60, 90, and 120 kg ha-1) at seven sites in Alberta, Saskatchewan, and Manitoba. When the preceding crop was GRM, the net revenue (NR) of canola or canola-barley was highest but insufficient to compensate for negative NR during the GRM year (2009). Canola as a preceding crop yielded the least NR for the canola and canola-barley phases of the rotation. The quadratic responses of NR for canola and barley to optimal N indicated that N applied could be reduced below 120 kg ha-1 without diminishing yield at some locations in western Canada. Over the entire 3-yr crop sequence, legume preceding crops (lentil or field pea) grown for seed provided the greatest returns. The GRM improved the yield of the following crops considerably but the increased canola and barley yields were not able to alleviate the lost NR during the preceding crop phase.
[Show abstract][Hide abstract] ABSTRACT: High costs of fertilizer in western Canada have generated interest in alternative N sources. Legumes produce N through fixation, and may increase soil residual and mineralizable N, thus reducing the need for fertilizer N in subsequent crops. Hybrid canola (Brassica napus L.) has a high N requirement for optimum yield, but knowledge of rotational effects of legumes on canola is limited. The objective was to determine the effects of legume and non-legume preceding crops on yield and quality of canola grown the following year and malting barley (Hordeum vulgare L.) grown after canola. Field pea (Pisum sativum L.), lentil (Lens culinaris Medik.), faba bean (Vicia faba L.), canola, and wheat (Triticum aestivum L.) harvested for grain, and faba bean grown as a green manure were direct-seeded at seven locations in 2009. Canola was seeded in 2010 and barley in 2011, with fertilizer N applied at 0, 30, 60, 90, and 120 kg ha–1. On average, all legumes, except faba bean for seed, produced higher canola and barley yields than when wheat was the preceding crop. Faba bean green manure produced the highest yields, while canola on canola produced the lowest canola yield. The legumes had little negative effect on canola oil or barley protein concentration. Yields of both crops increased with increasing N rate, but canola oil concentration decreased, and barley protein increased. The results indicate that growing legumes for seed before hybrid canola can improve canola and subsequent barley yield without negatively affecting canola oil or malting barley protein.
[Show abstract][Hide abstract] ABSTRACT: Canola-Brassica napus L.-is an economically major crop in many parts of the world. The seed yield of canola is often limited by poor plant establishment. This issue is serious in areas with short growing seasons, such as western Canada, where canola plants have a limited time span plasticity to adapt and compensate for yield losses due to poor or non-uniform plant establishment. The effect of spatial patterns of canola plant stands on seed yield is actually unknown. Therefore, we studied the impacts of uniformity of plant stands on pod formation, seed set, and crop yield of canola. Field experiments were conducted at 16 site-years across the different soil-climatic zones of the Canadian prairies. At each site-year, the cultivar InVigorA (R) 5440, a glufosinate-resistant hybrid, was sown at 100, 80, 60, 40, and 20 plants per square meter with uniform and non-uniform stands. We found that spatially uniform stands increased seed yield by up to 32 % at low-yielding sites and by up to 20 % at the high-yielding sites compared to non-uniform plant stands. This effect is mainly due to increased number of fertile pods. The yield increase was more pronounced with plant densities lower than 60 plants per square meter. Also, canola seed yield depended largely on plant survival during the hot summer and was less affected by the rate of seedling emergence. We conclude that canola yield can be increased by improving the uniformity of plant spatial distribution patterns in the field regardless of environmental conditions.
Preview · Article · Oct 2014 · Agronomy for Sustainable Development
[Show abstract][Hide abstract] ABSTRACT: Slow-release fertilizers could improve the productivity of field crops and reduce environmental pollution. So far, no slow-release fertilizers are suited for maize cultivation in semiarid areas of China. Therefore, we tested attapulgite-coated fertilizers. Attapulgite-coated fertilizers were prepared by dividing chemical fertilizers into three parts according to the nutrient demand of maize in its three main growth stages and coating each part with a layer of attapulgite. This design is novel and unique, satisfying the demands of maize throughout the whole growing season with slow release of nutrients from the coated layers. A field experiment was conducted in 2010 and 2011, using three fertilizer rates, in kg/ha: 94.22 nitrogen (N) and 22.49 phosphorus (P), 139.09 N and 38.98 P, and 254.23 N and 50.98 P. Five types of fertilizers were compared: 20 and 30 % attapulgite-coated chemical fertilizer, 20 and 30 % attapulgite-mixed chemical fertilizer, and chemical fertilizer only. The results show that the soil mineral N and available P of attapulgite-coated fertilizer has a slow-release behavior that allows a better synchronization between nutrient availability and plant needs. Attapulgite-coated fertilizer increased the grain yield by 15.1–18.4 %. The use of attapulgite-coated fertilizers also improved partial factor productivity of N fertilizer by 10.0–26.7 % and P fertilizer by 11.0–26.7 %, compared with the control fertilized without coated formulates. Given their good performance, the attapulgite-coated fertilizers could be a promising alternative slow-release fertilizer for sustainable agriculture in semiarid areas.
Full-text · Article · Jul 2014 · Agronomy for Sustainable Development