Fluxes of nitrous oxide and methane in commercial soybean, rice, and maize crops on the Santarem-Belterra plateau, Para State.
2008
OLIVEIRA JUNIOR, R. C. de | KELLER, M. | CRILL, P. M. | RAIMUNDO COSME DE OLIVEIRA JUNIOR, CPATU; M. KELLER, UNIVERSITY OF NEW HAMPSHIRE; P. M. CRILL, UNIVERSITY OF STOCKHOLM.
The west region of Para State, principally the municipality of the Belterra and Santarém, has tried since 2000 an expressive increase in their grain crops areas, specifically soybean, rice and, in 2007, corn. In 2005 the farmers planted 110,000ha of these crops. This brought a no avoid fertilizers applications, where nitrogen has contributed in the formulas to planting and cover application. After 2003, were installed throughfall and precipitation collectors (bulk deposition) to monitoring nutrients cycles in these planted areas on the forest and superficial water (rivers and streams), besides collect gas samples with static chambers in agricultural areas. Using liquid and gas chromatography were analyzed nitrate and ammonium, and nitrous oxide. The results shown that precipitation and throughfall waters have high nitrogen content, in which ammonium is prevalent in the precipitation and nitrate in throughfall, with richest factor of the 3.9 to nitrate and -0.2 to ammonium. Also, the fluxes values to nitrogen (monthly average) according to 3.4 kg N.ha-1 in throughfall, and 3.1 kg N.ha-1 in precipitation. The fluxes of the nitrous oxide were (average) 2.59 ng N.cm-2.hour-1 (conventional soybean), while in no till system this fluxes were 3.2 ng N.cm-2.hour-1. In the superficial waters were observed light undulation during seedbed period (rainy season), with average value of the 0.24 ppm, in the six rivers and streams studied. The principal conclusion is that nitrogen fertilizers used in the crops are going to the forest and the forest is using this nitrogen to supply its necessity to grown.
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