• Authors:
    • Martins,B. H.
    • Araujo-Junior,C. F.
    • Miyazawa,M.
    • Vieira,K. M.
    • Milori,D. M. B. P.
  • Source: Soil and Tillage Research
  • Volume: 153
  • Year: 2015
  • Summary: Soil organic matter (SOM) plays an important role for soil quality and productivity maintenance, acting as energy source, promoting biological diversity, enhancing terrestrial ecosystems composition. This study assessed the effects of long-term weed control and cover crops between coffee rows on SOM quality in a very clayey (80dagkg-1 of clay) Typic Haplorthox (Dystroferric Red Latosol) from State of Paraná, Southern Brazil. Seven weed control and cover crops were assessed between coffee rows: (i) hand weeding-HAWE; (ii) portable mechanical mower-PMOW; (iii) pré+post-emergence herbicides-HERB; (iv) peanut horse (Arachis hypogeae) cover crop-GMAY; (v) dwarf mucuna (Mucuna deeringiana) cover crop-GMMA; (vi) no-weed control between coffee row-SCAP; (vii) weed check-CONT. Soil samples were collected in the center of the inter-rows between coffee trees at four depths: 0-10cm, 10-20cm, 20-30cm, and 30-40cm. SOM quality assessment included total soil organic carbon (SOC) content and organic matter humification degree (HFIL) by laser-induced fluorescence spectroscopy (LIFS). C content was up to 26% higher for SCAP and CONT samples, compared to the other field conditions, denoting influence of plant material accumulation at top soil (0-10cm). Higher HFIL results (up to 47%) were observed at deeper layers, inferring incidence of less humified/labile structures at top soil, and condensed/recalcitrant character for organic matter at depth, regardless of cover crops and weed control method considered. In terms of weed density it was observed a higher negative impact on weed growth in areas under GMMA cover crop (decrease of 90.8% in weed density). The behavior may be attributed to the chemical composition of the species, ultimately leading to possible occurrence of allelopathic phenomenon. © 2015 Elsevier B.V.
  • Authors:
    • Ahmad, R.
    • Zahir, Z. A.
    • Khalid, M
    • Aon, M
  • Source: Article
  • Volume: 52
  • Issue: 3
  • Year: 2015
  • Summary: In calcareous soils, the effects of biochar characteristics on maize growth are least understood. In a laboratory study, citrus peel biochar (CPB) and green waste biochar (GWB) were produced by slow pyrolysis at 300°C with 20 min residence time. Electrical conductivity, pH, ash, and nutrients i.e. N, P, K, Ca, Mg, S, Zn and Mn content in GWB were greater than CPB. Citrus peel biochar had wider C:N, C:P and C:S ratios than GWB. Efficacy of these biochars was tested for maize growth and nutrient uptake, and chemical properties of calcareous soil. Maize hybrid (Syngenta-6621) was grown in a greenhouse pot trial by using calcareous soil amended either with CPB or GWB at application rates of 0.0, 0.5, 1.0, 1.5 and 2.0% (w/w) along with NPK fertilizers. Our results revealed that increasing rates of CPB, effectively improved maize plant height; fresh and dry weight; chlorophyll content and photosynthetic rate; and N, P and K uptake. At varying GWB application rates, maize fresh and dry weight; and N and P uptake was improved. Regarding plant growth and nutrient uptake, the overall response of CPB was better than GWB. At 2.0% application rate, CPB resulted better fresh weight (19%), dry weight (24%), plant height (20%), N uptake (42%), P uptake (36%) and K uptake (30%), than from the treatment having same rate of GWB. Due to biochar addition, the highest percentage of N and P recovery (5.3 and 6.6%, respectively) was obtained at 2.0% CPB application rate, while the highest K recovery (9.8%) was obtained at CPB application rate of 0.5%. At 2.0% application rate, CPB decreased soil pH up to 7.96 and increased soil organic carbon up to 1.25%, and GWB increased soil electrical conductivity up to 1.45 dS m -1. Conclusively, CPB produced at 300°C pyrolysis temperature with 20 min residence time, could be effectively used at the rate of 2.0%, for improving maize growth and nutrient uptake, and chemical characteristics of calcareous soil.
  • Authors:
    • Ju, X.
    • Norse, D.
