• 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:
    • 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:
    • Steinriede Jr., R. W.
    • Zablotowicz, R. M.
    • Locke, M. A.
    • Testa, S.
    • Reddy, K. N.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 77
  • Issue: 3
  • Year: 2013
  • Summary: Conservation practices are increasingly important components of sustainable management systems, and information about their influence on soil characteristics is needed. Soil parameters were assessed in no-till (NT) or minimum tillage (MT) cotton (Gossypium hirsutum L.) production near Stoneville, MS, Mississippi Delta region, that included cover crop (rye [Secale cereal L.] or Balansa clover [Trifolium michelianum Savi var. balansae (Boiss.) Azn.]) vs. no cover crop. Soils (0-2, 2-5, and 5-15 cm) were sampled (2001-2006) before cotton planting. Independent of tillage, both cover crops accumulated more soil C than no cover, and N was greatest under clover. Soils (0-15 cm) under clover had greater aggregate stability than rye or no cover. The major factor influencing bulk density and infiltration was proximity to crop row bed and wheel traffic, but infiltration rates were sixfold greater under MT than NT (P rye or no cover). Moderate tillage slightly increased abundance of both reniform nematodes and earthworms, but neither was affected by cover crop. Fluorescein diacetate hydrolytic activity was higher in clover (50%) and rye (20%) in surface soil than with no cover. Soil microbial community structure (total fatty acid methyl ester analysis) (2005-2006) indicated a significant cover crop effect but no tillage effect. Mycorrhizal bioindicator (16:1 w5c) was greater in soil with rye than clover or no cover; however, cotton mycorrhizal infection was 40% greater in fibrous roots from rye or clover plots than roots from plots with no cover. Collectively, cotton production with a cover crop and reduced tillage resulted in soil conditions indicative of soil quality.
  • Authors:
    • Garnier, J.
    • Sanz-Cobena, A.
    • Lassaletta, L.
    • Aguilera, E.
    • Vallejo, A.
  • Source: Agriculture Ecosystems and Enviroment
  • Volume: 164
  • Year: 2013
  • Summary: Environmental problems related to the use of synthetic fertilizers and to organic waste management have led to increased interest in the use of organic materials as an alternative source of nutrients for crops, but this is also associated with N 2O emissions. There has been an increasing amount of research into the effects of using different types of fertilization on N 2O emissions under Mediterranean climatic conditions, but the findings have sometimes been rather contradictory. Available information also suggests that water management could exert a high influence on N 2O emissions. In this context, we have reviewed the current scientific knowledge, including an analysis of the effect of fertilizer type and water management on direct N 2O emissions. A meta-analysis of compliant reviewed experiments revealed significantly lower N 2O emissions for organic as opposed to synthetic fertilizers (23% reduction). When organic materials were segregated in solid and liquid, only solid organic fertilizer emissions were significantly lower than those of synthetic fertilizers (28% reduction in cumulative emissions). The EF is similar to the IPCC factor in conventionally irrigated systems (0.98% N 2O-N N applied -1), but one order of magnitude lower in rainfed systems (0.08%). Drip irrigation produces intermediate emission levels (0.66%). Differences are driven by Mediterranean agro-climatic characteristics, which include low soil organic matter (SOM) content and a distinctive rainfall and temperature pattern. Interactions between environmental and management factors and the microbial processes involved in N 2O emissions are discussed in detail. Indirect emissions have not been fully accounted for, but when organic fertilizers are applied at similar N rates to synthetic fertilizers, they generally make smaller contributions to the leached NO 3- pool. The most promising practices for reducing N 2O through organic fertilization include: (i) minimizing water applications; (ii) minimizing bare soil; (iii) improving waste management; and (iv) tightening N cycling through N immobilization. The mitigation potential may be limited by: (i) residual effect; (ii) the long-term effects of fertilizers on SOM; (iii) lower yield-scaled performance; and (iv) total N availability from organic sources. Knowledge gaps identified in the review included: (i) insufficient sampling periods; (ii) high background emissions; (iii) the need to provide N 2O EF and yield-scaled EF; (iv) the need for more research on specific cropping systems; and (v) the need for full GHG balances. In conclusion, the available information suggests a potential of organic fertilizers and water-saving practices to mitigate N 2O emissions under Mediterranean climatic conditions, although further research is needed before it can be regarded as fully proven, understood and developed.
