Ramadan, S. A.; A. S. Antar; A. A. El-Leithi and I. E. Nasr El-Din ( 2009). Impact of different nitrogen forms and k added on n and k losses into drainage water under cotton cultivation in clay soil of north delta.J. Agric. Res. KafrEl-Sheikh Univ., 35 (2) 776-790 (2009)
Abstract: A field experiment was conducted to study the effect of applied fertilizer forms from nitrogen on N and K+ leaching through a clay soil into subsurface drains under cotton cultivation in north Delta (Egypt). The N-fertilizers forms (ammonium nitrate; ammonium sulphate and urea) were added to the soil with and without potassium sulphate fertilizer in recommended doses (70 and 48 unit/fed for N and K2O, respectively) in two equal doses after the first irrigation and the second one, respectively. Data showed that, total cumulative drain discharge throughout the five irrigation cycles under cotton cultivation were nearly the same in all treatments. The losses of NH+4-N in drainage water was less than the NO-3-N. The total losses of NH+4-N were 28.19, 23.33, 23.12, 21.13, 17.82 and 27.63 g N/fed for NH4NO3+K2SO4, NH4NO3, (NH4)2SO4+K2SO4, (NH4)2SO4, CO(NH2)2+K2SO4 and CO(NH2)2, respectively. Results indicated also that the losses amount of N-Nitrate in drainage water decreased by successive days of irrigation. Total losses of NO3-N under NH4NO3+K2SO4 and (NH4)2SO4+K2SO4 were higher than NH4NO3 and (NH4)2SO4 by 9.72 % and 6.47%, respectively. While, total NO3--N loss under CO(NH2)2+K2SO4 was lower than CO(NH2)2 by 6.16%. The highest total losses of NO3-N were found under NH4NO3+K2SO4 and NH4NO3 comparing with the other treatments. The results revealed that, by the end of season the total nitrogen losses were 4.67, 4.25, 4.05, 3.80, 3.78 and 4.02 kg N/fed for fertilizer treatments of ammonium nitrate +K-sulphate, ammonium nitrate, ammonium sulphate + K-sulphate, ammonium sulphate, urea + K-sulphate and urea, respectively. The total nitrogen fertilizer losses were 14.15, 12.89, 15.27, 14.34, 8.14 and 8.64 kg fertilizer /fed for the corresponding treatments. These losses represented 6.67, 6.08, 5.78, 5.43, 5.41 and 5.74% of the added N at the corresponding treatments, respectively. Total potassium losses were 1.15, 1.10, 1.18, 1.11, 0.96 and 1.06 kg K2O /fed for fertilizer treatments of ammonium nitrate + K-sulphate, ammonium nitrate, ammonium sulphate + K-sulphate, ammonium sulphate, urea + K-sulphate and urea, respectively whereas, total fertilizer losses were 2.39, 2.29, 2.46, 2.32, 2.01 and 2.21 kg fertilizer /fed for the corresponding treatments. The obtained results indicated that combination of N and K-fertilizers added to the soil, except urea, slightly increased losses of N in both NH+4 and NO-3 forms and K in the drainage water under cotton cultivation. So, the irrigation after the addition of such fertilizes must be controlled, to minimize nutrients losses into drainage water.
Keywords: (NH+4-N, NO3--N, K2O, losses, tile drainage, fertilizer forms, clay soil, cotton.)
