• Authors:
    • Sheaffer, C. C.
    • Fernandez, A. L.
    • Wyse, D. L.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 1
  • Year: 2015
  • Summary: Field pea ( Pisum sativum L.) and lentil ( Lens culinaris Medik.) have potential as grain-producing legumes in organic rotations, but their yield is limited by weed competition. Intercropping can control weeds and increase total grain productivity per land area compared to sole cropping. A field experiment was conducted to investigate the effect of intercropping on field pea and lentil yields. Intercrop treatments were spring wheat ( Triticum aestivum L.), oat ( Avena sativa L.), and radish ( Raphanus sativus L.), which were harvested for grain; and winter rye ( Secale cereale L.) and rapid-cycling brassica ( Brassica campestris L.), which were not harvested. Intercropped lentil yields and total (lentil plus intercrop) yields were lower than or equal to weeded and unweeded sole cropped lentils in 5 of 6 site-years. Intercropped pea yields and total (pea plus intercrop) yields were lower than or equal to weeded and unweeded sole cropped pea in all site-years. Unharvested intercrops showed variable effectiveness at suppressing weeds. In lentil, winter rye intercropping reduced weed biomass compared to the unweeded control in 4 site-years, and rapid-cycling brassica reduced weed biomass in 2 site-years. In pea, winter rye, and rapid-cycling brassica treatments reduced weed biomass in all site-years. However, reductions in weed biomass were not associated with increases in grain yield. Estimated net returns to intercropping were variable, but generally similar for sole crops and intercrops on average. We did not observe consistent agronomic or economic advantages to the use of intercrops with field pea and lentil in the Minnesota environments studied.
  • Authors:
    • Pal, M.
    • Chakraborty, D.
    • Sehgal,V. K.
    • Saha, S.
  • Source: Agriculture Journal
  • Volume: 203
  • Year: 2015
  • Summary: Experiments on chickpea ( Cicer arietinum L.) were performed in open-top chambers during 2010-11 and 2011-12 to assess effects of atmospheric CO 2 enrichment on the quality of seeds. Although no physical modification was observed, an increase in seed water uptake was recorded in plants grown under enriched atmospheric CO 2 condition. Germination of seeds reduced by 45-47%, while seed leachate conductivity increased by 10-17%. Seedling vigor decreased, although root and shoot lengths and seedling biomass showed negligible changes. Similarly, atmospheric CO 2 enrichment reduced field emergence of seedlings with no change in root characteristics of the emerged seedlings. A decrease in protease activity supports the reduced seed viability, although no change in grain phosphatase and alpha-amylase activities were recorded. Increase in carbon content in germinating seed-cotyledon along with decrease in N in cotyledon resulted in large increase in C:N ratio for the plants grown under enriched CO 2 condition. The starch content increased with no change in soluble sugar in germinating seed-cotyledons. This indicates more carbonaceous seeds from plants grown under enriched CO 2 environment. Results suggest that rising atmospheric CO 2 might have adverse impact on viability and germination of chickpea seeds, and cause nutritional imbalance through increase in C with dilution of N contents in germinating seed-cotyledons.
  • Authors:
    • Kankanen, H.
    • Lemola, R.
    • Valkama, E.
    • Turtola, E.
  • Source: Agronomy Journal
  • Volume: 203
  • Year: 2015
  • Summary: The growing of catch crops aims to prevent nutrient leaching in autumn after harvest and during the following winter, but due to competition, catch crops may also reduce yields of the main crop. We used meta-analysis to quantitatively review 35 studies conducted in Denmark, Sweden, Finland and Norway over the past four decades. These studies assessed the effect of both non-legume and legume catch crops undersown in spring cereals on nitrogen (N) leaching loss or its risk as estimated by the content of soil nitrate N(NO3--N) or its sum with ammonium N(NH4+-N) in late autumn. The meta-analysis also included the grain yield and N content of spring cereals. To identify sources of variation, we studied the effects of soil texture and management (ploughing time, the amount of N applied), as well as climatic (annual precipitation) and experimental conditions (duration of experiments, lysimeter vs. field experiments, the decade in which the experiment took place). Compared to control groups with no catch crops, non-legume catch crops, mainly ryegrass species, reduced N leaching loss by 50% on average, and soil nitrate N or inorganic N by 35% in autumn. Italian ryegrass depleted soil N more effectively (by 60%) than did perennial ryegrass or Westerwolds ryegrass (by 25%). In contrast, legumes (white and red clovers) did not diminish the risk for N leaching. Otherwise, the effect on N leaching and its risk were consistent across the studies conducted in different countries on clay and coarse-textured mineral soils with different ploughing times, N fertilization rates (<160 kg ha -1), and amounts of annual precipitation (480-1040 mm). Non-legume catch crops reduced grain yield by 3% with no changes in grain N content. In contrast, legumes and mixed catch crops increased both grain yield and grain N content by 6%. Therefore, in spring cereal production, non-legume catch crops represent a universal and effective method for reducing N leaching across the varieties of soils and weather conditions in the Nordic countries. Moreover, the trade-off between potential grain yield loss and environmental benefits seems tolerable and can be taken into account in environmental subsidy schemes.
