• Authors:
    • Laurent, F.
    • Ruelland, D.
  • Source: Journal of Hydrology
  • Volume: 409
  • Issue: 1-2
  • Year: 2011
  • Summary: The SWAT model was used to model the impacts of climate, soils and agricultural practices on nitrate flows in a 1310 km 2 catchment in western France. Spatialized data were used for natural features (climate, soil, topography), while agricultural activities, finely represented by crop sequences over 3 years, and their associated cultural practices were mapped by remote sensing. The model was calibrated and validated for discharge and nitrate flows at a gauging station. Results are analyzed with respect to leaching for each crop sequence and for each soil type, as nitrate leaching is highly sensitive to the soil and the crop sequence. The lowest risks were found in clayey soils and the highest in sandy soils and/or in sequences including maize. In collaboration with local stakeholders, five scenarios of alternative practices were simulated to evaluate their consequences for nitrogen flows: reduced fertilization, catch crops, shallow cultivation, no-till with catch crops and filter strips. The impacts of the conversion of a pasture into wheat and rapeseed were also assessed. At the catchment gauging station, our 9-year simulations showed a reduction in nitrate flow of 8% with filters strips, 11% with catch crops, 12% with no-till with catch crops, and 15% with reduced fertilization. Shallow cultivation had no impact on nitrate flow. Inversely, the conversion of temporary pastures, which accounts for 32% of the catchment area, to cereals and rapeseed increased nitrate flow by 18%. The impacts of each scenario varied in accordance with leaching at the parcel scale and with the proportion of area affected by the practice. The results show that modelling can improve our understanding of the impacts of agricultural practices on water quality at different scales.
  • Authors:
    • Lewis, D. B.
    • Kaye, J. P.
    • Jabbour, R.
    • Barbercheck, M. E.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 26
  • Issue: 4
  • Year: 2011
  • Summary: Weed management is one of the primary challenges for producers transitioning from conventional to organic agriculture. Tillage and the use of cover crops are two weed control tactics available to farmers transitioning to organic management, but little is known about their interactive effects on soil quality during the transition period. We investigated the response of soils to tillage and initial cover crop during the 3-year transition to organic in a cover crop-soybean ( Glycine max)-maize ( Zea mays) rotation in the Mid-Atlantic region of the USA. The tillage treatment contrasted full, inversion tillage with moldboard plowing (FT) versus reduced tillage with chisel plowing (RT). The cover crop treatment contrasted annual versus mostly perennial species during the first year of the rotation. The experiment was initiated twice (Start 1 and Start 2), in consecutive years in adjacent fields. By the end of the experiment, labile carbon, electrical conductivity, pH and soil moisture were all greater under RT than under FT in both starts. Soil organic matter and several other soil attributes were greater under RT than under FT in Start 1, but not in Start 2, perhaps owing to differences between starts in initial field conditions and realized weather. Soil attributes did not differ between the two cover crop treatments. Combining our soils results with agronomic and economic analyses on these plots suggests that using RT during the organic transition can increase soil quality without compromising yield and profitability.
  • Authors:
    • Li, W.
    • He, R.
  • Source: Journal of Yunnan Agricultural University
  • Volume: 26
  • Issue: 4
  • Year: 2011
  • Summary: Jianghuai region is one of the major grain producing areas in China, where planting has high energy consumption. In addition, greenhouse gases displacement of planting is larger than ever, and the phenomenon of straw burned is extremely serious. To solve the problem, the multifunctional no-till wheat and paddy planter was designed with the technique of mechanized cultivation of energy-saving emission reduction. Combing with controlled traffic tillage and strip chopping anti-blocking mechanism, it could be used to returning corn stalks to the filed, fertilizing, seeding, covering and so on. The filed experiment indicates that the machine can decrease operating power consumption, and its steering ability is outstanding.
  • Authors:
    • Liesch, A. M.
    • Krueger, E. S.
    • Ochsner, T. E.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Soils under continuous corn (Zea mays L.) silage production are oft en subjected to heavy traffic and tillage, which can degrade soil structure and physical properties. Cover crops have been shown to benefit soil structure, but the effects of double-cropping on soil structure and physical properties are unknown. Our objective was to compare the soil structure and physical properties under rye (Secale cereale L.) and corn silage double-cropping with those under continuous corn silage in Minnesota during the 2007-2008 cropping year. A conventional tillage corn silage system served as the control. Double-crop treatments were conventional tillage winter rye harvested in May or June followed by no-till corn silage. Relative to the control, the double-cropping systems exhibited superior soil structure with up to 57% better visual soil structure scores and up to 16% smaller mean weight aggregate diameter. Visual soil structure scores exhibited seasonal dynamics with significant treatment effects in November and June but not in May when the structural assessment was conducted shortly after preplant tillage in the control. The double-cropping system increased the resilience of the soil to traffic. The saturated hydraulic conductivity in wheel-tracked interrows was 375% higher in the double-cropping system relative to the control in July. Both the rye and the absence of tillage before corn planting may have contributed to this improved resilience. Heavy traffic and tillage in continuous corn silage production systems can degrade soil structure and physical properties; however, the rye-corn silage double-cropping system provided a measure of protection.
