Soil acidification and nitrogen release following application of nitrogen fertilizers

Nitrogen (N) fertilizers may acidify the soil mainly after nitrification followed by nitrate leaching. The rate of N released and the dynamic of its reactions in the soil may interfere in soil acidification. This experiment was carried out to evaluate the N release rate and the soil acidification caused by N fertilizer application. Treatments include urea, ammonium nitrate, and six coated fertilizers, all applied at the rate of 300 mg kg−1 N, in addition to control, with no N. They were homogeneously mixed with 100 g of soil and allocated in plastic pots with the moist soil. Mineral N and soil pH were evaluated at 4, 7, 14, 21, 28, 35, 42, 49, and 56 days after fertilizer application. All N fertilizers decreased linearly the soil pH over time, except for ammonium nitrate. Ammonium was the N form predominant in the soil up to day 35 for all fertilizers, except for ammonium nitrate. Urea coated with sulfur + polymers released 90% of its N only from 42nd day after application, differing from other fertilizers. Nitrogen coated fertilizers were not efficient in reducing soil acidification and only urea coated with sulfur plus polymers showed characteristics of a slow-release fertilizer.