Agronomic and physiological responses of sweet potato (Ipomoea batatas (L.) Lam) to varying levels of shade [Philippines]
1986
Mwanga, R.O.M.
Varietal differences were associated more with 0, 31, and 43% than with 52 and 67% shade. VSp-1 produced less tuberous root yield than UPL Sp-1 or BPI Sp-2 only at 0 and 43% shade at 19 weeks after planting. Relative to full solar radiation, yield and yield components, leaf area index, leaf area duration (LAD), specific leaf weight (SLW), net assimilation rate, harvest index (HI), dry matter production (DMP), crop growth rate (CGR), leaf number m-2 and branch count m-2 were reduced by 6 to 97%. Leaf production and relative leaf growth rates, transpiration and leaf temperature varied in their response to shading. Shading generally increased diffusive resistance, leaf area ratio, total leaf protein, chlorophyll and carotenoid contents. Competition for light rather than nutrients seemed to be the main factor limiting the performance of sweet potato u1545nder coconut palms relative to the monocrop. root fresh weight (RFW), fresh vine yield (FVY), LAR, CGR, LAD, DMP, marketable root number m-2 (MRN), HI, root dry matter, SLW and root bulking rate were highly correlated with tuberous root yield. Path coefficients analysis indicated that RFW, FVY, MRN, and HI contributed maximum direct effects to dry root yield and could be used as selection criteria under partial shade. Increased productivity in sweet potato-coconut intercrop and other multiple cropping systems, alleviation of the high level of malnutritiion in developing countries, increased material for feed and industrial purposes, improved mix animal and crop farm systems, and helping the small farmer to cope better with the agronomic and socio-economic risks involved in production, would be some of the implications of this st
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