• Authors:
    • Hoogenboom, G.
    • Yang, X. M.
    • Dou, S.
    • Yang, J. Y.
    • Yang, J. M.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 95
  • Issue: 3
  • Year: 2013
  • Summary: Simulation models are being regarded as an important tool to simulate crop growth, soil nutrient dynamics and soil carbon sequestration and fast use of the embedded knowledge of crop-soil processes. The Decision Support Systems for Agrotechnology Transfer (DSSAT) model was used to simulate long-term continuous maize growth from 1990 to 2007 in Gongzhuling, Northeast China. Three levels of N treatments were simulated, including: (1) no N (N0), (2) 165 kg N ha(-1) from synthetic fertilizer (N165) and (3) 50 kg N ha(-1) from synthetic fertilizer plus 115 kg N ha(-1) from farmyard manure (N165M). Both measured and simulated results showed that the maize yield was significantly lower in the N0 treatment. The measured maize yield was higher in N165M than N165 treatments after 2003. The maize yield was also affected by the weather, especially during drought years. The simulated soil organic C (SOC) content was in good agreement with the measured data in the 0-30 cm depth for all treatments. The SOC density in the 0-30 cm depth decreased by 4,393 kg C ha(-1) (18 %) in the N0 treatment and 4,186 kg C ha(-1) (17 %) in the N165 treatment, while it increased by 13,628 kg C ha(-1) (54 %) in the N165M treatment during 1990-2007, indicating that the combination of inorganic fertilizer and organic manure improved soil quality after 27 years of organic amendment from 1980. Soil mineral N levels were significantly higher in the N165 treatment just before planting (averaged 289 kg N ha(-1)), associated with more soil N leaching during the growing seasons (24-155 kg N ha(-1)) in some wet years, while soil mineral N levels were much lower in both the N0 (averaged 52 kg N ha(-1)) and N165M treatments (averaged 54 kg N ha(-1)) associated with less N leaching (< 10 kg N ha(-1)) compared with the N165 treatment. This indicated that the use of farmyard manure increased the soil organic matter and immobilized mineral N. The model results further indicated that complete crop residue removal from the field after harvest was a main reason for the decline of the SOC in the N165 treatment, suggesting that crop residue should be left on the soil to maintain the SOC balance and promote sustainable agriculture. Thus, we conclude that the DSSAT CENTURY-based module is a useful tool to simulate soil nitrogen dynamics and predict soil organic carbon sequestration in long-term field conditions.
  • Authors:
    • Zhang, W.
    • Huang, Y.
    • Yu, Y. Q.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 178
  • Year: 2013
  • Summary: The timing, magnitude, and regional distribution of soil organic carbon (SOC) changes are uncertain when factoring in climate change and agricultural management practices. The goal of this study is to analyze the implications of changes in climate and agricultural management for Chinese soil carbon sequestration over the next 40 years. We used the Agro-C model to simulate climate and agricultural management scenarios to investigate the combined impacts of climate change and management on future SOC stocks in China's croplands. The model was run for croplands on mineral soils in China, which make up a total of 130 M ha of cropland. The model used climate data (years 2011-2050) from the FGOALS and PRECIS climate models based on four Intergovernmental Panel on Climate Change (IPCC) emissions scenarios. Three equidistant agricultural management scenarios were used. S0 was a current scenario, and S2 was an optimal scenario. Under the S2 scenario, crop yields increased annually by 1%, the proportion of crop residue retained in the field reached 90% by 2050, and the area of no-tillage increased to 50% of the cultivated area by 2050. The S1 scenario applied half of the increased rates in crop yields, residue retention and no-tillage area values that were used in the S2 scenario. Across all croplands in China, the results suggest that SOC will increase under all combinations of climate and management and that the effect of climate change is much smaller than the effect of changes in agricultural management. Most croplands in China show a significant increase in SOC stocks, while very few zones (mainly in northeastern China) show a decrease. Rice paddy soils under the intensive farming management scenario show higher rates of carbon sequestration than dry-land soils. The maximum carbon sequestration potential of the croplands of China is estimated to be 2.39 Pg C under S2. Annual increases in SOC stocks could offset a maximum of 2.9% of the CO 2 emissions from fossil-fuel combustion in 2009. These results suggest that China's croplands, especially rice paddies, may play an important role in C sequestration and future climate change mitigation.
  • Authors:
    • Van Santen, E.
    • Arriaga, F. J.
