Changes in Soil Ph and Eh Of Rainfed Rice Fields With The Application of NPK Fertilizer and Rice Straw Compost

In Indonesia, rainfed rice fields (non-irrigated) account for only 26.5% of total rice production. The use of sub-optimal land, such as rainfed rice fields, can be used as an alternative. In general, these rainfed rice fields were infertile, they often experienced drought, and their irrigation systems depended on rain. pH and Eh soil are the main factors affecting the solubility and availability of nutrients and their transformation in the soil. Thusly, the purposes of this research were to determine the interaction effect of NPK fertilizer combined with rice straw compost on changes in soil pH and Eh in rainfed rice fields planted with rice. This research used a two-factor randomized block design (RBD). NPK fertilizer dosage (a) and composted rice straw dosage (k) made up the first and second factors, respectively. There were 3 treatments of NPK fertilizer doses, i.e. 0 (control); 150; and 300 kg ha -1 , while there were 6 doses of rice straw compost, 5; 7.5; 10; 12.5; 15; and 20 t ha -1 . Each treatment consisted of two experimental blocks, resulting in 36 experimental units. Soil observations were carried out three times, namely when the rice was 2 weeks after planting (WAP), 10 WAP, 17 WAP. Results showed the best treatment combination for lowering Eh soil at 2 WAP was a2k4 (300 kg ha -1 + 12.5 t ha -1 rice straw compost) with a value of Eh -251,2 mV. The effect of single-factor compost was best in increasing the soil pH at 2 WAP, which was 15 t ha -1 (k5) with a pH value of 7.28.