Impact of Rhizosphere on Competitive Effects of Neem (Azadirachta indica A. Juss.) on Associated Pigeonpea [Cajanus cajana (L.) Millsp.] in a Agroforestry System

Sustained agriculture has close intimacy with trees. However, the conventional agriculture had broken this intimacy especially by keeping trees away from the farm land for short term economic considerations. Tree may influence the associated crop either positively or negatively depending on its age, species, density, environment and management practices. Hence, understanding nature and extent of competitive effect is utmost important in adopting management practices to improve overall productivity.

An investigation was carried out to assess yield variation if any in pigeonpea and the primary ecological factors responsible for the same when it was grown in association with neem (25 years old) on field bunds in a traditional agroforestry system during 2018-19 in semi-arid tropics of Karnataka, India at three distances mainly 2-7.4, 7.4-12.8 and 12.8-18.2 m on E and W of N-S and N and S of E-W tree lines.

Averaged over directions significantly lower pigeonpea yield (3.76 q ha^-1) was recorded near the tree line at 2-7.4 m distance, while it increased with increase in the distance from tree line and was the highest (7.61 q ha^-1) at far away distance (12.8-18.2 m) at which yield was on par with control (without any trees), though soil near the tree line (2-7.4 m) recorded significantly higher soil organic carbon and microbial population (fungi, bacteria and actinomycetes) indicating better soil health and moisture. This leads to the conclusion that it is not merely the rhizosphere characteristics or neem root interference but the above ground factors particularly light availability to pigeonpea as influenced by neem canopy is important in the agroforesty system.