• Authors:
    • Pereira,E. I. P.
    • Suddick,E. C.
    • Mansour,I.
    • Mukome,F. N. D.
    • Parikh,S. J.
    • Scow,K.
    • Six,J.
  • Source: Biology and Fertility of Soils
  • Volume: 51
  • Issue: 5
  • Year: 2015
  • Summary: We investigated the effect of biochar type on plant performance and soil nitrogen (N) transformations in mesocosms representing an organic lettuce ( Lactuca sativa) production system. Five biochar materials were added to a silt loam soil: Douglas fir wood pyrolyzed at 410°C (W410), Douglas fir wood pyrolyzed at 510°C (W510), pine chip pyrolyzed at 550°C (PC), hogwaste wood pyrolyzed between 600 and 700°C (SWC), and walnut shell gasified at 900°C (WS). Soil pH and cation exchange capacity were significantly increased by WS biochar only. Gross mineralization increased in response to biochar materials with high H/C ratio (i.e., W410, W510, and SWC), which can be favorable for organic farming systems challenged by insufficient N mineralization during plant growth. Net nitrification was increased by W510, PC, and WS without correlating with the abundance of ammonia oxidizing gene ( amoA). Increases in N transformation rates did not translate into increases in plant productivity or leaf N content. WS biochar increased the abundance of amoA and nitrite reductase gene ( nirK), while SWC biochar decreased the abundance of amoA and nitrous oxide gene ( nosZ). Decreases in N 2O emissions were only observed in soil amended with W510 for 3 days out of the 42-day growing season without affecting total cumulative N 2O fluxes. This suggests that effects of biochar on decreasing N 2O emissions may be transient, which compromise biochar's potential to be used as a N 2O mitigation strategy in organic systems. Overall, our results confirm that different biochar materials can distinctively affect soil properties and N turnover.
  • Authors:
    • Prasad,J. V. N. S.
    • Rao,Ch S.
    • Ravichandra,K.
    • Jyothi,Ch N.
    • Babu,M. B. B. P.
    • Babu,V. R.
    • Raju,B. M. K.
    • Rao,B. B.
    • Rao,V. U. M.
    • Venkateswarlu,B.
    • Devasree Naik
    • Singh,V. P.
  • Source: Journal of Agrometeorology
  • Volume: 17
  • Issue: 1
  • Year: 2015
  • Summary: Carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2O) are important biogenic green house gases (GHGSs) from agricultural sector contributing to global warming. Temperature and rainfall play an important role in GHGS fluxes and information on their role in rainfed crops and systems is very scanty. Field studies were conducted at Hyderabad, India during 2012 rainy season to quantify GHGSs fluxes from two important food crops grown widely in rainfed regions viz. sorghum and pigeonpea. Quantum of fluxes ranged from 26-85 mg CO 2 - C m -2 h -1 in case of CO 2 and 18-68 g N 2O-N m -2 h -1 in case of N 2O at different stages of crop growth. Cumulative seasonal fluxes are 1.18 and 1.24 Mg CO 2-C ha -1 and 0.78 and 0.94 kg N 2O-N ha -1, in sorghum and pigeonpea, respectively. Ambient temperature and rainfall significantly influenced CO 2 fluxes. CO 2 fluxes increased with increase in temperature from 25.9°C to 31°C and fluxes were highest at 28.4°C in pigeonpea and at 27.7°C in sorghum. Quantum of CO 2 fluxes were highest at grain filling stage in sorghum and grand growth period in pigeonpea. N 2O fluxes increased with increase in temperature and moisture availability. These results provide evidence that rainfed crops in semi-arid regions contribute significant CO 2 and N 2O fluxes which are influenced by temperature and rainfall, thus warrant further studies.
  • Authors:
    • Rashti,Mehran Rezaei
    • Wang,Weijin
    • Moody,Phil
    • Chen,Chengrong
    • Ghadiri,Hossein
  • Source: Atmospheric Environment
  • Volume: 112
  • Year: 2015
  • Summary: The emission of nitrous oxide (N2O) from vegetable fields contributes to the global greenhouse gases budget. However, reliable estimation of N2O emissions from vegetable production in the word has been lack. Vegetable cropping systems are characterised with high N application rates, irrigation, intensive production and multiple planting-harvest cycles during the year. Improved understanding of the key factors controlling N2O production is critical for developing effective mitigation strategies for vegetable cropping systems under different climate, soil type and management practices. Based on a comprehensive literature review and data analysis, we estimated the global N2O emission from vegetable production using seasonal fertiliser-induced emission factors (EFs) and examined the relationship of the seasonal emissions and EFs to possible controlling factors. The global average seasonal EF for vegetable fields is around 0.94% of applied N fertiliser, which is very similar to the Intergovernmental Panel on Climate Change (IPCC) annual emission factor of 1.0% for all cropping systems. The total N2O emission from global vegetable production is estimated to be 9.5 x 10(7) kg N2O N yr(-1), accounting for 9.0% of the total N2O emissions from synthetic fertilisers. Stepwise multiple regression analysis on the relationships of soil properties, climatic factors and N application rates to seasonal N2O emissions and N2O EFs showed that N fertiliser application rate is the main regulator of seasonal N2O emission from vegetable fields but the seasonal EFs are negatively related to soil organic carbon (SOC) content. In fields receiving >= 250 kg ha(-1) N fertiliser, 67% (n = 23, P <= 0.01) of the variation in seasonal emissions can be explained by the combined effects of N application rate, mean water-filled pore space (WFPS) and air temperature, while 59% (n = 23, P <= 0.01) of the variation in seasonal EFs relates to temperature, mean WFPS and soil pH. The result also shows that in vegetable fields with mean seasonal air temperature higher than 14 degrees C, increases in SOC decrease the seasonal EF and total N2O emissions from fertiliser N. (C) 2015 Elsevier Ltd. All rights reserved.
