• Authors:
    • Irani,S.
    • Majidi,M. M.
    • Mirlohi,A.
    • Zargar,M.
    • Karami,M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: The physiological basis of genetic variation in drought response and its association with forage yield and drought tolerance indices is not clear in sainfoin ( Onobrychis viciifolia Scop.). In this study, 100 sainfoin genotypes from 10 ecotypes were clonally propagated and evaluated under non-stressed and water deficit conditions during 2 yr. Physiological traits including chlorophyll a, chlorophyll b, total chlorophyll, carotenoid content, proline content, relative water content (RWC), catalase (CAT), ascorbate peroxidase (APX), superoxide dismutase (SOD) activity, dry matter yield (DMY), and stress tolerance index (STI) were studied. Large genotypic variation was observed among ecotypes for most of the studied traits indicating that selection in this germplasm would be useful. The results showed that water deficit greatly influenced physiological traits that affected forage production. Water deficit decreased DMY and RWC while significantly increasing carotenoid content, free proline content, CAT, APX, and SOD activity in both years. The relationship between dry matter yield and STI with proline content showed that ecotypes with high DMY and STI under water deficit conditions had higher proline accumulation in their leaves. With regard to the STI and principal component analysis (PCA), ecotypes Baft, Najafabad, and Sirjan were found to be drought tolerant or moderately drought tolerant. These ecotypes showed significantly higher values for proline content under water deficit conditions.
  • Authors:
    • Jani,Arun D.
    • Grossman,Julie M.
    • Smyth,Thomas J.
    • Hu,Shuijin
  • Source: Plant and Soil
  • Volume: 393
  • Issue: 1-2
  • Year: 2015
  • Summary: Legume cover crops are primarily grown for their contribution to soil N pools, but the effect that this added N has on cover crop root decomposition and N release is poorly understood. Our primary objective was to determine the effect that soil N and root diameter size have on root decomposition and N release. We determined coarse (> 1-mm diameter) and fine (< 1-mm diameter) root distribution for crimson clover (Trifolium incarnatum) and hairy vetch (Vicia villosa Roth) using greenhouse-grown plants, and followed with a 12-week incubation in which coarse and fine roots from both species were incubated under natural and elevated (200 kg ha(-1)) soil N levels. Crimson clover and hairy vetch consisted primarily of fine roots (a parts per thousand yen79 %), which decomposed and released N faster than coarse roots. Soil N addition had a small positive effect on root decomposition, but an inconsistent effect on root N release. There was a net increase in soil inorganic N for all treatments after 12 weeks. These results improved our understanding of decomposition and N release from crimson clover and hairy vetch roots, and are valuable to farmers seeking to better manage soil C and N pools.
  • Authors:
    • N'Dayegamiye,A.
    • Whalen,J. K.
    • Tremblay,G.
    • Nyiraneza,J.
    • Grenier,M.
    • Drapeau,A.
    • Bipfubusa,M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Legume crops leave N-rich residues and improve soil properties that can boost the yield of subsequent crops. This study conducted at two sites in Quebec, eastern Canada, identified the most appropriate preceding legume crops for subsequent corn ( Zea mays L.) and wheat ( Triticum aestivum L.) yield and N nutrition. Legumes were established in 2011, in monoculture or mixed with grain crops, for a total of 13 treatments: common bean ( Phaseolus vulgaris L.), soybean ( Glycine max L.), dry pea ( Pisum sativum L.), hairy vetch ( Vicia villosa Roth), alfalfa ( Medicago sativa L.), and crimson clover ( Trifolium incarnatum L.), (hairy vetch/wheat, crimson clover/wheat, field pea/wheat, alfalfa/corn, hairy vetch/corn, crimson clover/corn) and a non-N fixing crop (corn) as the control. In 2012, each plot was split and five N fertilizer rates applied to corn and wheat. Four legume systems (alfalfa, hairy vetch, crimson clover, and hairy vetch/wheat) significantly increased the soil structure stability, alkaline phosphatase and dehydrogenase activities at warmer St-Mathieu-de-Beloeil location but not at the cooler St-Lambert-de-Lauzon site. These legumes also significantly increased yields and N nutrition of corn and wheat at St Mathieu-de-Beloeil and of wheat only at St-Lambert-de-Lauzon. Although legume N credit was found low (~30 kg N ha -1), the N fertilizer replacement value was 51 to 77 kg N ha -1 for corn and up to 37 kg N ha -1 for wheat, depending on the preceding legume crop. This suggests that indirect effects related to improved soil properties impacted positively corn and wheat yield and N nutrition.
