• Authors:
    • Sakai, R. H.
    • Ambrosano, E. J.
    • Melo, P. C. T. de
    • Negrini, A. C. A.
    • Schammass, E. A.
    • Rossi, F.
  • Source: HORTICULTURA BRASILEIRA
  • Volume: 28
  • Issue: 1
  • Year: 2010
  • Summary: The performance of lettuce in sole and intercropped with green manures was assessed under different establishment times. The lettuce fresh and dry weight, number of leaves per plant, diameter and length of head, and fresh and dry weight of green manure were evaluated. The intercropping design was additive and both cash and cover crops were planted in rows. The experimental design was of randomized complete blocks in split plot scheme, with six replicates. The plots represented the green manure sowing days (0, 20, 40 and 60 before transplanting of lettuce), and the sub-plots were assigned by cropping systems (lettuce in sole crop and intercropped with black oat, cowpea or white lupin). Simultaneous planting in the intercropping did not affect the lettuce performance. However, when the green manures were sown before lettuce, they influenced it in a negative way. Among the green manures, cowpea increased biomass and had a higher negative effect on lettuce performance compared to white lupin, which appeared to produce less competition. The sole crop and the intercropping with simultaneous planting of the green manures resulted in a better lettuce performance.
  • Authors:
    • Marangon, R.
    • Mondardo, J.
    • Martin, T.
    • Pavinato, P.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world, Brisbane, Australia, 1-6 August 2010. Division Symposium 3.2 Nutrient best management practices
  • Year: 2010
  • Summary: The use of phosphate fertilizer has promoted changes in phosphorus fractions and availability in soil, that highlights the requirement of more studies to understand phosphorus dynamics in soil, and to develop cultivation strategies to increase crop grain yield under phosphate fertilization. The work aimed to evaluate changes in soil phosphorus availability in sequential crop seasons, under effects of phosphate fertilizer sources and cover crop plants. The experiment was carried at Technological Federal University of Parana, Dois Vizinhos, PR, Brazil. The soil is a Ferralsol, with high level of available P. Experimental design was a factorial 3*8, in randomized blocks, with three replicates and 5*5 m plots. Treatments were composed of natural phosphate and soluble phosphate, and a control. During winter season, the seven cover crops were: vetch, white lupin, radish, ryegrass, black oat, clover and pigeon pea, and a witness with no cover crop. Brazilian Ferralsol, with high level of available P, does not increase plant grain yield with sources of phosphate fertilization. Available P in soil changes markedly with phosphate fertilization, especially in the surface layer (0-5 cm). Important results are expected in soil P availability after winter cover crops.
  • Authors:
    • Silva, R.
    • Rosolem, C.
  • Source: Communications in Soil Science and Plant Analysis
  • Volume: 41
  • Issue: 1
  • Year: 2010
  • Summary: Cation mobility in acidic soils with low organic-matter contents depends not only on sorption intensity but also on the solubility of the species present in soil solution. In general, the following leaching gradient is observed: potassium (K +) > magnesium (Mg 2+) > calcium (Ca 2+) > aluminum (Al 3+). To minimize nutrient losses and ameliorate the subsoil, soil solution must be changed, favoring higher mobility of M 2+ (metal ions) forms. This would be theoretically possible if plant residues were kept on the soil surface. An experiment was conducted in pots containing a Distroferric Red Latosol, with soil solution extractors installed at two depths. Pearl millet, black oat, and oilseed radish residues were laid on the soil surface, and nitrogen (as ammonium nitrate) was applied at rates ranging from 0 to 150 mg kg -1. Corn was grown for 52 days. Except for K + and ammonium (NH 4+), nitrogen rates and plant residues had little effect upon the concentrations and forms of the elements in the soil solution. Presence of cover crop residues on soil surface decreased the effect of nitrogen fertilizer on Ca leaching. More than 90% of the Ca 2+, Mg 2+, and K + were found as free ions. The Al 3+ was almost totally complexed as Al(OH 3) 0. Nitrogen application increased the concentrations of almost all the ions in soil solution, including Al 3+, although there was no modification in the leaching gradient.
