QUALITY OF RUN-OFF FROM AN IRRIGATED MARKET GARDEN AREA IN BRAZIL

This paper presents the results of a study carried out in Brazil to determine the effects of irrigation and fertiliser use on the quality characteristics of run-off from an agricultural area used for intensive cultivation of market garden produce. The results show that during dry weather the discharge of nutrients from the cultivated area when irrigation is taking place is equivalent to 7 kg ha-1 yr-1 N and 1 kg ha-1 yr-1 P. Considerable accumulation of nutrients took place in the soil during the growing season, over the 129-day survey period the nutrient content of the top soil increased by approximately 590 g m-2N and P and 780 g m-2K. This accumulation was derived from fertilisers which were applied at rates of 1136 kg ha-1N, 978 P and 1367 K. During wet weather the nutrients which had accumulated in the soil were washed out. © 1979.