  • Authors:
    • Northupl,B. K.
    • Rao,S. C.
  • Source: Crop Economics, Production & Management
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Continuous winter wheat ( Triticum aestivum L. em Thell.) is the foundation for most US Southern Great Plains (SGP) agriculture. Inorganic N fertilizers are important to wheat production, but increasing N prices have caused producers to reconsider growing legumes during summer fallow for green N. This study was conducted during 2008 to 2012 to determine the potential for using lablab [ Lablab purpureus (L.) Sweet cv. Rio Verde] to support wheat under conventional and no-till management compared with soybean [ Glycine max (L.) Merr. cv. Laredo] and three inorganic fertilizer treatments (none, 40, and 80 kg N ha -1). Legume seeds were inoculated and sown after wheat harvest each year, grown from June to August, and terminated in early September. Wheat was then sown with or without preplant tillage and grown to maturity. Grain yield, N concentration, and N accumulated in grain were analyzed to define N treatment, tillage system, and year effects. The amount and distribution of precipitation during 2008 to 2012 varied from 53 to 92% and 63 to 160% of the long-term averages for wheat (688 mm) and legume (162 mm) phases. Tillage effects were nonsignificant ( P<0.76), but N treatment * year interactions were significant for grain yield, N concentration, and N accumulated in grain ( P<0.01). The legumes resulted in some single-year increases in grain yield, but the overall yield response was inconsistent. The legume treatments reduced N concentration in wheat grain compared with the unfertilized control. These results show that neither legume was an effective short-term (≤4-yr) N source for systems of continuous wheat production in the SGP.
  • Authors:
    • Uzoma,K. C.
    • Smith,W.
    • Grant,B.
    • Desjardins,R. L.
    • Gao XiaoPeng
    • Hanis,K.
    • Tenuta,M.
    • Goglio,P.
    • Li,C. S.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 206
  • Year: 2015
  • Summary: Biogeochemical models are useful tools for integrating the effects of agricultural management on GHG emissions; however, their development is often hampered by the incomplete temporal and spatial representation of measurements. Adding to the problem is that a full complement of ancillary measurements necessary to understand and validate the soil processes responsible for GHG emissions is often not available. This study presents a rare case where continuous N 2O emissions, measured over seven years using a flux gradient technique, along with a robust set of ancillary measurements were used to assess the ability of the DNDC model for estimating N 2O emissions under varying crop-management regimes. The analysis revealed that the model estimated soil water content more precisely in the normal and wet years (ARE 3.4%) than during the dry years (ARE 11.5%). This was attributed to the model's inability to characterize episodic preferential flow through clay cracks. Soil mineral N across differing management regimes (ARE 2%) proved to be well estimated by DNDC. The model captured the relative differences in N 2O emissions between the annual (measured: 35.5 kg N 2O-N ha -1, modeled: 30.1 kg N 2O-N ha -1) and annual-perennial (measured: 26.6 kg N 2O-N ha -1, modeled: 21.2 kg N 2O-N ha -1) cropping systems over the 7 year period but overestimated emissions from alfalfa production and underestimated emissions after spring applied anhydrous ammonia. Model predictions compared well with the measured total N 2O emissions (ARE -11%) while Tier II comparison to measurements (ARE -75%) helped to illustrate the strengths of a mechanistic approach in characterizing the site specific drivers responsible for N 2O emissions. Overall this study demonstrated the benefits of having near continuous GHG flux measurements coupled with detailed ancillary measurements towards identifying soil process interactions responsible for regulating GHG emissions.
  • Authors:
    • Tribouillois,H.
    • Cruz,P.
    • Cohan,J. P.
