• Authors:
    • Halvorson, A. D.
    • Grosso, S. J. del
    • Alluvione, F.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Nitrogen fertilization is essential for optimizing crop yields; however, it increases N 2O emissions. The study objective was to compare N 2O emissions resulting from application of commercially available enhanced-efficiency N fertilizers with emissions from conventional dry granular urea in irrigated cropping systems. Nitrous oxide emissions were monitored from corn ( Zea mays L.) based rotations receiving fertilizer rates of 246 kg N ha -1 when in corn, 56 kg N ha -1 when in dry bean ( Phaseolus vulgaris L.), and 157 kg N ha -1 when in barley ( Hordeum vulgare L. ssp. vulgare). Cropping systems included conventional-till continuous corn (CT-CC), no-till continuous corn (NT-CC), no-till corn-dry bean (NT-CDb), and no-till corn-barley (NT-CB). In the NT-CC and CT-CC systems, a controlled-release, polymer-coated urea (ESN) and dry granular urea were compared. In the NT-CDb and NT-CB rotations, a stabilized urea source (SuperU) was compared with urea. Nitrous oxide fluxes were measured during two growing seasons using static, vented chambers and a gas chromatograph analyzer. Cumulative growing season N 2O emissions from urea and ESN application were not different under CT-CC, but ESN reduced N 2O emissions 49% compared with urea under NT-CC. Compared with urea, SuperU reduced N 2O emissions by 27% in dry bean and 54% in corn in the NT-CDb rotation and by 19% in barley and 51% in corn in the NT-CB rotation. This work shows that the use of no-till and enhanced-efficiency N fertilizers can potentially reduce N 2O emissions from irrigated systems.
  • Authors:
    • Ochsner, T. E.
    • Venterea, R. T.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Quantifying N2O emissions from corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields under different fertilizer regimes is essential to developing national inventories of greenhouse gas emissions. The objective of this study was to compare N2O emissions in plots managed for more than 15 yr under continuous corn (C/C) vs. a corn-soybean (C/S) rotation that were fertilized during the corn phase with either anhydrous NH3 (AA) or urea (U). During three growing seasons, N2O emissions from corn following corn were nearly identical to corn following soybean. In both systems, however, N2O emissions with AA were twice the emissions with U. After accounting for N2O emissions during the soybean phase, it was estimated that a shift from C/S to C/C would result in an increase in annual emissions of 0.78 kg N ha-1 (equivalent to 0.11 Mg CO2-C ha-1) when AA was used, compared with only 0.21 kg N ha-1 (0.03 Mg CO2-C ha-1) with U. In light of trends toward increased use of U, these results suggest that fertilizer-induced soil N2O emissions may decline in the future, at least per unit of applied N, although further study is needed in different soils and cropping systems. While soil CO2 emissions were 20% higher under C/C, crop residue from the prior year did not affect soil inorganic N or dissolved organic C during the subsequent season. We also compared different flux-calculation schemes, including a new method for correcting chamber-induced errors, and found that selection of a calculation method altered N2O emissions estimates by as much as 35%.
  • Authors:
    • López-Bellido, L.
    • López-Bellido, F. J.
    • Fontán, J. M.
    • López-Bellido, R. J.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Our objective was to determine the effect of tillage system, crop rotation, and N fertilization on soil organic carbon (SOC) storage in the 0- to 90-cm profile in a long-term (20-yr) experiment established in 1986 on a rainfed Mediterranean Vertisol in southern Spain. The treatments studied were: conventional tillage (CT) vs. no-tillage (NT); five crop rotations: wheat (Triticum aestivum L.)-chickpea (Cicer arietinum L.) (WC), wheat-sunflower (Helianthus annuus L.) (WS), wheat-bare fallow (WF), wheat-faba-bean (Vicia faba L.) (WFB), and continuous wheat (WW); and N fertilizer applied at four rates (0, 50, 100, and 150 kg N ha(-1)). The SOC content of soil samples was determined in 1995,1997,2000,2003, and 2006 for four different soil layers (0-15, 15-30, 30-60, and 60-90 cm). The application of N fertilizer did not influence SOC sequestration. The other treatments showed a gradual increase of total SOC content over time, although there were no differences between some consecutive years. The SOC accumulation was higher for 30- to 60- and 60- to 90-cm depths than other depths due to characteristic cracks of Vertisol. Over the 20 yr of the study, WW and WFB sequestered 21 and 15 Mg C ha(-1) more under NT than under CT, respectively. The other crop rotations did not show any difference in C sequestration between NT and CT. Under CT, WS sequestered more SOC than other rotations, while under NT, WW and WFB sequestered more SOC. In general, the crop rotation intensification and NT had a positive effect over time on SOC sequestration in this rainfed Mediterranean Vertisol.
