[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.
Field Crops Research 08/2015; 179. DOI:10.1016/j.fcr.2015.04.003 · 2.98 Impact Factor
[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.
[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.
Agronomy for Sustainable Development 04/2015; 35(2). DOI:10.1007/s13593-015-0286-1 · 3.99 Impact Factor
[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.
Canadian Journal of Plant Science 01/2015; 95(1):9-20. DOI:10.4141/cjps-2014-289 · 0.92 Impact Factor
[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: 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.
[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.
European Journal of Agronomy 11/2014; 62. DOI:10.1016/j.eja.2014.10.004 · 2.70 Impact Factor
[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.
Agronomy for Sustainable Development 10/2014; 34(4):793-801. DOI:10.1007/s13593-014-0218-5 · 3.99 Impact Factor
[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.
Agronomy for Sustainable Development 07/2014; 34(3). DOI:10.1007/s13593-013-0193-2 · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Endophytes are microorganisms that live within a plant without harming it. Bacterial endophytes were isolated from roots of potatoes (Solanum tuberosum L.) grown under different rotations (3 to 6 yr in length) and soil management (CONV, conventional; CONS, conservation) in irrigated cropping systems with dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.) spring wheat (Triticum aestivum L.) and timothy (Phleum pratense L.). The endophytes were characterized for nitrogen fixation potential, phytohormone production and phytopathogen-antagonistic properties. The nitrogen-fixing nitrogenase (nifH) gene was detected in potato grown in all rotations, presumably partly because the soil in all rotations contained Rhizobium leguminosarum bv. phaseoli from the dry bean phase. Sequence analysis revealed that it was homologous to the genes found in Burkholderia, Azospirillum, Ideonella, Pseudacidovorax and Bradyrhizobium species. Indole acetic acid (IAA) hormone production by endophytes isolated from potato grown under CONS management was 66% greater than that those isolated from potato grown under CONV management, and tended to be greater in longer than shorter rotations. When 12 endophytes were inoculated to dry bean, four increased shoot biomass by 27-34%, and six increased total (shoot + root) biomass by 25% on average. Endophytes from the longer CONS rotations (4-6 yr) resulted in significantly higher (by 9%) shoot biomass than the shortest CONS (3 yr) rotation. Six of 108 endophyte isolates exhibited antagonistic properties (reduced pathogen biomass by 12 to 58% in dual culture assays in liquid media) against potato pathogens Pectobacterium atrosepticum, Fusarium sambucinum and Clavibacter michiganensis subsp. epedonicus. All the six isolates were from CONS soil management. Therefore, the benefits of long rotations, with their associated CONS soil management, to crop productivity in these irrigated cropping systems probably include nutritional (biological nitrogen fixation and IAA hormone production) and disease-control benefits imparted by endophytic bacteria.
Canadian Journal of Plant Science 07/2014; 94(5):835-844. DOI:10.4141/cjps2013-356 · 0.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Improving nutrient management is critical to increase nutrient use efficiency, promote translocation of photoassimilates to sinks, and increase crop yield. In this study, we determined the effects of phosphorus (P) fertilization on dry matter (DM) and P accumulation, partitioning and remobilization from vegetative tissues to the grains in oilseed flax (Linum usitatissimum L.). We hypothesized that P accumulation and remobilization depended on the level of P supply and varied with vegetative tissues. The cultivar Baxuan 3 was sown under low P (LP, 15 kg P ha(-1)), moderate P (MP, 30 kg P ha(-1)), and high P (HP, 45 kg P ha(-1)) conditions along with a zero P control in a randomized complete block design, with three replicates, in 2011 and 2012. At mid-anthesis, leaf DM (average 1970 kg ha(-1)) and stem DM (average 1826 kg ha(-1)) were more than 20 times that of the nongrain reproductive DM (77 kg ha(-1)); as plants grew to maturity, the DM in the stem and nongrain reproductive parts increased but leaf DM decreased. Compared with the control, oilseed flax grown under the LP, MP, and HP conditions increased leaf DM by 76%, stem DM by 46%, nongrain reproductive DM by 39%, and improved grain yield by an average of 45%. The fertilized oilseed flax increased the P translocation from vegetative tissues to the grains by 150% in 2011 and 201% in 2012. The P content in leaves reached the peak at anthesis and then decreased rapidly to maturity, whereas P contents in the stem and nongrain reproductive parts increased gradually and reached the peak at maturity, showing that leaves are the major contributor to the grain P, whereas the stem and nongrain reproductive parts are stronger P-demanding organs in oilseed flax. We suggest that advanced techniques, such as P-32 labeling, may be used to further quantify the amount of P remobilized from the stems and nongrain reproductive parts to the grain.
