• Authors:
    • Al-Kaisi, M.
    • Guzman, J.
    • Parkin, T.
  • Source: SOIL SCIENCE SOCIETY OF AMERICA JOURNAL
  • Volume: 79
  • Issue: 2
  • Year: 2015
  • Summary: The removal of corn residue for bioethanol may require changes in current tillage and fertilization practices to minimize potential alterations to the soil environment that may lead to increase in greenhouse gas (GHG) emission. The objectives of this study were to examine how tillage, N fertilization rates, residue removal, and their interactions affect CO2, and N2O soil surface emissions. Greater CO2 emission coincided with higher soil temperatures typically observed with conventional tillage (CT) compared with no-tillage (NT), resulting in greater annual cumulative CO2 emission in CT (18.1 CO2 Mg ha-1 yr-1) compared with NT (16.2 CO2 Mg ha-1 yr-1) in 2009 and 2010 across sites. However, drier soil conditions during the growing season in 2011 lead to higher soil temperatures compared with 2009 and 2010. Consequently, annual cumulative CO2 emission from NT with 50 and 100% residue removal was (19.5 CO2 Mg ha-1 yr-1) greater than that from CT (17.8 CO2 Mg ha-1 yr-1) across all residue removal rates and from NT (17.5 CO2 Mg ha-1 yr-1) with no residue removal, respectively across all N rates in the Ames central site (AC) in 2011. In the Armstrong southwest site (ASW) site, there were no significant differences between tillage or residue removal rates for annual cumulative CO2 emission (19.9 CO2 Mg ha-1 yr-1) in 2011. Although N2O emission was considerably lower than CO2 emission, differences in N fertilization rates did have a significant impact on global warming potential once these gases were converted on the basis of their radiative forcing of the atmosphere.
  • Authors:
    • Dufour, J.
    • I., Diego
    • Peters, J. F.
  • Source: Science Article
  • Volume: 49
  • Issue: 8
  • Year: 2015
  • Summary: The application of biochar as a soil amendment is a potential strategy for carbon sequestration. In this paper, a slow pyrolysis system for generating heat and biochar from lignocellulosic energy crops is simulated and its life-cycle performance compared with that of direct biomass combustion. The use of the char as biochar is also contrasted with alternative use option's: cofiring in coal power plants, use as charcoal, and use as a fuel for heat generation. Additionally, the influence on the results of the longterm stability of the biochar in the soil, as well as of biochar effects on biomass yield, is evaluated. Negative greenhouse gas emissions are obtained for the biochar system, indicating a significant carbon abatement potential. However, this is achieved at the expense of lower energy efficiency and higher impacts in the other assessed categories when compared to direct biomass combustion. When comparing the different use options of the pyrolysis char, the most favorable result is obtained for char cofiring substituting fossil coal, even assuming high long-term stability of the char. Nevertheless, a high sensitivity to biomass yield increase is found for biochar systems, In this sense, biochar application to low-quality soils where high yield increases are expected would show a more favorable performance in terms of global warming.
  • Authors:
    • Qiu, W.
    • Beare, M. H.
    • Curtin, D.
    • Chantigny, M. H.
    • Curtin, D.
    • Beare, M. H.
    • Qiu, W.
    • Chantigny, M. H.