  • Authors:
    • Barfoot, P.
    • Brookes, G.
  • Source: GM crops & food
  • Volume: 4
  • Issue: 2
  • Year: 2013
  • Summary: Given the increasing awareness and appreciation of issues such as global warming and the impact of mankind's activities such as agriculture on the global environment, this paper updates previous assessments of the environmental impact of an important and relatively new technology, crop biotechnology has had on global agriculture. It focuses on the environmental impacts associated with changes in pesticide use and greenhouse gas emissions arising from the use of GM crops. The adoption of the technology has reduced pesticide spraying by 474 million kg (-8.9%) and, as a result, decreased the environmental impact associated with herbicide and insecticide use on these crops [as measured by the indicator the Environmental Impact Quotient (EIQ)] by 18.1%. The technology has also facilitated a significant reduction in the release of greenhouse gas emissions from this cropping area, which, in 2011, was equivalent to removing 10.22 million cars from the roads.
  • Authors:
    • Saad, A. A.
    • Das, S.
    • Sharma, A. R.
    • Bhattacharyya, R.
    • Das, T. K.
    • Pathak, H.
  • Source: European Journal of Agronomy
  • Volume: 51
  • Year: 2013
  • Summary: Sequestration of C in arable soils has been considered as a potential mechanism to mitigate the elevated levels of atmospheric greenhouse gases. We evaluated impacts of conservation agriculture on change in total soil organic C (SOC) and relationship between C addition and storage in a sandy loam soil of the Indo-Gangetic Plains. Cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) crops were grown during the first three years (2008-2011) and in the last year, maize (Zea mays L), wheat and green gram (Vigna radiate L.) were cultivated. Results indicate the plots under zero tillage with bed planting (ZT-B) and zero tillage with flat planting (ZT-F) had nearly 28 and 26% higher total SOC stock compared with conventional tillage and bed planting (CT-B) (similar to 5.5 Mg ha(-1)) in the 0-5 cm soil layer. Plots under ZT-B and ZT-F contained higher total SOC stocks in the 0-5 and 5-15 cm soil layers than CT-B plots. Although there were significant variations in total SOC stocks in the surface layers, SOC stocks were similar under all treatments in the 0-30 cm soil layer. Residue management had no impact on SOC stocks in all layers, despite plots under cotton/maize + wheat residue (C/M+W RES) contained similar to 13% higher total SOC concentration than no residue treated plots (N RES; similar to 7.6 g kg(-1)) in the 0-5 cm layer. Hence, tillage and residue management interaction effects were not significant. Although CT-B and ZT-F had similar maize aboveground biomass yields, CT-F treated plots yielded 16% less maize biomass than CT-B plots. However, both wheat and green gram (2012) yields were not affected by tillage. Plots under C/M + W RES had similar to 17, 13, 13 and 32% higher mean cotton, maize, wheat and green gram aboveground biomass yields than N RES plots, yielding similar to 16% higher estimated root (and rhizodeposition) C input in the 0-30 cm soil layer than N RES plots. About 9.3% of the gross C input contributed towards the increase in SOC content under the residue treated plots. However, similar to 7.6 and 10.2% of the gross C input contributed towards the increase in SOC content under CT and if, respectively. Thus, both ZT and partial or full residue retention is recommended for higher soil C retention and sustained crop productivity. (c) Elsevier B.V. All rights reserved.
  • Authors:
    • Wang, Y.-H.
    • Chen, B.-L.
