• Authors:
    • Six, J.
    • West, T. O.
  • Source: Climatic Change
  • Volume: 80
  • Issue: 1
  • Year: 2007
  • Summary: Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional plow tillage to no-till can increase soil C by an estimated 16 ± 3%, whereas increasing rotation intensity can increase soil C by an estimated 6 ± 3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly longer period (26 yr) than that for tillage cessation (21 yr). Sequestration strategies for grasslands have, on average, longer sequestration durations (33 yr) than for croplands. Estimates for sequestration rates and durations are mean values and can differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C steady state is reached. However, soils could potentially sequester additional C following additional changes in management until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes in land management.
  • Authors:
    • Ascough, J. C.,II
    • McMaster, G. S.
    • Andales, A. A.
    • Hansen, N. C.
    • Sherrod, L. A.
  • Source: Transactions of the ASABE
  • Volume: 50
  • Issue: 5
  • Year: 2007
  • Summary: Alternative agricultural management systems in the semi-arid Great Plains are receiving increasing attention. GPFARM is a farm/ranch decision support system (DSS) designed to assist in strategic management planning for land units from the field to the whole-farm level. This study evaluated the regional applicability and efficacy of GPFARM based on simulation model performance for dry mass grain yield, total soil profile water content, crop residue, and total soil profile residual NO 3-N across a range of dryland no-till experimental sites in eastern Colorado, USA. Field data were collected from 1987 through 1999 from an on-going, long-term experiment at three locations in eastern Colorado along a gradient of low (Sterling), medium (Stratton), and high (Walsh) potential evapotranspiration. Simulated crop alternatives were winter wheat ( Triticum aestivum), maize ( Zea mays), sorghum ( Sorghum bicolor), proso millet ( Panicum miliaceum), and fallow. Relative error (RE) of simulated mean, root mean square error (RMSE), and index of agreement (d) model evaluation statistics were calculated to compare modelled results to measured data. A one-way, fixed-effect ANOVA was also performed to determine differences among experimental locations. GPFARM simulated versus observed REs ranged from -3 to 35% for crop yield, 6 to 8% for total soil profile water content, -4 to 32% for crop residue, and -7 to -25% for total soil profile residual NO 3-N. For trend analysis (magnitudes and location differences), GPFARM simulations generally agreed with observed trends and showed that the model was able to simulate location differences for the majority of model output responses. GPFARM appears to be adequate for use in strategic planning of alternative cropping systems across eastern Colorado dryland locations; however, further improvements in the crop growth and environmental components of the simulation model (including improved parameterization) would improve its applicability for short-term tactical planning scenarios.
  • Authors:
    • Mielniczuk, J.
    • Vieira, F. C. B.
    • Dieckow, J.
    • Bayer, C.
    • Zanatta, J. A.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Conservation management systems can improve soil organic matter stocks and contribute to atmospheric C mitigation. This study was carried out in a 18-year long-term experiment conducted on a subtropical Acrisol in Southern Brazil to assess the potential of tillage systems [conventional tillage (CT) and no-till (NT)], cropping systems [oat/maize (O/M), vetch/maize (V/M) and oat + vetch/maize + cowpea (OV/MC)] and N fertilization [0 kg N ha-1 year-1 (0 N) and 180 kg N ha-1 year-1 (180 N)] for mitigating atmospheric C. For that, the soil organic carbon (SOC) accumulation and the C equivalent (CE) costs of the investigated management systems were taken into account in comparison to the CT O/M 0 N used as reference system. No-till is known to produce a less oxidative environment than CT and resulted in SOC accumulation, mainly in the 0-5 cm soil layer, at rates related to the addition of crop residues, which were increased by legume cover crops and N fertilization. Considering the reference treatment, the SOC accumulation rates in the 0-20 cm layer varied from 0.09 to 0.34 Mg ha-1 year-1 in CT and from 0.19 to 0.65 Mg ha-1 year-1 in NT. However, the SOC accumulation rates peaked during the first years (5th to 9th) after the adoption of the management practices and decreased exponentially over time, indicating that conservation soil management was a short-term strategy for atmospheric C mitigation. On the other hand, when the CE costs of tillage operations were taken into account, the benefits of NT to C mitigation compared to CT were enhanced. When CE costs related to N-based fertilizers were taken into account, the increases in SOC accumulation due to N did not necessarily improve atmospheric C mitigation, although this does not diminish the agricultural and economic importance of inorganic N fertilization.