    • Justes,E.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 207
  • Year: 2015
  • Summary: Cover crops are used during fallow periods to produce ecosystem services, especially those related to N management such as (i) capturing mineral-N from soil to reduce nitrate leaching, and (ii) improving N availability for the next main crop (green manuring). Bispecific mixtures consisting of legume and non-legume species could simultaneously produce these two services of nitrate saving and green manuring. The magnitude of these services can be estimated from indicators of agroecosystem functions such as crop growth rate, crop N acquisition rate and the C:N ratio of the cover crop. We developed a conceptual model for each indicator which was described using general linear models. A three-step procedure was used: (1) represent the behavior of each species based on a sub-model and calibrate each species in bispecific mixtures; (2) validate the complete-mixture models, corresponding to the sum of the two species sub-models, and the proportion of each species in the whole cover, and (3) validate the generality of sub-models and complete-mixture models to predict the agroecosystem function indicators of species in mixture not used for calibration. The combined use of (i) potential agroecosystem functions measured in sole crop in non-limiting conditions, (ii) difference in leaf functional traits, as indicators of plant strategies and (iii) environmental factors, was efficient in fitting and predicting the level of agroecosystem functions provided by a cover crop species in mixture in actual conditions. The models fitted for bispecific mixtures were efficient to represent the behavior of each species in mixture and to estimate the legume proportion which expressed the species dominance. The models were evaluated as satisfactory for crop growth rate and C:N ratio for their generality in predicting the agroecosystem functions provided in mixtures by other species not used in the model calibration step, which illustrates the relevance and robustness of the approach.
  • Authors:
    • Aengelo Rodrigues,M.
    • Dimande,Paulo
    • Pereira,Ermelinda L.
    • Ferreira,Isabel Q.
    • Freitas,Sara
    • Correia,Carlos M.
    • Moutinho-Pereira,Jose
    • Arrobas,Margarida
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 103
  • Issue: 2
  • Year: 2015
  • Summary: Cover cropping is a major challenge in the sustainable management of rainfed olive orchards. From a 5 year study (2009-2014), the effect of a mixture of early-maturing and self-reseeding annual legumes (Legs) grown as a cover crop in a rainfed olive orchard was compared with a cover of natural vegetation fertilized with 60 kg nitrogen (N) ha(-1) year(-1) (NV +N), and a cover of natural vegetation not fertilized (NV -N). The study took place in NE Portugal. The following were assessed: (1) the performance of the covers by measuring ground cover percentages, dry matter yields and N content in aboveground biomass; (2) the soil fertility through chemical and microbiological assays and by growing plants in pot experiments; and (3) the nutritional status of olive trees and olive yields. Legumes gave higher ground-cover percentages, produced more biomass and accumulated more N in shoots in comparison to natural vegetation, whether fertilized or not. The results showed intense biological activity [microbial carbon (C) and N, CO2-C evolved in a laboratory incubation, metabolic quotient, total culturable fungi and bacteria, and acid phosphatase activity] in the 0-10 cm soil layer of the treatments producing more biomass (Legs and NV +N). However, soil available N was greater in soil samples from the Legs plot. N recoveries by turnip (Brassica rapa var. rapa L.) and rye (Secale cereale L.) grown in pot experiments were 84.4 and 60.2 mg pot(-1) in soil samples from the Legs treatment and 29.4 and 27.1 mg pot(-1) and 14.2 and 13.6 mg pot(-1), respectively in NV +N and NV -N plots. Sown legumes appeared less effective in increasing organic C than natural vegetation. Nevertheless, in the Legs plot the increase of easily mineralizable C was proportionally higher than the increase of total organic C, which may mean that a more reactive pool of organic C is created, which may reduce the turnover of organic C and N in the soil. In the 10-20 cm soil layer, total organic C was significantly lower in Legs (14.0 g kg(-1)) than in NV -N (22.1 g kg(-1)) and N +NV (25.2 g kg(-1)) treatments, likely due to a priming effect caused by mineral N coming from the surface layer. Two years after the trial started, the N nutritional status of the olive trees was significantly higher in Legs than in natural vegetation plots even when 60 kg N ha(-1) year(-1) was applied. The cumulative olive yields in NV -N and NV +N plots were only 58.6 and 77.7 % in comparison to those found in the Legs plot, if only the last four harvests were considered, which were those influenced by the ground-cover treatments (2010-2013).
  • Authors:
    • Ashworth,A. J.
    • West,C. P.
    • Allen,F. L.
    • Keyser,P. D.
    • Weiss,S. A.
    • Tyler,D. D.
    • Taylor,A. M.
    • Warwick,K. L.