  • Authors:
    • Migliorati,M. de A.
    • Bell,M.
    • Grace,P. R.
    • Scheer,C.
    • Rowlings,D. W.
    • Liu Shen
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 204
  • Issue: 1
  • Year: 2015
  • Summary: Alternative sources of N are required to bolster subtropical cereal production without increasing N 2O emissions from these agro-ecosystems. The reintroduction of legumes in cereal cropping systems is a possible strategy to reduce synthetic N inputs but elevated N 2O losses have sometimes been observed after the incorporation of legume residues. However, the magnitude of these losses is highly dependent on local conditions and very little data are available for subtropical regions. The aim of this study was to assess whether, under subtropical conditions, the N mineralised from legume residues can substantially decrease the synthetic N input required by the subsequent cereal crop and reduce overall N 2O emissions during the cereal cropping phase. Using a fully automated measuring system, N 2O emissions were monitored in a cereal crop (sorghum) following a legume pasture and compared to the same crop in rotation with a grass pasture. Each crop rotation included a nil and a fertilised treatment to assess the N availability of the residues. The incorporation of legumes provided enough readily available N to effectively support crop development but the low labile C left by these residues is likely to have limited denitrification and therefore N 2O emissions. As a result, N 2O emissions intensities (kg N 2O-N yield -1 ha -1) were considerably lower in the legume histories than in the grass. Overall, these findings indicate that the C supplied by the crop residue can be more important than the soil NO 3- content in stimulating denitrification and that introducing a legume pasture in a subtropical cereal cropping system is a sustainable practice from both environmental and agronomic perspectives.
  • Authors:
    • O'Dea,Justin K.
    • Jones,Clain A.
    • Zabinski,Catherine A.
    • Miller,Perry R.
    • Keren,Ilai N.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 2
  • Year: 2015
  • Summary: In the North American northern Great Plains (NGP), legumes are promising summer fallow replacement/cropping intensification options that may decrease dependence on nitrogen (N) fertilizer in small grain systems and mitigate effects of soil organic matter (SOM) losses from summer fallow. Benefits may not be realized immediately in semiarid conditions though, and longer-term effects of legumes and intensified cropping in this region are unclear, particularly in no-till systems. We compared effects of four no-till wheat (Triticum aestivum L.) cropping systems-summer fallow-wheat (F-W), continuous wheat (CW), legume green manure (pea, Pisum sativum L.)-wheat (LGM-W), and pea-wheat (P-W)-on select soil attributes in an 8-year-old rotation study, and N fertilizer effects on C and N mineralization on a duplicate soil set in a laboratory experiment. We analyzed potentially mineralizable carbon and nitrogen (PMC and PMN) and mineralization trends with a nonlinear model, microbial biomass carbon (MB-C), and wet aggregate stability (WAS). Legume-containing systems generally resulted in higher PMC, PMN, and MB-C, while intensified systems (CW and P-W) had higher WAS. Half-lives of PMC were shortest in intensified systems, and were longest in legume systems (LGM-W and P-W) for PMN. Nitrogen addition depressed C and N mineralization, particularly in CW, and generally shortened the half-life of mineralizable C. Legumes may increase long-term, no-till NGP agroecosystem resilience and sustainability by (1) increasing the available N-supply (similar to 26-50 %) compared to wheat-only systems, thereby reducing the need for N fertilizer for subsequent crops, and (2) by potentially mitigating negative effects of SOM loss from summer fallow.
  • Authors:
    • Prasad,J. V. N. S.
