Nitrogen application affects yield and postharvest quality of okra (Hibiscus esculentus L. cv. 'Boyiatiou')

In Greece and Turkey, okra (Hibiscus esculentus L.) is cultivated for small pods (<= 4-5 cm), which are highly perishable after harvest. In this experiment, okra was cultivated at 4 levels of N (30, 150, 300 and 450 mg l(-1)) within the irrigation water. Pod yield was highest at 300 mg l(-1) N. High N increased the nitrate content and decreased dry matter without affecting pod colour (P <= 0.05). When pods were enclosed in polyethylene and stored for up to 10 days at 7 or 10 degrees C fresh weight decreased by 7% and 11-12% respectively, and by 20% and 28% respectively during 3 days subsequent shelf-life at 22 degrees C. Weight loss after 10 days at 7 degrees C and during shelf-life was higher in pods from 300-450 mg l(-1) N and was accompanied by a corresponding decrease in % dry matter. The loss of chlorophyll during storage (i.e. increase in a*) rose with storage time and N application level, accompanied by a decrease in b*. The nitrate concentration within the pods decreased with storage irrespective of N level. It is concluded that the rate of N application affects not only the production but also the quality of okra during storage. For the production of small-sized pods N application should not exceed 300 mg l(-1). Although pods from high N levels (300-450 mg l(-1) N) lose more weight, dry matter and chlorophyll than those from the lowest N level (30 mg l(-1) N), they may nevertheless be stored satisfactorily for up to 10 days at 7 degrees C, which permits a 3 day ambient shelf-life.