• Authors:
    • Zheng, J. F.
    • Pan, G. X.
    • Li, L. Q.
    • Zhang, X. H.
    • Zhang, A F.
    • Liu, Y. M.
    • Kibue, G. W.
    • Ye, Y. X.
    • Liu, X. Y.
    • Zheng, J. W.
  • Source: Agricultural Systems
  • Volume: 129
  • Year: 2014
  • Summary: Biochar's effects on improving soil fertility, enhancing crop productivity and reducing greenhouse gases (GHGs) emission from croplands had been well addressed in numerous short-term experiments with biochar soil amendment (BSA) mostly in a single crop season/cropping year. However, the persistence of these effects, after a single biochar application, has not yet been well known due to limited long-term field studies so far. Large scale BSA in agriculture is often commented on the high cost due to large amount of biochar in a single application. Here, we try to show the persistence of biochar effects on soil fertility and crop productivity improvement as well as GHGs emission reduction, using data from a field experiment with BSA for 5-crop seasons in central North China. A single amendment of biochar was performed at rates of 0 (C0), 20 (C20) and 40 t ha -1 (C40) before sowing of the first crop season. Emissions of CO 2, CH 4 and N 2O were monitored with static closed chamber method throughout the crop growing season for the 1st, 2nd and 5th cropping. Crop yield was measured and topsoil samples were collected at harvest of each crop season. BSA altered most of the soil physico-chemical properties with a significant increase over control in soil organic carbon (SOC) and available potassium (K) content. The increase in SOC and available K was consistent over the 5-crop seasons after BSA. Despite a significant yield increase in the first maize season, enhancement of crop yield was not consistent over crop seasons without corresponding to the changes in soil nutrient availability. BSA did not change seasonal total CO 2 efflux but greatly reduced N 2O emissions throughout the five seasons. This supported a stable nature of biochar carbon in soil, which played a consistent role in reducing N 2O emission, which showed inter-annual variation with changes in temperature and soil moisture conditions. The biochar effect was much more consistent under C40 than under C20 and with GHGs emission than with soil property and crop yield. Thus, our study suggested that biochar amended in dry land could sustain a low carbon production both of maize and wheat in terms of its efficient carbon sequestration, lower GHGs emission intensity and soil improvement over 5-crop seasons after a single amendment.
  • Authors:
    • Barth, G.
    • Pauletti, V.
    • Tomazi, M.
    • de Moraes, A.
    • Zanatta, J. A.
    • Bayer, C.
    • Dieckow, J.
    • Piva, J. T.
    • Piccolo, M. de C.
  • Source: Agriculture Ecosystems and Evviroment
  • Volume: 190
  • Issue: SI
  • Year: 2014
  • Summary: We assessed the impact of integrated crop-livestock (CL), with silage maize (Zea mays L.) in summer and grazed annual-ryegrass (Lolium multiflorum Lam.) in winter, and continuous crop (CC), with annualryegrass used only as cover-crop, on net greenhouse gas emission from soil (NetGHG-S) in a subtropical Ferralsol of a 3.5-year-old experiment in Brazil. Emissions from animal excreta in CL were estimated. Soil N2O fluxes after N application to maize were higher in CL (max. 181 mu g N2O-N m(-2) h(-1)) than in CC (max. 132 mu g N2O-N m(-2) h(-1)). The cumulative annual N2O emission from soil in CL surpassed that in CC by more than three-times (4.26 vs. 1.26 kg N2O-N ha(-1), p < 0.01), possibly because of supplementary N application to grazed ryegrass in CL (N was not applied in cover-crop ryegrass of CC) and a certain degree of soil compaction visually observed in the first few centimetres after grazing. The estimated annual N2O emission from excreta in CL was 2.35 kg N2O-N ha(-1). Cumulative annual CH4 emission was not affected significantly (1.65 in CL vs. 1.08 kg CH4-C ha(-1) in CC, p = 0.27). Soil organic carbon (OC) stocks were not affected by soil use systems, neither in 0-20-cm (67.88 in CL vs. 67.20 Mg ha(-1) in CC, p = 0.62) or 0-100-cm (234.74 in CL vs. 234.61 Mg ha(-1) in CC, p = 0.97). The NetGHG-S was 0.652 Mg CO2-C-eq ha(-1) year(-1) higher in CL than in CC. Crop-livestock emitted more N2O than CC and no soil OC sequestration occurred to offset that emission. Management of fertiliser- and excreta-N must be focused as a strategy to mitigate N2O fluxes in CL. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Retore, M.