  • Source: Article
  • Volume: 209
  • Year: 2015
  • Summary: China's successful achievement of food security in recent decades has resulted in serious damage to the environment upstream of the agricultural sector, on farm and downstream. The environmental costs of this damage are not only agro-ecosystem function and the long-term sustainability of food production, but also bio-physical including human health with impacts at all levels from the local to the global, and with economic loss estimates ranging from 7 to 10% of China's agricultural gross domestic product (GDP). This paper presents a systematic analysis of the causes and impacts of these environmental costs for China's cropping systems and crop-based livestock systems, and focuses on the nitrogen management. Since the 1980s most of the environmental costs have been related to the intensification of first grain production stimulated by high nitrogen fertilizer and irrigation subsidies, and then vegetable production and fruit trees, with the overuse and misuse of synthetic nitrogen fertilizer and manure being the dominant cause of eutrophication, soil acidification and high greenhouse gas emissions. However, during the last 10 years or so the expansion of intensive livestock production has become a serious cause of direct and indirect air and water pollution and is destined to be the main agricultural threat to China's environment in the long-term unless a holistic strategy for sustainable intensification is adopted for the next and future 5 Year Plans. This strategy should focus on improving nutrient management to limit nitrogen overuse, which is now the main cause of the economic losses from agriculture's damage to the environment.
  • Authors:
    • Cai, X.
    • Zhuang, Q.
    • Qin, Z.
  • Source: Original Research
  • Volume: 7
  • Issue: 6
  • Year: 2015
  • Summary: Growing biomass feedstocks from marginal lands is becoming an increasingly attractive choice for producing biofuel as an alternative energy to fossil fuels. Here, we used a biogeochemical model at ecosystem scale to estimate crop productivity and greenhouse gas (GHG) emissions from bioenergy crops grown on marginal lands in the United States. Two broadly tested cellulosic crops, switchgrass, and Miscanthus, were assumed to be grown on the abandoned land and mixed crop-vegetation land with marginal productivity. Production of biomass and biofuel as well as net carbon exchange and nitrous oxide emissions were estimated in a spatially explicit manner. We found that, cellulosic crops, especially Miscanthus could produce a considerable amount of biomass, and the effective ethanol yield is high on these marginal lands. For every hectare of marginal land, switchgrass and Miscanthus could produce 1.0-2.3kl and 2.9-6.9kl ethanol, respectively, depending on nitrogen fertilization rate and biofuel conversion efficiency. Nationally, both crop systems act as net GHG sources. Switchgrass has high global warming intensity (100-390g CO(2)eql(-1) ethanol), in terms of GHG emissions per unit ethanol produced. Miscanthus, however, emits only 21-36g CO(2)eq to produce every liter of ethanol. To reach the mandated cellulosic ethanol target in the United States, growing Miscanthus on the marginal lands could potentially save land and reduce GHG emissions in comparison to growing switchgrass. However, the ecosystem modeling is still limited by data availability and model deficiencies, further efforts should be made to classify crop-specific marginal land availability, improve model structure, and better integrate ecosystem modeling into life cycle assessment.
  • Authors:
    • Vogel, A.
    • Strecker, T.
    • Steinauer, K.
    • Richter, A.
    • Ramirez, N.
    • Pierce, S.
    • Rong, J.
    • HongYan, G.
    • FuXun, A.
    • Tilman, D.
    • Scheu, S.
    • Reich, P.
    • Power, S.
    • Roscher, C.
    • Niklaus, P.
    • Manning, P.
    • Milcu, A.
    • Thakur, M.
    • Eisenhauer, N.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 11
  • Year: 2015
  • Summary: Soil microbial biomass is a key determinant of carbon dynamics in the soil. Several studies have shown that soil microbial biomass significantly increases with plant species diversity, but it remains unclear whether plant species diversity can also stabilize soil microbial biomass in a changing environment. This question is particularly relevant as many global environmental change (GEC) factors, such as drought and nutrient enrichment, have been shown to reduce soil microbial biomass. Experiments with orthogonal manipulations of plant diversity and GEC factors can provide insights whether plant diversity can attenuate such detrimental effects on soil microbial biomass. Here, we present the analysis of 12 different studies with 14 unique orthogonal plant diversity * GEC manipulations in grasslands, where plant diversity and at least one GEC factor (elevated CO 2, nutrient enrichment, drought, earthworm presence, or warming) were manipulated. Our results show that higher plant diversity significantly enhances soil microbial biomass with the strongest effects in long-term field experiments. In contrast, GEC factors had inconsistent effects with only drought having a significant negative effect. Importantly, we report consistent non-significant effects for all 14 interactions between plant diversity and GEC factors, which indicates a limited potential of plant diversity to attenuate the effects of GEC factors on soil microbial biomass. We highlight that plant diversity is a major determinant of soil microbial biomass in experimental grasslands that can influence soil carbon dynamics irrespective of GEC.
