Effect of organic and inorganic nutrient sources on the yield of selected tropical vegetables

Abstract

Results from different experimental studies that compared organic and inorganic nutrient sources on yield of tropical vegetables were subjected to meta-analysis to quantify the overall effect of nutrients on crop yield. The selected studies reported organic to conventional yield comparisons on ten tropical vegetable crops viz. amaranthus (Amaranthus tricolor L.), brinjal (Solanum melongena L.), chilli (Capsicum annuum L.), okra (Abelmoschus esculentus (L.) Moench), tomato (Solanum lycopersicon L.), bitter gourd (Momordica charantia L.), coleus (Solenostemon rotundifolius (L.) Codd.), cowpea (Vigna unguiculata (L.) Walp), snake gourd (Trichosanthes anguina L.), and cucumber (Cucumis sativus L.). Random effect model of the statistical programming software Comprehensive Meta Analysis Version 2 was used in the analysis. Mean yield was used as the compared outcome and standard mean difference (SMD) between the treatment and control yield was used as the effect size metric. Forest plot results indicated the combined effect of the data from the selected studies of tropical region over a period of thirty years (1985–2015). The overall standard mean difference (SMD) of yields between organic and inorganic sources of nutrition showed significant increase in crop yield under organic nutritional sources. However, meta-analysis that combined the overall effect estimate of standard mean difference of yield between nutrition with organic sources and conventional recommended integrated POP nutrition indicated no significant difference in yields. It could also be inferred that the effect of organic nutrition was significant only when the dosage was considerably enhanced or supplemented with different sources of manures. The long term sustainability of organic nutrition in vegetable crops depended on the quantity and quality of organic manures applied, crop yield, quality and price of the produce.