Management of sewage sludge and mineral nitrogen in soil fertility over time

Abstract

The use of sewage sludge is a practice highly promising for the development of sustainable agricultural systems. The objective of this study was to assess the improvement in soil fertility management strategies on different sewage sludge and mineral nitrogen after seven application of this residue. The experiment was carried at the São Manuel Experimental Farm belonging to the faculty of Agronomic Sciences of UNESP, Botucatu, located in the county of São Manuel. It was adopted the experimental design in a randomized blocks consisting of six treatments and five repetitions defined as follows: T0 – without nitrogen fertilizer, T1 – mineral fertilizer nitrogen according to the crop needs, T2 – 50% nitrogen from sewage sludge and 50% in the form of chemical fertilizer, T3 – 100% of nitrogen recommended by the culture, from sewage sludge, T4 - 150% of nitrogen recommended by the culture, from sewage sludge and T5 – 200% of the nitrogen from the sewage sludge. It has done seven application of sewage sludge in crop (year 1 – sunflower, year 2 sunflower, year 3 – oats and bean, year 4 – triticale and sunflower, year 5 – wheat) and the first three applications were treated with sewage sludge and the other applications were composted sludge. In the depth 0-20 cm, the sewage sludge promoted an increase in levels of organic matter, P, S, H+Al, CEC and decreased in soil pH. In the depth of 20 to 40 cm the sewage sludge promoted a decrease in pH and increase in soil organic matter, P, H+Al, K, Ca, SB, CEC and S. Mineral N influence the increase in the depth S of 20-40 cm.