• Authors:
    • Piccolo, M. D. C.
    • Vieira, F. C. B.
    • Zanatta, J. A.
    • Gomes, J.
    • Bayer, C.
    • Dieckow, J.
    • Six, J.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 146
  • Issue: Pt. B
  • Year: 2015
  • Summary: Soil nitrous oxide (N2O) emissions are affected by management practices, but little information is available on the interactive effects of tillage, cropping systems and N sources in tropical and subtropical soils. In an 18-yr old experiment located in a subtropical Acrisol of Southern Brazil we conducted a sequence of two trials. The 1-year trial (October 2003-2004) was set to evaluate the long-term effects of tillage [CT: conventional; and NT: no-tillage] and cropping systems [O/M: black oat (Avena strigosa Schreb.)/maize (Zea mays L.); and V/M: vetch (Vicia sativa L.)/maize] on soil N2O emissions, either in the post-management period (45 days after desiccation and knife-rolling of winter cover crops) or in the whole year. The second and short-term trial (October-November 2004) was carried out to compare the impact of N sources [urea (mineral) and legume-residue of vetch (biologically fixed), both at 180kgNha-1] on soil N2O emissions during 53 days after cover-crop management. Air sampling was carried out by static chambers and N2O analysis by gas chromatography. In the 45-day post-management period of the 1-year trial, soil N2O emissions were practically not affected by tillage systems, but increased 4 times due to vetch residues (average of 0.40±0.08kgNha-1 in V/M versus 0.10±0.05kgNha-1 in O/M) and related with soil contents of NO3 --N, NH4 +-N, and dissolved organic C (DOC). Over the whole year, soil N2O emissions under CT were similar for grass- and legume-based cropping systems and averaged 0.43±0.17kgNha-1, while NT exacerbated N2O emissions in the legume-based cropping system (0.80±0.07kgNha-1 in V/M versus -0.07±0.06kgNha-1 in O/M). Maize yield was not affected by tillage, but increased from 2.32Mgha-1 in O/M to 4.44Mgha-1 in V/M. Yield-scaled N2O emissions varied from -33g N2O-NMg-1 grain in NT O/M to 179g N2O-NMg-1 grain in NT V/M, and were intermediate in CT soil (106 and 156g N2O-NMg-1grain in V/M and O/M cropping systems, respectively). In the short-term trial, the N2O emitted in excess relative to the control treatment (O/M without N fertilizer) was at least 3 times greater with urea-N (0.44% of applied N) than with legume-residue-Nsource (0.13% of applied N). Yield-scaled N2O emission after vetch residues management (67gNMg-1 grain) was half of that after urea-N application (152gNMg-1 grain). Partially supplying the maize N requirements with winter legume cover-crops may be a feasible strategy to mitigate soil N2O emissions in the subtropical conservation agriculture.
  • Authors:
    • Berger, T.
    • Siebold, M.
    • Gil, J.
  • Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
  • Volume: 199
  • Year: 2015
  • Summary: By combining crop, livestock and/or forestry activities in the same area, integrated systems (IS) can increase, organic matter content in the soil - which favors biomass production and allows for higher livestock stocking rates in pasturelands. The implementation of IS is therefore seen as a promising strategy for sustainable agricultural intensification in Brazil, particularly in Mato Grosso state (MT). However, despite the benefits associated with IS and incentives offered by the federal government to stimulate their dissemination, little is known about these systems or the challenges to implement them, and only a limited number of farmers have adopted IS so far. This paper presents a comprehensive assessment of all IS identified in Mato Grosso by 2012/13, which were mapped and described in terms of their main technical and non-technical features. These findings were combined with farm survey data set to provide a detailed account of the various technologies currently being disseminated, their individual diffusion levels and potential adoption constraints. Results generated through qualitative and quantitative research methods give an overview of IS' state of the art, reveal farmer perception of such technology and offer insights into the prospects for low-carbon agriculture in the region. The study's major findings are that IS are present in more than 40 of the 141 municipalities of MT, and the vast majority (89%) involve only crop and livestock. Farmers have adopted three different crop-livestock configurations, depending on their production strategy. Cultural aspects play a major role in farmer decisions to adopt IS, credit provision has not been relevant for IS adoption, and a broader dissemination of IS may occur as land transitions continue. (C) 2014 Elsevier B.V. All rights reserved.