    • Balkcom, K. S.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Tillage systems that promote minimal surface disturbance combined with high residue cover crops can sequester C, but additional research to quantify carbon sequestration with conservation agricultural systems is needed for modelers, policymakers, and landowners. A factorial arrangement of conservation tillage (no-till, fall paratill, spring paratill, and spring strip-till) and winter cover crops (no cover, rye [Secale cereale L], and wheat [Triticum aestivum L.]) were established in a corn/cotton (Zea mays L./Gossypium hirsutum L.) rotation from 2004 to 2009 to (i) evaluate cover crop biomass production and associated changes in soil organic carbon (SOC) to 15 cm, (ii) evaluate the potential of conservation systems to sequester SOC after years of conventional tillage, and (iii) compare measured changes in SOC to predicted soil conditioning index (SCI) values. Carbon returned to the soil each year averaged 2500 and 1340 kg C ha-1 for cover crops and corn residue, respectively. The average SOC sequestration rate in the top 15 cm was 926 ± 344 kg C ha-1 yr-1. Soil organic C values measured after 6 yr related well with predicted SCI values (r2 = 0.81; P = 0.0004). However, discrepancies between SCI and SOC values for conservation systems highlighted the need to improve the SCI for the Southeast U.S. Conservation systems following years of conventional monocropping were equivalent in their ability to sequester considerable amounts of C that will improve soil quality in the Coastal Plain of the southeastern USA. © Soil Science Society of America, All rights reserved.
  • Authors:
    • Montagne, C.
    • Lenssen, A. W.
    • Sainju, U. M.
    • Barsotti, J. L.
    • Hatfield, P. G.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Sheep (Ovis aries L.) grazing is an inexpensive method of weed control in dryland cropping systems, but little is known about its effect on net greenhouse gas (GHG) emissions. We evaluated the effect of sheep grazing compared with herbicide application for weed control on GHG (CO2, N2O, and CH4) emissions from May to October 2010 and 2011, net global warming potential (GWP), and greenhouse gas intensity (GHGI) in a silt loam under dryland cropping systems in western Montana. Treatments were two fallow management practices (sheep grazing [GRAZ] and herbicide application [CHEM]) and three cropping sequences (continuous alfalfa [Medicago sativa L.] [CA], continuous spring wheat [Triticum aestivum L.] [CSW], and spring wheat-pea [Pisum sativum L.]/barley [Hordeum vulgaris L.] hay-fallow [W-P/B-F]). Gas fluxes were measured at 3- to 14-d intervals with a vented, static chamber. Regardless of treatments, GHG fluxes peaked immediately following substantial precipitation (>12 mm) and N fertilization mostly from May to August. Total CO2 flux from May to October was greater under GRAZ with CA, but total N2O flux was greater under CHEM and GRAZ with CSW than other treatments. Total CH4 flux was greater with CA than W-P/B-F. Net GWP and GHGI were greater under GRAZ with W-P/B-F than most other treatments. Greater CH4 flux due to increased enteric fermentation as a result of longer duration of grazing during fallow, followed by reduced crop residue returned to the soil and/or C sequestration rate probably increased net GHG flux under GRAZ with W-P/B-F. Sheep grazing on a cropping sequence containing fallow may not reduce net GHG emissions compared with herbicide application for weed control on continuous crops.
  • Authors:
    • Bartlett, P.
    • Voroney, P.
    • Warland, J.
    • Chang, K. -H
    • Wagner-Riddle, C.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: The DayCENT model was employed to simulate the effects of conventional tillage (CT) and no-till (NT) practices on the dynamics of soil organic carbon (SOC) over 9 yr in a rotational cropping system in Southern Ontario, Canada. Observations of site properties and eddy covariance measurements were used to assess crop productivity, net ecosystem productivity (NEP), and SOC changes. The validated model captured the dynamics of grain yield and net primary production, which indicated that DayCENT can be used to simulate crop productivity for evaluating the effects of tillage on crop residues and heterotrophic respiration (Rh) dynamics. The simulation suggested that CT enhanced the annual Rh relative to NT by 38.4, 93.7 and 64.2 g C m-2 yr-1 for corn (Zea mays L.), soybean [Glycine max (L.) Merr], and winter wheat (Triticum aestivum L.), respectively. The combined effect of incorporating crop residues and increased cultivation factors enhanced Rh in CT by 35% relative to NT after disk cultivation in the spring. The simulated NEP varied with crop species, tillage practices, and timing/length of the growing season. The seasonal variation of the total SOC pool was greater in CT than NT because of tillage effects on C transfer from the active surface SOC pool to the active soil SOC pool at a rate of 50 to 100 g C m-2 yr-1. The NT method practiced during the study period accounted for a 10.7 g C m-2 yr-1 increase in the slow SOC pool. The validated DayCENT model may be applied for longer-term simulations in similar ecosystems for a variety of climate change experiment. © Soil Science Society of America.
