Saturday, 15 July 2006

Root Growth, Nutrition and Yield of Common Bean as Affected by Surface Application Lime and Gypsum under a No-Tillage System.

Carlos A.C. Crusciol, São Paulo State Univ, College of Agricultural Sciences, C.P.237, Botucatu, AL 18603-970, Brazil and Rogério P. Soratto, Mato Grosso do Sul State Univ, College of Agronomy, Cassilândia, 79540-000, Brazil.

Brazil has experienced an increase in grain crops production under no-till. However, most Brazilian agricultural soils present high acidity, high Al and low Ca, which reduces root growth, thus interfering in water and nutrient absorption and, consequently, in crop yield. Gypsum has been utilized as an alternative to reduce aluminum toxicity and increase Ca in soil without tilling because it is relatively more soluble than lime. The aim of the present work was to evaluate root growth, dry matter accumulation, mineral nutrition and grain yield of common bean (Phaseolus vulgaris), cv. Pérola, as affected by lime and gypsum applied on the soil surface during a no-tillage system implantation. The experiment was carried out in a Typic Acrustox with the following characteristics (0-0.20m): 4.2 pH in CaCl2; 20.9 g dm-3 of M.O.; 9.2 mg dm-3 of P (resin); 36.8 mmolc dm-3 of H+Al; 1.2 mmolc dm-3 de K; 14.0 mmolc dm-3 of Ca; 5.0 mmolc dm-3 of Mg; 58.0 mmolc dm-3 of CEC and 37% of base saturation. The soil had 545, 108 and 347 g kg-1 of sand, silt and clay, respectively. A randomized complete block design was used in a split-plot scheme, with four replications. The treatments were set out in October of 2002 and comprised four levels of dolomite limestone, with 71% PRNT: 0, 1,100, 2,700 and 4,200 kg ha-3, calculated to elevate the base saturation in the soil layer 0-0.20m to 50%, 70% and 90%, respectively, and gypsum (0 and 2,100 kg ha-3) applied to the soil surface. Lime, gypsum and lime+gypsum application increased root length, root surface area and root dry matter of common bean in the arable layer. With gypsum liming provided a linear increase in common bean dry matter yield. Irrespective of gypsum application, liming provided a quadratic increase in potassium level in the leaves due to increased K levels in the soil. Although Ca levels in the more superficial soil layers (0,0–0,2 m) were increased by liming as well as by gypsum application, the content of this element in common bean leaves was not affected. Gypsum increased magnesium level in leaves. Liming resulted in a linear increase in Mg absorption only when gypsum was applied. It must be emphasized that gypsum is an excellent source of sulfur. However, when gypsum was not applied, liming provided a quadratic increase in sulfur level in the leaves, but when gypsum was applied liming had no effect. In the absence of gypsum, yield response to lime was quadratic with a maximum at 2,075 kg ha-3. When gypsum was applied there was no response to lime. Surface lime application can improve chemical soil conditions, root growth, plant nutrition and, consequently, increase yields.

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