Resource use and crop productivity in a colophospermum mopane tree based agroecosystem in indian desert

Abstract

A 9-year-old plantation of Colophospermum mopane (Kirk et Benth) kirk ex J. Leonard at a spacing of 5m x 5m was selected to study tree crop interaction with a view to find out suitability of this species for integration in agriculture land. Different treatments were (i) fixed crop of Vigna radiata (FC), (ii) rotation crop (Vigna radiata rotated by non-legume crop, RC) (iii) sole agriculture crop (AC), and (iv) sole tree (TC). Vigna radiata (L.) Wilczek (mungbean) was sown on 21 June 2003. Micro-plots of 1m X 1 m size were laid at 1m (near), 2.5 m (middle of two trees) and 3.5 m (centre of four trees) from the selected trees for sampling and yield recording. Tree height, dbh and crown diameter differed significantly (P < 0.05) between the plots. Soil water content was lowest (P < 0.05) in tree-integrated plots but it increased in deeper soil layers. SWC varied through non-significant in August, lowest (P < 0.05) at 1 m in September to significantly (P < 0.01) different between sampling distances in December 2003 suggesting exhaustive use of soil water by trees. Soil organic matter, available PO4-P, NO3-N and NH4-N did not differ among the treatments and micro-plots though these nutrients differed in soil layers. Tree water use from 0-25 cm in August, 25-50 cm in September and 50-75 cm soil layer in December 2003 indicated a competitive nature of C. mopane with the associated V. radiata crop reducing population and yield up to a level of 97%. Reduction in grain was relatively greater than husk (pods after grain removal). Seedling population and yield were lowest at 1 m distance and increased with distance from the trees. Leaf water status of V. radiata was highest at 1m and it decrease with distance with a lowest value in AC plots. Relative neighbour effect values indicated a transition from strong competitive to weak facilitative nature of C. mopane and suggested the dominance of competitive effects during crop growth. Conclusively, integration of C. mopane reduces crop yield when rainfall is sufficient only for agriculture crop. Trenching around tree to reduce root overlapping between tree and agriculture crop and therefore competition for resources may be beneficial and enhance crop yield. © 2012, ALÖKI Kft.