PENGARUH BAHAN ORGANIK TERHADAP KETERSEDIAAN FOSFOR PADA TANAH-TANAH KAYA Al DAN Fe
The availability of P that can be absorbed by plants in the soil is generally very low, because P in the soil are manily in adsorbed form. Addition of organic matter can improve the availability of P in the soil, because organic acids that are resulted by decomposition of organic matter have an ability to make chelation of Al and Fe so P may become available. The aim of this research was to study effect of organic matter in releasing and preventing adsorption of P and to study wether the effect of organic matter is better if it is applied before or after P fertilization. This research consisted of five treatments: (1) Soil + straw compost + P fertilizer 2 weeks later, (2) Soil + P fertilizer + straw compost after 2 weeks, (3) Soil + cow manure compost + P fertilizer after 2 weeks, (4) Soil + P fertilizer + cow manure compost after 2 weeks, and (5 ) Soil + P fertilizer. The kind of soil were used in this research Andosol, Latosol, Podsolic. Each treatment on the three soils was incubated for 1 and 2 months. The results showed that treatment of organic matter and P fertilizer addition is increasing pH and P-availability, as well as lowering the Al-dd and Fe-availability on the three soils. Cow manure compost gives a higher effect than straw compost. The addition of organic matter after P fertilization to improve releasing adsorbtion of P and preventing adsorption of P on Latosol and Podsolic. The addition of cow manure compost on Andosol increasing P-availability is better if it is done before P fertilization, meanwhile organic matter addition after P fertilization.
Keywords: Availability of P, compost, organic matter, P Sorption