    • Silva, W. M.
    • Concenco, G.
    • Zanatta, J. A.
    • Tomazi, M.
    • Mercante, F. M.
    • Salton, J. C.
  • Source: Agriculture Ecosystems and Enviroment
  • Volume: 190
  • Issue: SI
  • Year: 2014
  • Summary: Performance of soil management systems was initiated in 1995 in a field experiment in Dourados, MS, Brazil, with the following systems: CS - conventional tillage; NTS - no-tillage; ICLS - integrated crop-livestock with soybean (Glycine max (L) Merr.) and pasture under no-till, rotating every two years, and PP - permanent pasture. Pastures (Brachiaria decumbens) were grazed by heifers with stocking rate adjusted to constant supply of forage. The hypothesis was that rotation of crops and pastures would be more efficient and present beneficial effects to the environment. More complex and diversified production systems may exhibit synergism between components to result in better soil physical structure, greater efficiency in use of nutrients by plants, greater accumulation of labile fractions of soil organic matter, greater diversity and biological activity in soil, and lower occurrence of nematodes and weeds. Better soil conditions in ICLS allowed greater resilience; over the years of assessment soybean and pasture yields were less affected by drought and frost. The ICLS was very efficient, accumulating soil C and reducing emissions of greenhouse gases. Soil quality was improved in integrated systems with larger number of components and greater interaction between these components (ICLS) compared to simple systems. Based on soil attributes, we affirmed in this long-term study that the ICLS system is agronomically and environmentally efficient and sustainable. (C) 2013 Elsevier B.V. All rights reserved.
  • Authors:
    • Korth, K.
    • Chen, P.
    • Gbur, E. E.
    • Brye, K. R.
    • Smith, F.
  • Source: Soil Science
  • Volume: 179
  • Issue: 3
  • Year: 2014
  • Summary: One of the most significant contributors to the greenhouse effect is carbon dioxide (CO2) gas in the atmosphere. Soil respiration, the combined production of CO2 from soil, as a result of root and microorganism respiration, is the largest flux of CO2 from the terrestrial ecosystem to the atmosphere. Considering land use can greatly impact soil C storage and cycling, agricultural management practices can also greatly affect soil respiration and CO2 emissions. Therefore, the effects of long-term residue management (i.e., residue burning and nonburning, and conventional [CT] and no-tillage [NT]) and residue level (i.e., high and low) on soil respiration during the soybean [Glycine max (L.) Merr.] growing season were examined over 2 consecutive years (i.e., 2011 and 2012) in a wheat (Triticum aestivum L.)-soybean, double-crop system in a silt-loam soil (Aquic Fraglossudalf) in the Mississippi River Delta region of eastern Arkansas after more than 9 years of consistent management. Soil respiration rates from individual plots ranged from 0.53 to 40.7 and from 0.17 to 13.1 mol CO2.m(-2).s(-1) throughout the 2011 and 2012 soybean growing seasons, respectively, and differed (P < 0.05) among treatment combinations on two and five of nine and 11 measurement dates in 2011 and 2012, respectively. Regardless of residue level, soil respiration was generally greater (P < 0.05) from CT than NT. Estimated season-long CO2 emissions were 10.2% less (18.5 Mg CO2 ha(-1)) from residue burning than from non-burning (20.6 Mg CO2.ha(-1); P = 0.032). Averaged over years and all other field treatments, estimated season-long CO2 emissions were 15.5% greater from CT (21.0 Mg CO2 ha(-1)) than from NT (18.1Mg CO2 ha(-1); P = 0.020). Understanding long-term management effects on soil C losses, such as soil respiration, from common and widespread agricultural systems, such as the wheat-soybean, double-crop system, in eastern Arkansas can help improve policies for soil and environmental sustainability throughout the lower Mississippi River Delta region.
