• Authors:
    • Corbeels, M.
    • Rufino, M. C.
    • Nyamangara, J.
    • Giller, K. E.
    • Rusinamhodzi, L.
    • van Wijk, M. T.
  • Source: Agronomy for Sustainable Development
  • Volume: 31
  • Issue: 4
  • Year: 2011
  • Summary: Conservation agriculture involves reduced tillage, permanent soil cover and crop rotations to enhance soil fertility and to supply food from a dwindling land resource. Recently, conservation agriculture has been promoted in Southern Africa, mainly for maize-based farming systems. However, maize yields under rain-fed conditions are often variable. There is therefore a need to identify factors that influence crop yield under conservation agriculture and rain-fed conditions. Here, we studied maize grain yield data from experiments lasting 5 years and more under rain-fed conditions. We assessed the effect of long-term tillage and residue retention on maize grain yield under contrasting soil textures, nitrogen input and climate. Yield variability was measured by stability analysis. Our results show an increase in maize yield over time with conservation agriculture practices that include rotation and high input use in low rainfall areas. But we observed no difference in system stability under those conditions. We observed a strong relationship between maize grain yield and annual rainfall. Our meta-analysis gave the following findings: (1) 92% of the data show that mulch cover in high rainfall areas leads to lower yields due to waterlogging; (2) 85% of data show that soil texture is important in the temporal development of conservation agriculture effects, improved yields are likely on well-drained soils; (3) 73% of the data show that conservation agriculture practices require high inputs especially N for improved yield; (4) 63% of data show that increased yields are obtained with rotation but calculations often do not include the variations in rainfall within and between seasons; (5) 56% of the data show that reduced tillage with no mulch cover leads to lower yields in semi-arid areas; and (6) when adequate fertiliser is available, rainfall is the most important determinant of yield in southern Africa. It is clear from our results that conservation agriculture needs to be targeted and adapted to specific biophysical conditions for improved impact.
  • Authors:
    • Shipitalo, M. J.
    • Owens, L. B.
  • Source: Journal of Environmental Quality
  • Volume: 40
  • Issue: 4
  • Year: 2011
  • Summary: Residual herbicides regularly used in conjunction with conservation tillage to produce corn ( Zea mays L.) and soybean [ Glycine max (L.) Merr] are often detected in surface water at concentrations that exceed their U.S. maximum contaminant levels (MCL) and ecological standards. These risks might be reduced by planting glyphosate-tolerant varieties of these crops and totally or partially replacing the residual herbicides alachlor, atrazine, linuron, and metribuzin with glyphosate, a contact herbicide that has a short half-life and is strongly sorbed to soil. Therefore, we applied both herbicide types at typical rates and times to two chisel-plowed and two no-till watersheds in a 2-yr corn/soybean rotation and at half rates to three disked watersheds in a 3-yr corn/soybean/wheat-red clover ( Triticum aestivum L.- Trifolium pratense L.) rotation and monitored herbicide losses in surface runoff for three crop years. Average dissolved glyphosate loss for all tillage practices, as a percentage of the amount applied, was significantly less ( P≤0.05) than the losses of atrazine (21.4*), alachlor (3.5*), and linuron (8.7*) in corn-crop years. Annual, flow-weighted, concentration of atrazine was as high as 41.3 g L -1, much greater than its 3 g L -1 MCL. Likewise, annual, flow-weighted alachlor concentration (MCL=2 g L -1) was as high as 11.2 and 4.9 g L -1 in corn- and soybean-crop years, respectively. In only one runoff event during the 18 watershed-years it was applied did glyphosate concentration exceed its 700 g L -1 MCL and the highest, annual, flow-weighted concentration was 3.9 g L -1. Planting glyphosate-tolerant corn and soybean and using glyphosate in lieu of some residual herbicides should reduce the impact of the production of these crops on surface water quality.
  • Authors:
    • Mahapatra, B. S.
    • Saini, S. K.
    • Shweta
    • Singh, R. K.
