Effects of coconut partial shading on mungbean morphological characteristics and yield

Increasing coconut farm productivity through intercropping will provide more profit for the farmers compared to coconut monocropping. However, partial shading by coconut trees has been known to have adverse effect on the intercrop. This study was conducted to determine the performance of 24 mungbean entries grown as intercrop and monocrop at Quezon Agricultural Regional Experiment Station (QARES) in Tiaong, Quezon [Philippines] on July to September of 2017. Under coconut, the photosynthetically active radiation (PAR) was much reduced since PAR on a sunny day ranged from 397.03 umol m-2s-1 at 8am to 1508.01 umol m-2s-1 at 12 noon while in the open, PAR at 8 am was 1,733.14 umol m-2s-1 and 2,199.96 umol m-2s-1 at 12 noon. All mungbean entries grown under coconut had higher plant count relative to those grown in the open probably as a result of higher moisture conservation that favored seed germination. However, a significant reduction in the number of days to flowering (NDF) was observed among plants grown under coconut while partial shading of coconut had no significant effect on mungbean's growth habit, biomass production and partitioning, internode distance as well as leaf area. On the other hand, the average yield obtained from mungbean grown as intercrop was significantly reduced by 65%, although the significant shade-variety interaction indicated differential response among varieties. Pag-asa 5 had the largest yield (715.17 kg/ha) under open field, while Pag-asa 3 had the highest yield (224.03 kg/ha) under coconut. PHL 18241 had the least reduction among entries while Pag-asa 5 had the largest yield reduction. The calculated harvest index (HI) did not show significant differences between growing conditions although HI under coconut was reduced by 28%. Yield had significant positive correlation with NDF, HI and root dry weight but was negatively correlated with plant stand, growth habit and green leaves dry weight.