  • Authors:
    • Reicosky, D. C.
    • Panosso, A. R.
    • de Figueiredo, E. B.
    • La Scala, N.
  • Source: GCB Bioenergy
  • Volume: 7
  • Issue: 2
  • Year: 2015
  • Summary: New management strategies should be identified to increase the potential of bioenergy crops to minimize climate change. This study quantified the impact of sugarcane (Saccharum spp.) harvest systems, straw and soil management on carbon dioxide (CO2) fluxes prior to crop replanting carried out on February 2010 in southern Brazil. The soil studied was classified as Haplustult (USDA Soil Taxonomy). Three sugarcane harvest systems were considered: burned (BH) and green harvest with straw maintained on (GH SM) or removed from (GH SR) the soil surface. Our hypothesis is that intensive tillage and the management of sugarcane crop straw could lead to higher CO2 emissions from soil. We measured CO2 emissions in no-till (NT) conditions and after conventional tillage (CT), and with or without dolomite and agricultural gypsum applications. Soil CO2 emissions were measured with a Li Cor chamber (Model Li-8100). Water content of soil and soil temperature readings were first taken 24 h after tillage, over the next 25 days after tillage with 18 measurement days. The removal of sugarcane straw from the soil surface resulted in the rapid reduction of water content of soil (6% in volume) followed by a 64% increase in soil CO2-C emissions, supporting our hypothesis. Additional soil CO2-C emissions caused by removal of crop straw were 253 kg CO2-C ha-1, which is as high as CO2-C losses induced by tillage. Dolomite and agricultural gypsum applications did not always increase CO2 emissions, especially when applied on soil surface with crop straw and tilled. The conversion from burned to green harvest systems can improve the soil C sequestration rate in sugarcane crops when combined with reduced tillage and straw maintenance on soil surface. The effect of straw removal and related CO2 emission for electricity generation should be considered in further studies from sugarcane areas. © 2014 John Wiley & Sons Ltd.
  • Authors:
    • Bernasconi, M.
    • Marengo, J. A.
  • Source: CLIMATIC CHANGE
  • Volume: 129
  • Issue: 1-2
  • Year: 2015
  • Summary: The focus of this study is to investigate the risk of aridification in the semiarid lands of Northeast Brazil, using a variety of observational information and climate change projections for the future, by means of aridity indices. We use the Budyko and United Nations aridity indices to assess the extent of areas with semi-arid and arid conditions in the present, and for the future out to 2100. Climate projections are derived from the downscaling of the HadCM3 model for the A1B scenario using the Eta regional model with horizontal resolution of 40 km. Consistent with global climate model projections from IPCC AR5, regional climate change projections suggest an increase in dryness in the region, with rainfall reductions, temperature increases and water deficits and longer dry spells, leading to drought and arid conditions expected to prevail by the second half of the 21th century. The area with arid conditions is projected to grow to cover areas currently with dry sub humid conditions, and become larger by 2100. This increase in aridity, combined with land degradation may increase the risk of desertification.
  • Authors:
    • Ramos-Cairo, P. A.
    • Frois de Andrade, M. A.
    • Santos, J. L.
  • Source: Agriculture Journal
  • Volume: 49
  • Issue: 2
  • Year: 2015
  • Summary: Nitrogen (N) and potassium (K) are the major nutrients required for coffee plants growth and development. Soil water deficit reduces nutrients uptake, causing negative effects on photosynthesis and water relations of plants. Within certain limits, the increase in N and K concentration in soil solution could result in higher nutrient uptake, softening physiological disturbs caused by the water deficit. This study aimed to evaluate water relations and photosynthesis of young coffee plants grown in 16 L pots in a greenhouse. Treatments were three N and three K doses: conventional (urea 12 g plant -1 and KCl 4 g plant -1), doubled and tripled; and two water regimes: irrigated (soil at field capacity) and non-irrigated. Thus, treatments were arranged in a factorial 3*3*2, with three replicates in a completely randomized design. Water stress effects on leaf water potential and relative water content are softened by increase in N and K doses. However, transpiration, stomatal conductance and net photosynthesis are decreased by water stress, regardless of N and K doses. Increase in K doses reduces transpiration and stomatal conductance, regardless of water regime. This study suggests that increases in N and K could partially protect young coffee plants against the water stress, as they contribute to mitigate negative effects in plant water status; however, they do not prevent a decrease in net photosynthesis.