  • Source: Indian Journal of Agricultural Sciences
  • Volume: 81
  • Issue: 2
  • Year: 2011
  • Summary: To ameliorate the ill effects of traditional rice-wheat cropping system efforts have been made to develop several resource conservation technologies. Conventional method of wheat sowing requires intensive pre-planting cultivation, which are labour, time and energy intensive. The field experiment was conducted at Govind Ballabh Pant University of Agriculture and Technology, Pantnagar during rainy season of 2005-06 to winter season of 2006-07. Maximum mean grain (4 237 kg/ha) and straw (6 235 kg/ha) yields of wheat were obtained from direct-seeded rice plots. Nutrient uptake (NPK) by the wheat crop was highest under direct-seeded rice due to rice establishment methods. Maximum mean grain (4 535 kg/ha) and straw (6 423 kg/ha) yields were obtained under zero till. The mean wheat grains/spike under zero till drill wheat was 0.79, 6.93 and 4.09% more than that of strip till drill, bed planted and conventional wheat, respectively. Zero till drill wheat exhibited significantly higher nutrient uptake than that of conventional, bed planted and strip till drill wheat.
  • Authors:
    • Lal, R.
    • Stavi, I.
  • Source: Geomorphology
  • Volume: 125
  • Issue: 1
  • Year: 2011
  • Summary: Erosion and deposition processes affect the physical quality of the soil. Thus, the objective of this study was to assess the effects of these processes on a long-term no-till corn agroecosystem in a humid-temperate region of the Midwest U.S. The study was conducted under on-farm conditions, in a field which experiences erosional and depositional processes. At the end of the dormant season, soil characteristics were tested for two depths (0-5 and 5-10 cm) in uneroded (UN), eroded (ER), and depositional (DP) sites. The data showed that UN and ER were characterized by the highest and lowest soil shear strength (137.3 and 78.1 KPa, respectively) and organic carbon concentration (35.6 and 30.3 g kg -1, respectively). The highest and lowest aggregate stability (85.4% and 73.6%, respectively) and mean weight diameter (2.9 and 1.6 mm, respectively) were observed in UN and DP. The highest and lowest penetration resistance (4.82 and 4.57 MPa, respectively) and bulk density (1.49 and 1.33 Mg m -3, respectively) were measured in ER and DP. An opposite trend was observed for the C:N ratio (8.2 and 9.6, respectively), and the value's color variable (4.6 and 4.9, respectively). No significant differences among the erosional phases were measured in the soil's total nitrogen concentration, hue and chroma color variables, texture, hydraulic conductivity, and intrinsic permeability. The erodibility factor was the lowest and highest in DP and ER (0.00326 and 0.00397 Mg ha h ha -1 MJ -1 mm -1, respectively), and the effect of erosional phase on this factor was close to significant. In general, the effect of erosion and deposition on soil characteristics decreased with an increase in soil depth. This study suggests that the occurrence of positive feedbacks in ER and DP have led to accelerated erosional and depositional processes and the continuous degradation of the soil quality. A range of management practices should be considered in order to mitigate these processes and reduce negative impact on crop yields in such agroecosystems.
  • Authors:
    • Wilhelm, W. W.
    • Varvel, G. E.
  • Source: Soil & Tillage Research
  • Volume: 114
  • Issue: 1
  • Year: 2011
  • Summary: Emphasis and interest in carbon (C) and nitrogen (N) storage (sequestration) in soils has greatly increased in the last few years, especially C with its' potential to help alleviate or offset some of the negative effects of the increase in greenhouse gases in the atmosphere. Several questions still exist with regard to what management practices optimize C storage in the soil profile. A long-term rainfed study conducted in eastern Nebraska provided the opportunity to determine both the effects of different tillage treatments and cropping systems on soil N and soil organic C (SOC) levels throughout the soil profile. The study included six primary tillage systems (chisel, disk, plow, no-till, ridge-till, and subtill) with three cropping systems [continuous corn (CC), continuous soybean (CSB), and soybean-corn (SB-C)]. Soil samples were collected to a depth of 150-cm in depth increments of 0-15-, 15-30-, 15-30-, 30-60-, 60-90-, 90-120-, and 120-150-cm increments and composited by depth in the fall of 1999 after harvest and analyzed for total N and SOC. Significant differences in total N and SOC levels were obtained between tillage treatments and cropping systems in both surface depths of 0-15-, 15-30-cm, but also in the 30-60-cm depth. Total N and SOC accumulations throughout the profile (both calculated by depth and for equivalent masses of soil) were significantly affected by both tillage treatment and cropping system, with those in no-till the greatest among tillage treatments and those in CC the greatest among cropping systems. Soil N and SOC levels were increased at deeper depths in the profile, especially in those tillage systems with the least amount of soil disturbance. Most significant was the fact that soil N and SOC was sequestered deeper in the profile, which would strongly suggest that N and C at these depths would be less likely to be lost if the soil was tilled.