    • Beamer,K. P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Biological N 2 fixation (BNF) via legume intercrops can provide an alternative to inorganic N fertilizer and thereby minimize the economic and environmental costs of bioenergy feedstock and forage production. The objectives of this study were to (i) verify switchgrass ( Panicum virgatum L.) as a non-N 2-fixing reference plant for distinguishing between soil- and atmosphere-derived N; (ii) determine BNF levels via the 15N enrichment method for one cool-season legume (red clover [ Trifolium pratense L.]) and three warm-season legumes ([partridge pea] [ Chamaecrista fasciculate Michx.], sunn hemp [ Crotalaria juncea L.], and pigeonpea [ Cajanus cajan (L.) Millsp.]) when intercropped into switchgrass and a near relative, guineagrass ( Panicum maximum L.); and (iii) evaluate the validity of the N-difference method by comparing it against the 15N enrichment technique in humid temperate and semiarid tropical climates. The results revealed little difference in the N assimilation rates of legume and non-N 2-fixing reference plants, suggesting that switchgrass is an appropriate reference species. Annual fixation for red clover was greatest, followed by partridge pea, and lastly sunn hemp in temperate systems (87, 84, and 35 kg ha -1, respectively), all of which tended to supply greater amounts of N in subsequent seasons. Considerably greater BNF occurred in tropical intercrop systems (exceeding 240 kg ha -1). Consequently, the BNF of selected legumes approximates or exceeds recommended N fertilizer rates (67 kg N ha -1) in both humid temperate and semiarid tropical pasture and feedstock systems. The N-difference method did not provide estimates for BNF that were comparable to 15N-enrichment-derived values ( P>0.05).
  • Authors:
    • Lupwayi, N.
    • Blackshaw, R.
    • Li, L
    • Pearson, D.
    • Larney, F.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Dry bean ( Phaseolus vulgaris L.) production on the Canadian prairies has traditionally used wide rows, inter-row cultivation, and undercutting at harvest. Recent breeding efforts have produced cultivars with more upright growth which are better suited to solid-seeded narrow-row production systems. A 12 yr (2000-2011) study compared conservation (CONS) and conventional (CONV) management for dry bean in 3- to 6-yr rotations. The CONS rotations included reduced tillage, cover crops, feedlot manure compost, and solid-seeded narrow-row dry bean. Effects of CONS management on plant density were inconsistent with some years showing lower density when seeded into high-residue conditions. On average, there was a 3 d maturity advantage with CONS (103 d) vs. CONV (106 d) management. The CONS rotations showed significantly higher mean incidence (19%) of white mold [ Sclerotinia sclerotiorum (Lib.) de Bary] than CONV rotations (6%). Averaging across 12 yr, there was no significant rotation effect on yield ( P=0.19) showing that CONS production performed as good as CONV production. In the last 2 yr (2010-2011) of the study, in an attempt to reduce harvest losses, CONS dry bean was undercut rather than direct combined. This led to significantly higher (25%) yield with CONS (3311 kg ha -1) vs. CONV management (2651 kg ha -1). Our results provide incentive for more rapid adoption of conservation-oriented soil and crop management practices for dry bean production on the Canadian prairies, including narrow rows, reduced tillage, cover crops, and feedlot manure compost addition.
  • Authors:
    • Tanaka, D.
    • Nichols, K.
    • Schmer, M.
    • Archer, D.
    • Hendrickson, J.
    • Liebig, M.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: Cover crops can expand ecosystem services, though sound management recommendations for their use within semiarid cropping systems is currently constrained by a lack of information. This study was conducted to determine agroecosystem responses to late-summer seeded cover crops under no-till management, with particular emphasis on soil attributes. Short-term effects of late-summer seeded cover crops on soil water, available N, near-surface soil quality, and residue cover were investigated during three consecutive years on the Area IV Soil Conservation Districts Research Farm near Mandan, ND. Mean aboveground cover crop biomass was highly variable across years (1430, 96, and 937 kg ha -1 in 2008, 2009, and 2010, respectively), and was strongly affected by precipitation received within 14 d following cover crop seeding. During years with appreciable biomass production (2008 and 2010), cover crops significantly reduced available N in the 0.9-m depth the following spring ( P=0.0291 and 0.0464, respectively). Cover crop effects on soil water were subtle, and no differences in soil water were found between cover crop treatments and a no cover crop control before seeding cash crops the following spring. Late-summer seeded cover crops did not affect near-surface soil properties or soil coverage by residue. Soil responses to late-summer seeded cover crops did not differ between cover crop mixtures and monocultures. Late-summer seeded cover crops may enhance ecosystem services provided by semiarid cropping systems through biomass production and N conservation, though achieving these benefits in a consistent manner appears dependent on timely precipitation following cover crop seeding.