  • Authors:
    • Myers, G.
    • Dodla, S.
    • Zhang, Z.
    • Liu, S.
    • Wang, J.
    • Tian, Z.
  • Source: Science of the Total Environment
  • Volume: 533
  • Year: 2015
  • Summary: Nitrogen (N) fertilization affects both ammonia (NH3) and greenhouse gas (GHG) emissions that have implications in air quality and global warming potential. Different cropping systems practice varying N fertilizations. The aim of this study was to investigate the effects of applications of polymer-coated urea and urea treated with N process inhibitors: NBPT [N-(n-butyl) thiophosphoric triamide], urease inhibitor, and DCD [Dicyandiamide], nitrification inhibitor, on NH3 and GHG emissions from a cotton production systemin the Mississippi delta region. A two-year field experiment consisting of five treatments including the Check (unfertilized), urea, polymer-coated urea (ESN), urea + NBPT, and urea + DCD was conducted over 2013 and 2014 in a Cancienne loam (Fine-silty, mixed, superactive, nonacid, hyperthermic Fluvaquentic Epiaquepts). Ammonia and GHG samples were collected using active and passive chamber methods, respectively, and characterized. The results showed that the N loss to the atmosphere following urea-N application was dominated by a significantly higher emission of N2O-N than NH3-N and the most N2O-N and NH3-N emissions were during the first 30-50 days. Among different N treatments compared to regular urea, NBPT was the most effective in reducing NH3-N volatilization (by 58-63%), whereas DCD the most significant in mitigating N2O-N emissions (by 75%). Polymer-coated urea (ESN) and NBPT also significantly reduced N2O-N losses (both by 52%) over urea. The emission factors (EFs) for urea, ESN, urea-NBPT, urea + DCD were 1.9%, 1.0%, 0.2%, 0.8% for NH3-N, and 8.3%, 3.4%, 3.9%, 1.0% for N2O-N, respectively. There were no significant effects of different N treatments on CO2-C and CH4-C fluxes. Overall both of these N stabilizers and polymer-coated urea could be used as a mitigation strategy for reducing N2O emission while urease inhibitor NBPT for reducing NH3 emission in the subtropical cotton production system of the Mississippi delta region. (C) 2015 Elsevier B.V. All rights reserved.
  • Authors:
    • Johnson, J.
    • Ortiz, B. V.
    • Woli, P.
    • Hoogenboom, G.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 6
  • Year: 2015
  • Summary: The winter wheat ( Triticum aestivum L.) growing season in the southeastern United States occurs during the period when the climate of this region is strongly influenced by El Nino-Southern Oscillation (ENSO). The ENSO-based interannual climate variability might influence growth, maturity, and yield of winter wheat. Because different maturity groups of wheat cultivars head at different times of the year, the groups are expected to have different impacts of climate variability. This study examined whether the yield difference between early and late maturity groups of winter wheat cultivars grown in this region were associated with ENSO-based climate. Data on yield, planting date, and heading date were obtained for a number of wheat cultivars grown at four locations in Georgia during the 1975 to 2012 period. Wheat cultivars were classified according to heading date as early or late maturity, and yield differences between maturity groups and among ENSO phases were examined using the Wilcoxon rank sum test. Results showed that the early maturity group could out-yield the late maturity group in southern locations during La Nina, whereas the late group could out-yield the early group in northern locations during El Nino. Of all ENSO phases, La Nina was associated with the largest yields. During El Nino, the yield difference between early and late groups increased with an increase in latitude, whereas during La Nina, the yield difference increased with a decrease in latitude. These findings might be helpful to wheat growers in this region in optimizing decisions regarding planting date and cultivar selection to reduce the risks related to climate variability.
  • Authors:
    • Rust, J.
    • Kimber, S.
    • Herridge, D.
    • Rose, T.
    • Zwieten, L. V.
    • Cowie, A.
    • Morris, S.
  • Source: Article
  • Volume: 395
  • Issue: 1/2
  • Year: 2015
  • Summary: Background and aims: Acid soils constrain legume growth and biochars have been shown to address these constraints and enhance biological N 2 fixation in glasshouse studies. A dissection of causal mechanisms from multiple crop field studies is lacking. Methods: In a sub-tropical field study, faba bean ( Vicia faba L.) was cultivated in rotation with corn ( Zea mays) following amendment of two contrasting biochars, compost and lime in a rhodic ferralsol. Key soil parameters and plant nutrient uptake were investigated alongside stable 15N isotope methodologies to elucidate the causal mechanisms for enhanced biological N 2 fixation and crop productivity. Results: Biological N 2 fixation was associated with plant Mo uptake, which was driven by reductions in soil acidity following lime and papermill (PM) biochar amendment. In contrast, crop yield was associated with plant P and B uptake, and amelioration of soil pH constraints. These were most effectively ameliorated by PM biochar as it addressed both pH constraints and low soil nutrient status. Conclusions: While liming resulted in the highest biological N 2 fixation, biochars provided greater benefits to faba bean yield by addressing P nutrition and ameliorating Al toxicity.
