Frações de fósforo em experimento de longa duração em milho consorciado com Brachiaria brizantha cv. Marandu, sob diferentes fontes de nitrogênio

Abstract

The soil phosphorus adsorption to mineral colloids is the result of their ability to form high-energy binding compounds. Even if the total content of the element in the soil are high relative to that required to plants, just a small fraction thereof has low binding energy enables desorption and their availability to the plants. This behavior is more pronounced in tropical areas where soils are highly weathered and high in iron and aluminum oxides, and low pH, as in the Cerrado. There are some plants such as the genus Brachiaria spp., Which have the ability to release substances that increase phosphorus availability in the soil, which leads to having an increased attention for such use. The intercropped with corn and B. brizantha cv. Marandu is a way to better match use in soil, favoring the cycling of this nutrient. The study objective was to evaluate the effect of corn intercropped with B. brizantha cv. Marandu and nitrogen sources in phosphorus fractions in soil as well as in corn yields. The experiment began in 2005, but the study was conducted in the agricultural year 2013/2014 in the municipality of Maracaju-MS, where treatments were willing factorial 2 x 4, two factors studied, and the intercropped (presence or absence of B. brizantha cv Marandu in corn.); and sources of nitrogen (without nitrogen, urea, urea + ammonium sulfate and ammonium sulfate) arranged in randomized block design with four replications. He gathered up soil samples for chemical analysis and fractionation of P in four depths (0-5, 5-10, 10-20 and 20-40 cm) after the corn harvest in autumn / winter 2013, as well as determination in corn crop in 2013. The use of ammonium sulphate provided greater labile phosphorus accumulation throughout the soil profile, especially in the organic fraction extracted by NaHCO3 and reduce non-labile forms. The cultivation of B. brizantha cv. Marandu intercropped with maize increased availability of phosphorus labile form without nitrogen fertilization, and reduced phosphorus fraction bound to iron and aluminum. The corn intercropped with B. brizantha cv. Marandu provided increased corn productivity.