  • Authors:
    • Cecagno, D.
    • Costa, S. E. V. G. de A.
    • Martins, A. P.
    • Anghinoni, I.
    • Assmann, J. M.
    • Carlos, F. S.
    • Carvalho, P. C. de F.
  • Source: Web Of Knowledge
  • Volume: 190
  • Year: 2014
  • Summary: Managing grazing stocks in integrated crop-livestock (ICL) systems under no-tillage is a key variable for reaching equilibrium in soil C and N budgets. Understanding how different plant and animal residues affect soil C and N stocks in these systems goes beyond soil dynamics since these elements are crucial for the functioning of the soil-plant-atmosphere system. The objective of this research was to determine soil C and N fractions, stocks, budgets and the carbon management index as affected by nine years of ICL with grazing intensities under no-tillage conditions. The experiment established in May 2001 in a Rhodic Hapludult (Oxisol) of southern Brazil was composed of black oat ( Avena sativa) plus ryegrass ( Lolium multiflorum) pasture in winter and soybean ( Glycine max) crop in summer. Treatments were regulated by grazing pressures to maintain forage at 10, 20, 30 and 40 cm high (G10, G20, G30 and G40, respectively). Non-grazed (NG) treatment was the control. Changes in soil C and N stocks and fractions (particulate and mineral-associated) were assessed in the ninth year of the experiment. Moderate and light grazing intensities (G20, G30 and G40) resulted in similar increases in total organic C, particulate organic C, total N, and particulate organic N compared with NG treatment. Soil C additions ranged from 0.54 to 8.68 Mg ha -1 from NG to the other grazing treatments. The G10 led to a soil N loss of 1.17 Mg ha -1 due to soil organic matter degradation. The carbon management index (CMI) values, compared with native forest (NF) as a reference, indicated soil quality loss and degradation under high grazing intensity (G10). For a positive contribution to the soil system, ICL must be managed with moderate grazing intensities and adjustment of N additions through N fixation or fertilization.
  • Authors:
    • Salton, J. C.
    • Knicker, H.
    • Dick, D. P.
    • Conceicao, P. C.
    • Dieckow, J.
    • Bayer, C.
    • Boeni, M.
    • Macedo, M. C. M.
  • Source: Web Of Knowledge
  • Volume: 190
  • Year: 2014
  • Summary: Integrated crop-livestock (ICL) is a promising land use system for the Brazilian Cerrado, but little is known about what this system might change in chemical composition of soil organic matter. In three long-term experiments (9-11 years old), located on Cerrado Ferralsols in Dourados, Maracaju and Campo Grande (Mato Grosso do Sul State, Brazil), we assessed the impact of continuous cropland (CC), ICL, and permanent pasture of Brachiaria decumbens (PP) on the C concentration and composition of the free light fraction (FLF), occluded light fraction (OLF) and heavy fraction (HF) of soil in the 0-5 cm layer. CPMAS 13C NMR spectroscopy was used to determine the percentage of alkyl, O-alkyl, aromatic and carboxyl C types. In Dourados and Maracaju, PP had the highest concentrations of organic C in whole soil and physical fractions, while ICL was intermediate and CC lowest. In Campo Grande, soil organic C concentration was similar among management systems. Distribution of organic C across physical fractions was not affected by management nor by experimental site, and on average the FLF, OLF and HF contained 7%, 26% and 67% of the total storage, respectively. Signal peaks of the four main C types appeared in all CPMAS 13C NMR spectra, but at different intensities. O-alkyl was the major C type (about 50%), carboxyl was the minor representative (generally less than 10%) and alkyl and aromatic C were intermediates. From FLF to OLF, the alkyl and aromatic C concentrations increased, possibly due to selective preservation of waxes, resins, cutin, suberin and lignin. The HF had greater O-alkyl and lower aromatic C concentrations than OLF, which might have been related to the accumulation of microbial carbohydrates on mineral surfaces of the HF. Along the sequence CC-ICL-PP, the most evident changes were greater of O-alkyl and lower alkyl C types, practically in all fractions and sites. In FLF and OLF, these changes were attributed to greater biomass input and less seed drill-induced disturbance of soil surface (lower decomposition of residues) in the PP and ICL. Additionally, in OLF, greater O-alkyl concentration in PP and ICL was attributed to physical protection of particulate organic matter derived from grass roots occluded inside soil aggregates. Our results suggest that PP and ICL systems increased or maintained soil organic C concentrations compared to CC, associated with a qualitative increase of the chemically labile O-alkyl C type which was possibly related to greater biomass addition and less soil disturbance.
