Phosphorus Fertilization of Sugarbeet in Subtropical India

Abstract

Field experiments were conducted in northwest India to study the response of sugarbeet (Beta vulgaris L.) to phosphorus (P) fe rtilizer on ten sites of varied P availability (3.1 to 11.2 mg kg-I sodium bicarbonate­ extractable P) . Responses to P application were un­ likely above a critical soil P level of 5.1 mg kg-I. On soils with initial P levels of 0 to 3.5 or 3.6 to 5.1 mg kg-I, root and sugar yield increases were obtained with P fertilizer additions of up to 26 and 13 kg ha- I , respectively. At a responsive site (3.1 mg kg-I P), yields of root and top, relative to no-added-P controls, were 242 and 182% at 60 days of growth, but only 37 and 1%, respectively, at 203 days (harvest). Percent sucrose was greater at 150 and 180 days of growth, but not at final harvest. P absorption decreased with age; tops contained 81 % of total P at60 days, and 45% at har­ vest. The apparent recovery of applied P varied from ha25.4 to 14.2% at harvest w ith P rates of 13 to 52 kg P 1 • Th ese P application rates increased post- harvest available P soil levels by 0.4 to 3.8 mg kg1 above the no-P control.