Morphology, yield and quality of ashwagandha (Withania somnifera L. Dunal) roots and its cultivation economics as influenced by tillage depth and plant population density

摘要

Ashwagandha (Withania somnifera L. Dunal; Solanaceae) is being cultivated around the world mainly for its root which has rejuvenative properties. Field experiments during 1999-2001 under semi-arid tropical conditions of Hyderabad, India studied theeffect of tillage depths (15 and 30 cm) and plant population densities (20, 40, 60 and 80 plants m~(-2)) on root morphology, yield and quality and cultivation economics of ashwagandha. Preparatory tillage to 30 cm depth in combination with a density of 60 plants m~(-2) gave the highest root yield of 1.2 t ha~(-1) which was 50 percent higher than that following 15 cm tillage depth and the same density. This is attributed to the favourable effect of the former treatment leading to 33, 37 and 21 percent increases in plant height, number of branches per plant and shoot biomass yield, respectively. Further, this treatment produced most (68 percent) best quality root pieces. Main root length, length of lateral roots and diameter of lateral roots were significantly increased, while the diameter of main root and the number of laterals decreased. Furthermore, increase in plant density from 20-80 plants m~(-2) increased production of best quality roots from 42 percent to 59 percent under shallow tillage and from 53 percent to 71 percent of root yield under deep tillage. The implications of change in root morphology are discussed in the light of production of different grades of roots, their market preferences and economics. Deep tillage was equally advantageous for seed production, but plant population density for maximum seed yield (211 kg ha~(-1)) was lower at 40 than at 60 plants m~(-2) for maximum root yield. Maximum gross and net returns and benefit-cost ratio occurred following the highest root yield.