  • Authors:
    • Amado, T. J. C.
    • Pontelli, C. B.
    • Santi, A. L.
    • Viana, J. H. M.
    • Sulzbach, L. A. de S.
  • Source: Brazilian Journal of Agricultural Research (PAB)
  • Volume: 42
  • Issue: 8
  • Year: 2007
  • Summary: The objective of this work was to analyze the spatial and temporal yield variability of soybean, corn and wheat in a 57 ha cropland, without irrigation, under no-till for more than ten years in a Typic Hapludox, located in Palmeira das Missões, RS. Yield data of crops from 2000 to 2005 were collected using a combine equipped with yield monitor. Statistical and geostatistical analysis were performed to monitor the range of the spatial variability and its spatial dependence, as well as its behavior over the years. Soybean, corn and wheat yield present spatial variability, which is maintained over time. In dry years, yield variance coefficient increases compared to wet years. Corn was more efficient than soybean to identify spatial yield variability in the cropland.
  • Authors:
    • Grace,P.
  • Source: Healthy Soils Symposium
  • Year: 2007
  • Authors:
    • McGregor, A.
    • Slattery, B.
    • Ugalde, D.
    • Brungs, A.
    • Kaebernick, M.
  • Source: Soil & Tillage Research
  • Volume: 97
  • Issue: 2
  • Year: 2007
  • 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.
  • 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.
  • 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.
  • Authors:
    • Jin, H.
    • Hongwen, L.
    • Xiaoyan, W.
    • McHugh, A. D.
    • Wenying, L.
    • Huanwen, G.
    • Kuhn, N. J.
  • Source: Soil & Tillage Research
  • Volume: 94
  • Issue: 2
  • Year: 2007
  • Summary: Soil compaction caused by random traffic or repetitive tillage has been shown to reduce water use efficiency, and thus crop yield due to reduced porosity, decreased water infiltration and availability of nutrients. Conservation tillage coupled with subsoiling in northern China is widely believed to reduce soil compaction, which was created after many years of no-till. However, limited research has been conducted on the most effective time interval for subsoiling, under conservation tillage. Data from conservation tillage demonstration sites operating for 10 years in northern China were used to conduct a comparative study of subsoiling interval under conservation tillage. Three modes of traditional tillage, subsoiling with soil cover and no-till with soil cover were compared using 10 years of soil bulk density, water content, yield and water use efficiency data. Cost benefit analysis was conducted on subsoiling time interval under conservation tillage. Yield and power consumption were assessed by based on the use of a single pass combine subsoiler and planter. Annual subsoiling was effective in reducing bulk density by only 4.9% compared with no-till treatments on the silty loam soils of the Loess plateau, but provided no extra benefit in terms of soil water loss, yield increase or water utilization. With the exception of bulk density, no-till and subsoiling with cover were vastly superior in increasing water use (+10.5%) efficiency and yield (+12.9%) compared to traditional tillage methods. Four years of no-till followed by one subsoiling reduced mechanical inputs by 62%, providing an economic benefit of 49% for maize and 209% for wheat production compared to traditional tillage. Annual subsoiling reduced inputs by 25% with an increased economic benefit of 23% for maize and 135% for wheat production. Yield and power consumption was improved by 5% and 20%, respectively, by combining subsoiling with the planting operation in one pass compared with multipass operations of subsoiling and planting. A key conclusion from this is that annual subsoiling in dryland areas of northern China is uneconomical and unwarranted. Four years of no-till operations followed by 1 year subsoiling provided some relief from accumulated soil compaction. However, minimum soil disturbance and maximum soil cover are key elements of no-till for saving water and improving yields. Improved yields and reduced farm power consumption could provide a significant base on which to promote combined planter and subsoiling operations throughout northern China. Further research is required to develop a better understanding of the linkages between conservation tillage, soil quality and yield, aimed at designing most appropriate conservation tillage schemes.