• Authors:
    • Yeluripati, J. B.
    • Wilson, B. R.
    • Smith, P.
    • Hulugalle, N. R.
    • Senapati, N.
    • Daniel, H.
    • Ghosh, S.
    • Lockwood, P.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 143
  • Year: 2014
  • Summary: The performance of the Rothamsted Carbon Model (RothC) in simulating soil carbon (SOC) storage in cotton based cropping systems under different tillage management practices on an irrigated Vertisol in semi-arid, subtropics was evaluated using data from a long-term (1994-2012) cotton cropping systems experiment near Narrabri in north-western New South Wales, Australia. The experimental treatments were continuous cotton/conventional tillage (CC/CT), continuous cotton/minimum tillage (CC/MT), and cotton-wheat (Triticum aestivum L.) rotation/minimum tillage (CW/MT). Soil carbon (C) input was calculated by published functions that relate crop yield to soil C input. Measured values showed a loss in SOC of 34%, 24% and 31% of the initial SOC storages within 19 years (1994-2012) under CC/CT, CC/MT, and CW/MT, respectively. RothC satisfactorily simulated the dynamics of SOC in cotton based cropping systems under minimum tillage (CC/MT and CW/MT), whereas the model performance was poor under intensive conventional tillage (CC/CT). The model RothC overestimated SOC storage in cotton cropping under conventional intensive tillage management system. This over estimation could not be attributed to the overestimation of soil C inputs, or errors in initial quantification of SOC pools for model initialization, or the ratio of incoming decomposable plant materials to resistant plant materials. Among other different factors affecting SOC dynamics and its modelling under intensive tillage in tropics and sub-tropics, we conclude that factors for tillage and soil erosion might be needed when modelling SOC dynamics using RothC under intensive tillage management system in the tropics and the sub-tropics.
  • Authors:
    • Dyck, M.
    • Shahidi, B. M. R.
    • Malhi, S. S.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 144
  • Year: 2014
  • Summary: Agricultural soils under long-term zero tillage (no-till) management have been well known to sequester atmospheric carbon (C) in soil organic matter as well as to reduce emissions of major greenhouse gases. This fact aided the development of the present C offset market around the world and is the basis for no tillage or conservation tillage agriculture as a potential low cost means of reducing greenhouse gas (GHG) emissions. The province of Alberta, Canada currently has C offset protocols under which companies that fail to achieve targeted emission reduction can purchase C credits from agricultural farms that have changed tillage management practices. Our study aimed at quantifying the major GHG carbon dioxide (CO2) emissions from two major agricultural soil types in Western Canada (i.e., Black Chernozem and Gray Luvisol) managed under long-term (~30 years) no-till after tillage reversal. We also studied the influences of soil temperature and soil moisture, nitrogen (N) fertilization (i.e., no N vs. 100kgNha-1) and inherent soil fertility on the magnitude of tillage reversal impact on soil CO2 emissions. Our study revealed that the CO2 emissions were higher after tillage reversal irrespective of N fertilizer applications, soil types and soil physical environment. Comparative study between historic soil C sequestration after the adoption of long-term no-till and the GHG emissions in the form of CO2 fluxes after tillage reversal on these study plots showed that the short-term rates of C emissions after tillage reversal were higher than the long-term rates of C sequestration. However, since the time scales for comparing the sequestration and emission rates were so different, these results are expected and reasonable. These results, however, indicate that increased soil C storage resulting from changes in agricultural management practices are reversible and that the potential for C sequestration is dependent on the long-term trends of management practices.
  • Authors:
    • Wight, J. P.
    • Hons, F. M.
    • Storlien, J. O.