  • Authors:
    • Liu, K.
    • Wiatrak, P.
  • Source: International Journal of Plant Production
  • Volume: 5
  • Issue: 4
  • Year: 2011
  • Summary: Nitrogen (N) application management needs to be refined for low yielding environments under dryland conditions. This 3-yr study examined nitrogen fertilization management effects on corn ( Zea mays L.) plant characteristics and grain yield in rain fed environment under conventional tillage system. Nitrogen fertilization management consisted of two timing methods of N application [all N at planting and as split with 35 kg N ha -1 applied at planting and remaining N applied at vegetative (V) 6 growth stage] and five N rates (0, 45, 90, 135, and 180 kg N ha -1). Insufficient rainfall at reproductive stage in 2008 and 2009 likely resulted in significant reduction of grain yield compared with grain yield in 2007, average 2.9 vs. 5.9 Mg ha -1. Grain yield increased with N application up to 45 kg ha -1; however, no further increase in N application resulted in increased yields. Plant height, ear height, relative chlorophyll (SPAD) content, and normalized difference vegetation index (NDVI) at reproductive (R 1) stage increased with increasing N rate up to 90, 90, 135, and 90 kg N ha -1, respectively. Corn grain yield significantly correlated with plant height at R 1, SPAD at V 8, NDVI and LAI at V 8 and R 1 stage. The combination of plant height, NDVI, and LAI of R 1 stage explained most of the variability of grain yield (r-square=0.71). The fertilization timing had no effect on corn grain yield and plant characteristics. These observations showed that applying more than 45 kg N ha -1 to corn under dryland conditions with insufficient rainfall, especially during corn pollination, may not significantly increase grain yields.
  • Authors:
    • Liu, K. S.
    • Wiatrak, P.
  • Source: American Journal of Agricultural and Biological Sciences
  • Volume: 6
  • Issue: 1
  • Year: 2011
  • Summary: Problem statement: Nitrogen application timing and Nitrogen (N) rate are two important factors to influence corn production in No-Tillage (NT) system, but N recommendations may need to be revised due to insufficient rainfall in dryland rain-fed environment. Approach: This study was to determine the effects of two N application timing (planting and split application at planting and V6 corn growth stage) and five N rates (0, 45, 90, 135 and 180 kg N ha -1) on corn plant characteristics and grain yield under rain-fed and low corn yield environment. Plant characteristics included the measurement of plant height, ear height, relative chlorophyll content (SPAD) and normalized Difference Vegetation Index (NDVI). Results: Plant height and ear height at R1 stage, SPAD at R1 and NDVI at V8 and R1 increased significantly with increasing N rates, while N application timing had no effect on measured canopy characteristics. Grain yield increased from 2.2-3.8 Mg ha -1 as N rate changed from 0-180 kg ha -1. However, applying more than 90 kg N ha -1 did not significantly increase grain yields. The N application timing did not influence yield. Strong correlations were observed among corn plant characteristics and between plant NDVI at V8 and R1 stages and grain yields. Conclusion: These results indicate that N application timing was not important factor to affect corn plant characteristics and grain yield under rain-fed and low corn yield dryland conditions and we may not expect a significant grain yield increase with application exceeding 90 kg N ha -1 under these conditions. Plant NDVI at V8 and R1 stage could be a good indicator to predict corn grain yield.
  • Authors:
    • Mchunu, C. N.
    • Lorentz, S.
    • Jewitt, G.
    • Manson, A.
    • Chaplot, V.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 4
  • Year: 2011
  • Summary: Although no-till (NT) is now practiced in many countries of the world, for most smallholders, the crop residues are of such a value that they cannot be left on the soil surfaces to promote soil protection, thus potentially limiting NT benefits and adoption. In this study our main objective was to evaluate runoff, soil, and soil organic carbon (SOC) losses from traditional small-scale maize ( Zea mays) field under conventional tillage (T) and NT, with crop residues cover of less than 10% during the rainy season, in South Africa. Six runoff plots of 22.5 m 2 (2.25*10 m) under NT and T since 2002 were considered. At each plot, soil bulk density (rho b) and SOC content of the 0-0.02 m layer were estimated at nine pits. Top-soil SOC stocks were 26% higher under NT than under T ( P=0.001). The NT reduced soil losses by 68% (96.8 vs. 301.5 g m -2 yr -1, P=0.001) and SOC losses by 52% (7.7 vs. 16.2 g C m -2 yr -1, P=0.001), and differences in runoff were not significant. Dissolved organic carbon accounted for about 10% of total SOC losses and showed significantly higher concentrations under T than NT (1.49 versus 0.86 mg C m -2 yr -1). The less erosion in NT compared to T was explained by a greater occurrence under NT of indurated crusts, less prone to soil losses. These results showed the potential of NT even with low crop residue cover (<10%) to significantly reduce soil and SOC losses by water under small-scale agriculture.
  • Authors:
    • Figueiredo, G. C.
    • Medeiros, J. C.
    • Giarola, N. F. B.