  • Authors:
    • Robertson, G. P.
    • Grace, P. R.
    • Bohm, S.
    • McSwiney, C. P.
  • Source: Journal of Natural Resources and Life Sciences Education
  • Volume: 39
  • Year: 2010
  • Summary: Opportunities for farmers to participate in greenhouse gas (GHG) credit markets require that growers, students, extension educators, offset aggregators, and other stakeholders understand the impact of agricultural practices on GHG emissions. The Farming Systems Greenhouse Gas Emissions Calculator, a web-based tool linked to the SOCRATES soil carbon process model, provides a simple introduction to the concepts and magnitudes of gas emissions associated with crop management. Users choose a county of interest on an introductory screen and are taken to the input/output window, where they choose crops, yields, tillage practices, or nitrogen fertilizer rates. Default values are provided based on convention and county averages. Outputs include major contributors of greenhouse gases in field crops: soil carbon change, nitrous oxide (N2O) emission, fuel use, and fertilizer. We contrast conventional tillage and no-till in a corn-soybean-wheat (Zea mays L.-Glycine max (L.) Merr.-Triticum aestivum L.) rotation and compare continuous corn fertilized at 101 and 134 kg N ha-1 yr-1. In corn years, N2O was the dominant GHG, due to high fertilizer requirements for corn. No-till management reduced greenhouse gas emissions by 50% due to net soil carbon storage. Continuous corn fertilized at 101 kg N ha-1 yr-1 emitted 1.25 Mg CO2 equivalents ha-1 yr-1 compared with 1.42 Mg CO2 equivalents ha-1 yr-1 at 134 kg N ha-1 yr-1, providing a 12% GHG savings. The calculator demonstrates how cropping systems and management choices affect greenhouse gas emissions in field crops.
  • Authors:
    • Franzluebbers,A. J.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Conservation management of degraded land has the potential to build soil fertility, restore soil functions, and mitigate greenhouse gas emissions as a consequence of surface soil organic matter accumulation. Literature from the southeastern United States was reviewed and synthesized to: (i) quantitatively evaluate the magnitude and rate of soil organic C (SOC) sequestration with conservation agricultural management; (ii) evaluate how conservation management affects surface SOC accumulation and its implications on ecosystem services; and (iii) recommend practical soil sampling strategies based on spatial and temporal issues to improve the detection of statistically significant SOC sequestration. Soil organic C sequestration was 0.45 ± 0.04 Mg C ha-1 yr-1 (mean ± standard error, n = 147, 20 ± 1 cm depth, 11 ± 1 yr) with conservation tillage compared with conventional tillage cropland. Establishment of perennial pastures sequestered 0.84 ± 0.11 Mg C ha-1 yr-1 (n = 35, 25 ± 2 cm depth, 17 ± 1 yr). Stratification of SOC with depth was common under conservation agricultural management and appears to be integrally linked to abatement of soil erosion, improvement in water quality, and SOC sequestration. Sampling of conservation management systems should ideally occur repeatedly with time in controlled and replicated experiments, but there is also an urgent need for chronosequence and paired-field surveys of SOC on working farms in the region to validate and expand the scope of inference of experimental results. Landowners in the southeastern United States have great potential to restore soil fertility and mitigate greenhouse gas emissions with the adoption of and improvement in conservation agricultural systems (e.g., continuous no-till, high-residue crop rotations, high organic matter inputs).
