• Authors:
    • Zhang, X.
    • Zheng, J.
    • Li, L.
    • Hussain, Q.
    • Pan, G.
    • Liu, Y.
    • Zhang, A.
  • Source: Plant and Soil
  • Volume: 351
  • Issue: 1-2
  • Year: 2012
  • Summary: A field experiment was conducted to investigate the effect of biochar on maize yield and greenhouse gases (GHGs) in a calcareous loamy soil poor in organic carbon from Henan, central great plain, China. Biochar was applied at rates of 0, 20 and 40 t ha(-1) with or without N fertilization. With N fertilization, urea was applied at 300 kg N ha(-1), of which 60% was applied as basal fertilizer and 40% as supplementary fertilizer during crop growth. Soil emissions of CO2, CH4 and N2O were monitored using closed chambers at 7 days intervals throughout the whole maize growing season (WMGS). Biochar amendments significantly increased maize production but decreased GHGs. Maize yield was increased by 15.8% and 7.3% without N fertilization, and by 8.8% and 12.1% with N fertilization under biochar amendment at 20 t ha(-1) and 40 t ha(-1), respectively. Total N2O emission was decreased by 10.7% and by 41.8% under biochar amendment at 20 t ha(-1) and 40 t ha(-1) compared to no biochar amendment with N fertilization. The high rate of biochar (40 t ha(-1)) increased the total CO2 emission by 12% without N fertilization. Overall, biochar amendments of 20 t ha(-1) and 40 t ha(-1) decreased the total global warming potential (GWP) of CH4 and N2O by 9.8% and by 41.5% without N fertilization, and by 23.8% and 47.6% with N fertilization, respectively. Biochar amendments also decreased soil bulk density and increased soil total N contents but had no effect on soil mineral N. These results suggest that application of biochar to calcareous and infertile dry croplands poor in soil organic carbon will enhance crop productivity and reduce GHGs emissions.
  • Authors:
    • Cotrufo, M. F.
    • Stewart, C. E.
    • Zheng, J.
  • Source: Journal of Environmental Quality
  • Volume: 41
  • Issue: 5
  • Year: 2012
  • Summary: Biochar (BC) application to agricultural soils could potentially sequester recalcitrant C, increase N retention, increase water holding capacity, and decrease greenhouse gas (GHG) emissions. Biochar addition to soils can alter soil N cycling and in some cases decrease extractable mineral N (NO3- and NH4+) and N2O emissions. These benefits are not uniformly observed across varying soil types, N fertilization, and BC properties. To determine the effects of BC addition on N retention and GHG flux, we added two sizes (>250 and <250 mu m) of oak-derived BC (10% w/w) to two soils (aridic Argiustoll and aquic Haplustoll) with and without N fertilizer and measured extractable NO3- and NH4+ and GHG efflux (N2O, CO2, and CH4) in a 123-d laboratory incubation. Biochar had no effect on NO3-, NH4+, or N2O in the unfertilized treatments of either soil. Biochar decreased cumulative extractable NO3- in N fertilized treatments by 8% but had mixed effects on NH4+. Greenhouse gas efflux differed substantially between the two soils, but generally with N fertilizer BC addition decreased N2O 3 to 60%, increased CO2 10 to 21%, and increased CH4 emissions 5 to 72%. Soil pH and total treatment N (soil + fertilizer + BC) predicted soil N2O flux well across these two different soils. Expressed as CO2 equivalents, BC significantly reduced GHG emissions only in the N-fertilized silt loam by decreasing N2O flux. In unfertilized soils, CO2 was the dominant GHG component, and the direction of the flux was mediated by positive or negative BC effects on soil CO2 flux. On the basis of our data, the use of BC appears to be an effective management strategy to reduce N leaching and GHG emissions, particularly in neutral to acidic soils with high N content.
  • Authors:
    • Urquiaga, S.
    • Martellotto, E. E.
    • Jantalia, C. P.
    • Alves, B. J. R.
    • Alvarez, C. R.
    • Costantini, A.
    • Alvarez, C.
  • Source: NUTRIENT CYCLING IN AGROECOSYSTEMS
  • Volume: 94
  • Issue: 2-3
  • Year: 2012
  • Summary: The aim of this study was to analyze the influence of different crop sequences (soybean-corn and soybean-soybean) and tillage systems (no tillage and reduced tillage) on nitrous oxide (N2O) soil emissions under field conditions. The experiment was carried out in Manfredi, Crdoba province, Argentina on an Entic Haplustoll and N2O emissions were measured in the field during a year. N2O fluxes were low during winter, but in late spring it peaked. For fallow, N-NO3-content was the most important variable to explain N2O emissions. For growing period water-filled pores was the main variable explaining N2O emissions. Nitrogen fertilization of corn crop increased N2O-N emissions, whereas no significant differences were found due to the tillage system. Measured annual N2O-N emissions were generally lower than those calculated using the methodology proposed by the Intergovernmental Panel on Climate Change.