  • Authors:
    • Allan, D. L.
    • Tallaksen, J.
    • Johnson, J. M. F.
    • Dalzell, B. J.
    • Barbour, N. W.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 4
  • Year: 2013
  • Summary: Cellulosic biofuel production may generate new markets and revenue for farmers. However, residue removal may cause environmental problems such as soil erosion and soil organic matter (SOM) loss. The objective of this study was to determine the amounts of residue necessary for SOM maintenance under different tillage and residue removal scenarios for corn-soybean [Zea mays L.-Glycine max (L.) Merr.] and continuous corn rotations for a site in west-central Minnesota. We employed a process-based model (CQESTR) to evaluate management practices and quantify SOM changes over time. Results showed that conventional tillage resulted in SOM loss regardless of the amount of residue returned. Under no-till, residue amount was important in determining SOM accumulation or depletion. For the upper 30 cm of soil, average annual rates of 3.65 and 2.25 Mg crop residue ha-1 yr-1 were sufficient to maintain SOM for corn-soybean and continuous corn rotations, respectively. Soil OM in soil layers below 30 cm was predicted to decrease in all scenarios as a result of low root inputs. When considered over the upper 60 cm (maximum soil depth sampled), only continuous corn with no-till was sufficient to maintain SOM. Results from this work are important because they show that, for these management scenarios, no-till management is necessary for SOM maintenance and that determining whether SOM is accumulating or declining depends on the soil depth considered. At current yields observed in this study area, only continuous corn with no-till may generate enough residue to maintain or increase SOM. © Soil Science Society of America.
  • Authors:
    • Halvorson, A. D.
    • Jantalia, C. P.
    • Follett, R. F.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Conventional tillage (CT) with high N rates and irrigation is used more frequently than no-till (NT) for growing continuous corn (Zea mays L.) in the central Great Plains of the United States. The objective of this study was to evaluate soil organic C (SOC) stocks throughout the soil profile as well as the potential for maintaining or sequestering SOC within the soil profile (0- 120 cm) under irrigated, continuous corn as affected by NT and CT and three N rates. Isotopic δ13C techniques provided information about the fate of C added to soil by corn (C4-C) and of residual C3-C from cool-season plants grown before this study. Relative contributions of C4-C and C3-C to SOC stocks after 8 yr were determined. Retention of C4-C from corn was measured under NT and CT. Nitrogen fertilization slowed losses of C3-C and improved retention of C 4-C. No-till was superior to CT in maintaining SOC. Deep soil sampling to 120 cm and the use of stable C isotope techniques allowed evaluation of changes in SOC stocks during the 8-yr period. Change in SOC under NT vs. CT resulted from greater loss of C3-C stocks under CT throughout the soil profile. Irrigated corn has a low potential to sequester SOC in the central Great Plains, especially under CT. The results of this study indicate that stability of the soil organic matter and its perceived "recalcitrance" is altered by environmental and biological controls. © Soil Science Society of America.
  • Authors:
    • Zobeck, T. M.
    • Moore-Kucera, J.
    • Fultz, L. M.
    • Acosta-Martfnez, V.
    • Allen, V. G.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 5
  • Year: 2013
  • Summary: Integrated crop-livestock (ICL) systems that utilize perennial or high-residue no-till annual forages may build soil organic matter and, thus, enhance aggregate stability, water retention, nutrient cycling, and C storage. We examined long-term effects of ICL management on soil organic C (SOC) pools compared with continuous cotton [CTN; (Gossypium hirsutum L.)] at the system and individual vegetation levels, both using limited irrigation (65 and 77% replacement of évapotranspiration, respectively). Soil samples collected in 1997 (baseline) and 2010 were fractionated into four water stable aggregate-size classes: macroaggregate (>250 μn), microaggregate (53-250 urn), and silt + clay (250 urn), microaggregates (53-250 urn), and silt + clay (<53 urn). Reduced tillage and increased vegetation inputs under WW-B. Dahl Old World bluestem [Bothriochloa bladhii (Retz) S.T. Blake; bluestem], a component of the ICL, resulted in increased mean weight diameter (1.5 mm in bluestem vs. 0.40 mm in CTN) and higher proportions of macroaggregates (59%) than under CTN. A continued increase in SOC was measured in the ICL following 13 yr with 22% more SOC relative to CTN. The results from the detailed soil aggregate C fractionation revealed that an ICL under limited irrigation enhanced SOC stored in protected, recalcitrant aggregate pools (intra-aggregate microaggregate SOC of 8.2 and 5.4 mg g-1 macroaggregate in the ICL and CTN, respectively). These benefits impart important ecosystem services such as potential C sequestration and reduced erosion potential, which are especially important in these semiarid soils. © Soil Science Society of America, All rights reserved.