  • Authors:
    • Halvorson, A. D.
    • Archer, D. W.
  • Source: Soil Science Society of America Journal
  • Volume: 74
  • Issue: 2
  • Year: 2010
  • Summary: Recent soil and crop management technologies have potential for mitigating greenhouse gas emissions; however, these management strategies must be profitable if they are to be adopted by producers. The economic feasibility of reducing net greenhouse gas emissions in irrigated cropping systems was evaluated for 5 yr on a Fort Collins clay loam soil (a fine-loamy, mixed, superactive, mesic Aridic Haplustalf). Cropping systems included conventional tillage continuous corn (Zea mays L.) (CT-CC), no-till continuous corn (NT-CC), and no-till corn-bean (NT-CB) including 1 yr soybean [Glycine max (L.) Merr.] and 1 yr dry bean (Phaseolus vulgaris L.). The study included six N fertilization rates ranging from 0 to 246 kg ha-1. Results showed highest average net returns for NT-CB, exceeding net returns for NT-CC and CT-CC by US$182 and US$228 ha-1, respectively, at economically optimum N fertilizer rates. Net global warming potential (GWP) generally increased with increasing N fertilizer rate with the exception of NT-CC, where net GWP initially declined and then increased at higher N rates. Combining economic and net GWP measurements showed that producers have an economic incentive to switch from CT-CC to NT-CB, increasing annual average net returns by US$228 ha-1 while reducing annual net GWP by 929 kg CO2 equivalents ha-1. The greatest GWP reductions (1463 kg CO2 equivalents ha-1) could be achieved by switching from CT-CC to NT-CC while also increasing net returns, but the presence of a more profitable NT-CB alternative means NT-CC is unlikely to be chosen without additional economic incentives.
  • Authors:
    • Adamczewski, K.
    • Kaczmarek, S.
    • Matysiak, K.
  • Source: Acta Scientiarum Polonorum - Agricultura
  • Volume: 9
  • Issue: 4
  • Year: 2010
  • Summary: The aim of this study was to compare the herbicidal efficiency of mixture florasulam+2,4-D (Mustang 306 SE) in spring wheat cultivar Bryza, spring barley cultivar Antek and oat cultivar Cwa sown in monocrops and two-species mixtures. Field experiments were carried out in 2005-2007 at the Experimental Station in Winna Gora (5212′N; 1727′E), owned by the Institute of Plant Protection - National Research Institute in Poznan. Herbicyd Mustang 306 SE was applied in a dose of 0.5 dm 3.ha -1 at 3-5 leaf stage of cereals using the knapsack sprayer Gloria. The analysis of weed infestation of cereal stand was made with the quantitative-weighing method twice in the growing period (3-4 weeks after the application and 7-8 weeks after the application). Efficiency of herbicide action in mixtures was compared with its effectiveness in monocrops of individual species. From the analyses made it follows that of the cereal mixtures, the barley-oat mixture was infested in the least degree, and the wheat-oat mixture in the most degree. Strongest effect of cultivation in mixtures on reduction of weed infestation was noticeable on the control treatments, where the herbicide was not applied, whereas the cereal cultivation system (pure or mixed sowing) not always differentiated the herbicide efficiency. Cereal grain yields in mixtures after the application of mixture florasulam+2,4-D were significantly higher than yields of at least one of the component, and yields of mixtures harvested from the control treatments exceeded grain yields of both cereal species in monocrops.
  • Authors:
    • Chianu, J.
    • Kimetu, J.
    • Waswa, B.
    • Vanlauwe, B.
    • Kihara, J.
    • Bationo, A.
