821. Nitrous oxide fluxes measurements from an intensively managed irrigated pasture using micrometeorological techniques

• Authors:
  • Denmead, O. T.
  • Kelly, K. B.
  • Baigent, R.
  • Leuning, R.
  • Phillips, F. A.
• Source: Agricultural and Forest Meteorology
• Volume: 143
• Issue: 1-2
• Year: 2007

822. Comparison of chamber and micrometeorological techniques to determine N<SUB>2</SUB>O emissions for an irrigated pasture used for dairy production

• Authors:
  • Baigent, R.
  • Leuning, R.
  • Kelly, K.
  • Phillips, F.
• Source: Non-CO2 greenhouse gas fluxes in Australian landscapes
• Year: 2007

823. Legume effect for enhancing productivity and nutrient use-efficiency in major cropping systems - an Indian perspective: a review.

• Authors:
  • Bandyopadhyay, K. K.
  • Wanjari, R. H.
  • Manna, M. C.
  • Misra, A. K.
  • Mohanty, M.
  • Rao, A. S.
  • Ghosh, P. K.
• Source: Journal of Sustainable Agriculture
• Volume: 30
• Issue: 1
• Year: 2007
• Summary: This article deals with the beneficial effect of important legumes on increasing productivity and nutrient use efficiency in various systems. Sorghum, pearl millet, maize, and castor are mainstay in dry lands and marginal and sub-marginal lands. Sorghum yield increased when sown after cowpea, green gram, and groundnut. Grain legumes like groundnut or cowpea provide an equivalent to 60 kg N ha on the subsequent crop of pearl millet. Various studies have shown that among legume/cereal intercropping system, the combination of maize/pigeon pea is considered to be highly suitable with a minimum competition for nutrients, while legume/legume intercropping system, pigeon pea/groundnut system is the most efficient one in terms of resource use-efficiency. In alley cropping system, Leucaena leucocephala (Subabul) prunings provide N to the extent of 75 kg, which benefits the intercrop castor and sorghum. Nitrogen economy through intercropped legume is still a researchable issue because the key point for leguminous crop grown in intercropping system is the problem of nodulation. Incorporation of whole plant of summer green gram/black gram into soil (after picking pods) before transplanting rice resulted in the economizing (40-60 kg N ha -1, 30 kg P 2O 5, and 15 kg K 2O per ha) of rice in rice-wheat system. Similarly, 6-8 weeks old green manure crop of sunhemp or dhaincha accumulates approximately 3-4 t ha -1 dry matter and 100-120 kg N ha -1 which, when incorporated in situ, supplements up to 50% of the total N requirement of rice. Legumes with indeterminate growth are more efficient in N 2 fixation than determinate types. Fodder legumes in general are more potent in increasing the productivity of succeeding cereals. The carryover of N for succeeding crops may be 60-120 kg in berseem, 75 kg in Indian clover, 75 kg in cluster bean, 35-60 kg in fodder cowpea, 68 kg in chickpea, 55 kg in black gram, 54-58 kg in groundnut, 50-51 kg in soyabean, 50 kg in Lathyrus, and 36-42 kg per ha in pigeon pea. Direct and residual effect of partially acidulated material and mixture of rock phosphate + single superphosphate were observed to be better when these were applied to green gram in winter season than to rice in rainy season simply because of legume effect.

824. On-farm crop performances and water use efficiency of zero till wheat in low land rice ecosystem.

• Authors:
  • Goswami, S. B.
  • Saha, S.
  • Dutta, S.
• Source: National Seminar on Ecorestoration of Soil and Water Resources Towards Efficient Crop Production
• Year: 2007
• Summary: On-farm field experiments were undertaken in Chakdah Block, West Bengal, India, to study the impact of surface sowing, sowing by zero till seed drill (ZT) and conventional sowing with normal tillage (CT) in lowland rice fields on the growth and yield performances of wheat cv. 'UP 262', sown in the 1st, 3rd and 4th weeks of November during 2005-06 and 2006-07. For sowing under zero till, the seed rate was high (150 kg/ha). The depth of irrigation for ZT was 4 cm (3 h/bigha) compared to CT of 6 cm (4.5 h/bigha). Three irrigations were applied at crown root initiation, maximum tillering and flowering stages. The wheat plant height, tillering, panicle length, grains per spike and test weight were significantly affected by ZT and surface sowing compared to CT. Effective tiller production was higher under ZT with 3 irrigations than ZT with 2 irrigations or surface sowing. ZT with 3 irrigations (226 mm total water use) recorded the highest grain yield of 24.6 q/ha, which was a 21.8% yield increase over CT with 3 irrigations (243 mm total water use). ZT with 2 irrigations (189 mm total water use) decreased the grain yield by 111.8% over ZT with 3 irrigations. The water use efficiency was higher (8.5-8.71 kg ha -1 mma -1) under ZT with 3 irrigations over ZT with 2 irrigations or CT with 3 irrigations.