  • Source: Agronomyhttps://dl.sciencesocieties.org/publications/sssaj/articles/79/3/858 Journal
  • Volume: 79
  • Issue: 3
  • Year: 2015
  • Summary: Water-extractable organic matter has been shown to increase as temperature increases (from 20 to 80°C), with the rate of increase being soil dependent. We examined whether biodegradation during overnight soil-water extraction may influence the temperature response of extractable C and N. Dissolved organic N (DON) and C (DOC), and NH4-N were determined after 16 h of soil-water extraction at either 80 or 50°C (previous work in our laboratory suggested that biodegradation in soil-water suspensions peaks at ~50°C). For both DOC and DON, there were large differences among soils in their temperature responses (e.g., the increase in DON between 50 and 80°C ranged from 29 to 148 mg kg-1). More NH4-N was generated at 50 than at 80°C. Ammonium N produced at 50°C was largely attributable to mineralization (it was almost eliminated when microbial activity was suppressed by extracting with 2 mol L-1 KCI at 50°C). The small amounts of NH4-N found at 80°C were probably of abiotic origin (e.g., thermal degradation of soil organic N). Our results suggested that dissolved organic matter (DOM) was mineralized during the 50°C extraction. The release of DOM was thus underestimated at 50°C and, as a consequence, the temperature response of DOM between 50 and 80°C was overestimated (mineralization at 50°C accounted for most of the variability in the temperature response of DOM). We conclude that the temperature response of DOM can be affected by biodegradation during extraction and that an extraction at 80°C has the important merit that biodegradation during extraction should be negligible. © Soil Science Society of America, 5585 Guilford Rd., Madison Wl 53711 USA.
  • Authors:
    • Dold,Christian
    • Becker,Mathias
  • Source: Journal of Plant Nutrition and Soil Science
  • Volume: 178
  • Issue: 4
  • Year: 2015
  • Summary: Lake Naivasha is a freshwater lake in the East African Rift Valley. With continued lake level declines between 1980 and 2011, the newly exposed land areas were gradually taken for agricultural use. The resulting chronosequences allow for an analysis of the effects of land use duration on nutrient dynamics and agricultural production. Transects representing land use durations of 0-30 (cropland) and 15-30 years (pasture) were established on soils formed on alluvial deposits and lacustrine sediments. We assessed changes in topsoil nitrogen (N) stocks (t ha(-1)), ammonium mineralization potential (N-supplying capacity), and plant-available P with increasing durations of land use. An additional greenhouse experiment studied the responses of kikuyu grass (Cenchrus clandestinus) and maize (Zea mays) in potted topsoil collected from differnt land-use types and chronosequence positions. With increasing duration of land use we noted a significant decline (P < 5%) in soil N contents under both pasture and cropland uses, following a model of exponential decay. The N stocks decreased at 84kgha(-1) a(-1) and a decay rate constant of 0.019a(-1) in pasture soil within 15 years, and at 75kgha(-1) a(-1) with a decay rate-constant of 0.013 a(-1) in cropland soil within 30 years. While the ammonium-N mineralization potential also decreased with land use duration, the trends were significant only in lacustrine pasture soils. Plant-available P did not show any trends that were related to the duration of land use. Kikuyu grass and maize accumulated less dry matter and N as the duration of use increased. This biomass accumulation was significantly related to soil N. A continued mineralization of soil organic matter has possibly contributed to the observed soil N depletion over time. The continuous agricultural use of the littoral wetland zone of Lake Naivasha is likely to entail declining production potentials for both pastures and food crops.
  • Authors:
    • Macdonald,B. C. T.
    • Rochester,I. J.
    • Nadelko,A.
  • Source: Web Of Knowledge
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Excessive N fertilizer use leads to enhanced nitrous oxide (N 2O) emissions from cotton ( Gossypium hirsutum L.) production systems. The objective of the study was to quantify nitrous oxide emissions from the ridges within a furrow-irrigated field during the growth of a cotton crop that had been fertilized with urea at 0, 120, 200, or 320 kg N ha -1. No measurements were taken from the furrows; we assumed similar N 2O emissions from the furrows in this system. The N 2O emissions increased exponentially with N fertilizer rate. Over the cotton-growing season, N 2O emissions totalled 0.51, 0.95, 0.78, and 10.62 kg N 2O-N ha -1, for the four respective N fertilizer rates. The cotton phase of the cotton-faba bean ( Vicia faba L.)-fallow rotation was the main contributor to the total N 2O emission. Over this 2-yr rotation, emissions totalled 1.23, 1.65, 1.44, and 11.48 kg N 2O-N ha -1. However, <0.35% of the N fertilizer applied was emitted as N 2O for the complete rotation where the economic optimal N fertilizer rate for the cotton crop was not exceeded. More than 3.5% of the N fertilizer was emitted as N 2O where 320 kg N ha -1 was applied, which was estimated to represent about 11 kg N ha -1. These data indicate that supra-optimal N fertilizer applications increase the net emissions of N 2O from the ridges in high-yielding furrow-irrigated cropping systems. The N 2O emissions could be decreased further by reducing or eliminating the time in fallow.
