Perdas de nitrogênio por volatilização e lixiviação provenientes de fertilizantes granulados NK e NS / Nitrogen losses by volatilization and leaching from a granulated fertilizer NK and NS

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

In order to evaluate the volatilization of N-NH3 and leaching of N from granulated mixtures NK (urea and potassium chloride) and NS (urea and ammonium sulfate) in two soils, two experiments were conducted in a greenhouse with controlled temperature and humidity. The experiment followed a completely randomized design, in factorial 12 x 2 x 2 + control treatment (without N), with 3 repetitions. The factors evaluated were: (a) nitrogen fertilizer - commercial urea (UR), ammonium sulfate (SA), urea + KCl (NK) in six different proportions, urea + SA (NS) in four different proportions ; (b) forms of incorporation - absence and incorporated at 5cm; and (c) soil pH at natural pH levels and at pH 6.5, which resulted in 49 treatments with 3 repetitions, totaling 147 experimental units. Two soils (Fragiudult and Udult), packed into PVC columns, were used in different seasons. The fertilizers were applied at the amount equivalent to 120 kg N ha-1. The volatilized N-NH3 was trapped by an ammonia free semi-open static collector (SALE) for 21 days in 9 collections. At the end of the trapping of volatilized ammonia, the columns had their moisture increased with de- ionized water for soil saturation, aiming to force solution leaching. De-ionized water was added to simulate a rainfall of 200 mm per day-1. After this rain, three additional rainy days were simulated with a rainfall equivalent to 50 mm day-1. The collection of the leached solutions was done once a day for 4 days. The samples were analyzed for their content of ammonium + nitrate + nitrite. Immediately after leaching, the samples were removed from the soil columns with the help of a 9 mm PVC tube, used as a probe, and separated into three 20 cm sections, going from the top to the base of the columns. The samples were analyzed to determinate ammonium and nitrate + nitrite using the Bremner methodology, with MgO and Devard formula, respectively. In the test conditions, granulated NK and NS fertilizers enriched with KCI and (NH4)2 SO4 were not efficient in reducing the N-NH3 losses by leaching, in the two soil classes. The greatest losses from leaching were showed by the reference treatments (SA and UR). The granulated fertilizers presented levels of biuret above permitted by legislation. Biuret inhibited the nitrification of N-NO4 +, with smaller losses and larger proportions of N-NH4 + in relation to N-NO3 - in the two soil classes. This occurred because the reduction in the N-NH4 + oxidation, principally in the clayey soil, where this inhibition was more intense. The most efficient fertilizers (captured N/applied N) in the sandy soil (Fragiudult) were: NS-1; NK-3 (pH 5.5); NK-1 e NK-3 (pH 6.5). For the clayey soil (Udult) all NK and NS granulated fertilizers presented efficiency above 94%.

ASSUNTO(S)

ciencia do solo urea ammonium sulfate efficiency. sulfato de amônio nitrogen fertilizer uréia eficiência. fertilizantes nitrogenados

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