825. Net biome productivity of irrigated and rainfed maize-soybean rotations: modeling vs. Measurements.

• Authors:
  • Arkebauer, T. J.
  • Grant, R. F.
  • Dobermann, A.
  • Hubbard, K. G.
  • Schimelfenig, T. T.
  • Verma, S. B.
  • Suyker, A. E.
  • Walters, D. T.
• Source: Agronomy Journal
• Volume: 99
• Issue: 6
• Year: 2007
• Summary: Estimates of agricultural C sequestration require an understanding of how net ecosystem productivity (NEP) and net biome productivity (NBP) are affected by land use. Such estimates will most likely be made using mathematical models that have undergone well-constrained tests against field measurements of CO 2 exchange as affected by management. We tested a hydraulically driven soil-plant-atmosphere C and water transfer scheme in ecosys against CO 2 and energy exchange measured by eddy covariance (EC) over irrigated and rainfed no-till maize-soybean rotations at Mead, NE. Correlations between modeled and measured fluxes ( R2>0.8) indicated that <20% of variation in EC fluxes could not be explained by the model. Annual aggregations of modeled fluxes indicated that NEP of irrigated and rainfed soybean in 2002 was -30 and -9 g C m -2 yr -1 (net C source) while NEP of irrigated and rainfed maize in 2003 was 615 and 397 g C m -2 yr -1 (net C sink). These NEPs were within the range of uncertainty in annual NEP estimated from gap-filled EC fluxes. When grain harvests were subtracted from NEP to calculate NBP, both the modeled and measured maize-soybean rotations became net C sources of 40 to 80 g C m -2 yr -1 during 2002 and 2003. Long-term model runs (100 yr) under repeated 2001-2004 weather sequences indicated that a rainfed no-till maize-soybean rotation at Mead would lose about 30 g C m -2 yr -1. Irrigating this rotation would raise SOC by an average of 6 g C m -2 yr -1 over rainfed values. Modeled and measured results indicated only limited opportunity for long-term soil C storage in irrigated or rainfed maize-soybean rotations under the soil, climate, and management typical of intensive crop production in the U.S. Midwest.

826. Irrigated, no-till corn and barley response to nitrogen in northern Colorado

• Authors:
  • Reule, C. A.
  • Halvorson, A. D.
• Source: Agronomy Journal
• Volume: 99
• Issue: 6
• Year: 2007
• Summary: Converting irrigated, conventional-till (CT) systems to no-till (NT) production systems can potentially reduce soil erosion, fossil fuel consumption, and greenhouse gas emissions. Nitrogen fertilization effects on irrigated corn (Zea mays L.) and malting barley (Hordeum distichon L.) yields in a corn-barley rotation were evaluated for 6 yr on a clay loam soil to determine the viability of using a NT system and N needs for optimum crop yield. Six N treatments were established with N rates varying from 0 to 224 kg N ha(-1) for corn and 0 to 1.12 kg N ha(-1) for barley. Corn and barley grain yields were significantly increased by N fertilization each of 3 yr in the rotation. Three year average corn grain yields were near maximum with an available N (AN) (soil + fertilizer + irrigation water N) level of 274 kg N ha(-1). Barley yields increased linearly with increasing N rate with grain protein content near 130 kg protein Mg-1 grain at the highest N rate. Nitrogen use efficiency (NUE) by corn and barley, based on grain N removal, decreased with increasing AN level and ranged from 204 to 39 and 68 to 31 kg grain kg(-1) AN for the low and high N treatments for corn and barley, respectively. Total plant N uptake required to produce one Mg grain at near maximum yield in this study averaged 21 kg N for corn and 27 kg N for barley. Corn and barley residue production increased with increasing N rate. Irrigated, NT corn yields obtained in this corn-barley rotation were acceptable (>10 Mg ha(-1)) for northern Colorado; however, barley yields did not meet our expected yield goal of 5.4 Mg ha(-1) with the N rates used in this study, but grain protein was near maximum for malting barley. An irrigated, NT corn-barley production system appears to be feasible in northern Colorado.