[Show abstract][Hide abstract] ABSTRACT: Abstract
This study evaluated the effects of plastic mulched ridge-furrow cropping on soil biochemical properties and
maize (Zea mays L.) nutrient uptake in a semi-arid environment. Three treatments were evaluated from 2008
to 2010: no mulch (narrow ridges with crop seeded next to ridges), half mulch (as per no mulch, except narrow
ridges were mulched), and full mulch (alternate narrow and wide ridges, all mulched with maize seeded in
furrows). Compared to the no mulch treatment, full mulch increased maize grain yield by 50% in 2008 and
25% in 2010, but reduced yield by 21% in 2009 after low precipitation in early growth. Half mulch had a
similar grain yield to no mulch in the three cropping years, suggesting half mulch is not an effective pattern for
maize cropping in the area. Mulch treatments increased aboveground nitrogen (N) uptake by 21−34% and
phosphorus (P) uptake by 21−42% in 2008, and by 16−32% and 14−29%, respectively, in 2010; but in 2009
mulching did not affect N uptake and decreased P uptake. Soil microbial biomass and activities of urease,
β-glucosidase and phosphatase at the 0−15 cm depth were generally higher during vegetative growth but lower
during reproductive growth under mulch treatments than no mulch. Mulching treatments increased carbon (C)
loss of buried maize residues (marginally by 5−9%), and decreased light soil organic C (15−27%) and
carbohydrate C (12−23%) concentrations and mineralizable C and N (8−36%) at harvest in the 0−20 cm
depth compared with no mulch, indicating that mulching promotes mineralization and nutrient release in soil
during cropping seasons. As a result of these biological changes, mineral N concentration under mulch was
markedly increased after sowing in upper soil layers compared with no mulch. Therefore, our results suggest
that mulched cropping stimulated soil microbial activity and N availability, and thus contributed to increasing
maize grain yield and nutrient uptake compared with no mulch.
[Show abstract][Hide abstract] ABSTRACT: Intercropping is used to increase grain production in many areas of the world. However, this increasing crop yield costs large amounts of water used by intercropped plants. In addition, intercropping usually requires higher inputs that induce greenhouse gas emissions. Actually, it is unknown whether intercropping can be effective in water-limited arid areas. Here, we measured crop yield, water consumption, soil respiration, and carbon emissions of wheat-maize intercropping under different tillage and crop residue management options. A field experiment was conducted at Wuwei in northwest China in 2011 and 2012. Our results show that wheat-maize intercropping increased grain yield by 61 % in 2011 and 63 % in 2012 compared with the average yield of monoculture crops. The intercropping under reduced tillage with stubble mulching yielded 15.9 t ha−1 in 2011 and 15.5 t ha−1 in 2012, an increase of 7.8 % in 2011 and 8.1 % in 2012, compared to conventional tillage. Wheat-maize intercropping had carbon emission of 2,400 kg C ha−1 during the growing season, about 7 % less than monoculture maize, of 2,580 kg C ha−1. Reduced tillage decreased C emission over conventional tillage by 6.7 % for the intercropping, 5.9 % for monoculture maize, and 7.1 % for monoculture wheat. Compared to monoculture maize, wheat-maize intercropping used more water but emitted 3.4 kg C per hectare per millimeter of water used, which was 23 % lower than monoculture maize. Overall, our findings show that maize-wheat intercropping with reduced tillage coupled with stubble mulching can be used to increase grain production while effectively lower carbon emissions in arid areas.
Agronomy for Sustainable Development 04/2014; 35(2):701-711. DOI:10.1007/s13593-014-0257-y · 3.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Agroecosystems are dynamic systems that experience frequent chemical inputs and changes in plant cover. The objective of this study was to test whether abiotic (soil chemical properties and climate) and biotic (plant host identity) factors influence the spatial and temporal structuring of arbuscular mycorrhizal fungal (AMF) communities in a semiarid prairie agroecosystem. 454 GS FLX+ high throughput sequencing technology was successfully utilized to characterize the AMF communities based on long reads (mean length 751.7 bp) and generated high resolution data with excellent taxonomic coverage. The composition of the AMF community colonizing roots of the three crops (pea, lentil, and wheat) significantly differed, but plant host identity had a minimal effect on the composition of the AMF community in the soil. We observed a temporal shift in the composition of AMF communities in the roots and surrounding soil of the crops during the growing season. This temporal shift was particularly evident in the root associated AMF community and was correlated with soil phosphate flux and climatic variables. In contrast, the spatial structuring of the AMF community in the site was correlated with soil pH and electrical conductivity. Individual AMF taxa were significantly correlated with pH, electrical conductivity and phosphate flux, and these relationships were phylogenetically conserved at the genus level within the Glomeromycota.
[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
Advances in Agronomy 01/2014; 126:149-202. DOI:10.1016/B978-0-12-800132-5.00002-X · 3.89 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study determined key factors affecting canola productivity in western Canada and evaluated the differences among soil-climatic zones in canola crops responding to the key agronomic factors. A total of 68 canola farm fields were randomly selected in western Canada, and multiple correspondence analysis, coupled with multivariate predictive model with partial least squares projection and regressions, was used to analyze the data set. Canola produced in Alberta averaged 2500 kg ha(-1), and was 23% greater than canola produced in southern Saskatchewan, 10% greater than canola produced in northern Saskatchewan, and 59% greater than canola produced in Manitoba. Canola produced on chem-fallow averaged 2557 kg ha(-1), and was 17% greater than canola grown on cereal stubble, or 43% greater than canola grown on pea/lentil, corn stubble. Canola grown on canola stubble produced 54% of the seed yield as canola grown on cereal stubble, or 46% of the seed yield as canola grown on chem-fallow. Shallow and earlier seeding with narrow row spacing increased canola seed yields consistently. Canola receiving K fertilizer increased seed yield by an average of 25% compared with those receiving no K fertilizer. Straight combine resulted in 500 kg ha(-1) or 24% more seed yield than conventional swath-combine method. Those key factors may serve as the first-hand information in the development of sound guidelines for less experienced canola producers in western Canada.
Canadian Journal of Plant Science 01/2014; 94(1):131-139. DOI:10.4141/cjps2013-121 · 0.92 Impact Factor