Nutrient dynamics in sugar cane. II. NO3-N and NH4-N lateral and vertical movement in the soil

Abstract

Sugar cane plots in a Red-Yellow Podzolic sandy soil were monitored for vertical and lateral urea movement. Treatments were: no N, 60 kg/ha of N at planting time, and 20 kg/ha of N at planting time plus 40 kg/ha of N 90 days after. Soil samples were taken from five depths (20 cm each) before planting and 3, 6, 11 and 16 months after it. Each plot was sampled in the furrow and at distances of 30 and 62 cm from it. Samples were extracted with 2N KCl and analyzed for NH₄-N and NO₃-N concentrations. NH₄-N concentrations oscillated around 3 ppm, with small variations among sample positions and sampling times. NO₃-N concentrations varied significantly among depths in the first three sampling periods (zero, three and six months); at the third and sixth month the sampling distance to the furrow had also a significant effect upon NO₃-N concentrations in samples bellow 40 cm. The maximum NO₃-N accumulation (17 ppm) occurred at a depth of 40-60 cm, in the furrow line, three months after the single 60 kg/ha of N application. Independently of depth and location, samples collected 11 and 16 months (harvest) after planting showed less than 1 ppm NO₃-N. The eluviation curves showed a fast vertical NO₃-N movement down the profile.