827. The myth of nitrogen fertilization for soil carbon sequestration

• Authors:
  • Boast, C. W.
  • Ellsworth, T. R.
  • Mulvaney, R. L.
  • Khan, S. A.
• Source: Journal of Environmental Quality
• Volume: 36
• Issue: 6
• Year: 2007
• Summary: Intensive use of N fertilizers in modern agriculture is motivated by the economic value of high grain yields and is generally perceived to sequester soil organic C by increasing the input of crop residues. This perception is at odds with a century of soil organic C data reported herein for Morrow Plots, the world's oldest experimental site under continuous corn (Zea mays L.). After 40 to 50 yr of synthetic fertilization that exceeded grain N removal by 60 to 190%, a net decline occurred in soil C despite increasingly massive residue C incorporation, the decline being more extensive for a corn-soybean (Glycine max L. Merr.) or corn-oats (Avena sativa L.)-hay rotation than for continuous corn and of greater intensity for the profile (0-46 cm) than the surface soil. These findings implicate fertilizer N in promoting the decomposition of crop residues and soil organic matter and are consistent with data from numerous cropping experiments involving synthetic N fertilization in the USA Corn Belt and elsewhere, although not with the interpretation usually provided. These are important implications for soil C sequestration because the yield-based input of fertilizer N has commonly exceeded grain N removal for corn production on fertile soils since the 1960s. To mitigate the ongoing consequences of soil deterioration, atmospheric CO2 enrichment, and NO3- pollution of ground and surface waters, N fertilization should be managed by site-specific assessment of soil N availability. Current fertilizer N managment practices, if combined with corn stover removal for bioenergy production; exacerbate soil C loss.

828. Adoption of conservation tillage in California: current status and future perspectives

• Authors:
  • Harben, R.
  • Beyer, J.
  • Dusault, A.
  • Fry, R.
  • Shrestha, A.
  • Klonsky, K. M.
  • Mitchell, J. P.
• Source: Australian Journal of Experimental Agriculture
• Volume: 47
• Issue: 12
• Year: 2007
• Summary: While there have been several similarities between the development of cropping systems in Australia and California ( including climate, the need for irrigation and very diverse, highly specialised crop rotations), the historical patterns of conservation tillage development in the two regions have been quite different. Current estimates indicate that conservation tillage ( CT) practices are used on less than 2% of annual crop acreage in California's Central Valley. Tillage management systems have changed relatively little since irrigation and cropping intensification began throughout this region, more than 60 years ago. The University of California ( UC) and United States Department of Agriculture ( USDA) Natural Resource Conservation Service ( NRCS) CT Workgroup is a diverse group of UC, NRCS, farmer, private sector, environmental group and other public agency people. It has provided wide- ranging services aimed at developing information on reduced tillage alternatives for California's production valleys. In a short span of 7 years, the CT Workgroup has grown to over 1000 members and has conducted over 60 demonstration evaluations of CT systems. While CT is still quite new in California, a growing number of farmers has become increasingly interested in it, for both economic and environmental reasons. They are now pursuing a wide range of activities and approaches aimed at developing sustainable CT systems. As successful CT systems continue to be demonstrated, the rate of adoption is expected to increase.

829. Precise Soil Management as a Tool to Reduce CH4 and N2O Emissions from Agricultural Soils

• Authors:
  • Dolfing, J.
  • Rappoldt, C.
  • Hol, J. M. G.
  • Mosquera, J.
• Volume: 2010
• Year: 2007
• Summary: Soil compaction stimulates the emission of nitrous oxide (N2O) and methane (CH4) from agricultural soils. N2O and CH4 are potent greenhouse gases, with a global warming potential respectively 296 times and 23 times greater than CO2. Agricultural soils are an important source of N2O. Hence there is much interest in a systematic evaluation of management options that are available to minimize agricultural greenhouse gas emissions, in particular N2O soil emissions. One such option would be to minimize soil compaction due to the use of heavy machinery. Soil compaction in arable land is relatively general. Here we report that emissions of N2O and CH4 from an arable field where soil compaction was minimized through application of the so-called "rijpaden" (riding track) system was substantially lower than from plots where a traditional system was used. Laboratory experiments were used to underpin these observations. From these observations we developed a simple calculation model that relates N2O emission to gas filled pore space and soil respiration as input parameters. We suggest to implement the riding track system on clay rather than sand as farmers benefit from lower compaction in terms of lower risk of compaction and better accessibility of fields for work. The potential reduction of the N2O emission from arable farming in the Netherlands is estimated at ~169 ton N2O-N per year (~0.1 Mton CO2-equivalent). This calculation is based on several assumptions and would benefit from testing assumptions and monitoring effects in agricultural day to day practice.

830. A decade of advances in cover crops: Cover crops with limited irrigation can increase yields, crop quality, and nutrient and water use efficiencies while protecting the environment

• Authors:
  • Essah, S. Y. C.
  • Sparks, R. T.
  • Dillon, M. A.
  • Delgado, J. A.
• Source: Journal of Soil and Water Conservation
• Volume: 62
• Issue: 5
• Year: 2007
• Summary: This literature review examines a decade of advances in cover crops including how cover crops with limited irrigation can increase yields, crop quality, and nutrient and water use efficiencies while protecting the environment.