  • Authors:
    • Singh, H.
    • Singh, P.
    • Toor, A. S.
    • Brar, K.
    • Benbi, D. K.
  • Source: Web Of Knowledge
  • Volume: 92
  • Issue: 1
  • Year: 2012
  • Summary: Labile fractions of soil organic C are considered important indicators of soil quality as these can respond rapidly to land-use changes and agricultural management. We studied the impact of three different land-use systems viz. poplar-based agroforestry involving wheat-legume rotation, rice-wheat and maize-wheat agroecosystems, on dynamics of total organic C (TOC), oxidisable soil organic C (SOC), very labile, labile, less labile, and recalcitrant C fractions, water extractable organic carbon (WEOC), hot water soluble C (HWC), microbial biomass C (MBC), and mineralizable C in the semi-arid subtropical India. The maize-wheat and agroforestry systems had 65-88% higher SOC stocks than the rice-wheat system and were characterized by predominantly labile C. About 56-60% of the total organic C in maize-wheat and agroforestry systems occurred as labile and very labile C compared to 37% under rice-wheat rotation. Contrarily, the majority of organic C (63%) in rice-wheat soils was stabilized in less labile and recalcitrant forms. The HWC and MBC were also higher in maize-wheat and agroforestry systems as opposed to the rice-wheat system. In the discriminant function analysis, a composite of indicators involving TOC, recalcitrant C and total N correctly distinguished the soils under the three systems. The results suggested that in agroforestry and maize-wheat systems the organic C in soils was less stable and thus could be lost following the land-use change.
  • Authors:
    • Huang, S. M.
    • Yang, X. Y.
    • Zhang, W. J.
    • Wang, X. J.
    • Xu, M. G.
    • Cong, R. H.
    • Wang, B. R.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 93
  • Issue: 2
  • Year: 2012
  • Summary: Soil carbon dynamics would be influenced by fertilization management in the agro-ecosystem. In this study, we analyze carbon inputs and soil organic carbon (SOC) dynamics under wheat-corn double cropping system based on four long-term experimental sites in different climate zones of China. We examine soil carbon responses to various carbon inputs by using linear (S = aA - b) and non-linear () equations. The term S is the SOC change rate; a, the proportion of C inputs incorporated into soil; b, minimum change rate of SOC; S (M) , the asymptotic maximum value at SOC change rate approaching infinity (Mg C ha(-1) year(-1)); S (L) , the decomposition rate of SOC substrates, and K (S) , a constant value (or 'half-saturation constant'). The S value is fitted using linear equation with SOC data over the duration of the experiment. The annual C input (A) is estimated by measured crop biomass and C input from manure. Different amounts of balanced fertilization show little impact on the C inputs derived by plants, reaching to similar to.5 Mg C ha(-1) year(-1). The SOC change rate is much higher under the manure application than treatments with chemical fertilizers only. Statistical analysis shows that the linear and non-linear equations perform equally well (p < 0.01) within the experimental data interval. But the non-linear equation is more suitable for specific purpose. Using the non-linear equation, we can predict that minimum C input to maintain the current SOC level would be 0.33-1.32 Mg C ha(-1) year(-1) at the most sites but only 0.03 Mg C ha(-1) year(-1) at the Changping site. The chemical nitrogen and phosphate fertilization yield sufficient carbon biomass inputs to maintain the current SOC levels. However, to increase SOC at 1 Mg C ha(-1) year(-1), soils need over 10 Mg C ha(-1) year(-1) at most sites. Our results suggest that the increment of SOC stocks would be mainly related to the additional carbon inputs for the long-term perspectives.
  • Authors:
    • Chen, X.
    • Yang, X. D.
    • Anderson, N. J.
    • Dong, X. H.
    • Shen, J.
  • Source: Global Change Biology
  • Volume: 18
  • Issue: 7
  • Year: 2012
  • Summary: Floodplain lakes may play an important role in the cycling of organic matter at the landscape scale. For those lakes on the middle and lower reaches of the Yangtze (MLY) floodplain which are subjected to intense anthropogenic disturbance, carbon burial rates should, theoretically, be substantial due to the high nutrient input, increased primary production and high sediment accumulation rates. There are more than 600 lakes >1 km 2 on the Yangtze floodplain including 18 lakes >100 km 2 and most are shallow and eutrophic. 210Pb-dated cores were combined with total organic carbon (TOC) analyses to determine annual C accumulation rates (C AR; g C m -2 yr -1) and the total C stock (since ~1850). The sediment TOC content is relatively low with an average <2% in most lakes. C AR ranged from ~5 to 373 g C m -2 yr -1, resulting in C standing stocks of 0.60-15.3 kg C m -2 (mean: ~5 kg C m -2) since ~1850. A multicore study of Chaohu lake (770 km 2) indicated that spatial variability of C burial was not a significant problem for regional upscaling. The possible effect of changes in lake size and catchment land use on C burial was examined at Taibai lake and indicated that lake shrinkage and declining arable agriculture had limited effects on C AR. The organic C standing stock in individual lakes is, however, significantly dependent on lake size, allowing a simple linear scaling for all the MLY lakes. Total regional C sequestration was ~80 Tg C since ~1850, equivalent to ~11% of C sequestration by soils, but in ~3% of the land area. Shallow lakes from MLY are a substantial regional C sink, although strong mineralization occurs due to their shallow nature and their role as C sinks is threatened due to lake drainage.
