ABSTRACT
A pot experiment was carried out to investigate the comparative effect of city finished compost and NPK fertilizer on the growth and availability of phosphorus to radish (Raphanus sativus L.). An air dried sandy loam soil was mixed with five rates of city finished compost (CFC) equivalent to 0, 5, 10, 20, 40 ton ha–1 and three rates of NPK fertilizer equivalent to 50% (N-P-K = 69-16-35 kg ha–1), 100% (N-P-K = 137-32-70 kg ha–1 K) and 150% (N-P-K = 206-48-105 kg ha–1). Four plants were harvested at 45 days of growth and remaining one plant was harvested at 90 days of growth and separated into leaves and bulbs. After harvest, soil samples were collected from each pot to measure soil pH and available P extracted by Olsen, Mehlich-3, Kelowna and Bray & Kurtz-1 extractants. The growth parameters (length of leaves and bulbs, fresh and dry weight of leaves and bulbs), relative dry matter yield, plant P concentrations, P uptake by radish, soil pH, and available P increased by the rates of CFC and NPK fertilizer treatments. Among the treatments, growth performance of radish was better with the highest rate of 40 t ha–1 CFC treatments. The results obtained from the 5 and 10 t ha–1 CFC treatment were comparable with the results of 50% and 100% NPK fertilizer treatments respectively. Similar effects of amendments were obtained in the case of plant P concentration, uptake of P by plant, soil pH and available soil P concentration. Available P and soil pH showed very strong and positive correlation (P < 0.001) with dry matter yield, P uptake by plant. The P extracted by various extractants also showed strong positive correlation (r = 0.973 to 0.994; P < 0.001 ) each other indicating the suitability of any of the extractants to predict available P. Results of the present study indicated that 10 t ha–1 city finished compost could be used instead of 100% to obtain similar yield and to improve soil conditions.