  • Authors:
    • Reis, F. B. D.
    • Chaer, G. M.
    • De Sousa, D. M. G.
    • Lopes, A. A. D. C.
    • Goedert, W. J.
    • Mendes, I. D.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 2
  • Year: 2013
  • Summary: An interpretative framework for microbial biomass C (MBC), basal respiration, and the activity of soil enzymes cellulase, β-glucosidase, arylsulfatase, and acid phosphatase was developed for the clayey Oxisols of the Brazilian Cerrado. Soil samples (0-10-cm depth) were collected from 24 treatments from three long-term experiments and analyzed to determine their microbial attributes and soil organic C (SOC). These treatments presented a large range of Mehlich-extractable P and cumulative corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields. The critical levels for the microbial indicators were defined based on criteria similar to those used in soil nutrient calibration tests. The microbial indicators were interpreted as a function of the relative cumulative yields (RCYs) of corn and soybean and the SOC using linear regression models. Adequacy classes for each microbial indicator as a function of the RCY and SOC were established based on the following criteria: ≤40%: low; 41 to 80%: moderate; and >80%: adequate. The critical levels equivalent to 80% of the RCY for MBC, basal respiration, cellulase, β-glucosidase, acid phosphatase, and arylsulfatase were: 375 mg C kg -1, 90 mg CO2-C kg-1, 105 mg glucose kg -1 d-1, 115 mg p-nitrophenol kg-1 h -1, 1160 mg p-nitrophenol kg-1 h-1, and 90 mg p-nitrophenol kg-1 h-1, respectively. Similar critical levels were obtained when SOC was used as the interpretation criterion. The interpretation tables provided in this study establish, for the first time, reference values for the soil microbial indicators based on crop yields and constitute a first approximation. Their applicability to other conditions must be evaluated.
  • Authors:
    • Treloges, V.
    • Saenjan, P.
    • Rasche, F.
    • Vityakon, P.
    • Puttaso, A.
    • Cadisch, G.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: The influence of residue quality on soil organic C (SOC) retention has been called into question. A field experiment in Northeast Thailand, in which contrasting quality organic residues were applied yearly for 13 yr, was used to determine quantities, locations, and stability of SOC in the soil matrix and identify residue quality parameters affecting SOC stabilization in a tropical sandy-textured soil. Total organic C (TOC) content was highest in intermediate- quality tamarind (Tamarindus indica L.) at 3.58 g kg-1 (intermediate N, lignin, and polyphenol contents), followed by groundnut (Arachis hypogaea L.) stover at 2.63 g kg-1 (high N), dipterocarp (Dipterocarpus tuberculatus Roxb.) at 2.63 g kg-1 (low N, high lignin and polyphenols), and rice (Oryza sativa L.) straw at 1.77 g kg-1 (high cellulose). Microaggregates (Mi) (0.053-0.25 mm) stored the highest C content (34-49% of TOC), with tamarind having the highest C content. Carbon in large macroaggregates (>2 mm), small macroaggregates (0.25-2 mm), and free organic matter (>0.053 mm) was significantly positively correlated with C, lignin, and polyphenols. Carbon in microaggregates and fine particles (<0.053 mm) was significantly negatively correlated with C/N ratio. Soil fraction C was negatively correlated with residue cellulose contents. Protected C lost through mineralization in Mi was lower in tamarind (7% Mi-C) followed by groundnut (9.5%), dipterocarp (17.7%), and rice straw (18.6%). It was significantly positively correlated with cellulose and C/N ratios but negatively correlated with N contents. Possible mechanisms of aggregate formation are based on microbial synthesis of both persistent (humic substances) and transient (polysaccharides) binding agents as influenced by residue quality. The results showed clearly that residue quality plays an important role in SOC accumulation in tropical sandy soils.