The paper describes a tree/crop interface (TCI) experiment designed to investigate
the effects of row orientation using Leueaena leucocephala Lain. Each TCI plot consisted of
a regularly pruned Leueaena hedge in the middle and 12 crop rows on either side. Eight such
plots were arranged at 45 ° around a sole Leucaena plot with rows oriented in four compass
directions viz., North-South, East-West, Northeast-Southwest and Northwest-Southeast.
Results of four years from 1984 to 1987 did not show any effect of row orientation, and
similarly, no effect was seen on crop rows due to their location on the windward or leeward
side of the hedge. The TCI effect was positive on the first crop row in the first year because
Leucaena grew slowly, but depressed the yield of the first 4 to 6 crop rows (1.8 to 2.7 m from
hedge) in subsequent years. The negative effect of Leueaena was noted more on sunflower in
a relatively dry year than on sorghum in other years.
Results from the TCI plots were used to estimate the yield of five hedgerow intercropping
(HI) systems with varying alley widths (2.7 to 9.9 m). Comparison with sole stands of Leucaena
and crops indicated that HI was more productive particularly at close alley widths. For
example, hedges spaced at 2.7 m and 3.6 m averaged 37% and 25% higher productivity than
the respective sole stands; but this advantage may be an overestimation of the real potential.
The relevance of TCI experiments for studying agroforestry systems, their merits and
limitations, especially of the design employed in this study are discussed.