Pengaruh Bahan Organik terhadap Ketersediaan Fosfor pada Tanah-Tanah Kaya Al dan Fe

Abstract

Phosphorus (P) is one of the essential nutrients for plants. However, 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 (Andosol, Latosol, Podsolic) was added with straw compost and 2 weeks later P fertilizer was added, (2) Soil (Andosol, Latosol, Podsolic) was added with P fertilizer and after 2 weeks straw compost was added, (3) Soil (Andosol, Latosol, Podsolic) was added with cow manure compost and after 2 weeks P fertilizer was added, (4) Soil (Andosol, Latosol, Podsolic) was added with P fertilizer and after 2 weeks cow manure compost was added, and (5 ) Soil (Andosol, Latosol, Podsolic) was added with P fertilizer only. 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 more effective in increasing pH and P-availability, as well as lowering the Al-dd and Fe-availability on the three soils than the treatment of only addition of P fertilizer. Cow manure compost gives a higher effect than straw compost. The addition of organic matter to improve releasing adsorbtion of P and preventing adsorption of P on Latosol and Podsolic, meanwhile for Andosol effect of organic matter is less visible. Latosol and Podsolic, the addition of organic matter is better if it is done after P fertilization, meanwhile for Andosol the addition of organic matter is better if it is done before P fertilization. The highest available-P of Andosol is in the treatment is soil was added with cow manure compost and after 2 weeks P fertilizer was added is 10.67 ppm, meanwhile available-P for Latosol is soil was added with P fertilizer and after 2 weeks cow manure compost was added is 90.95 ppm, and Podsolic is Soil was added with P fertilizer and after 2 weeks cow manure compost was added is 40.73 ppm.