    • Heilman, J. L.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 5
  • Year: 2014
  • Summary: Modern bioenergy feedstocks, such as bioenergy sorghum [Sorghum bicolor (L.) Moench], are being developed to supply future cellulosic biofuel demands. How these cropping systems impact greenhouse gas (GHG) emission of CO2and N2O from the soil is unknown and field research is necessary to elucidate the effects of agronomic management practices on soil trace gas emissions. We studied the effects of N fertilization (0 vs. 280 kg urea-N ha-1), residue management (0 vs. 50% of sorghum biomass returned), crop sequence (corn [Zea mays L.]-sorghum vs. sorghum-sorghum), and their interactions on CO2and N2O emissions from bioenergy production scenarios on a Weswood (finesilty, mixed, superactive, thermic Udifluventic Haplustept) silty clay loam soil in central Texas. Gas fluxes were measured approximately weekly throughout the 2010 and 2011 growing season and at a reduced rate during the fallow season with a photoacoustic gas analyzer integrated with a static chamber. Overall, CO2and N2O fluxes were relatively higher than those observed by others in the United States despite drought conditions throughout much of 2010 and 2011. Highest emissions of both gases were observed during the growing season, often following a precipitation-irrigation event and shortly after N fertilization. Residue return increased cumulative CO2emissions each year, probably due to increased heterotrophic microbial activity. Nitrogen addition significantly increased cumulative emissions of N2O both years but only impacted cumulative CO2emissions in 2011. While crop rotation impacted biomass yield, it had no significant effect on cumulative CO2or N2O emissions. Additional research is needed to identify the optimal N and residue application rates that provide high yields with minimal soil GHG emissions and aid in sustaining long-term soil quality.
  • Authors:
    • Andrews, S. S.
    • Kwon, H.
    • Ugarte, C. M.
    • Wander, M. M.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Increased understanding of the influences of management practices on soil properties and associated ecosystem function is needed to improve tools used to administer conservation programs in the United States. This study used meta-analysis to assess the influence of cropping systems (conventional, conservation with minimum tillage, conservation with no-till, and organic systems) and management practices (nitrogen [N] fertility and rotation length) on soil organic carbon (SOC). These factors are considered by tools that evaluate conservation performance and provision of ecosystem services. We also reviewed the literature to determine whether this approach could be applied to other proxy variables (erosion rates, soil erodibility factor [K values], available phosphorus [P], and nitrous oxide [N2O]). Data mining was used to populate a database with variables representing practices used by the Natural Resource Conservation Service's Conservation Measurement Tool (CMT) to determine eligibility for the Conservation Stewardship Program. Data collected from 55 peer-reviewed studies was categorized based on sampling depth (0 to 10, 0 to 15, 0 to 20, and 0 to 30 cm [0 to 3.9, 0 to 5.9, 0 to 7.8, and 0 to 11.8 in]). The magnitude of the effect estimated by meta-analysis was then compared to scores assigned to practices in the soil quality module of the CMT. Meta-analysis of data from the 0 to 20 cm (0 to 7.8 in) depth suggested that rates of SOC accrual were similar in organic systems using diversified crop rotations and conservation systems using inorganic fertility sources, increasing SOC by 9% compared to the conventional control. In comparisons at the 0 to 30 cm (0 to 11.8 in) depth, results from conservation systems using no-till and organic systems diverged, with conservation systems relying on no-till producing no gains while organic systems produced a 29% increase in SOC. While the use of organic amendments generally increased SOC, the magnitude of the effect was more modest than suggested by current CMT weighting. In addition, our results suggested that quality of manure, which is not differentiated in the CMT, influences the magnitude of the effect and that addition of wet manure may decrease SOC. A comparison of rotation length showed cropping systems with rotations of 3 years or longer were better able to increase SOC than shorter rotations. These findings suggested that the CMT generally ranks practices appropriately and shows how meta-analysis could be used to adjust credits awarded for use of reduced or no-till practices or different fertility sources.
  • Authors:
    • Liang, L.
    • Jia, Z.
    • Wang, X.