  • Authors:
    • Garcia, R.
    • Werle, R.
    • Rosolem, C.
  • Source: REVISTA BRASILEIRA DE CIENCIA DO SOLO
  • Volume: 34
  • Issue: 6
  • Year: 2010
  • Summary: Crop species with the C 4 photosynthetic pathway are more efficient in assimilating N than C 3 plants, which results in different N amounts prone to be washed from its straw by rain water. Such differences may affect N recycling in agricultural systems where these species are grown as cover crops. In this experiment, phytomass production and N leaching from the straw of grasses with different photosynthetic pathways were studied in response to N application. Pearl millet ( Pennisetum glaucum) and congo grass ( Brachiaria ruziziensis) with the C 4 photosynthetic pathway, and black oat ( Avena Strigosa) and triticale (* Triticosecale), with the C 3 photosynthetic pathway, were grown for 47 days. After determining dry matter yields and N and C contents, a 30 mm rainfall was simulated over 8 t ha -1 of dry matter of each plant residue and the leached amounts of ammonium and nitrate were determined. C 4 grasses responded to higher fertilizer rates, whereas N contents in plant tissue were lower. The amount of N leached from C 4 grass residues was lower, probably because the C/N ratio is higher and N is more tightly bound to organic compounds. When planning a crop rotation system it is important to take into account the difference in N release of different plant residues which may affect N nutrition of the subsequent crop.
  • Authors:
    • Fernandes, M. F.
    • Chaer, G. M.
  • Source: Proceedings of the 19th World Congress of Soil Science: Soil solutions for a changing world
  • Year: 2010
  • Summary: Soil biological and biochemical properties have been proposed as sensitive indicators of soil degradation. Nevertheless, their potential to predict the deterioration of major soil functions related to physical stability, and water and nutrient storage and fluxes has not been validated under experimental conditions. The sensitivity of 16 biological and biochemical variables was contrasted with other eight of chemical or physical nature in a gradient of soil degradation induced by cycles of one, two, three, or four tillage events, plus a no-till control. Twenty-four variables were analysed in soil samples (0-20 cm) collected 60 d after the last cycle. Out of these, 22 were significantly affected by soil disturbance. Six biological (microbial biomass-C, -N, and -C to N ratio; qMic; FDA and urease), two physical (water stable aggregates and aggregate mean diameter) and one chemical variable (org-P) were highly sensitive to soil disturbance. Soil bulk density, invertase activity, organic C and CEC were only slightly sensitive to tillage, whereas qCO 2 and xylanase were not significantly affected by tillage frequency. Although some biological and biochemical properties were highly responsive to soil degradation, there was no general trend of superiority of these variables over those of chemical and physical natures regarding the sensitivity to soil degradation.
  • Authors:
    • Piccolo, M. de C.
    • Feigl, B. J.
    • Cerri, C. C.
    • Cerri, C. E. P.
    • Frazao, L. A.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 135
  • Issue: 3
  • Year: 2010
  • Summary: The Brazilian Cerrado soils were incorporated into the agricultural production process in the 1970s. The introduction of pastures and/or annual crops utilizing different management systems produced changes in the dynamics of soil organic matter. This study evaluated the microbial attributes of a Typic Quartzipsamment (Arenosols in FAO classification) in native vegetation, pastures, and soybean cultivation under conventional (CT) and no-till (NT) systems. The soil samples (0-5, 5-10 and 10-20 cm layers) were collected in July 2005 and February 2006 from different systems: native Cerrado (CE), CT for 4 years with soybean (CT4 S), CT for 4 years with soybean in rotation with millet (CT4 S/M), an area that has been under pasture for 22 years (PA22), and an area that remained under pasture for 13 years, followed by NT with soybean in rotation with millet for 5 years (NT5). Soil inorganic N (nitrate and ammonium), microbial C and N and basal respiration were determined. The soil metabolic quotient (qCO 2) and the C mic:C org ratios were calculated. The predominant form of inorganic N in the native Cerrado (CE) and in the pasture area (PA22) was ammonium, while the conventional system (CT4 S/M) and no-till system (NT5) areas presented higher nitrogen availability for crops in the form of nitrate. The microbial C and N concentrations increased in the wet season, and the highest values were found in the Cerrado (CE) and in pasture (PA22) areas, where the permanent soil cover and the lack of soil disturbance by agricultural practices allowed more favorable conditions for microbial development. The CT4 S area presented the highest qCO 2 index and the lowest C mic:C total ratio, indicating that the conversion of total carbon into microbial carbon is less efficient in this system. Since sandy soils are more susceptible to degradation, the use of more conservationist management systems promotes more favorable conditions to microbial development and maintenance.
