KANDUNGAN AMONIUM DAN KALIUM TANAH DAN SERAPANNYA SERTA HASIL PADI AKIBAT PERBEDAAN PENGOLAHAN TANAH YANG DIPUPUK NITROGEN DAN KALIUM PADA TANAH SAWAH

Tillage system can influence organic matter, nitrogen (N), and potassium (K) in the soil solution. Ammonium (N-NH +) buffer capacity is influenced by K+ in the soil solution. The objective of this study was to determine the content of N-NH + and K exchangeable (K-ex.) and its uptake as well as yield of rice ( Oryza sativa L.) in the lowland rice fields under intensive/conventional tillage (CT) and no-tillage (NT) with application of nitrogen (N) and potassium (K) fertilizers. The experiment was conducted during rainy season 1999/2000 (8th growth season) in Kedaloman village, Talangpadang, Tanggamus, Lampung Province. The study was part of long-term research established since dry season 1996. The experiment was set up in a completely randomized block design with three replications. There were three treatments allocated in a factorial arrangement, i.e. (1) tillage system (CT and NT); (2) K fertilizer (without K and 49.8 kg ha-1 K); and (3) N fertilizer (46, 115, and 184 kg ha-1 N). Results of the study showed that N-NH + content and K uptake was affected by the interaction of tillage system, N and K fertilizers. When 49.8 kg ha-1 K was supplied, application of 184 kg ha-1 N produced higher N-NH + content and K uptake than 46 kg ha-1 N on both CT and NT. K-ex. and N uptakes on NT was 18% and 9% higher than those on CT, respectively. Application of nitrogen at 184 kg ha-1 N had the highest effect on K-ex., N uptake, and yield of rice. Application of 49.8 kg K ha-1 produced K-ex.12% higher than without K. In conclusion the N-NH +, K-ex., N and K uptake, and yield of rice were strongly determined by N fertilizer rather than the tillage system or K application.