  • Authors:
    • Muirhead, B.
    • Nelson, P. N.
    • Bass, A. M.
    • Agegnehu, G.
    • Wright,Graeme
    • Bird,Michael I.
  • Source: Article
  • Volume: 213
  • Year: 2015
  • Summary: This study investigated the effects of biochar and compost, applied individually or together, on soil fertility, peanut yield and greenhouse gas (GHG) emissions on a Ferralsol in north Queensland, Australia. The treatments were (1) inorganic fertilizer only (F) as a control; (2) 10 t ha(-1) biochar + F (B +F); (3) 25 t compost +F (Com +F) ha-1; (4) 2.5t B ha(-1) + 25 t Com ha-1 mixed on site +F; and (5) 25 t ha(-1) cocomposted biochar-compost + F (COMBI + F). Application of B and COMBI increased seed yield by 23% and 24%, respectively. Biochar, compost and their mixtures significantly improved plant nutrient availability and use, which appeared critical in improving peanut performance. Soil organic carbon (SOC) increased from 0.93% (F only) to 1.25% (B amended), soil water content (SWC) from 18% (F only) to over 23% (B amended) and CEC from 8.9 cmol(+)/kg (F only) to over 103 cmol(+)/kg (organic amended). Peanut yield was significantly positively correlated with leaf chlorophyll content, nodulation number (NN), leaf nutrient concentration, SOC and SWC for the organic amendments. Fluxes of CO2 were highest for the F treatment and lowest for the COMBI treatment, whereas N2O flux was highest for the F treatment and all organic amended plots reduced N2O flux relative to the control. Principal component analysis indicates that 24 out of 30 characters in the first principal component (PRIN1) individually contributed substantial effects to the total variation between the treatments. Our study concludes that applications of B, Cam, B +Com or COMBI have strong potential to, over time, improve SOC, SWC, soil nutrient status, peanut yield and abate GHG fluxes on tropical Ferralsols. Crown Copyright (C) 2015 Published by Elsevier B.V. All rights reserved.
  • Authors:
    • Mohanty, S. R.
    • Dunfield, P.
    • Dubey, G.
    • Kollah, B.
  • Source: Article
  • Volume: 20
  • Issue: 8
  • Year: 2015
  • Summary: Experiments were carried out to determine how the incorporation of biomass from the bioenergy crop Jatropha curcas into a tropical vertisol affects the biogeochemical processes important for greenhouse gas (GHG) fluxes, specifically methane (CH 4) production, carbon dioxide (CO 2) production, and CH 4 consumption. Leaf biomass of J. curcas was incorporated at 0.1, 0.5, and 1% ( w/w) into soil maintained under 60% of moisture-holding capacity (MHC). Biomass addition significantly stimulated potential CH 4 and CO 2 production while inhibiting potential CH 4 consumption. When 1% of J. curcas biomass was added to soil, potential CH 4 production increased nearly 50-fold over 60 days, from 2.45 g CH 4?g -1 soilday -1 in unamended soil to 115 gg -1day -1 in soil containing leaf biomass. Soil CO 2 production also doubled when the J. curcas biomass was added. The potential CH 4 consumption rate of soil was inhibited almost completely by 1% of added biomass. The culturable methanotroph population was positively correlated with the CH 4 consumption rate ( r=0.961, p<0.0001) and was inhibited 20-fold by 1% of biomass addition. In contrast, the total population of aerobic heterotrophs culturable on a complex medium increased from 11 to 59*10 6 of colony-forming units (CFU) g -1 of soil after biomass addition. Significant positive correlation was observed between the total heterotroph population and both CH 4 production ( r=0.861, p=0.0003) and CO 2 production ( r=0.863, p=0.0002). Our study shows that biomass from the bioenergy crop J. curcas can affect soil biogeochemical processes that control GHG emissions. We propose that a high incorporation of J. curcas biomass could dramatically change the CH 4 flux in tropical soil by simultaneously increasing CH 4 production and decreasing CH 4 consumption, and we therefore recommend that biomass incorporation to soil be minimized (<0.1%) as a strategy to mitigate GHG emission.