  • Authors:
    • Payne, W. A.
  • Source: Advances in Agronomy
  • Volume: 105
  • Year: 2010
  • Summary: Sustainability of biofuels is a contentious but old topic that has reemerged with increased use of crops as feedstocks. There are vastly different land requirements for different feedstocks, and disagreement on the energy balance of their conversion to biofuel. To be sustainable, biofuel systems should (1) have favorable economics, (2) conserve natural resources, (3) preserve ecology, and (4) promote social justice. With the possible exception of sugarcane production in Brazil, it seems unlikely that ethanol production from crops will be economically viable without government support. Less is known on cellulosic feedstock economics because there are no commercial-scale plants. Natural resources that may be affected include soil, water, and air. In the United States, agricultural intensification has been associated with greater soil conservation, but this depended on retaining residue that may serve as cellulosic feedstocks. The "water footprint" of bioenergy from crops is much greater than for other forms of energy, although cellulosic feedstocks would have a smaller footprint. Most studies have found that first-generation biofuels reduce greenhouse gas emissions 20-60%, and second generation ones by 70-90%, if effects from land-use change are excluded. But land-use change may incur large carbon losses, and can affect ecological preservation, including biodiversity. Social justice is by far the most contentious sustainability issue. Expanding biofuel production was a major cause of food insecurity and political instability in 2008. There is a large debate on whether biofuels will always contribute to food insecurity, social justice, and environmental degradation in poor countries.
  • Authors:
    • Liang,Biqing
    • Lehmann,Johannes
    • Sohi,Saran P.
    • Thies,Janice E.
    • Luizão,Flavio J.
    • Trujillo,Lucerina
    • Gaunt,John
    • Solomon,Dawit
    • Grossman,Julie
    • Neves,Eduardo G.
    • O'Neill,Brendan
  • Source: Organic Geochemistry
  • Volume: 41
  • Issue: 2
  • Year: 2010
  • Summary: Black carbon (BC) is an important fraction of many soils worldwide and plays an important role in global C biogeochemistry. However, few studies have examined how it influences the mineralization of added organic matter (AOM) and its incorporation into soil physical fractions and whether BC decomposition is increased by AOM. BC-rich Anthrosols and BC-poor adjacent soils from the Central Amazon (Brazil) were incubated for 532 days either with or without addition of 13C-isotopically different plant residue. Total C mineralization from the BC-rich Anthrosols with AOM was 25.5% (P < 0.05) lower than with mineralization from the BC-poor adjacent soils. The AOM contributed to a significantly (P < 0.05) higher proportion to the total C mineralized in the BC-rich Anthrosols (91–92%) than the BC-poor adjacent soils (69–80%). The AOM was incorporated more rapidly in BC-rich than BC-poor soils from the separated free light fraction through the intra-aggregate light fraction into the stable organo-mineral fraction and up to 340% more AOM was found in the organo-mineral fraction. This more rapid stabilization was observed despite a significantly (P < 0.05) lower metabolic quotient for BC-rich Anthrosols. The microbial biomass (MB) was up to 125% greater (P < 0.05) in BC-rich Anthrosols than BC-poor adjacent soils. To account for increased MB adsorption onto BC during fumigation extraction, a correction factor was developed via addition of a 13C-enriched microbial culture. The recovery was found to be 21–41% lower (P < 0.05) for BC-rich than BC-poor soils due to re-adsorption of MB onto BC. Mineralization of native soil C was enhanced to a significantly greater degree in BC-poor adjacent soils compared to BC-rich Anthrosols as a result of AOM. No positive priming by way of cometabolism due to AOM could be found for aged BC in the soils.
