• Authors:
    • Alves, M. C.
    • Arf, O.
    • Silva, M. G. da
    • Buzetti, S.
  • Source: Bragantia
  • Volume: 67
  • Issue: 2
  • Year: 2008
  • Summary: The soil physical properties are influenced by different soil tillage as well as by crop rotation. Field studies were conducted in Selviria, Mato Grosso do Sul, Brazil, in 2003/04, to evaluate the shoot dry matter production, soil covering percentage and the influence of crop rotation and tillage system on soil physical properties of a Rhodic Hapludox and to evaluate irrigated winter common bean yield. The treatments consisted of soil tillage systems (heavy harrow, chisel plough and no-tillage) and 6 rotations sown in the summer (maize, maize + black velvet bean, maize + brachiaria grass, soyabean, rice and sunn hemp). The crop rotations that presented larger soil coverage and shoot dry matter production were sunn hemp, maize + black velvet bean, maize + braquiaria grass and maize. No-tillage resulted in larger values of penetration resistance at 0.00-0.10 m layer. Except for macroporosity at the 0-0,1 m layer, the properties humidity, macroporosity, microporosity and total porosity of soil were not influenced by soil tillage systems. Despite differences in some yield components of common bean due to certain soil tillage or crop succession, the irrigated winter common bean crop yield was not affected.
  • Authors:
    • Suzuki, L. G. A. S.
    • Alves, M. C.
    • Suzuki, L. E. A. S.
    • Rodrigues, R. A. F.
  • Source: Científica, Jaboticabal
  • Volume: 36
  • Issue: 2
  • Year: 2008
  • Summary: The objective of this study was to verify the biomass yield potential of different cover crops in a Cerrado region, in Selviria, Mato Grosso do Sul, Brazil. The work was conducted in the Experimental University Farm of the Paulista State University (UNESP). The experimental design was the randomized complete blocks in strips with splitsplit plot: the plots were the cover crops Mucuna aterrima, Pennisetum americanum, Crotalaria juncea, Cajanus cajan and a fallow area; the split plots were the no-tillage and the conventional tillage, and the splitsplit plots were corn ( Zea mays L.), soybean ( Glycine max (L.) Merrill), and cotton ( Gossypium hirsutum L.) crops. In the winter irrigated Phaseolus vulgaris L. was the crop. In the spring/summer season the cover crop with the greatest biomass yield was Pennisetum americanum. Crotalaria juncea and the fallow area showed medium results while Mucuna aterrima and Cajanus cajan were those with the least yields. Pennisetum americanum was the crop cover with the biggest production potential of dry biomass. The cultivation systems did not influence the dry biomass of the cover crops. Only Pennisetum americanum production was influenced by crop sequence.
  • Authors:
    • Wilhelm, W. W.
    • Varvel, G. E.
  • Source: Agronomy Journal
  • Volume: 100
  • Issue: 4
  • Year: 2008
  • Summary: Proposals promoting the use of massive amounts of crop residues and other lignocellulosic biomass for biofuel production have increased the need for evaluation of the sustainability of cropping practices and their effect on environment quality. Our objective was to evaluate the effects of crop rotation and N fertilizer management and their stover production characteristics on soil organic carbon (SOC) levels in a long-term high-yielding irrigated study in the western Corn Belt. An irrigated monoculture corn ( Zea mays L.), monoculture soybean [ Glycine max (L.) Merr.], and soybean-corn cropping systems study was initiated in 1991 on a uniform site in the Platte Valley near Shelton, NE. Soil samples were collected in 1991 before initiation of the study and in the spring of 2005 and analyzed for SOC. Significant differences in total SOC values were obtained between rotations and N rates at the 0- to 7.5- and 0- to 15-cm depths in 2005 and all total SOC values were equal to or greater than SOC values obtained in 1991. Residue production was greater than 6 Mg ha -1, a level that appears to be sufficient to maintain SOC levels, in all systems. Can residue amounts above this level be harvested sustainably for biofuel production in cropping systems similar to these? Though these results suggest that a portion of corn stover could be harvested without reducing SOC under the conditions of this investigation, the direct impact of stover removal remains to be evaluated.
  • Authors:
    • Egli, D. B.
  • Source: Field Crops Research
  • Volume: 106
  • Issue: 1
  • Year: 2008
  • Summary: The increases in crop yield that played an important role in maintaining adequate food supplies in the past may not continue in the future. Soybean ( Glycine max L. Merrill) county yield trends (1972-2003) were examined for evidence of plateaus using data (National Agricultural Statistics Service) for 162 counties (215 data sets) in six production systems [Iowa, Nebraska (irrigated and non-irrigated), Kentucky and Arkansas (irrigated and non-irrigated)] representing a range in yield potential. Average yield (1999-2003) was highest in irrigated production in Nebraska (3403 kg ha -1) and lowest in non-irrigated areas in Arkansas (1482 kg ha -1). Average yield in the highest yielding county in each system was 31-88% higher than the lowest. Linear regression of yield versus time was significant ( P=0.05) in 169 data sets and a linear-plateau model reached convergence (with the intersection point in the mid-1990s) in 35 of these data sets, but it was significantly ( P=0.10) better in only three data sets (
  • Authors:
    • Graef, G. L.