    • Qiang, Z.-Y.
    • Dai, Y.-J.
    • Zhou, Z.-G.
    • He, X.-Y.
  • Source: Chinese Journal of Applied Ecology OR Ying yong sheng tai xue bao = The journal of applied ecology / Zhongguo sheng tai xue xue hui, Zhongguo ke xue yuan Shenyang ying yong sheng tai yan jiu suo zhu ban
  • Volume: 24
  • Issue: 12
  • Year: 2013
  • Summary: To study the effect of temperature increase in boll period (13-Jul. to 24-Aug.) on cotton yield and fiber quality under the global warming background, a pot experiment with cotton cultivar Simian 3 was carried out in half-open-top greenhouse in Pailou experiment station (32 degrees 02' N, 118 degrees 50' E) of Nanjing Agricultural University in 2010 and 2011. The results indicated that when the temperature was increased by 2-3 degrees C (with an average daily temperature of 31.1 to 35.2 degrees C), the biomass declined by 10%, while the cotton yield declined by 30%-40%. The fiber quality also changed significantly with the relative indices responding differently. The micronaire value and fiber strength increased, the fiber length reduced while the fiber uniformity and elongation rate changed little. The plant photosynthesis capability, the biomass accumulation and the ability of carbohydrates transferring to sink organs all deceased. The soluble amino acids, soluble sugar, sucrose and C/N decreased significantly, while the starch content increased significantly. The allocation in vegetative organs was increased while that in reproductive organs was reduced, which in turn declined the economical index. The lower fruit branches were affected little under increased temperature condition while the middle, upper and top branches were affected greatly. The results indicated that, under the 2-3 degrees C warmer condition, the cotton plants experienced the high temperature stress, both the photosynthesis ability and the carbohydrates transportation from-source to sink were decreased, leading to the decline of cotton yield.
  • Authors:
    • Payero, J.
    • Rowlings, D. W.
    • Grace, P. R.
    • Scheer, C.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 95
  • Issue: 1
  • Year: 2013
  • Summary: Irrigation is known to stimulate soil microbial carbon and nitrogen turnover and potentially the emissions of nitrous oxide (N2O) and carbon dioxide (CO2). We conducted a study to evaluate the effect of three different irrigation intensities on soil N2O and CO2 fluxes and to determine if irrigation management can be used to mitigate N2O emissions from irrigated cotton on black vertisols in South-Eastern Queensland, Australia. Fluxes were measured over the entire 2009/2010 cotton growing season with a fully automated chamber system that measured emissions on a sub-daily basis. Irrigation intensity had a significant effect on CO2 emission. More frequent irrigation stimulated soil respiration and seasonal CO2 fluxes ranged from 2.7 to 4.1 Mg-C ha(-1) for the treatments with the lowest and highest irrigation frequency, respectively. N2O emission happened episodic with highest emissions when heavy rainfall or irrigation coincided with elevated soil mineral N levels and seasonal emissions ranged from 0.80 to 1.07 kg N2O-N ha(-1) for the different treatments. Emission factors (EF = proportion of N fertilizer emitted as N2O) over the cotton cropping season, uncorrected for background emissions, ranged from 0.40 to 0.53 % of total N applied for the different treatments. There was no significant effect of the different irrigation treatments on soil N2O fluxes because highest emission happened in all treatments following heavy rainfall caused by a series of summer thunderstorms which overrode the effect of the irrigation treatment. However, higher irrigation intensity increased the cotton yield and therefore reduced the N2O intensity (N2O emission per lint yield) of this cropping system. Our data suggest that there is only limited scope to reduce absolute N2O emissions by different irrigation intensities in irrigated cotton systems with summer dominated rainfall. However, the significant impact of the irrigation treatments on the N2O intensity clearly shows that irrigation can easily be used to optimize the N2O intensity of such a system.
  • Authors:
    • Hulugalle, N. R.