  • Authors:
    • Holan, S. H.
    • Goyne, K. W.
    • Veum, K. S.
    • Motavalli, P. P.
  • Source: Geoderma
  • Volume: 167-168
  • Year: 2011
  • Summary: Conservation management practices including upland vegetative filter strips (VFS) and no-till cultivation have the potential to enhance soil carbon sequestration and other ecosystem services in agroecosystems. A modified two-factor analysis of variance (ANOVA) with subsamples was used to compare SOC and TN on a concentration, soil volume and soil mass basis in claypan soils planted to different conservation management practices and as a function of landscape position. The three conservation management practices (no-till cultivation, grass VFS and agroforestry VFS) and four landscape positions (summit, shoulder, backslope and footslope) investigated were compared 10 years after VFS establishment in a no-till system planted to maize ( Zea mays. L.)-soybean ( Glycine max (L.) Merr.) rotation. Two soil depth increments (0-5 cm and 5-13 cm) were modeled separately to test for treatment effects. In the surface layer, mean SOC concentration was significantly greater in the VFS soils compared to no-till. On a soil volume or mass basis, no significant differences in SOC stocks were found among treatment means. Concentration and mass based TN values were significantly greater in the grass VFS relative to no-till in the surface layer. A rapid slaking stability test, developed to separate particulate, adsorbed and occluded organic carbon (PAO-C) and nitrogen (PAO-N), showed that VFS soils had significantly greater mean PAO-C and PAO-N concentrations, soil volume and soil mass based stocks than no-till. In addition, comparison of SOC:TN and PAO-C:PAO-N ratios suggest reduced decomposition and mineralization of SOC in the PAO fraction. No significant treatment effects were detected in total or PAO soil fractions in the subsurface layer or among landscape position in either depth increment. Study results emphasize the need to compare soil carbon and nitrogen stocks on a soil volume and/or soil mass basis using bulk density measurements. Additionally, the rapid PAO separation technique was found to be a good indicator of early changes in SOC and TN in the systems studied. Overall, this research indicates that grass VFS may sequester TN more rapidly than agroforestry VFS and that a greater proportion of SOC and TN may be stabilized in VFS soils compared to no-till.
  • Authors:
    • Edwards, J.
    • Godsey, C.
    • Vitale, J. D.
    • Taylor, R.
  • Source: Journal of Soil and Water Conservation
  • Volume: 66
  • Issue: 4
  • Year: 2011
  • Summary: Conservation tillage had initial roots in the Great Plains, but the current adoption of conservation tillage, especially no-till, lags behind in the rest of the United States. This paper documents the results of a recent survey of Oklahoma producers, which was conducted to assess the current status of conservation tillage in the state. Based on responses from 1,703 producers, econometric analysis was conducted to identify factors explaining the observed use of conservation tillage practices in Oklahoma. The survey found that conventional tillage remains the most common tillage practice among Oklahoma producers. According to the survey, conventional tillage is used on 43.2% of the state's total acreage, conservation tillage on 26.7% of the total acreage, and reduced tillage on the remaining 30.1% of the crop acreage. A Tobit model was developed to explain patterns of tillage use based on producer characteristics and their perceptions on how conservation tillage performs relative to conventional tillage according to various economic and agronomic factors. The Tobit model identified operator age, farm size, crop rotation, knowledge, and erosion control as highly significant factors explaining the observed use of conservation tillage. The model results also identified potential constraints to conservation tillage adoption and use in the Southern Plains, suggesting that the unique needs of mixed crop-livestock farming systems, and the dominant winter wheat ( Triticum aestivum L.) monoculture, hinder further diffusion of conservation tillage. Future policy should consider addressing the needs of Oklahoma producers, particularly crop producers heavily engaged in livestock activities, as well as finding viable rotation crops to provide alternatives for the winter wheat monoculture.
  • Authors:
    • Wu, Z. J.
    • Zhu, A. N.
    • Chen, L. J.
    • Chen, Z. H.
    • Wang, J. B.
