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In zero tillage systems, the accumulation of residues in the soil surface and the use of crop rotation with leguminous plants and/or grasses can change soil nutrient dynamics. The objective of this work was to verify the main alterations of some chemical characteristics of soil and plant, with emphasis in the concentration of aluminum, calcium, phosphorus and silicon in the soil solution of the root system environment and in the leaves of the maize crop under zero tillage system in relation to conventional tillage system. The chemical characterization of the soil solution was carried out in two experiments (1 and 2). In experiment 1 no differences were observed between the systems for aluminum and phosphorus concentration in the soil solution. However, the soils under the zero tilling system presented greater amounts of calcium, magnesium and potassium and lower silicon concentrations in the soil solution, when compared with the other system. In experiment 2, soil solution of the zero tillage system showed smaller concentration of aluminum and phosphorus and greater concentration of silicon when compared with the other system. The total amount of silicon and macronutrients accumulated was greater in the soil under the zero tillage system. The zero tillage system promotes changes in the concentrations of Si, Ca and Al in the soil solution in comparison with the conventional tillage system. [ABSTRACT FROM AUTHOR]

The study was carried out from April 2007 to May 2008, on a Planossolo Háplico (Albaqualf), in Pelotas, RS, Brazil. The treatments comprised the castor bean cultivars 'AL Guarany 2002' and 'Lyra', with five rates of phosphate (0; 30; 60; 90 and 120kg ha-1 of P2O5.).These were arranged as a randomized complete block in a factorial design with three replications. Castor bean nutritional status and yield performance were evaluated. The phosphate fertilization altered castor bean foliar concentrations of nitrogen, calcium, boron, and iron. For boron, this effect was limited to the 'Lyra' cultivar. The 'AL Guarany 2002' cultivar demanded more phophorus than 'Lyra' cultivar. Phosphate fertilization increased grain yield of both castor bean cultivars. Yield increased with the use of up to 156kg ha-1 of P2O5., for 'AL Guarany 2002' cultivar, and of up to 90kg ha-1 of P2O5., for 'Lyra' cultivar. The rates of maximum economic efficiency for 'AL Guarany 2002' and 'Lyra' cultivars were, respectively, 134kg ha-1 and 78kg ha-1 of P2O5. [ABSTRACT FROM AUTHOR]

Effect of crop-livestock production systems with annual winter and summer pastures on soil fertility under no-tillage. The objective of this study, which employed a randomized complete block design, with four replicates, was to evaluate, after eight years (1995 to 2003), the soil fertility of a typical dystrophic red latosol (typic hapludox) located in Coxilha, Rio Grande do Sul State, Brazil, in six crop-livestock production systems (ILP): I) wheat/soybean, black oats + common vetch pasture/corn; II) wheat/soybean, black oat + common vetch + ryegrass pasture/corn; III) wheat/soybean, black oat + common vetch pasture/pearl millet pasture; IV) wheat/soybean, black oat + common vetch + ryegrass pasture/pearl millet pasture; V) wheat/soybean, oats/soybean, and black oat + common vetch pasture/pearl millet pasture; and VI) wheat/soybean, oats/soybean, and black oat + common vetch + ryegrass pasture/pearl millet pasture). Soil core samples were also collected in a fragment of subtropical forest adjacent to the experiment. After eight years, acidification in the top soil layer was observed. The exchangeable Mg and K and extractable P were affected by mixed-crop production models. The soil layers of 0-5 and 5-10 cm presented higher values of soil organic matter, P, and K. The reverse occurred with values of pH and exchangeable Al. The levels of soil organic matter, P, K and Ca + Mg decreased with soil depth. The crop systems studied presented higher values of C in the soil than the subtropical forest. [ABSTRACT FROM AUTHOR]