  • Authors:
    • Biscaia, R. C. M.
    • Araújo, A. G.
    • Merten, G. H.
    • Barbosa, G. M. C.
    • Conte, O.
  • Source: Article
  • Volume: 152
  • Year: 2015
  • Summary: No-till is widely used to control soil erosion in agricultural areas in Brazil and is currently practiced on about 30. Mha. However, studies have shown that no-till is not as efficient in controlling surface runoff losses as it is in reducing soil loss. The objective of this study is to evaluate soil and surface runoff losses on small and large plots with differing slope lengths, cropping sequences and tillage systems in southern Brazil. Surface runoff and soil losses under natural rainfall erosion plots (3.5. ×. 11. m, 3.5. ×. 22. m, 50. ×. 100. m, and 100. ×. 100. m) were evaluated in two experiments in a well-drained Oxisol (>60% clay) with 9% and 7% slopes, respectively. The experiment extended over 14 years comparing 4 different soil management systems: (a) bare soil plots with slope length 22. m; (b) bare soil plots with slope length 11. m; (c) sequence of wheat (Triticum aestivum)/soybean [. Glycine max (L.) Merr] with disk plow. +. lighter off-set disk-harrow (DP+LD); and (d) sequence of wheat/soybean under no-till (NT). In another experiment using large field plots, three soil tillage regimens (DP. +. LD; heavy off-set disk-harrow. +. lighter off-set disk-harrow (HD. +. LD), and NT) were compared over the course of a 5-yr. crop sequence of black oats (Avena estrigosa)/soybean-black oats/corn (Zea mays L.)-wheat/soybean- black oats/soybean -blue lupine (Lupinus angustifolium)/corn. Results for both experiments show that, when compared with conventional soil tillage (DP. +. LD or HD. +. LD), soil losses for NT were >. 70% lower. However, the benefit of reduced surface runoff losses was less evident, suggesting the need to implement additional practices to control surface runoff to avoid transport of pollutants to waterways. © 2015 Elsevier B.V.
  • Authors:
    • Raucci,G. S.
    • Moreira,C. S.
    • Alves,P. A.
    • Mello,F. F. C.
    • Frazão,L. D. A.
    • Cerri,C. E. P.
    • Cerri,C. C.
  • Source: Journal of Cleaner Production
  • Volume: 96
  • Year: 2015
  • Summary: Abstract In recent years, the debate about environmental impacts and the sustainability of agricultural products has increased. Environmental impact indicators are increasingly being demanded for policy and decision-making processes. Consumers are more and more concerned about the quality of food products and now looking for those with a low environmental impact, with a particular attention to greenhouse gas (GHG) emissions. There are few studies regarding the GHG emissions associated with the Brazilian soybean production. The aim of this study was to evaluate the main sources of GHG in soybean production in the State of Mato Grosso, Brazil. Our analysis considered the Life Cycle Assessment (LCA) from cradle to farm gate. We evaluated 55 farms in the crop years of 2007/08, 2008/09 and 2009/10, accounting for 180,000 ha of soybean cultivation area and totaling 114 individual situations. The results indicated that the largest source of GHG in the soybean production is the decomposition of crop residues (36%), followed by fuel use (19%), fertilizer application (16%), liming (13%), pesticides (7%), seeds (8%) and electricity consumed at the farms (2eq kg-1 of soybean produced. We also categorized the results based on land use intensity and production areas. This study contributed to identify the main sources of GHG in the soybean production and indicate mitigation priorities associated to the soybean cultivation in Brazil. Further studies, including field experiments, should contribute to a better understanding of the profile of emissions from crop residues in Brazil. © 2014 Elsevier Ltd. All rights reserved.
  • Authors:
    • Reichert,J. M.
    • Rodrigues,M. F.
    • Bervald,C. M. P.
    • Brunetto,G.
    • Kato,O. R.
