Effects of Soil Amendments on Postharvest Quality on Okra Fruits
*Adewoyin O.B.
Department of Horticulture, Federal College of Agriculture, Akure, Ondo State Nigeria
Accepted on May 02, 2012
Abstract
In Nigeria farmers apply fertilizers arbitrarily without considering the resultant effect on soil and the postharvest quality of crops. This study was therefore designed to investigate the effects of NPK fertilizer 20:10:10 on the postharvest quality of okra fruit (Abelmoschus esculentus L. Moen). Okra seeds NHE-47 were sown in the field at the National Institute of Horticultural Research (NIHORT), Idi-Ishin, Ibadan, Nigeria in 2001 at a spacing of 50 cm x 25 cm. The fertilizer NPK 20-10-10 at these levels 0 kg/ha, 300 kg/ha, 450 kg/ha and 600 kg/ha were applied in two splits. The growth parameters measured were plant height, number of leaves, dry and fresh weight of leaf, stem and roots. The experimental design for the field experiment was complete randomized block design replicated three times. Harvested okra fruits were subjected to two storage conditions; cold storage (refrigerator) at 40C and ambient condition at 27.80C for 21 days. Postharvest parameters measured were firmness, disease incidence, weight loss, Vitamins A and C, protein and fat contents. The experimental design was randomised complete block design replicated three times. Data generated were subjected to analysis of variance (ANOVA) and means were separated using Duncan Multiple Range Test (DMRT) at p ≤ 0.05.
The application rate of 450kg/ha gave the best response in growth and yield. The trend in yield can be ranked as follows 450 kg/ha > 300 kg/ha > 600 kg/ha > 0 kg/ha. It was observed that the varying levels of NPK fertilizer had no significant difference on the firmness and disease incidence of okra fruit. There were significant differences in the weight loss of okra fruit. Increase in levels of fertilizer rate had increase in weight loss, following this trend 600 kg/ha > 450 kg/ha > 300 kg/ha > 0 kg/ha. Fertilizer application rate had no significant effect on vitamin C, vitamin A, fat and protein content of okra fruit. The fertilizer application rate of 300 kg/ha had Vitamin. C content value of 207.0 mg/kg, fat content value of 1.56%, protein value content of 21.3% and Vitamin A content of 288.6 mg/kg. At 450kg/ha, the Vitamin C content was 229.8 mg/kg, Vitamin A content was 89.9 mg/kg, fat and protein content were 24.9% and 1.9% respectively.
Cold storage at 4 0C gave a better fruit firmness, less weight loss, reduced disease incidence and less degradation of Vitamin A and C, fat and protein content compared to fruits stored at the ambient temperature of 27.80C. Fertilizer application rate of 450kg/ha NPK 20:10:10 gave the best growth yield performance while varying fertilizer levels had no significant difference on firmness and disease incidence of okra fruit. Increase in fertilizer rate increases fruit weight loss.