Abstract
Recently introduced to India, African white yam, despite its superior yield and quality attributes as well as compatibility in diverse cropping systems, is not a popular choice in the coconut-based cropping systems of South India for want of suitable production techniques. The effect of three organic manures (farmyard manure at 10 t ha-1, coir pith compost at 5 t ha-1, and green manuring in situ with sunnhemp) and three levels each of N and K (40, 80, and 120 kg ha-1) on assimilation and partitioning of biomass and growth parameters of white yam intercropped in a coconut garden was examined during 1998-2000. Coir pith compost application was associated with higher dry matter (DM) accumulation in the whole plant, higher leaf area index (LAI) almost throughout the seasonal course, and net assimilation rate (NAR) and crop growth rate (CGR) up to six months. Nitrogen supply at 120 kg ha-1 promoted LAI at all stages (0.54-4.55), NAR, relative growth rate (RGR), and CGR during the initial growth phase (2. 7 g m-2 day-1, 26.49 mg g-1 day-1, and 3.46 g m-2 day-1, respectively) and leaf and vine DM production almost throughout the crop growth (155.53 and 119.06 g plant-1 respectively, at 8th month). Towards harvest, a decline in NAR and RGR was observed at higher rates of N application. Accumulation of biomass in the tuber was favoured by N at 80 kg ha-1 in 1998-1999 and 120 kg ha-1 in 1999-2000. Potassium nutrition at 120 kg ha-1 was beneficial in promoting leaf, vine, and tuber DM production (tuber DM of 546.49 g plaor1) and resulted in greater plant biomass (802.15 g plaor1). Higher levels of K also enhanced LAI, NAR, CGR, and RGR at the initial and active growth phases as well as harvest index (HI) (0.68). Combined use of coir pith compost and N and K at higher rates (80 or 120 kg ha-1) at a constant dose of P (60 kg ha-1) favoured DM production and the physiological parameters eventually resulting in higher white yam production under intercropping in the coconut garden.