  • Authors:
    • Holou, R. A. Y.
    • Stevens, G.
  • Source: GCB (Global Change Biology) Bioenergy
  • Volume: 4
  • Issue: 3
  • Year: 2012
  • Summary: The objective of this research was to determine the optimum nitrogen fertilizer rate for producing sweet sorghum (a promising biofuel crop) juice, sugar, and bagasse on silt loam, sandy loam, and clay soils in Missouri. Seven nitrogen fertilization rates were applied, ranging from 0 to 134 kg N ha -1. Regardless of the soil and year, the juice content of sweet sorghum stalk averaged 68.8% by weight. The juice yield ranged from 15.2 to 71.1 m 3 ha -1. Soil and N rate significantly impacted the juice yield ( P
  • Authors:
    • Finlay, L. A.
    • Hulugalle, N. R.
    • Weaver, T. B.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 2
  • Year: 2012
  • Summary: Cover crops in minimum or no-tilled systems are usually killed by applying one or more herbicides, thus significantly increasing costs. Applying herbicides at lower rates with mechanical interventions that do not disturb or bury cover crop residues can, however, reduce costs. Our objective was to develop a management system with the above-mentioned features for prostrate cover crops on permanent beds in an irrigated Vertisol. The implement developed consisted of a toolbar to which were attached spring-loaded pairs of parallel coulter discs, one set of nozzles between the individual coulter discs that directed a contact herbicide to the bed surfaces to kill the cover crop and a second set of nozzles located to direct the cheaper glyphosate to the furrow to kill weeds. The management system killed a prostrate cover crop with less trafficking, reduced the use of more toxic herbicides, carbon footprint, labor and risk to operators. Maximum depth of compaction was more but average increase was less than that with the boom sprayer control.
  • Authors:
    • Lawton-Rauh, A.
    • Agudelo, P.
    • Leach, M.
  • Source: Plant Disease
  • Volume: 96
  • Issue: 1
  • Year: 2012
  • Summary: Rotylenchulus reniformis is a highly variable nematode species and an economically important pest in many cotton fields across the southeastern United States. Rotation with resistant or poor host crops is a method for management of reniform nematode. We studied the effect of six planting schemes covering four 120-day planting cycles on the predominant genotype of R. reniformis. Rotations used were: (i) cotton to corn; (ii) susceptible soybean to corn; (iii) resistant soybean to cotton; (iv) corn to cotton; (v) continuous susceptible soybean; (vi) continuous cotton. After each 120-day cycle, amplified fragment length polymorphisms (AFLPs) produced from four primer pairs were used to determine the effect of crop rotation on the predominant genotype of reniform nematode. A total of 279 polymorphic bands were scored using four primer combinations. Distinct changes in genotype composition were observed following rotations with resistant soybean or corn. Rotations involving soybean (susceptible and resistant) had the greatest effect on population structure. The characterization of field population variability of reniform nematode and of population responses to host plants used in rotations can help extend the durability of resistant varieties and can help identify effective rotation schemes.
  • Authors:
    • Tivet, F.
    • Khamxaykhay, C.
    • Rattanatray, B.
    • Jullien, F.
    • Quoc, H. T.
    • Lestrelin, G.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 27
  • Issue: 1
  • Year: 2012
  • Summary: Over the past half-century, major efforts have been made worldwide to develop sustainable alternatives to agricultural tillage. In line with these efforts, two main research development initiatives have supported the experimentation and dissemination of conservation agriculture (CA) in Laos. Here we present the results of a 4-year monitoring and evaluation study conducted in 21 villages targeted for dissemination. In a context of rapid transition to intensive commercial agriculture in Laos, CA has become an important constituent of agricultural landscapes. However, there are significant variations in adoption rates across the study region. Statistical and qualitative evidence suggests that experimentation and adoption are not contingent upon farm-level variables such as capital, labor, age and education. While access to land helps shape local decision-making, the land tenure threshold under which farmers are not willing to experiment with alternative cropping systems is relatively low and highly variable in both space and time. Rather, experience and awareness of land degradation, production costs, social cohesion and leadership appear to be key factors in explaining most variations in local adoption rates. These results indicate that the practice of CA is not necessarily incompatible with smallholder farming. However, while complex crop associations and rotations are necessary for integrated weed control and reduced chemical use, their diffusion would require a broader transformation of the agricultural industry and the current market demand.