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

Document Type: Research Paper

Authors

Agricultural University of Athens, Laboratory of Vegetable Production, 75 Iera Odos, 11855 Athens, Greece.

Abstract

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 oC fresh weight decreased by 7% and 11-12% respectively, and by 20% and 28% respectively during 3 days subsequent shelf-life at 22 oC. Weight loss after 10 days at 7 oC 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 oC, which permits a 3 day ambient shelf-life.

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