  • Source: Plant, Soil and Environment
  • Volume: 57
  • Issue: 6
  • Year: 2011
  • Summary: The effects of tillage and residue input amounts on soil phosphatase (alkaline phosphomonoesterase ALP, acid phosphomonoesterase ACP, phosphodiesterase PD, and inorganic pyrophosphatase IPP) activities and soil phosphorus (P) forms (total P, organic P, and available P) were evaluated using soils collected from a three-year experiment. The results showed that no-till increased soil total and organic P, but not available P as compared to conventional tillage treatments. Total P was increased as inputs of crop residue increased for no-till treatment. There were higher ALP and IPP activities in no-till treatments, while higher PD activity was found in tillage treatments and tillage had no significant effect on ACP activity. Overall phosphatase activities increased with an increase of crop residue amounts. Soil total P was correlated negatively with PD activity and positively with other phosphatase activities. Organic P had a positive correlation with ACP activity, but a negative correlation with PD activity. Available P had no significant correlation with phosphatase activities. Our data suggests that no-till and residue input could increase soil P contents and enhance the activities of phosphatase.
  • Authors:
    • Miller, P.
    • Lawrence, R. L.
    • Watts, J. D.
    • Montagne, C.
  • Source: Climactic Change
  • Volume: 108
  • Issue: 1/2
  • Year: 2011
  • Summary: A pilot cropland carbon sequestration program within north central Montana has allowed farmers to receive carbon credit for management adjustments associated with changing from tillage-based agricultural systems to no-till. Carbon credit can also be obtained by adopting conservation reserve, where cropland is planted into perennial vegetation. Summer fallowing is also considered within the crediting process as credit is not given in years that a field is left un-vegetated. The carbon sequestration program has been advocated as a means to mitigate climate change while providing an added source of income for Montana farmers. There is lack of data, however, pertaining to the percentage of lands within this region that have not converted to no-till management, lands under certain crop intensities (e.g. those that are cropped every growing season vs. those that use a fallow-crop-fallow system), or cropland that have converted to perennial vegetation outside of the popular Conservation Reserve Program. Data is also sparse concerning the amount of soil organic carbon that might be sequestered given a conversion to no-till or conservation reserve. This study established regional percentage estimates of cropland under no-till, various degrees of crop intensity, and conservation reserve within north central Montana. Literature-based carbon sequestration estimates were used to generate carbon gain data associated with the conversation to no-till and to conservation reserve. These estimates were then applied to the area-based cropland statistics to estimate potential regional carbon sequestration associated with these management changes.
  • Authors:
    • Hilker, T.
    • Lawrence, R. L.
    • Powell, S. L.
    • Watts, J. D.
  • Source: Remote Sensing of Environment
  • Volume: 115
  • Issue: 1
  • Year: 2011
  • Summary: Conservation tillage management has been advocated for carbon sequestration and soil quality preservation purposes. Past satellite image analyses have had difficulty in differentiating between no-till (NT) and minimal tillage (MT) conservation classes due to similarities in surface residues, and may have been restricted by the availability of cloud-free satellite imagery. This study hypothesized that the inclusion of high temporal data into the classification process would increase conservation tillage accuracy due to the added likelihood of capturing spectral changes in MT fields following a tillage disturbance. Classification accuracies were evaluated for Random Forest models based on 250-m and 500-m MODIS, 30-m Landsat, and 30-m synthetic reflectance values. Synthetic (30-m) data derived from the Spatial and Temporal Adaptive Reflectance Fusion Model (STARFM) were evaluated because high frequency Landsat image sets are often unavailable within a cropping season due to cloud issues. Classification results from a five-date Landsat model were substantially better than those reported by previous classification tillage studies, with 94% total and >= 88% class producer's accuracies. Landsat-derived models based on individual image scenes (May through August) yielded poor MT classifications, but a monthly increase in accuracy illustrated the importance of temporal sampling for capturing regional tillage disturbance signatures. MODIS-based model accuracies (90% total; >= 82% class) were lower than in the five-date Landsat model, but were higher than previous image-based and survey-based tillage classification results. Almost all the STARFM prediction-based models had classification accuracies higher than, or comparable to, the MODIS-based results (>90% total; >= 84% class) but the resulting model accuracies were dependent on the MODIS/Landsat base pairs used to generate the STARFM predictions. Also evident within the STARFM prediction-based models was the ability for high frequency data series to compensate for degraded synthetic spectral values when classifying field-based tillage. The decision to use MODIS or STARFM-based data within conservation tillage analysis is likely situation dependent. A MODIS-based approach requires little data processing and could be more efficient for large-area mapping; however a STARFM-based analysis might be more appropriate in mixed-pixel situations that could potentially compromise classification accuracy.