Residual effect of nitrogenous fertilizers on some properties of a soil

Abstract

An experiment was made in pots with four repetitions using an acid soil with poor fertility in order to test the residual values of urea fertilizer (with and without sulphur), ammonium nitrate and ammonium sulphate. In the beginning the pH were correct up to 6,0 and applications of phosphate and potassium fertilizers in quantities of 90 and 120 kg/ha of P(2)0(5)and K(2)0 were respectively done. The quantities of N were 0, 120 and 240 kg/ha. The test plant was corn (Zea mays L.). In the following year this test was repeated without pH correction and without adding nitrogenous fertilizers. In the subsequent year the same experiment was repeated making however, pH corrections in two repetitions of each treatment. After havesting the residual effects of the employed fertilizers were studied using the following items as avaluation parameters: contents of exclangeable Al and H, potencial H, pH and nitrogen of the soils. The main conclusions were as follows: a. There was no residual effect of the nitrogen treatments when the nitrogen content of the soil was taben as a reference point. b. Refering to the exchangeable Al , the treatments that received pH correction showed no residual effect of the nitrogenous fertilizers, but in the abence of the corrective the ammonium sulphate presented a con siderable effect. The others showed less pronounced effects . c. In a general way, what concerns the potencial and exchangeable H there was no residual effect of the nitrogenous fertilizers in the treatments with corrections but in those that did not receive lime there was some residual effect especially of ammonium sulphate.