Release pattern of ammonium, nitrate, and potassium from Slow-Release Fertilizer (SRF) in the Soil

Abstract

The low efficiency of nitrogen and potassium fertilization is one of the pressing problems in tropical agriculture. This is because the humid tropical climate, like what Indonesia has, which is characterized by high rainfall, causes a high rate of leaching of nitrogen and potassium in the soil. To improve fertilization efficiency, one practical option is to find a method of slowing down the release of available nutrients in the soil. Thus, the purpose of this study was to evaluate the pattern and rate of the release of nitrogen (in the form of ammonium and nitrate) and potassium from slow- release fertilizer (SRF). This study used three types of fertilizers, namely: SRF (13-8-10), SRF (19-12-15) and Mutiara granule fertilizer (16-16-16). Treatment dosages used corresponded to 600 kg/ha and 1200 kg/ha, with three replications, and observed over a 10-week incubation period. The results showed that ammonium release from SRF fertilizer in the first week that ranged 28.94% - 41.45%, then decreased progressively with incubation time, while that of nitrate ranged 5.77 - 7.21%, but increased over time. On the other hand, the potassium from SRF fertilizer was released by rates of 9.56% -24.58% during the first week, increasing with incubation time. The same pattern of nutrient release was observed in the case of Mutiara fertilizer, however at much greater rates compared to SRF, viz.: for ammonium (44.56 - 46.91%, at decreasing rate afterwards with incubation time), nitrate (26.33 - 30.10%, at increasing rates afterwards), as well as for potassium (15.39 - 15.75%, at increasing rates afterwards). In summary, the SRF (13-8-10), applied at a dosage corresponding to 1200 kg/ha yielded the slowest rate of nutrient release in the soil.