  • Authors:
    • Sun, O. J.
    • Wang, E.
    • Luo, Z.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 139
  • Issue: 1-2
  • Year: 2010
  • Summary: Adopting no-tillage in agro-ecosystems has been widely recommended as a means of enhancing carbon (C) sequestration in soils. However, study results are inconsistent and varying from significant increase to significant decrease. It is unclear whether this variability is caused by environmental, or management factors or by sampling errors and analysis methodology. Using meta-analysis, we assessed the response of soil organic carbon (SOC) to conversion of management practice from conventional tillage (CT) to no-tillage (NT) based on global data from 69 paired-experiments, where soil sampling extended deeper than 40 cm. We found that cultivation of natural soils for more than 5 years, on average, resulted in soil C loss of more than 20 t ha-1, with no significant difference between CT and NT. Conversion from CT to NT changed distribution of C in the soil profile significantly, but did not increase the total SOC except in double cropping systems. After adopting NT, soil C increased by 3.15 +- 2.42 t ha-1 (mean ± 95% confidence interval) in the surface 10 cm of soil, but declined by 3.30 ± 1.61 t ha-1 in the 20-40 cm soil layer. Overall, adopting NT did not enhance soil total C stock down to 40 cm. Increased number of crop species in rotation resulted in less C accumulation in the surface soil and greater C loss in deeper layer. Increased crop frequency seemed to have the opposite effect and significantly increased soil C by 11% in the 0-60 cm soil. Neither mean annual temperature and mean annual rainfall nor nitrogen fertilization and duration of adopting NT affected the response of soil C stock to the adoption of NT. Our results highlight that the role of adopting NT in sequestrating C is greatly regulated by cropping systems. Increasing cropping frequency might be a more efficient strategy to sequester C in agro-ecosystems. More information on the effects of increasing crop species and frequency on soil C input and decomposition processes is needed to further our understanding on the potential ability of C sequestration in agricultural soils.
  • Authors:
    • Batlle-Bayer, L.
    • Batjes, N. H.
    • Bindraban, P. S.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 137
  • Issue: 1-2
  • Year: 2010
  • Summary: This paper reviews current knowledge on changes in carbon stocks upon land use conversion in the Brazilian Cerrado. First, we briefly characterize the savanna ecosystem and summarize the main published data on C stocks under natural conditions. The effects of increased land use pressure in the Cerrado and current uncertainties of estimations of changes in land cover and land use are reviewed next. Thereafter, we focus on soil organic carbon (SOC) dynamics due to changes in land use, particularly conversion to pastures and soybean-based cropping systems, and effects of management practices such as soil fertilization, crop rotations and tillage practices. Most studies considered here suggest that more intensive agriculture, which include no-till practices and the implementation of best or recommended management practices (RMP), reduces SOC losses after land use conversion from conventional tillage-based, monocropping systems; however, these studies focussed on the first 0.3 m of soil, or less, and seldom considered full carbon accounting. To better estimate possible global warming mitigation with agriculture in the Cerrado more comprehensive studies are needed that analyse fluxes of the biogenic greenhouse gases (GHG; CO 2, N 2O and CH 4) to determine the net global warming potential (GWP). Follow up studies should include the application of an integrated modelling system, comprised of a Geographic Information System (GIS) linked to dynamic modelling tools, to analyse SOC dynamics and make projections for possible changes in net C flows in the Cerrado region upon defined changes in soil use and management.