• Authors:
    • Chenu, C.
    • Burlot, A.
    • Barre, P.
    • Virto, I.
  • Source: Biogeochemistry
  • Volume: 108
  • Issue: 1-3
  • Year: 2012
  • Summary: Conversion to no-till (NT) is usually associated to increased soil organic carbon (SOC) stocks in comparison to inversion tillage (IT). However, an important and unexplained variability in the changes in SOC with NT adoption exists, which impedes accurate prediction of its potential for C sequestration. We performed a meta-analysis with pedo-climatic and crop factors observed to influence SOC storage under NT at local and regional scales, in order to determine those better explaining this variability at a global scale. We studied SOC stocks (0-30 cm) in an equivalent soil mass, climatic and soil characteristics in 92 NT-IT paired cases. A sub-base with the 35 pairs providing C inputs was used to test their effect. Greater SOC stocks were observed with NT, with a smaller difference than often described (6.7%, i.e. 3.4 Mg C ha(-1)). Crop C inputs differences was the only factor significantly and positively related to SOC stock differences between NT and IT, explaining 30% of their variability. The variability in SOC storage induced by NT conversion seems largely related to the variability of the crop production response. Changes at the agro-ecosystem level, not only in soil, should be considered when assessing the potential of NT for C sequestration.
  • 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:
    • Easter, M.
    • Alvaro-Fuentes, J.
    • Paustian, K.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 155
  • Year: 2012
  • Summary: The interactive effects of climate change and atmospheric CO 2 rise could have potential effects on both soil organic carbon (SOC) storage and the capability of certain management practices to sequester atmospheric carbon (C) in soils. In this study, we present the first regional estimation of SOC stock changes under climate change in Spanish agroecosystems. The Century model was applied over a 80-yr period (i.e., from 2007 to 2087) to an agricultural area of 40,498 km 2 located in northeast Spain under five different climate scenarios. The model predicted an increase in SOC storage in the 0-30 cm soil depth in all the climate change scenarios tested (i.e., ECHAM4-A2, ECHAM4-B2, CGCM2-A2 and CGCM2-B2). Among climate change scenarios, SOC stock changes ranged from 0.15 to 0.32 Tg C yr -1. The Century model also predicted differences in SOC sequestration among agricultural classes. At the end of the simulation period, the greatest SOC stocks were found in the rainfed arable land under monoculture and no-tillage (MC-NT) class and in the grape-olive (GO) class with average stocks greater than 80 Mg C ha -1. On the contrary, both the alfalfa (AF) and the cereal-fallow (CF) classes showed the lowest SOC stocks with predicted values lower than 60 Mg C ha -1. Under climate change conditions, Spanish agricultural soils could act as potential atmospheric C sinks. Nevertheless, both the magnitude of the change in climate and the adoption of beneficial management practices could be critical in maximizing SOC sequestration.
  • Authors:
    • Huggins, D. R.
    • Brown, T. T.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012
  • Summary: Knowledge of soil organic carbon (SOC) changes that occur under different agricultural practices is important for policy development, carbon (C) marketing, and sustainable land management. Our objective was to quantify agricultural impacts on SOC sequestration for dryland cropping systems in different agroclimatic zones (ACZs) of the Pacific Northwest (PNW). Data from 131 SOC studies were analyzed to assess land management-induced changes in SOC, including the conversion of native ecosystems to agricultural crops, conversion from conventional tillage (CT) to no-tillage (NT), and alternative crop rotations and management practices. Cumulative probabilities of SOC change were developed for assessing uncertainties inherent in SOC studies and for informing SOC markets. These analyses showed that 75% of converted native land lost at least 0.14 to 0.70 Mg C ha(-1) y(-1) (0.06 to 0.31 tn C ac(-1) yr(-1)) over an average of 55 to 74 years depending on ACZ. Converting from CT to NT was predicted to increase SOC at least 0.12 to 0.21 Mg C ha(-1) y(-1) (0.05 to 0.09 tn C ac(-1) yr(-1)) over 10 to 12 years in 75% of studies analyzed and was also ACZ specific. Compared to annual cropping, mixed perennial-annual systems would be expected to gain at least 0.69 Mg C ha(-1) y(-1) (0.31 tn C ac(-1) ha(-1)) over 12 years in 75% of ACZ 2 sites. Other conclusions were that (1) SOC databases are lacking for low precipitation areas of the PNW; such as the dryland wheat-fallow region; (2) baseline sampling of SOC prior to management change is largely nonexistent for PNW databases except for a few notable cases; (3) soil erosion processes have likely impacted SOC and contributed to large variability among studies; (4) sampling methodologies and analyses for SOC have been inconsistent, thereby contributing to SOC variability; and (5) a validated C model for the PNW would aid evaluation of SOC changes due to management, particularly for specific farms and sites with unique SOC history and circumstances.