  • Source: JOURNAL OF SOIL AND WATER CONSERVATION
  • Volume: 69
  • Issue: 5
  • Year: 2014
  • Summary: Field experiments were conducted from 2008 to 2010 in the Weibei Highlands of China to study the effects of straw incorporation on soil moisture, evapotranspiration (ET), and rainfall-use efficiency (RUE) of maize (Zea mays L.) under semiarid conditions in dark loessial soil. The straw application rates were at low straw ([LS] 4.5 t ha(-1)), medium straw ([MS] 9 t ha(-1)), and high straw ([HS] 13.5 t ha(-1)) rates combined with fixed levels of chemical fertilizers compared with only chemical fertilizers. Straw incorporation significantly increased surface soil moisture at the grain filling stage of maize and significantly improved RUE in the whole growth period of maize. Evapotransipiration at the ten leaf collar to tasseling and the grain filling to maturity stages of maize were significantly increased by straw incorporation. However, ET at the tasseling to grain filling stage of maize was significantly reduced by straw incorporation. Medium straw and HS treatments significantly improved surface soil moisture at the tasseling stage of maize and RUE at the five leaf collar to maturity stage of maize. Increasing straw application rates significantly reduced ET at the grain filling to maturity stage of maize. With increasing experimental years, LS treatment significantly improved surface soil moisture at the five leaf collar to tasseling stage of maize and RUE at the five and ten leaf collar stage of maize, MS treatment significantly increased surface soil moisture at the five and ten leaf collar stages of maize, and HS treatment significantly reduced ET at the sowing to five leaf collar stage of maize. We conclude that a reasonable combination application of straw and chemical fertilizers could make full use of surface soil moisture, inhibit soil evaporation, reduce the ineffective evaporation of crop, and increase RUE at a different growth period of maize and grain yield. In this experiment, the optimum straw application rate for improving RUE and grain yield was MS treatment.
  • Authors:
    • Wuest, S.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 78
  • Issue: 4
  • Year: 2014
  • Summary: Long-term changes in total soil organic C usually occur gradually. These long-term trends might be obscured by smaller, rapid changes in soil C due to seasonal inputs of plant residues, roots, and exudates, or decomposition of such inputs. Yet there is little, if any, data describing the magnitude of seasonal changes in soil C. If seasonal fluctuations in soil C are substantial, then important implications exist for accurate comparison of soil C between sites, between treatments, and even in the same experimental unit over time. Thirty-nine consecutive monthly soil samples were taken from a field experiment planted every year with winter wheat (Triticum aestivum L.) in the Pacific Northwest, United States. The variation in soil organic C was 14 to 16% of the mean over the 39-mo period in the top 250 kg m-2 equivalent mass (~0- to 20-cm depth). Two to eight percent could be identified as a regular seasonal pattern. The no-till management system had the greatest seasonal fluctuation, and the timing of the annual maximum was different from that of the tilled soil management treatments. In the shallower soil layer (~0-7 cm), total soil organic C varied 12 to 29% in which 4 to 13% could be attributed to a 12-mo seasonal pattern. Given the small magnitude of changes in soil C being measured and modeled in many agricultural and natural systems, soil samples taken at a single point in time are likely to encounter substantial but hidden measurement variability. The variability may be compounded by factors of the timing of sampling in relation to natural soil organic matter cycles and differences in the cycle due to treatment and weather. Sampling plans, which account for seasonal fluctuation and the different fluctuation patterns under different soil situations, will improve measurement accuracy.
  • Authors:
    • Williams, M.
    • Maratha, P.
    • Killi, D.
    • Forristal, D.
    • Lanigan, G.
    • Osborne, B.
    • Prescher, A.
    • Helmy, M.
    • Hastings, A.
    • Abdalla, M.
    • Rueangritsarakul, K.
    • Smith, P.
    • Nolan, P.
    • Jones, M. B.