    • Elmore, R. W.
    • Cassman, K. G.
    • Dobermann, A.
    • Setiyono, T. D.
    • Bastidas, A. M.
    • Specht, J . E.
  • Source: Crop Science
  • Volume: 48
  • Issue: 2
  • Year: 2008
  • Summary: The sensitivity of soybean [ Glycine max (L.) Merr.] main stem node accrual to ambient temperature has been documented in greenhouse-grown plants but not with field-grown plants in the north-central United States. Biweekly V-node and R-stage, stem node number, internode length, and other traits were quantified in an irrigated split-plot, four-replicate, randomized complete block experiment conducted in Lincoln, NE, in 2003-2004. Main plots were early-, mid-, late-May, and mid-June sowing dates. Subplots were 14 cultivars of maturity groups 3.0 to 3.9. Node appearance was surprisingly linear from V1 to R5, despite the large increase in daily temperature from early May (10-15degreesC) to July (20-25degreesC). The 2003 and 2004 May planting date regressions exhibited near-identical slopes of 0.27 node d -1 (i.e., one node every 3.7 d). Cold-induced delays in germination and emergence did delay the V1 date (relative to planting date), so the primary effect of temperature was the V1 start date of linearity in node appearance. With one exception, earlier sowings led to more nodes (earlier V1 start dates) but also resulted in shorter internodes at nodes 3 to 9 (cooler coincident temperatures), thereby generating a curved response of plant height to delayed plantings. Delaying planting after 1 May led to significant linear seed yield declines of 17 kg ha -1 d -1 in 2003 and 43 kg ha -1 d -1 in 2004, denoting the importance of early planting for capturing the yield potential available in soybean production, when moisture supply is not limiting.
  • Authors:
    • McMahon,Thomas A.
    • Kiem,Anthony S.
    • Peel,Murray C.
    • Jordan,Phillip W.
    • Pegram,Geoffrey G. S.
  • Source: Journal of Hydrometeorology
  • Volume: 9
  • Issue: 6
  • Year: 2008
  • Summary: This paper introduces a new approach to stochastically generating rainfall sequences that can take into account natural climate phenomena, such as the El Nino-Southern Oscillation and the interdecadal Pacific oscillation. The approach is also amenable to modeling projected affects of anthropogenic climate change. The method uses a relatively new technique, empirical mode decomposition (EMD), to decompose a historical rainfall series into several independent time series that have different average periods and amplitudes. These time series are then recombined to form an intradecadal time series and an interdecadal time series. After separate stochastic generation of these two series, because they are independent, they can be recombined by summation to form a replicate equivalent to the historical data. The approach was applied to generate 6-monthly rainfall totals for six rainfall stations located near Canberra, Australia. The cross correlations were preserved by carrying out the stochastic analysis using the Matalas multisite model. The results were compared with those obtained using a traditional autoregressive lag-one [AR(1)], and it was found that the new EMD stochastic model performed satisfactorily. The new approach is able to realistically reproduce multiyear-multidecadal dry and wet epochs that are characteristic of Australia's climate and are not satisfactorily modeled using traditional stochastic rainfall generation methods. The method has two advantages over the traditional AR(1) approach, namely, that it can simulate nonstationarity characteristics in the historical time series, and it is easy to alter the decomposed time series components to examine the impact of anthropogenic climate change.
  • Authors:
    • Payero, J. O.
    • Schneekloth, J. P.
    • Klocke, N. L.
  • Source: Transactions of the ASABE
  • Volume: 50
  • Issue: 6
  • Year: 2007
  • Summary: Dwindling water supplies for irrigation are prompting alternative management choices by irrigators. Limited irrigation, where less water is applied than full crop demand, may be a viable approach. Application of limited irrigation to maize ( Zea mays) was examined in a study conducted at the West Central Research and Extension Centre of the University of Nebraska-Lincoln at North Platte, Nebraska, USA. Maize was grown in crop rotations with dryland, limited irrigation, or full irrigation management from 1985 to 1999. Crop rotations included maize following maize (continuous maize), maize following wheat ( Triticum aestivum), followed by soyabean ( Glycine max) (wheat-maize-soyabean), and maize following soyabean (maize-soyabean). Full irrigation was managed to meet crop evapotranspiration requirements (ETc). Limited irrigation was managed with a seasonal target of no more than 150 mm applied. Precipitation patterns influenced the outcomes of measured parameters. Dryland yields had the most variation, while fully irrigated yields varied the least. Limited irrigation yields were 80 to 90% of fully irrigated yields, but the limited irrigation plots received about half the applied water. Grain yields were significantly different among irrigation treatments. Yields were not significantly different among rotation treatments for all years and water treatments. For soil water parameters, more statistical differences were detected among the water management treatments than among the crop rotation treatments. Economic projections of these management practices showed that full irrigation produced the most income if water was available. Limited irrigation increased income significantly from dryland management.
