Yield and yield components of papaya grown on Coto clay (Typic Eutrustox) and fertilized with chicken manure

A field experiment was established on Coto clay (Typic Eutrustox) to evaluate the use of chicken manure as fertilizer for papaya. Four manure rates (0, 5,10 and 15 t/ha) were evaluated in all possible combinations with four rates of inorganic fertilizer (0, 56, 112 and 224 g/plant/month of 15-15-15). Fresh and dry weight of papaya leaves (petioles and blades) increased significantly with manure applications, but no effect of inorganic fertilizer treatments was observed. Phosphorus and potassium concentration in papaya blades was higher in plots receiving 15 t/ha of chicken manure. Fertilizer applications increased K content in blades and decreased magnesium content. Both manure and fertilizer treatments increased fruit yield. The application of 10 and 15 t/ha of manure resulted in fruit yields of 42.19 and 54.76 t/ha. These yields were significantly higher than the yields obtained with the 0 and 5 t/ha treatments. The 0, 56,112 and 224 g/plant/month fertilizer treatments resulted in fruit yields of 28.11, 42.60, 37.22 and 38.25 t/ha, respectively. The yield of the 0 fertilizer treatment was significantly lower, but no significant difference was observed among the other fertilizer treatments. Chicken manure applications increased soil available phosphorus (Bray 1-P) from 16.57 to 28.64 mg/kg, and soil exchangeable potassium from 0.12 to 0.19 cmol c /kg. Fertilizer applications had no significant effect on these two parameters. A significant correlation was observed between papaya yield and Bray 1-P. A Pearson correlation coefficient of 0.65 was obtained when both manure and inorganic fertilizer plots were considered. The correlation coefficient increased to 0.82 when only manure-treated plots were considered, but decreased to 0.25 when only fertilizer-treated plots were considered. Manure applications were more effective in increasing soil available phosphorus than fertilizer applications. Manure applications apparently prevent phosphorus fixation on Coto clay, increasing soil available phosphorus and thus favoring higher fruit yields.