    • Rao,Ch S.
    • Ravichandra,K.
    • Jyothi,Ch N.
    • Babu,M. B. B. P.
    • Babu,V. R.
    • Raju,B. M. K.
    • Rao,B. B.
    • Rao,V. U. M.
    • Venkateswarlu,B.
    • Devasree Naik
    • Singh,V. P.
  • Source: Journal of Agrometeorology
  • Volume: 17
  • Issue: 1
  • Year: 2015
  • Summary: Carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) are important biogenic green house gases (GHGSs) from agricultural sector contributing to global warming. Temperature and rainfall play an important role in GHGS fluxes and information on their role in rainfed crops and systems is very scanty. Field studies were conducted at Hyderabad, India during 2012 rainy season to quantify GHGSs fluxes from two important food crops grown widely in rainfed regions viz. sorghum and pigeonpea. Quantum of fluxes ranged from 26-85 mg CO 2 - C m -2 h -1 in case of CO 2 and 18-68 g N 2O-N m -2 h -1 in case of N 2O at different stages of crop growth. Cumulative seasonal fluxes are 1.18 and 1.24 Mg CO 2-C ha -1 and 0.78 and 0.94 kg N 2O-N ha -1, in sorghum and pigeonpea, respectively. Ambient temperature and rainfall significantly influenced CO 2 fluxes. CO 2 fluxes increased with increase in temperature from 25.9°C to 31°C and fluxes were highest at 28.4°C in pigeonpea and at 27.7°C in sorghum. Quantum of CO 2 fluxes were highest at grain filling stage in sorghum and grand growth period in pigeonpea. N 2O fluxes increased with increase in temperature and moisture availability. These results provide evidence that rainfed crops in semi-arid regions contribute significant CO 2 and N 2O fluxes which are influenced by temperature and rainfall, thus warrant further studies.
  • Authors:
    • Russell,J. R.
    • Bisinger,J. J.
  • Source: Journal of Animal Science
  • Volume: 93
  • Issue: 6
  • Year: 2015
  • Summary: Beyond grazing, managed grasslands provide ecological services that may offer economic incentives for multifunctional use. Increasing biodiversity of plant communities may maximize net primary production by optimizing utilization of available light, water, and nutrient resources; enhance production stability in response to climatic stress; reduce invasion of exotic species; increase soil OM; reduce nutrient leaching or loading in surface runoff; and provide wildlife habitat. Strategically managed grazing may increase biodiversity of cool-season pastures by creating disturbance in plant communities through herbivory, treading, nutrient cycling, and plant seed dispersal. Soil OM will increase carbon and nutrient sequestration and water-holding capacity of soils and is greater in grazed pastures than nongrazed grasslands or land used for row crop or hay production. However, results of studies evaluating the effects of different grazing management systems on soil OM are limited and inconsistent. Although roots and organic residues of pasture forages create soil macropores that reduce soil compaction, grazing has increased soil bulk density or penetration resistance regardless of stocking rates or systems. But the effects of the duration of grazing and rest periods on soil compaction need further evaluation. Because vegetative cover dissipates the energy of falling raindrops and plant stems and tillers reduce the rate of surface water flow, managing grazing to maintain adequate vegetative cover will minimize the effects of treading on water infiltration in both upland and riparian locations. Through increased diversity of the plant community with alterations of habitat structure, grazing systems can be developed that enhance habitat for wildlife and insect pollinators. Although grazing management may enhance the ecological services provided by grasslands, environmental responses are controlled by variations in climate, soil, landscape position, and plant community resulting in considerable spatial and temporal variation in the responses. Furthermore, a single grazing management system may not maximize livestock productivity and each of the potential ecological services provided by grasslands. Therefore, production and ecological goals must be integrated to identify the optimal grazing management system.
  • Authors:
    • Apolinario,V. X. O.
    • Dubeux,J. C. B.
    • Lira,M. A.
    • Ferreira,R. L. C.
    • Mello,A. C. L.
    • Santos,M. V. F.
    • Sampaio,E. V. S. B.