  • Authors:
    • Machado,S.
    • Pritchett,L.
    • Petrie,S.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Winter wheat ( Triticum aestivum L.)-summer fallow (WW-SF) using conventional tillage (CT), the predominant cropping system in eastern Oregon, has increased soil erosion and depleted soil organic carbon (SOC). This research evaluates no-tillage (NT) systems designed to reduce these negative impacts on soil. In this long-term experiment (2004-2010), WW-SF using CT was compared with annual winter wheat (WW-WW), annual spring wheat (SW-SW), annual spring barley ( Hordeum vulgare L.) (SB-SB), winter wheat-chemical fallow (WW-CF), winter wheat-winter pea ( Pisum sativum L.) (WW-WP), and winter wheat-spring barley-chemical fallow rotation (WW-SB-CF), using NT. Measurements included, phenology, plant population, grain yield and yield components, residues, SOC, soil moisture, and precipitation. Water-use efficiency (WUE) was derived from precipitation and yield data. Under annual cropping, WW-WP and SB-SB produced higher yields than WW-WW and SW-SW. Grain yields in rotations with fallow (WW-SF, WW-CF, and WW-SB-CF) were not significantly different. On an annual basis, SB-SB and WW-WP produced the highest and lowest yields, respectively. The WUEs of fallow rotations, SB-SB, and SW-SW, were not different but were higher than WUEs of WW-WP and WW-WW. Residue cover and SOC were highest under annual cropping systems and lowest following peas in WW-WP and SF in WW-SF. We conclude that rotations with fallow using NT (WW-CF and WW-SB-CF) can replace the traditional WW-SF system without yield penalty.
  • Authors:
    • Franklin,D.
    • Bender-Özenç,D.
    • Özenç,N.
    • Cabrera,M.
  • Source: Soil Science Society of America Journal
  • Volume: 79
  • Issue: 5
  • Year: 2015
  • Summary: composts and soil conditioners may be useful soil amendments to provide organic matter as well as nutrients such as n and P, but net n mineralized and P released can vary greatly among materials. consequently, it is important to identify the material characteristics that control these processes. Furthermore, the magnitude of these processes may be affected by particle size. we conducted two laboratory studies at 30°c to: (i) identify variables that can be used to estimate n mineralized and Mehlich-1 P released from 14 composts and soil conditioners; and (ii) evaluate net n mineralized from three size fractions (<1.0 mm, 1.0-2.0, and 2.0-4.0 mm) of five different composts. organic n content and c/n ratio explained 83% of the variability in the amount of net n mineralized or immobilized per unit of material from the 14 composts or conditioners in 214 d. similarly, organic n content and total P content explained 99% of the variability in the amount of Mehlich-1 P released per unit of material. in the study with size fractions, we found that larger size fractions (1-4 mm) mineralized more n (4% of applied n) than the 0-to 1-mm size fraction (0.5%). these results indicate that sieving composts to obtain specific size fractions may affect the rate of n mineralization. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.
  • Authors:
    • Castellano, M. J.
    • Sawyer, J. E.
    • Jeske, E. S.
    • Hofmockel, K. S.
    • Drijber, R. A.
    • Bach, E. M.
