Nitrogen and phosphorus in water from cultivated area of cotton in two cropping systems

Abstract

Nitrogen and phosphorus are the main nutrients that restore soil fertility, however, in excess, it is the main responsible for the process of eutrophication of water. Thus, this study aimed to evaluate the nitrogen and phosphorus levels in percolated water and runoff in an Oxisol cultivated with cotton in conventional tillage (PC) and minimum tillage (CM). The experiment was conducted on the Island Stream watershed in Campo Verde municipality, MT, Brazil. There were installed plots whose dimensions were 3.5 m x 11 m, being placed at the end portion of a box for storing rainwater. Water samples were collected (in the period of harvests of 2005 and 2006) in the, lysimeters, water the soil solution and monitoring wells. There was determined the concentrations of nitrogen in form of nitrite (NO2-) and nitrate (NO3-) and phosphorus in the form phosphate (PO4-2) in both PC and CM management systems. In the PC there was a higher concentration of NO3- in the percolated water and water from the soil solution in the most studied depth (1.30 m), and the conservation management system (CM) were found lower supply of nutrients (N and P).