  • Authors:
    • Lal,R.
  • Source: Mitigation and Adaptation Strategies for Global Change
  • Volume: 12
  • Issue: 2
  • Year: 2007
  • Summary: World soils have been a major source of enrichment of atmospheric concentration of CO 2 ever since the dawn of settled agriculture, about 10 000 years ago. Historic emission of soil C is estimated at 7812 Pg out of the total terrestrial emission of 13655 Pg, and post-industrial fossil fuel emission of 27030 Pg. Most soils in agricultural ecosystems have lost 50 to 75% of their antecedent soil C pool, with the magnitude of loss ranging from 30 to 60 Mg C/ha. The depletion of soil organic carbon (SOC) pool is exacerbated by soil drainage, plowing, removal of crop residue, biomass burning, subsistence or low-input agriculture, and soil degradation by erosion and other processes. The magnitude of soil C depletion is high in coarse-textured soils (e.g., sandy texture, excessive internal drainage, low activity clays and poor aggregation), prone to soil erosion and other degradative processes. Thus, most agricultural soils contain soil C pool below their ecological potential. Adoption of recommend management practices (e.g., no-till farming with crop residue mulch, incorporation of forages in the rotation cycle, maintaining a positive nutrient balance, use of manure and other biosolids), conversion of agriculturally marginal soils to a perennial land use, and restoration of degraded soils and wetlands can enhance the SOC pool. Cultivation of peatlands and harvesting of peatland moss must be strongly discouraged, and restoration of degraded soils and ecosystems encouraged especially in developing countries. The rate of SOC sequestration is 300 to 500 Kg C/ha/yr under intensive agricultural practices, and 0.8 to 1.0 Mg/ha/yr through restoration of wetlands. In soils with severe depletion of SOC pool, the rate of SOC sequestration with adoption of restorative measures which add a considerable amount of biomass to the soil, and irrigated farming may be 1.0 to 1.5 Mg/ha/yr. Principal mechanisms of soil C sequestration include aggregation, high humification rate of biosolids applied to soil, deep transfer into the sub-soil horizons, formation of secondary carbonates and leaching of bicarbonates into the ground water. The rate of formation of secondary carbonates may be 10 to 15 Kg/ha/yr, and the rate of leaching of bicarbonates with good quality irrigation water may be 0.25 to 1.0 Mg C/ha/yr. The global potential of soil C sequestration is 0.6 to 1.2 Pg C/yr which can off-set about 15% of the fossil fuel emissions.
  • Authors:
    • Zhang,X. C.
    • Liu,W. Z.
  • Source: Field Crops Research
  • Volume: 100
  • Issue: 2-3
  • Year: 2007
  • Summary: Matching fertilizer rates with available water supplies in water-scarce environments remains a major challenge for improving water use efficiency and crop yield. The objectives are to (i) develop a new approach to characterizing interrelations of yield ( Y), evapotranspiration (ET), water use efficiency (WUE), and soil fertility using an elasticity index, and (ii) to further derive optimal-coupling domains of water and fertilizer inputs using maize data of 1997 and 1998, as an example. The experiment was an incomplete factorial design with two factors (water supply and fertilizer input) with five levels each, and had a total of 13 treatments with three replicates each. A maize cultivar (Zhongdan 2, Zea mays L.) was grown in a loessial silt loam in the hilly region of the Loess Plateau of China. Irrigation was hand applied at predetermined amounts as needed, and fertilizers including nitrogen, phosphate, and yard manure were applied at planting and jointing at predetermined rates. Approaches on how to use the crop-water production function and elasticity index (EI) to characterize the interrelations of Y, ET, and WUE were presented, and further extended to derive the optimal-coupling domains of water and fertilizer inputs. Yield responses to water and fertilizer inputs followed a quadratic function with a positive interactive term. When constrained by local maximum yields, the optimal-coupling domain took a half-ellipse form with the global maximum WUE and Y (or maximum ET) corresponding to the left and right end points on its long axis. As water supply increased, WUE reached its maximum before yield did. If water supply is limiting, fertilizer rates that maximize WUE rather than yield should be used; otherwise, seeking maximum yield may be desirable. For irrigation management, total water supply to maize should not exceed 550 mm in the region. Furthermore, the optimal domain can be used to determine optimal fertilizer rates for any given water supply, which may be estimated from seasonal climate forecasts in the case of dryland farming or based on available water supply for future irrigation. For a given water supply, fertilizer rates should be between the rate of reaching local maximum WUE and the rate of reaching local maximum yield.
  • Authors:
    • Chen, D.
    • Kelly, K.
    • Li, Y.
  • Source: ASA-CSSA-SSSA International Annual Meetings (November 4-8, 2007)
  • Year: 2007