Foliar application of moringa leaf extract, potassium and zinc influence yield and fruit quality of 'Kinnow' mandarin

'Kinnow' mandarin (Citrus nobilis L. x Citrus deliciosa T.) is the most important commercial citrus cultivar grown in Pakistan. Poor nutrient management practices in citrus orchards had significantly reduced its yield and fruit quality. Recent reports of Moringa olifera as a promising growth enhancer showed its potential for application in agriculture sector. Moringa leaf extract (MLE) is enriched with phytohormones, phenolics and minerals. Hence, present study was conducted to evaluate efficacy of MLE alone or in combination with zinc (Zn) (as ZnSO4) and potassium (K) (as K2SO4) on 'Kinnow' mandarin during two consecutive years (2013-2015). In first experiment, trees were sprayed with 3% MLE, 0.6% ZnSO4 and 0.25% K2SO4 alone and in combination with 3% MLE at fruit set stage (year-I); whilst, in second experiment trees were sprayed with 3% MLE at pre-mature stage and 3% MLE, 0.6% ZnSO4 and 0.25% K2SO4 at fruit set stage (year-II). Data were collected regarding leaf nutrient and ascorbic acid contents, yield and fruit quality. Leaf nitrogen (N), phosphorous (P), K, calcium (Ca), manganese (Mn) and Zn were significantly increased with all treatments in both experiments. Combined application of MLE, K and Zn at fruit set stage in both experiments resulted in significantly lower fruit drop and higher fruit set, yield, fruit weight, juice weight, soluble solid contents (SSC), vitamin C, sugars, total antioxidants and total phenolic contents. Activities of SOD and CAT enzymes in fruit juice were significantly increased with 3% MLE application in both experiments. Conclusively, combined foliar application of 3% MLE, 0.6% ZnSO4 and 0.25% K2SO4 at fruit set stage can be used effectively to improve leaf nutrient status, fruit yield and quality of 'Kinnow' mandarin trees. (C) 2016 Elsevier B.V. All rights reserved.