    • Schumacher,M. V.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 204
  • Year: 2015
  • Summary: No-tillage planting in mechanically-chopped secondary-forest seeks to replace slash-and-burning agriculture. We evaluated the effect of horizontal (HC) and vertical (VC) chopping-and-mulching mechanisms on vegetation fragmentation and decomposition rate and nutrient release from chopped residue, and on cassava production in eastern Amazon. Chopped-and-mulched residue was classified into four residue-size (Fs 1=1-7, Fs 2=7-25, Fs 3=25-35, and Fs 4=>35 mm) and six residue-type (with husk/bark - WB, partially chopped - PC, compact - C, partially shredded into fibers - PS, completely shredded into fibers - CS, and formless residue - F) classes. In litter-bags, residual dry matter (DM) was determined at five different days after chopping-and-mulching and residue distribution on soil surface (DAD), whereas release of N, P, K, Ca, and Mg was evaluated at four days. Residues-size and -type classes showed similar decomposition behavior, with a reduction of approximately 60% of initial DM at 90 DAD. Nevertheless, reduction in DM was slow, where 52 days are necessary for half of labile residue to be decomposed, with part of labile and recalcitrant residue remaining on soil surface. DM and nutrients in residue reduced over time. DM was 25% for residues-size classes for HC, 20% for VC, and 26% for residue-type classes, on average, at 300 DAD. Nutrients remaining in residues at 300 DAD were 26% and 27% of N, 26% and 22% of P, 29% and 22% of K, 16% and 15% of Ca, and 17% and 23% of Mg, respectively for HC and VC. Release of nutrients was, generally, greater for smaller residue-size classes, similar between chopping-and-mulching mechanisms, and did not affect cassava yield.
  • Authors:
    • Santana,T. A. de
    • Oliveira,P. S.
    • Silva,L. D.
    • Laviola,B. G.
    • Almeida,A. A. F. de
    • Gomes,F. P.
  • Source: Biomass and Bioenergy
  • Volume: 75
  • Year: 2015
  • Summary: In order to quantify the water use efficiency and water consumption during the early growth of Jatropha curcas L., three genotypes were grown in pots under greenhouse conditions, and subjected to two watering regimes: irrigated (substrate matric potential (Psi m) of -9.8 to -7.4 kPa) and water deficit (Psi m=-98.6 to -33.5 kPa). Independent of watering regime, the genotypes did not differ on the variables analyzed. Despite the reduction of substrate water content in water deficit treatment, no significant decrease (p<0.05) of leaf water potential (Psi w) was observed, which suggests some water redistribution from the succulent stems of J. curcas. The values of net photosynthetic rate ( A), stomatal conductance ( gs), and transpiration ( E) were reduced to 80, 90 and 85%, respectively, as compared to control plants. Moreover, drought led to 78% reduction in hydraulic conductance ( KL ). At the end of the experiment, the average water consumption in water deficit plants was 27% lower than in control plants. Drought-induced decrease in biomass production led to reduction of water use efficiency of biomass (WUE Biomass). However, due to the more significant effect on gs and E than A at 66 DAIT, intrinsic ( A/gs) and instantaneous efficiency ( A/E), water use increased 50% and 27%, respectively. The results showed that there was no intergenotypic variation for the traits evaluated, and that the reduction of water availability in the substrate proved to be an effective technique in the increase of photosynthetic efficiency of water use in plants of J. curcas, reducing water consumption in this species.
  • Authors:
    • Buller,L. S.
    • Bergier,I.
    • Ortega,E.
    • Moraes,A.
    • Bayma-Silva,G.
    • Zanetti,M. R.
  • Source: Agricultural Systems
  • Volume: 137
  • Year: 2015
  • Summary: Greenhouse gas emissions and climate change has been partially attributed to agricultural expansion by deforestation, while the pressure to assure food, fiber and energy for the future generations leads to the intensification of agricultural systems. The transition to more efficient systems is actually considered an important strategy to reduce deforestation and to spare land for other uses, including the recovery of environmental services and ecohydrological processes in the drainage basin such as carbon sink and water regulation. The Brazilian Federal Program for Low Carbon Agriculture (ABC Program) intends to reduce carbon emissions by stimulating technological processes that neutralize emissions or enhance the sinking of greenhouse gases. A pilot farm has been established to assess an intensive animal-plant farming system that incorporates anaerobic digestion for biogas, power generation and organic fertilizer production. Emergy Synthesis was chosen as a methodological tool to assess and to diagnosis the farm system design. The modified emergy assessment including externalities (greenhouse gas emissions) improves the understanding of integrated crop-livestock systems efficiency in internal recycling of nutrients and power conversion. The adoption of manure treatment in intensified agricultural systems can effectively contribute to enhance environmental and economic performances.