Assessment of amending Christmas Island Rock Phosphate with rice straw and rice husk composts in enhancing phosphorus availability for growth of maize (Zea mays L.) in a tropical acid soil

Phosphorus (P) availability is commonly low in tropical soils because soluble inorganic P is fixed by aluminium (Al) and iron (Fe) oxides in Rengam acidic soil. To overcome this problem, soils are applied with lime and inorganic P fertilizer to increase the soil pH and enhance P availability in soils. However, these practices are not economical and not environmental friendly. Organic amendments can be used to increase P availability through hinder adsorption or precipitation of P in acidic soil. Therefore, this study is conducted to (i) compare the quality of compost derived from rice straw (RS) and rice husk (RH), (ii) identify the effect of amending CIRP with composts (RS and RH) on improving P availability, and (iii) determine the effect of amending CIRP with composts (RS and RH) on improving nutrient uptake, use efficiency and dry matter production of Z. mays cultivated in a tropical acid soil. The selected physico-chemical changes were evaluated during composting of RS and RH in order to compare the quality of compost. Incubation study and pot experiment were carried out to determine the effects of treatments on soil P availability, nutrient uptake, use efficiency, and dry matter production of Z. mays F1 hybrid sweet corn 801 variety cultivated in a tropical acid soil. Hence, Christmas Island Rock Phosphate (CIRP) fertilizer was amended with compost applied at varying rates of 5, 10, 15, and 20 t ha-1 of RS/RH compost, respectively. Physico-chemical soil properties, nutrient uptake, use efficiency and dry matter production of Z. mays were assessed to determine the effect of the treatments. Results indicate that the physico-chemical properties of RS and RH composts in present study are within the standard reference range as suggested by the U.S Composting Council (2002) for a good quality of mature compost. RS and RH compost amendment showed its effectiveness in enhancing soil P availability. Treatments applied with CIRP amended with RS and RH compost was found to increase soil available P during incubation period and at pot experiment in the Rengam acidic soil. The results also reveal that the highest concentration of soil P availability was accumulated in the treatments with highest rate of RS compost (RST5). The increase P concentrations, uptake and use efficiency in plant tissues due to compost application indicated an increase P availability for plant uptake. Conclusively, the suitable rate of compost application to improve P availability is 20 t ha-1 of RS compost in Rengam acidic soil at Jeli, Kelantan, Malaysia because it shows the most pronounced effect for P availability, P nutrient accumulation, improving use efficiency and dry matter of maize.