    • Muir,J. P.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Warm-climate grasslands can be degraded by overgrazing and reduced soil fertility. However, legume trees integrated into these systems (silvopasture) can provide long-term marketable wood for sale and add N to the system. In addition, tree legumes can improve livestock diet by providing high crude protein forage. Our research assessed biomass and N accumulation by tree legumes: gliricidia [ Gliricidia sepium (Jacq.) Kunthe] and sabia ( Mimosa caesalpiniifolia Benth.) grown in conventionally grazed signal grass ( Brachiaria decumbens Stapf) pasture. The seedlings were planted in 2008 and growth rates were measured in 2012 and 2013. One year after the seedlings were planted, in July 2009, the pastures were grazed. Aboveground biomass doubled from 25 to 50 Mg ha -1 between February 2012 and August 2013. The thickest branches contributed the most ( p≤0.05) biomass: 58% for gliricidia and 54% for sabia. Leaves represented the smallest ( p≤0.05) fraction: 7 to 13% for gliricidia and 4 to 14% for sabia. Leaf and branch nutrient concentrations varied little ( p>0.05) between species and sampling periods. Gliricidia leaf N ranged from 33.6 to 38.0 g kg -1, while sabia leaf N ranged from 26.9 to 38.5 g kg -1. Biologically fixed N in leaves ranged from 30 to 121 kg ha -1. Sabia branches had less moisture and greater lignin, density, and gross calorific power than gliricidia. While thicker branches represent most of the aboveground tree biomass, leaves and thin branches have greater N concentration, representing an important return pathway to the soil.
  • Authors:
    • Feng ZhaoZhong
    • Rutting,T.
    • Pleijel,H.
    • Wallin,G.
    • Reich,P. B.
    • Kammann,C. I.
    • Newton,P. C. D.
    • Kobayashi,K.
    • Luo YunJian
    • Uddling,J.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: A key part of the uncertainty in terrestrial feedbacks on climate change is related to how and to what extent nitrogen (N) availability constrains the stimulation of terrestrial productivity by elevated CO 2 (eCO 2), and whether or not this constraint will become stronger over time. We explored the ecosystem-scale relationship between responses of plant productivity and N acquisition to eCO 2 in free-air CO 2 enrichment (FACE) experiments in grassland, cropland and forest ecosystems and found that: (i) in all three ecosystem types, this relationship was positive, linear and strong ( r2=0.68), but exhibited a negative intercept such that plant N acquisition was decreased by 10% when eCO 2 caused neutral or modest changes in productivity. As the ecosystems were markedly N limited, plants with minimal productivity responses to eCO 2 likely acquired less N than ambient CO 2-grown counterparts because access was decreased, and not because demand was lower. (ii) Plant N concentration was lower under eCO 2, and this decrease was independent of the presence or magnitude of eCO 2-induced productivity enhancement, refuting the long-held hypothesis that this effect results from growth dilution. (iii) Effects of eCO 2 on productivity and N acquisition did not diminish over time, while the typical eCO 2-induced decrease in plant N concentration did. Our results suggest that, at the decennial timescale covered by FACE studies, N limitation of eCO 2-induced terrestrial productivity enhancement is associated with negative effects of eCO 2 on plant N acquisition rather than with growth dilution of plant N or processes leading to progressive N limitation.
  • Authors:
    • Hou,Yong
    • Ma,Lin
    • Sardi,Katalin
    • Sisak,Istvan
    • Ma,Wenqi
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Nitrogen (N) emissions from food production can cause serious environmental problems. Mitigation strategies require insights of N cycles in this complex system. A substance flow analysis for N in the Hungary food production and processing chain over the period 1961-2010 was conducted. Our results show that the history of the total N input and output for the Hungary food chain consists of four distinct periods: 1961-1974 a rapid increase; 1974-1988 a steady increase; 1988-1992 a sharp decrease; 1992-2010 a period of large annual variations. The total N input to the food chain largely depended on N fertilizer input (on average 83 % of total input). Nitrogen losses were the largest outflows, particularly via ammonia emissions and denitrification from agricultural systems. The N use efficiency (NUE) for crop production sharply decreased from 1961 to 1974, but went up since the late 1980s. The NUE of animal production increased from 11 % in 1961 to 20 % in 2010. The N cost of food production in Hungary largely varied from 3 to 10 kg kg(-1) during 1961-2010, which was related to changes in fertilizer use and human dietary preferences. Increased dependence of crop yield on weather was observed since the early 1990s where large decrease in N fertilizer use occurred. The observed weather-dependence has resulted in large yearly variations in crop yields, the NUE of crop production and also the food N cost, which may pose a threat to food security of Hungary.