  • Authors:
    • Singh, B. P.
    • Fang, Y. Y.
    • Singh, B.
  • Source: Agriculture Ecosystems and Environment
  • Volume: 191
  • Year: 2014
  • Summary: Temperature sensitivity of biochar-C in soils is not well understood. To acquire this information, we incubated two delta 13C-depleted (-36.3 or -36.5 per mil) wood biochars produced at 450 and 550°C, under controlled laboratory conditions at 20, 40 and 60°C in four contrasting soils (Inceptisol, Entisol, Oxisol and Vertisol). The respired CO 2 and associated delta 13C were analysed periodically (12-22 times) over two years. The temperature sensitivity of biochar-C and native SOC mineralisation was computed as: (i) averaged Q 10 (Q 10a) for the whole (2-year) time series using a temperature-incorporated mineralisation model to estimate a temperature scaling function for the exponential Q 10 model; (ii) instantaneous Q 10 (Q 10i) by using a time series of C mineralisation rates for a simple Q 10 model; and (iii) cumulative Q 10 (Q 10c) by using cumulative C mineralised over certain incubation periods for a simple Q 10 model. The mineralisation rates of biochar-C and native SOC increased with increasing temperature and their temperature sensitivities were significantly ( p<0.001) affected by soil type. For example, biochar-C Q 10a was the greatest (also for native SOC) in the Vertisol (2.74-2.77), followed by Inceptisol (2.47-2.66) and Entisol (2.39-2.45), and the smallest in the Oxisol (1.93-2.20) for the 20-40°C range. Biochar and native SOC Q 10a were the smallest in the Vertisol for the 40-60°C range. Biochar-C Q 10a was not influenced by biochar type (450 or 550°C). The presence of biochar decreased Q 10a of the native SOC in the Entisol, Vertisol and Inceptisol, but this influence did not occur in the Oxisol, especially at 20-40°C. The temperature sensitivity of biochar-C (Q 10a and Q 10c) and SOC (Q 10a and Q 10i) decreased with increasing incubation temperature range. The Q 10i values of biochar-C and SOC increased with time in the 20-40°C range. Even though biochar-C was found to be more stable than native SOC (based on their mineralisation rate constants), the Q 10a, Q 10c and Q 10i values for biochar-C were either smaller or similar to that of native SOC. In conclusion, the findings of this study which was conducted in the absence of plant suggest that soil characteristics can alter the temperature sensitivity of biochar-C. Furthermore, biochar can decrease the temperature sensitivity of native SOC mineralisation and consequently enhance C sequestration in soil under climate warming.
  • Authors:
    • Schoenau, J. J.
    • Malhi, S. S.
    • Fan, .
    • Xu, M.
    • Feng, W.
    • Six, J.
    • Plante, A. F.