  • Source: Experimental Agriculture
  • Volume: 46
  • Issue: 1
  • Year: 2010
  • Summary: Many food production systems in sub-Saharan Africa are constrained by phosphorus (P).We hypothesized that within legume-cereal rotation systems: targeting P to the legume phase leads to higher system productivity, and that use of grain legumes leads to better economic returns than use of herbaceous legumes. Four P application regimes: (i) no P, (ii) P applied every season, (iii) P applied in season 1 only and (iv) P applied in season 2 only were tested for four seasons in three cropping systems (continuous maize, mucuna-maize rotation and soybean-maize rotation) in a split plot experiment set up in Nyabeda, western Kenya. Treatments where P was applied were better than no P treatments.While continuous cereal systems showed the need for application of P every second season, rotation systems involvingmucuna and soyabean indicated that application in one out of three seasons could be sufficient. Nitrogen fertilizer equivalence was 52 to >90 kg N ha -1 for soyabean and 37 to >90 kg N ha -1 for mucuna, depending on P fertilization and season. Analysis of marginal rates of return (MRR) showed that soybean-maize rotation with one application of P was the most economically viable option, with an MRR of at least 147% compared to other non-dominated options.
  • Authors:
    • Yifru, A.
    • Taye, B.
  • Source: World Journal of Agricultural Sciences
  • Volume: 6
  • Issue: 5
  • Year: 2010
  • Summary: A study to examine soil fertility status was conducted in the highlands of Southeast Ethiopia situated within latitude 0707′N and longitude 4010′E at altitude 2200 m to 2400 m above sea level. Twenty five farmers who are knowledgeable about soils of the area are purposively selected to provide insight into different soil fertility management practices. Local methods used to identify different soils and to assess the fertility status. Farmers used soil color, texture, water holding capacity, fertilizer requirement (inherent fertility) and workability as a criteria to identify different soil types. However, soil color and texture were commonly used by farmers to describe soil quality. Farmers preferred black and clay soils to white and sandy soils due to their high water holding capacity and inherent fertility. Besides, soil samples were randomly collected from the farmer's field under continuous cereal production systems. The study made up thirty-two sites and each site covered 400 m 2 sampling area. Composite samples of surface and subsurface soils were collected using special auger from three depths (0-10, 10-20, 20-30 cm). The laboratory analysis result indicated the soils are low in cation exchange capacity, low to medium in organic matter, slightly acidic to neutral, very high in base saturation, low to medium in exchangeable bases and moderate in both total nitrogen and available phosphorus. These soils are low to moderate in fertility that requires quite reasonable management. As a summary, the combined effect of both qualitative (local indicators of soil fertility) and quantitative (technical indicators of soil fertility) information would result in better assessment of soil fertility pattern and soil fertility management strategies to ensure food security program.
  • Authors:
    • Bidders, C. L.
    • Laloy, E.
  • Source: Journal of Environmental Quality
  • Volume: 39
  • Issue: 3
  • Year: 2010
  • Summary: The management of winter cover crops is likely to influence their performance in reducing runoff and erosion during the intercropping period that precedes spring crops but also during the subsequent spring crop This study investigated the impact of two dates of destruction and burial of a rye (Secale cereale L.) and ryegrass (Lolium multifloruni Lint) cover crop on runoff and erosion, focusing on a continuous silage maize (Zea mays L) cropping system Thirty erosion plots with various intercrop management options were monitored for 3 yr at two sues. During the intercropping period. cover crops reduced runoff and erosion by more than 94% compared with muffled, post-maize harvest plots Rough tillage after maize harvest proved equally effective as a late sown cover crop There was no effect of cover crop destruction and burial dates on runoff and erosion during the intercropping period. probably because rough tillage for cover crop burial compensates for the lack of soil cover During two of the monitored maize seasons. it was observed that plots that had been covered during the previous intercropping period lost 40 to 90% less soil compared with maize plots that had been left bare during the intercropping period The burial of an aboveground cover crop biomass in excess of 1 5 t ha (1) was a necessary, yet not always sufficient. condition to induce a residual effect. Because of the possible beneficial residual effect of cover crop burial on erosion reduction, the sowing of a cover crop should be preferred over rough tillage after maize harvest