  • Authors:
    • Reitsma, K.
    • Carlson, G. C.
    • Gelderman, R. H.
    • Stone, J.
    • Clay, S. A.
    • Chang, J. Y.
    • Clay, D. E.
    • Jones, M.
    • Janssen, L.
    • Schumacher, T.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: The corn (Zea mays L.)-based ethanol carbon footprint is impacted by many factors including the soil's C sequestration potential. The study's objective was to determine the South Dakota corn-based ethanol surface SOC sequestration potential and associated partial C footprint. Calculated short-term C sequestration potentials were compared with long-term sequestration rates calculated from 95,214 producer soil samples collected between 1985 and 2010. National Agricultural Statistics Service (NASS) grain yields, measured root/shoot ratios and harvest indexes, soil organic C (SOC) and nonharvested C (NHC) first-order rate constants, measured SOC benchmarks [81,391 composite soil samples (0-15 cm) collected between 1985 and 1998], and 34,704 production surveys were used to calculate the short-term sequestration potentials. The SOC short-term, area weighted sequestration potential for the 2004 to 2007 time period was 181 kg C (ha * yr) -1. This relatively low rate was attributed to a drought that reduced the amount of NHC returned to soil. For the 2008 to 2010 time period, the area weighted short-term sequestration rate was 341 kg (ha * yr) -1. This rate was similar to the long-term measured rate of 368 kg C (ha * yr) -1. Findings from these independent SOC sequestration assessments supports the hypothesis that many of the regions surface soils are C sinks when seeded with corn. Based on short-term C sequestration rates, corn yields, and the corn conversion rate to ethanol, the area weighted surface SOC footprints for the 2004 to 2007 and 2008 to 2010 time periods was -10.4 and -15.4 g CO 2 equ MJ -1, respectively.
  • 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:
    • 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.
  • Authors:
    • Rocha, H. S.
    • Souza, A. P. de
    • Carvalho, D. F. de
    • Lima, M. E. de
    • Guerra, J. G. M.
  • Source: Revista Brasileira de Engenharia Agrícola e Ambiental
  • Volume: 16
  • Issue: 6
  • Year: 2012
  • Summary: This study was carried out in the municipality of Seropedica-RJ, in order to determine, under organic farming and no tillage system, the yield of eggplants under different irrigation depths and cropping systems (intercropped with legumes and alone). The experimental design was in randomized blocks in a split plot design with four replications. The plots were characterized by the treatments corresponding to different water depths (40, 70, 100, 120% ETc), and the sub plots, the intercropping systems with cowpea and eggplant alone. Cropping systems did not influence the final yield of eggplant. However, considering the different irrigation depths, the highest commercial yield (65.41 Mg ha -1) was obtained for a total depth of 690.04 mm (106.8% ETc). The lower applied depth provided lower quality of fruit compared with that observed in the higher depths. The rate of fruit discard was 3 and 14%, respectively, for the higher and lower depths of irrigation.
  • Authors:
    • Kutu, F. R.
  • Source: African Journal of Agricultural Research
  • Volume: 7
  • Issue: 26
  • Year: 2012
  • Summary: Conservation agriculture experiment was conducted under irrigated and dryland conditions during 2007/2008-summer cropping season to determine a suitable soil-crop management practice for increase maize yield. The study consisted of tillage practices (conventional, minimum and zero), cropping systems (sole and intercrop plots) and fertilizer regimes (unfertilized control, low, adjusted low and optimum) as treatments. Minimum and zero tillage practices constituted the conservation agriculture tillage practices while supplementation of low fertilizer rate with seed inoculation using growth enhancing microbial inoculant constituted the adjusted low fertilizer rate. Fertilizer application gave a significant (P
  • Authors:
    • Horwath, W. R.
    • Wroble, J. F.
    • Munk, D. S.
    • Wallender, W. W.
    • Singh, P. N.
    • Mitchell, J. P.
    • Hogan, P.
    • Roy, R.
    • Hanson, B. R.
  • Source: California Agriculture
  • Volume: 66
  • Issue: 2
  • Year: 2012
  • Summary: Reducing tillage and maintaining crop residues on the soil surface could improve the water use efficiency of California crop production. In two field studies comparing no-tillage with standard tillage operations (following wheat silage harvest and before corn seeding), we estimated that 0.89 and 0.97 inches more water was retained in the no-tillage soil than in the tilled soil. In three field studies on residue coverage, we recorded that about 0.56, 0.58 and 0.42 inches more water was retained in residue-covered soil than in bare soil following 6 to 7 days of overhead sprinkler irrigation. Assuming a seasonal crop evapotranspiration demand of 30 inches, coupling no-tillage with practices preserving high residues could reduce summer soil evaporative losses by about 4 inches (13%). However, practical factors, including the need for different equipment and management approaches, will need to be considered before adopting these practices.