  • Source: Canadian Journal of Soil Science
  • Volume: 94
  • Issue: 3
  • Year: 2014
  • Summary: Agricultural soils are typically depleted in soil organic matter compared with their undisturbed counterparts, thus reducing their fertility. Organic amendments, particularly manures, provide the opportunity to restore soil organic matter stocks, improve soil fertility and potentially sequester atmospheric carbon (C). The application of the soil C saturation theory can help identify soils with large C storage potentials. The goal of this study was to test whether soil C saturation can be observed in various soil types in agricultural ecosystems receiving long-term manure amendments. Seven long-term agricultural field experiments from China and Canada were selected for this study. Manure amendments increased C concentrations in bulk soil, particulate organic matter+sand, and silt+clay fractions in all the experiments. The increase in C concentrations of silt+clay did not fit the asymptotic regression as a function of C inputs better than the linear regression, indicating that silt+clay did not exhibit C saturation behavior. However, 44% of calculated C loading values for silt+clay were greater than the presumed maximal C loading, suggesting that this maximum may be greater than 1 mg C m -2 for many soils. The influences of soil mineral surface properties on C concentrations of silt+clay fractions were site specific. Fine soil particles did not exhibit C saturation behavior likely because current C inputs were insufficient to fill the large C saturation deficits of intensely cultivated soils, suggesting these soils may continue to act as sinks for atmospheric C.
  • Authors:
    • Wang, X. G.
    • Zhu, B.
    • Hua, K. K.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 98
  • Issue: 2
  • Year: 2014
  • Summary: Runoff is a major driver for dissolved organic carbon (DOC) diffusing into aquatic ecosystems. Transport of DOC in runoff is important in the C cycle of soils in an agricultural ecosystem. This study provides a combined dataset on DOC loss pathways and fluxes from sloping upland in the purple soil area of southwestern China. A free-drain lysimeter experiment was conducted to quantify DOC loss through overland flow (2010-2012), interflow (2010-2012) and sediment (2011-2012). Average annual cumulative discharges of overland and interflow were 58.3 +/- A 3.1 and 289.4 +/- A 5.4 mm, accounting for 6.8 and 33.8 % of the totals during the entire rainy season, respectively. Average annual cumulative sediment loss flux was 183.5 +/- A 14.6 g m(-2). Average DOC concentrations in overland flow and interflow were 3.44 +/- A 0.36 and 3.04 +/- A 0.24 mg L-1, respectively. Average DOC content in sediment was 73.76 +/- A 4.09 mg kg(-1). The relationship between DOC concentration and discharge in overland flow events could be described by a significant exponential decaying function (R = 0.53, P = 0.027). Average annual DOC loss fluxes through overland flow, interflow and sediment were 163.6 +/- A 28.5, 865.5 +/- A 82.5 and 9.4 +/- A 1.5 mg m(-2), respectively, and total DOC loss was 1,038.5 +/- A 112.5 mg m(-2). The results suggest that interflow is the major driver of DOC leaching loss on sloping upland. It is shown that interflow is fundamentally important for reducing DOC loss on sloping croplands in the Sichuan Basin and possibly beyond.
  • Authors:
    • Asseng, S.
    • Zhu, Y.
    • Cao, W. X.
    • Tian, L. Y.
    • Liu, L. L.
    • Liu, B.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 2
  • Year: 2014
  • Summary: Wheat is sensitive to high temperatures, but the spatial and temporal variability of high temperature and its impact on yield are often not known. An analysis of historical climate and yield data was undertaken to characterize the spatial and temporal variability of heat stress between heading and maturity and its impact on wheat grain yield in China. Several heat stress indices were developed to quantify heat intensity, frequency, and duration between heading and maturity based on measured maximum temperature records of the last 50 years from 166 stations in the main wheat-growing region of China. Surprisingly, heat stress between heading and maturity was more severe in the generally cooler northern wheat-growing regions than the generally warmer southern regions of China, because of the delayed time of heading with low temperatures during the earlier growing season and the exposure of the post-heading phase into the warmer part of the year. Heat stress between heading and maturity has increased in the last decades in most of the main winter wheat production areas of China, but the rate was higher in the south than in the north. The correlation between measured grain yields and post-heading heat stress and average temperature were statistically significant in the entire wheat-producing region, and explained about 29% of the observed spatial and temporal yield variability. A heat stress index considering the duration and intensity of heat between heading and maturity was required to describe the correlation of heat stress and yield variability. Because heat stress is a major cause of yield loss and the number of heat events is projected to increase in the future, quantifying the future impact of heat stress on wheat production and developing appropriate adaptation and mitigation strategies are critical for developing food security policies in China and elsewhere.