Effect of Combination of Soil Improvers and N, P, K Fertilizer on Organic C, Total N, Uptake N, and Yield of Lowland Rice (Oryza sativa L.) in Inceptisols from Jatinangor, West Java, Indonesia

Intensive inorganic fertilization in conventional agriculture can cause a decrease in soil quality. Modification through balanced fertilization with soil amendments is expected to improve soil quality and increase plant productivity. The experiment aimed to evaluate the effect of a combination of soil improver and N, P, K fertilizer on lowland rice (Oryza sativa L.) with a focus on increasing organic C, total N, and uptake N, as well as finding the dose that provides the best lowland rice yields in Inceptisols from Jatinangor, West Java, Indonesia. Field experiments using plastic buckets as experimental units for 5 months were carried out and arranged based on a Completely Randomized Block Design (CRBD) with eight treatment groups, including Control (A), recommended N, P, K dose (B), soil improvers (C), ½ soil improvers and ¾ recommended NPK dose (D), ¾ soil improvers and ¾ recommended N, P, K dose (E), soil improvers and ¾ recommended N, P, K dose (F), 1½ soil improvers and ¾ recommended N, P, K dose (G), as well as soil improvers and recommended N, P, K dose (H). The results showed was that there is an influence of the combination of soil improvers and N, P, and K fertilizer in increasing organic C, total N, uptake N, and rice yield. This experiment concluded that the dose of 1 soil improvers (8 Mg ha-1) and ¾ recommended N, P, K dose (262.5 kg ha-1 Urea, 37.5 kg ha-1 SP-36, and 37.5 kg ha-1 KCl) was the best treatment in increasing rice yields and it is necessary to carry out experiments on rice yields with a higher level of heterogeneity.