  • Authors:
    • Sun YuCheng
    • Guo HuiJuan
    • Yuan Liang
    • Wei JiaNing
    • Zhang WenHao
    • Ge Feng
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 7
  • Year: 2015
  • Summary: Stomata help plants regulate CO 2 absorption and water vapor release in response to various environmental changes, and plants decrease their stomatal apertures and enhance their water status under elevated CO 2. Although the bottom-up effect of elevated CO 2 on insect performance has been extensively studied, few reports have considered how insect fitness is altered by elevated CO 2-induced changes in host plant water status. We tested the hypothesis that aphids induce stomatal closure and increase host water potential, which facilitates their passive feeding, and that this induction can be enhanced by elevated CO 2. Our results showed that aphid infestation triggered the abscisic acid (ABA) signaling pathway to decrease the stomatal apertures of Medicago truncatula, which consequently decreased leaf transpiration and helped maintain leaf water potential. These effects increased xylem-feeding time and decreased hemolymph osmolarity, which thereby enhanced phloem-feeding time and increased aphid abundance. Furthermore, elevated CO 2 up-regulated an ABA-independent enzyme, carbonic anhydrase, which led to further decrease in stomatal aperture for aphid-infested plants. Thus, the effects of elevated CO 2 and aphid infestation on stomatal closure synergistically improved the water status of the host plant. The results indicate that aphid infestation enhances aphid feeding under ambient CO 2 and that this enhancement is increased under elevated CO 2.
  • Authors:
    • Viger,M.
    • Hancock,R. D.
    • Miglietta,F.
    • Taylor,G.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 4
  • Year: 2015
  • Summary: Biochar is a carbon (C)-rich solid formed when biomass is used to produce bioenergy. This 'black carbon' has been suggested as a solution to climate change, potentially reducing global anthropogenic emissions of greenhouse gases by 12%, as well as promoting increased crop growth. How biochar application to soil leads to better crop yields remains open to speculation. Using the model plant Arabidopsis and the crop plant lettuce (Lactuca sativa L.), we found increased plant growth in both species following biochar application. Statistically significant increases for Arabidopsis in leaf area (130%), rosette diameter (61%) and root length (100%) were observed with similar findings in lettuce, where biochar application also increased leaf cell expansion. For the first time, global gene expression arrays were used on biochar-treated plants, enabling us to identify the growth-promoting plant hormones, brassinosteroid and auxin, and their signalling molecules, as key to this growth stimulation, with limited impacts on genes controlling photosynthesis. In addition, genes for cell wall loosening were promoted as were those for increased activity in membrane transporters for sugar, nutrients and aquaporins for better water and nutrient uptake and movement of sugars for metabolism in the plant. Positive growth effects were accompanied by down-regulation of a large suite of plant defence genes, including the jasmonic acid biosynthetic pathway, defensins and most categories of secondary metabolites. Such genes are critical for plant protection against insect and pathogen attack, as well as defence against stresses including drought. We propose a conceptual model to explain these effects in this biochar type, hypothesizing a role for additional K+ supply in biochar amended soils, leading to Ca2+ and Reactive Oxygen Species (ROS) -mediated signalling underpinning growth and defence signalling responses. © 2014 John Wiley & Sons Ltd.
  • Authors:
    • Bekele,A.
    • Roy,J. L.
    • Young,M. A.