    • Fracetto, F. J. C.
    • Silva, A. P. da
    • Cerri, C. E. P.
  • Source: Plant Soil
  • Volume: 338
  • Issue: 1-2
  • Year: 2011
  • Summary: The decomposition rate of soil organic matter (SOM) is affected by soil management practices and particularly by the physical and hydraulic attributes of the soil. Previous studies have indicated that the SOM decomposition is influenced by the Least Limiting Water Range (LLWR). Therefore, the objective of this study was to relate the C-CO 2 emissions to the LLWR of the surficial layer of soil under two management systems: no-tillage (NT), conducted for 20 years, and conventional tillage (CT). Soil in NT presented greater soil organic carbon (SOC) stocks than in CT. Emissions of C-CO 2 were greater in the NT than in the CT, because of the greater carbon stocks in the soil surface layer and the greater biological activity (due to the improvement of the soil structure) in NT as compared to CT. The use of LLWR associated with the measurement of C-CO 2 emissions from the soil could help to predict the efficacy of the adopted management system for trapping carbon in the soil.
  • Authors:
    • Ziadi, N.
    • Angers, D. A.
    • Morel, C.
    • Parent, L. E.
    • Messiga, A. J.
  • Source: Geoderma
  • Volume: 164
  • Issue: 3-4
  • Year: 2011
  • Summary: Under long-term cultivation, greater accumulations of soil organic matter (SOM) and phosphorus (P) are found in the surface soil layer under no-till (NT) versus mouldboard ploughing (MP) practices. Our objective was to evaluate the effects of NT and MP practices on concomitant SOM and P distribution and sorption characteristics among water-stable aggregates and non-aggregated particles. The study was conducted in Quebec, Canada, as part of a long-term corn and soybean rotation experiment (established since 1992) on a clay loam soil of the St-Blaise series (Dark Grey Gleysol). Soil samples were collected in the fall of 2007 in the 0-5 cm layer from plots under NT and MP receiving 35 kg P ha -1 and 160 kg N ha -1. Samples were separated into three water-stable aggregate-sized classes (macro, 2000-250 m; meso, 250-180 m; micro, 180-53 m) and (silt+clay)-sized particles (<53 m) using wet-sieving. Macro aggregates made up 60.2 and 48.5% of total soil weight under NT and MP, respectively. In wet-sieved soils from NT plots, water-extractable P (Pw) concentration increased in the order (silt+clay)-sized particles < micro- < meso- < macro-aggregates; under MP, micro-, meso-, and macro-aggregate fractions had the same Pw concentration, while the (silt+clay)-sized particles showed the lowest Pw concentration. The hierarchy observed among aggregate-sized classes under NT in relation to Pw concentration was also observed for carbon content, indicating that Pw is influenced by soil aggregation as driven by SOM accumulation. The lower Pw concentration in (silt+clay)-sized particles could be explained by a greater retention of P by reactive oxides and highly disordered alumino-silicates present on (silt+clay)-sized particles, thereby reducing the soluble P released from these particles. One important aspect of this study is the contrasting P sorption characteristics of solid particles under NT and MP. The P sorption maxima (S max value) of the (silt+clay)-sized particles was twice that of the water-stable aggregates. Sorption characteristics reflect the hierarchy observed under NT for organic C and Pw, indicating a closer link between SOM and P dynamics within soil aggregates in contrast with MP.
  • Authors:
    • Cirilo, A. G.
    • Otegui, M. E.
    • Munaro, E. M.
    • D'Andrea, K. E.
    • Eyherabide, G. H.
  • Source: Crop Science
  • Volume: 51
  • Issue: 3
  • Year: 2011
  • Summary: Maize ( Zea mays L.) hybrid vigor for plant grain yield (PGY) is associated with heterosis for plant biomass at maturity (aboveground biomass at physiological maturity [Biomass PM]), kernel number per plant (KNP), and harvest index (HI); however, no evidence of the effects of nitrogen (N) availability or combination of abiotic stresses on heterosis for physiological components of PGY has been reported. The objective of this study was to determine the response of heterosis for ecophysiological traits related to PGY at contrasting N supply levels in a set of six inbred lines and 12 derived hybrids. Field experiments were conducted in five growing seasons at low nitrogen (LN; no N added) and high nitrogen (HN) supply (200 or 400 kg N ha -1) under irrigation and dryland farming. Increased PGY (65% for hybrids and 30% for inbreds) was ascribed to similar increase in Biomass PM as no increase in HI was found. Heterosis for PGY was higher under HN (137%) than LN (87%). A similar response was observed for traits related to light capture and biomass accumulation. Heterosis for HI did not differ between HN (31%) and LN (28%). Heterosis for PGY was associated ( p<0.01) with heterosis for KNP, Biomass PM, radiation use efficiency (RUE) during grain filling, HI, and traits related to maximum light capture. Heterosis for PGY at LN was also correlated with heterosis for RUE at critical period (i.e., 30 d bracketing silking) and kernel weight. Under the combined effect of N and drought, PGY heterosis was reduced and more affected at HN (59%) than at LN (70%).