  • Source: Crop and Pasture Science
  • Volume: 64
  • Issue: 8
  • Year: 2013
  • Summary: Partial mitigation of global warming caused by accelerated emissions of greenhouse gases such as carbon dioxide may be possible by storing atmospheric carbon in soils. Carbon storage is influenced by processes and properties that affect soil aggregation, such as clay and silt concentrations and mineralogy, intensity and frequency of wet/dry cycles, and microbial activity. Microbial activity, in turn, is influenced by factors such as temperature, nutrient and water availability, and residue quality. The objective of this study was to assess the influence of average annual maximum temperature on soil carbon storage in Vertosols under cotton-based farming systems. This paper reports a re-evaluation of results obtained from a series of experiments on cotton-farming systems conducted in eastern Australia between 1993 and 2010. The experimental sites were in the Macquarie and Namoi Valleys of New South Wales, and the Darling Downs and Central Highlands of Queensland. Average soil organic carbon storage in the 0-0.6m depth was highest in a Black Vertosol in Central Queensland and lowest in a Grey Vertosol that was irrigated with treated sewage effluent at Narrabri. At other sites, average values were generally comparable and ranged from 65 to 85 t C/ha. Climatic parameters such as ambient maximum temperature, T-max, and rainfall at rainfed sites (but not irrigated sites) were also related to soil organic carbon storage. At most sites, variations in carbon storage with average ambient maximum temperature were described by Gaussian models or bell-shaped curves, which are characteristic of microbial decomposition. Carbon storage occurred at peak rates only for a very limited temperature range at any one site, with these temperatures increasing with decreasing distance from the equator. The exception was a site near Narrabri that was irrigated with treated sewage effluent, where the relationship between soil organic carbon and T-max was linear. The decrease or absence of change in soil carbon storage with time reported in many Australian studies of annual cropping systems may be due to carbon storage occurring within a limited temperature range, whereas intra-seasonal average maximum temperatures can range widely. Further research needs to be conducted under field conditions to confirm these observations.
  • Authors:
    • Finlay, L. A.
    • Weaver, T. B.
    • Hulugalle, N. R.
    • Heimoana, V.
  • Source: CROP & PASTURE SCIENCE
  • Volume: 64
  • Issue: 8
  • Year: 2013
  • Summary: Long-term studies of soil organic carbon dynamics in two- and three-crop rotations in irrigated cotton (Gossypium hirsutum L.) based cropping systems under varying stubble management practices in Australian Vertosols are relatively few. Our objective was to quantify soil organic carbon dynamics during a 9-year period in four irrigated, cotton-based cropping systems sown on permanent beds in a Vertosol with restricted subsoil drainage near Narrabri in north-western New South Wales, Australia. The experimental treatments were: cotton-cotton (CC); cotton-vetch (Vicia villosa Roth. in 2002-06, Vicia benghalensis L. in 2007-11) (CV); cotton-wheat (Triticum aestivum L.), where wheat stubble was incorporated (CW); and cotton-wheat-vetch, where wheat stubble was retained as in-situ mulch (CWV). Vetch was terminated during or just before flowering by a combination of mowing and contact herbicides, and the residues were retained as in situ mulch. Estimates of carbon sequestered by above- and below-ground biomass inputs were in the order CWV>>CW=CV>CC. Carbon concentrations in the 0-1.2m depth and carbon storage in the 0-0.3 and 0-1.2m depths were similar among all cropping systems. Net carbon sequestration rates did not differ among cropping systems and did not change significantly with time in the 0-0.3m depth, but net losses occurred in the 0-1.2m depth. The discrepancy between measured and estimated values of sequestered carbon suggests that either the value of 5% used to estimate carbon sequestration from biomass inputs was an overestimate for this site, or post-sequestration losses may have been high. The latter has not been investigated in Australian Vertosols. Future research efforts should identify the cause and quantify the magnitude of these losses of organic carbon from soil.