  • Source: Canadian Journal of Soil Science
  • Volume: 95
  • Issue: 3
  • Year: 2015
  • Summary: Interest in the use of biochar as soil amendment has grown recently. However, studies evaluating its potential use for reclamation of disturbed agricultural lands are lacking. We studied the effects of amending clay, loam, and sand subsoil substrates with wood biochar pyrolized at 800°C, oxidized lignite (humalite), or labile organic mix (sawdust, wheat straw, and alfalfa; LOM) on soil organic carbon (C), microbial biomass, dry aggregated size distribution and penetration resistance in greenhouse. We also considered the co-application of LOM and biochar or humalite to the subsoil substrates as treatments where C from either biochar or humalite represented a stable form of C. The amount and composition of the mix of organic amendments was determined for each subsoil so that organic C levels of reconstructed topsoil would be equivalent to that of the corresponding native topsoil in the long term. Field pea ( Pisum sativum L.) and barley ( Hordeum vulgare L.) were grown in rotation in four sequential greenhouse studies. Results from soil analysis at the end of study II and study IV showed that subsoils amended with biochar or humalite had higher organic C than those with LOM only, regardless of soil type. Labile organic mix added alone or together with biochar or humalite to subsoil increased microbial biomass and decreased geometric mean diameter of the dry soil aggregates. The effects of biochar or humalite-only amendment on these soil properties were not significant relative to the unamended subsoil substrate. Simultaneous application of biochar or humalite with LOM can potentially be used for topsoil reconstruction and reclamation of disturbed agricultural lands, and to maintain soil quality in the long term. However, long-term field studies are required to ascertain the longevity of the desirable properties reported in this study and to assess effects associated with aging of biochar or humalite in the soil.
  • Authors:
    • Brady,M. V.
    • Hedlund,K.
    • Rong-Gang Cong
    • Hemerik,L.
    • Hotes,S.
    • Machado,S.
    • Mattsson,L.
    • Schulz,E.
    • Thomsen,I. K.
  • Source: Agronomy Journal
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Soil biodiversity through its delivery of ecosystem functions and attendant supporting ecosystem services - benefits soil organisms generate for farmers - underpins agricultural production. Yet lack of practical methods to value the long-term effects of current farming practices results, inevitably, in short-sighted management decisions. We present a method for valuing changes in supporting soil ecosystem services and associated soil natural capital - the value of the stock of soil organisms - in agriculture, based on resultant changes in future farm income streams. We assume that a relative change in soil organic C (SOC) concentration is correlated with changes in soil biodiversity and the generation of supporting ecosystem services. To quantify the effects of changes in supporting services on agricultural productivity, we fitted production functions to data from long-term field experiments in Europe and the United States. The different agricultural treatments at each site resulted in significant changes in SOC concentrations with time. Declines in associated services are shown to reduce both maximum yield and fertilizer-use efficiency in the future. The average depreciation of soil natural capital, for a 1% relative reduction in SOC concentration, was 144 Euro ha -1 (SD 47 Euro ha -1) when discounting future values to their current value at 3%; the variation was explained by site-specific factors and the current SOC concentration. Moreover, the results show that soil ecosystem services cannot be fully replaced by purchased inputs; they are imperfect substitutes. We anticipate that our results will both encourage and make it possible to include the value of soil natural capital in decisions.
  • Authors:
    • Brookes,G.
    • Barfoot,P.
  • Source: GM Crops & Food
  • Volume: 7
  • Issue: 2
  • Year: 2015
  • Summary: This paper updates previous assessments of how crop biotechnology has changed the environmental impact of 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 since their first widespread commercial use in the mid 1990s. The adoption of GM insect resistant and herbicide tolerant technology has reduced pesticide spraying by 553 million kg (-8.6%) 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 19.1%. The technology has also facilitated important cuts in fuel use and tillage changes, resulting in a significant reduction in the release of greenhouse gas emissions from the GM cropping area. In 2013, this was equivalent to removing 12.4 million cars from the roads.
  • Authors:
    • Congreves,K. A.
    • Van Eerd,L. L.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 102
  • Issue: 3
  • Year: 2015
  • Summary: Vegetables are important horticultural commodities with high farm gate values and nutritional quality. For many vegetables, growers apply large amounts of N fertilizer (> 200 kg N ha(-1)) to increase yield and profits, but such high N fertilizer applications can pose a significant threat for N loss and environmental contamination via denitrification, volatilization, leaching, runoff, and erosion. Nitrogen losses can reduce air and water quality by contributing to greenhouse gas emissions, ground-level ozone and particulate matter production, ground and surface water contamination, and eutrophication. The processes governing N loss include a complex of biological, physical, and chemical factors, which are impacted by management practices, climatic conditions and soil properties. Therefore, we reviewed and evaluated various management practices for minimizing N loss in N-intensive vegetable production within a temperate climate. Most soil nutrient management practices have focused on reducing N loss throughout the growing season, but the risk for N loss is very high after harvesting vegetables with low N harvest indices, low C:N ratios, and high quantities of N in crop residues, such as most Brassica oleracea L. crops. Amending soil with organic C material may present a novel strategy for reducing N losses after harvest by 37 %, compared to the typical practice of incorporating N-rich vegetable crop residues. Research must focus on testing new and innovative methods of minimizing post-harvest N loss in intensive horticulture.
  • 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.