Impact of nodule damage byRivellia angulataon N2-fixation, growth, and yield of pigeonpea (Cajanus cajanL. Millsp.) grown in a Vertisol

摘要

Damage caused byRivellia angulatalarvae to pigeonpea root nodules at the ICRISAT center in India was greater in the crop grown on Vertisols (up to 86) compared to that on Alfisols (20). Attempts to quantify the field effects of nodule damage on growth and yield of pigeonpea in a Vertisol, involving many heavy applications of soil insecticides (aldrin and hexachlorocyclohexane) failed because the insecticides did not control the pest and adversely affected the growth of the pigeonpea and the subsequent crop of sorghum (Sorgorum bicolorL. Moench). The impact of nodule damage on pigeonpea growth, yield and nutrient uptake was successfully studied in greenhouse-grown plants at three N levels. In this pot study, artificial inoculation withRivelliasp. led to substantial nodule damage (70). The results of this damage were a significant overall reduction in nodule dry weight (46), acetylene reduction activity (31), total leaf area (36), chlorophyll content of leaves (39) and shoot dry weight (23) 68 days after sowing. At maturity,Rivelliasp. infestation caused significant reductions in top dry weight (22), root and nodule dry weight (27), seed dry weight (14), and total N (29) and P uptake (19). The problems and prospects of manipulating nodule damage so as to reduce N losses in pigeonpea are discussed.