  • Source: Geoderma
  • Volume: 223-225
  • Year: 2014
  • Summary: Field management activities have significant impacts on greenhouse gas (GHG) emissions from cropland soils. In this study, the effectiveness of combining reduced tillage with a mustard cover crop (RT-CC) to mitigate present and future GHG emissions from a fertilized spring barley field in the southeast of Ireland was assessed. The field site which had a free-draining sandy loam soil with low soil moisture holding capacity, had been managed for three years prior to measurements under two different tillage systems; conventional (CT) and RT-CC. Field measurements of soil CO2, N2O and CH4 emissions, crop biomass, water filled pore space (WFPS), soil temperature and soil nitrate were made to capture both steady state conditions as well as the management events. Field data were used to validate the DNDC (DeNitrification-DeComposition) model and future GHG emissions under two sets of climate projections were predicted. Although fertilizer use was the same for both treatments the RT-CC treatment had significantly (p < 0.05) higher N2O emissions for both present and future climate. However, the inclusion of a cover crop with the RT treatment increased predicted soil organic carbon (SOC), which more than compensated for the higher N2O flux resulting in a lower total GHG balance (TGGB) compared with the CT treatment. Results show that the effectiveness of RT-CC in mitigating GHG emissions will depend crucially on the magnitude of compensatory increases in carbon dioxide uptake by the cover crop that will contribute to a reduction in the total GHG balance.
  • Authors:
    • Zgorelec, Z.
    • Bilandzija, D.
    • Kisic, I.
  • Source: Agriculturae Conspectus Scientificus
  • Volume: 79
  • Issue: 1
  • Year: 2014
  • Summary: Soil carbon stocks are highly vulnerable to human activities (such as tillage), which can decrease carbon stocks significantly. These activities break down soil's organic matter and some carbon is converted to carbon dioxide (CO 2). A part of CO 2 (a greenhouse gas that is one of the main contributor to global warming) is lost from the soil by soil respiration (soil CO 2 efflux). The aim of our study is to determine the soil carbon loss by soil CO 2 efflux under different tillage treatments. The experimental site is characterized by continental climate. Field experiment with six different tillage treatments usually used in this area was set up on Stagnic Luvisols in Daruvar, central lowland Croatia in 1994 with investigation aim on determination of soil degradation by water erosion and later, in 2011, expanded to the research on soil CO 2 efflux. Tillage treatments differed in tools that were used, depth and direction of tillage. Tillage treatments were: black fallow (BF), ploughing up/down the slope to 30 cm (PUDS), no-tillage (NT), ploughing across the slope to 30 cm (PAS), very deep ploughing across the slope to 50 cm (VDPAS) and subsoiling (50 cm) plus ploughing (30 cm) across the slope (SSPAS). Field measurements of soil CO 2 concentrations were conducted during one year (n=14) from November 2011 till November 2012, when cover crop was corn ( Zea mays L.). Preliminary soil sampling for determination of soil total carbon content was conducted in April 2011. This paper presents results of soil total carbon content in the soil surface layer (0-30 cm), the variations of CO 2-C efflux during the year, soil carbon loss by CO 2-C efflux and correlation between soil total carbon content and CO 2-C efflux. The range of soil surface total carbon content varied from 19083.7 kg/ha at BF treatment up to 31073.6 kg/ha at SSPAS treatment. The treatment with the lowest average measured CO 2-C efflux was BF. The average CO 2-C efflux at BF treatment was 7.9 kg CO 2-C/ha/day where CO 2-C efflux varied from 2.3 kg CO 2-C/ha/day up to 22.6 kg CO 2-C/ha/day. The treatment with the highest average measured CO 2-C efflux was NT. Range of CO 2-C efflux at NT treatment varied from 7.8 kg CO 2-C/ha/day up to 65.8 kg CO 2-C/ha/day and the average CO 2-C efflux was 24.4 kg CO 2-C/ha/day. Daily soil total carbon loss by soil respiration ranged from 0.04% at BF treatment up to 0.09% at NT treatment. Soil CO 2-C efflux was fully positively correlated with soil total carbon content (r=0.91). After all mentioned, it can be stated that in these agro-ecological conditions, best tillage practice in sustainable plant production in terms of the lowest daily soil total carbon loss (0.06%) by soil respiration is ploughing to 30 cm (PUDS and PAS). Still, it is necessary to conduct the total soil carbon balance in the future research for better understanding of soil carbon gains and losses.
