Risco de impacto ambiental por nitrato em área de várzea cultivada com milho sob diferentes doses de nitrogênio.

Abstract

The aim of this work is to verify the pollution potentiality for nitrate in meadow areas cultivated with corn with different rates of nitrogen in the urea form. The experiment was conduct in a meadow belonging to ESALQ/USP, with system of implanted drainage. The experimental design was randomized complete blocks, with 5 treatments (0,0, 50, 100, 150 and 200 kg N have-1) and 3 repetitions. Each parcel possessed an underground drain, an observation well, a tensiometer and an extrator. The effluents collected in the drains, in the observation wells and in the extractors were analyzed the method of the brucina. In the months of nov/04 to march/05 rained 562 mm. The NO3 - concentrations in all of the points of collection of water were smaller than 10 mg L-1. It conclude that the manuring nitrogen of up to 200 kg ha-1 in the culture of the corn, 2,5 times superior to the recommendation for the bulletin 100 of IAC, didn't affect the quality of water in the discharges of the drains for nitrate, therefore it didn't contribute to the increase of the pollution of the river Piracicaba and to the environment.