    • Brown, K. H.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 4
  • Year: 2014
  • Summary: Global maize production alters an enormous soil organic C (SOC) stock, ultimately affecting greenhouse gas concentrations and the capacity of agroecosystems to buffer climate variability. Inorganic N fertilizer is perhaps the most important factor affecting SOC within maize-based systems due to its effects on crop residue production and SOC mineralization. Using a continuous maize cropping system with a 13 year N fertilizer gradient (0-269kg Nha(-1)yr(-1)) that created a large range in crop residue inputs (3.60-9.94 Mgdry matter ha(-1)yr(-1)), we provide the first agronomic assessment of long-term N fertilizer effects on SOC with direct reference to N rates that are empirically determined to be insufficient, optimum, and excessive. Across the N fertilizer gradient, SOC in physico-chemically protected pools was not affected by N fertilizer rate or residue inputs. However, unprotected particulate organic matter (POM) fractions increased with residue inputs. Although N fertilizer was negatively linearly correlated with POM C/N ratios, the slope of this relationship decreased from the least decomposed POM pools (coarse POM) to the most decomposed POM pools (fine intra-aggregate POM). Moreover, C/N ratios of protected pools did not vary across N rates, suggesting little effect of N fertilizer on soil organic matter (SOM) after decomposition of POM. Comparing a N rate within 4% of agronomic optimum (208kg Nha(-1)yr(-1)) and an excessive N rate (269kg Nha(-1)yr(-1)), there were no differences between SOC amount, SOM C/N ratios, or microbial biomass and composition. These data suggest that excessive N fertilizer had little effect on SOM and they complement agronomic assessments of environmental N losses, that demonstrate N2O and NO3 emissions exponentially increase when agronomic optimum N is surpassed.
  • Authors:
    • Gatere, L.
    • DeClerck, F.
    • Blanco-Canqui, H.
    • Palm, C.
    • Grace, P.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 187
  • Issue: April
  • Year: 2014
  • Summary: Conservation agriculture (CA) changes soil properties and processes compared to conventional agriculture. These changes can, in turn, affect the delivery of ecosystem services, including climate regulation through carbon sequestration and greenhouse gas emissions, and regulation and provision of water through soil physical, chemical and biological properties. Conservation agriculture can also affect the underlying biodiversity that supports many ecosystem services. In this overview, we summarize the current status of the science, the gaps in understanding, and highlight some research priorities for ecosystem services in conservational agriculture. The review is based on global literature but also addresses the potential and limitations of conservation agriculture for low productivity, smallholder farming systems, particularly in Sub Saharan Africa and South Asia. There is clear evidence that topsoil organic matter increases with conservation agriculture and with it other soil properties and processes that reduce erosion and runoff and increase water quality. The impacts on other ecosystem services are less clear. Only about half the 100+ studies comparing soil carbon sequestration with no-till and conventional tillage indicated increased sequestration with no till; this is despite continued claims that conservation agriculture sequesters soil carbon. The same can be said for other ecosystem services. Some studies report higher greenhouse gas emissions (nitrous oxide and methane) with conservation agriculture compared to conventional, while others find lower emissions. Soil moisture retention can be higher with conservation agriculture, resulting in higher and more stable yields during dry seasons but the amounts of residues and soil organic matter levels required to attain higher soil moisture content is not known. Biodiversity is higher in CA compared to conventional practices. In general, this higher diversity can be related to increased ecosystem services such as pest control or pollination but strong evidence of cause and effect or good estimates of magnitude of impact are few and these effects are not consistent. The delivery of ecosystem services with conservation agriculture will vary with the climate, soils and crop rotations but there is insufficient information to support a predictive understanding of where conservation agriculture results in better delivery of ecosystem services compared to conventional practices. Establishing a set of strategically located experimental sites that compare CA with conventional agriculture on a range of soil-climate types would facilitate establishing a predictive understanding of the relative controls of different factors (soil, climate, and management) on ES outcomes, and ultimately in assessing the feasibility of CA or CA practices in different sites and socioeconomic situations. The feasibility of conservation agriculture for recuperating degraded soils and increasing crop yields on low productivity, smallholder farming systems in the tropics and subtropics is discussed. It is clear that the biggest obstacle to improving soils and other ES through conservation agriculture in these situations is the lack of residues produced and the competition for alternate, higher value use of residues. This limitation, as well as others, point to a phased approach to promoting conservation agriculture in these regions and careful consideration of the feasibility of conservation agriculture based on evidence in different agroecological and socioeconomic conditions.
  • 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.