Effects of Pruning and Plant Nutrition Management on Growth, Development and Yield of Cashew Nut

Abstract

Cashew nut   (Anacardium occidentale) is an economic crop of Uttaradit, the largest production area of Thailand. Cashew nut farming of Uttaradit is rainfed, grown on severely acidic soil without agricultural practice. The unhealthy flowering and low productivity are seriously problematics. The objective of this study was to investigate the farmer practice for enhancing yield of cashew nut. The study was carried out in farmer’s field and 15 years-old of cashew nut trees with 4-6 m of crown radii were selected. The experimental design was 2x2 factorial in randomized complete block (RCB) with 10 replications. There were 2 factors; 1) pruning: semi-circle pruning with 60% of light was allowed to the tree and 2) fertilizer management: dolomite and soil fertilizer rate, determined from soil test results, were applied during the early of rainy season. Moreover, commercial foliar fertilizer, 6-32-32 + trace elements, enriched with glucose at rates of 50g+50g per 20 L were sprayed weekly prior 1^st leaf flushing until before nuts were fully developed. The results showed that fertilizer management affected all growth stages considering from leaf flushing, inflorescence size, number of nuts per inflorescence, nut weight, and yield. Whereas, pruning only affected the last three parameters.  The pruning + fertilizer treatment induced 100% leaf flushing and flowering concurrently. The larger size, 25-28 cm length, of inflorescences were observed after 3 weeks of spraying. Either pruning or fertilizer treatment lead 75-78% of leaf flushing and gave significantly smaller size of inflorescences with16-17 cm length (P<0.01). The interactions between 2 factors that influenced number of nuts per inflorescence, nut weight, and yield were discovered. This study discovered that pruning + fertilizer treatment extended the period of nut development to harvesting up to 4 months. Furthermore, the treatment supply sufficient nutrition for the growing period.  At a result, there were 12.80 nuts per inflorescence, each nut weight 6.5 g and the given yield was 10.93 kg/tree. On contrary, other treatments demonstrated significantly smaller (P<0.01) in terms of nuts per inflorescence (1.19-3.29), weight (3.83-4.87 g per nut) and yield (2.32-3.94 kg/tree).   In conclusion, pruning and fertilizer management such as soil pH improvement and soil fertilizer application are highly recommended in the early of rainy season.     The foliar fertilizer enriched with glucose were also recommended to spray weekly from leaf flushing to nut developing period.