  • Authors:
    • Castellano, M. J.
    • Sawyer, J. E.
    • Jeske, E. S.
    • Hofmockel, K. S.
    • Drijber, R. A.
    • Bach, E. M.
    • Brown, K. H.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 4
  • Year: 2014
  • Summary: Global maize production alters an enormous soil organic C (SOC) stock, ultimately affecting greenhouse gas concentrations and the capacity of agroecosystems to buffer climate variability. Inorganic N fertilizer is perhaps the most important factor affecting SOC within maize-based systems due to its effects on crop residue production and SOC mineralization. Using a continuous maize cropping system with a 13 year N fertilizer gradient (0-269kg Nha(-1)yr(-1)) that created a large range in crop residue inputs (3.60-9.94 Mgdry matter ha(-1)yr(-1)), we provide the first agronomic assessment of long-term N fertilizer effects on SOC with direct reference to N rates that are empirically determined to be insufficient, optimum, and excessive. Across the N fertilizer gradient, SOC in physico-chemically protected pools was not affected by N fertilizer rate or residue inputs. However, unprotected particulate organic matter (POM) fractions increased with residue inputs. Although N fertilizer was negatively linearly correlated with POM C/N ratios, the slope of this relationship decreased from the least decomposed POM pools (coarse POM) to the most decomposed POM pools (fine intra-aggregate POM). Moreover, C/N ratios of protected pools did not vary across N rates, suggesting little effect of N fertilizer on soil organic matter (SOM) after decomposition of POM. Comparing a N rate within 4% of agronomic optimum (208kg Nha(-1)yr(-1)) and an excessive N rate (269kg Nha(-1)yr(-1)), there were no differences between SOC amount, SOM C/N ratios, or microbial biomass and composition. These data suggest that excessive N fertilizer had little effect on SOM and they complement agronomic assessments of environmental N losses, that demonstrate N2O and NO3 emissions exponentially increase when agronomic optimum N is surpassed.
  • Authors:
    • Pan, G.
    • Parton, W. J.
    • Ogle, S. M.
    • Cheng, K.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 3
  • Year: 2014
  • Summary: Understanding the potential for greenhouse gas (GHG) mitigation in agricultural lands is a critical challenge for climate change policy. This study uses the DAYCENT ecosystem model to predict GHG mitigation potentials associated with soil management in Chinese cropland systems. Application of ecosystem models, such as DAYCENT, requires the evaluation of model performance with data sets from experiments relevant to the climate and management of the study region. DAYCENT was evaluated with data from 350 cropland experiments in China, including measurements of nitrous oxide emissions (N2O), methane emissions (CH4), and soil organic carbon (SOC) stock changes. In general, the model was reasonably accurate with R2 values for model predictions vs. measurements ranging from 0.71 to 0.85. Modeling efficiency varied from 0.65 for SOC stock changes to 0.83 for crop yields. Mitigation potentials were estimated on a yield basis (Mg CO2-equivalent Mg−1Yield). The results demonstrate that the largest decrease in GHG emissions in rainfed systems are associated with combined effect of reducing mineral N fertilization, organic matter amendments and reduced-till coupled with straw return, estimated at 0.31 to 0.83 Mg CO2-equivalent Mg−1Yield. A mitigation potential of 0.08 to 0.36 Mg CO2-equivalent Mg−1Yield is possible by reducing N chemical fertilizer rates, along with intermittent flooding in paddy rice cropping systems.