Effect of intercrop spacing and nitrogen fertilizer on establishment of Leucaena leucocephala in alley cropping

One of the reasons for the low rate of adoption of alley cropping in the hu mid tropics is the problem of establishing the desired hedgerow trees. A sp lit plot experimental design trial was set up to investigate the effects of 4 levels of nitrogen (N) fertilizer (0, 30, 60, and 120 kg N ha(-1)) on th e growth of leucaena leucocephala (Lam.) de Wit in an intercrop with maize. Maize (Ekona 83TZ SR Y) was planted at 0, 25, 50, and 75 cm from Leucaena hedgerows planted on the same day. Leucaena plants were harvested at 3, 6, and 12 months after planting for biomass yield, N uptake, nodulation and my corrhization. Results showed that at 0, 25, and 50 cm Leucaena/maize interc rop, there was no effect of N on Leucaena biomass. Leucaena biomass yield a t 75-cm spacing compared favorably with the biomass of Leucaena sole croppe d that had received 0, 30, and 60 kg N ha(-1). Application of 120 kg N ha(- 1) to sole Leucaena increased biomass yield significantly above all the int ercrop spacings. Measurement of the solar radiation in the system showed th at there was a close relationship between the amount of solar radiation rec eived by Leucaena and its biomass yield; Maize intercropped closer than 75 cm from Leucaena hedges reduced radiation received by Leucaena by 72% at 25 cm compared with 29% at 75 cm. This effect reduced Leucaena biomass yield at 25-cm spacing by 50%. This study showed that Leucaena can be established in intercrop with maize, but it requires about 75-cm intercrop spacing wit h crop and about 120 kg N ha(-1) for good establishment. Leucaena/maize int ercrop at 75-cm spacing enables Leucaena to receive about 72% solar radiati on and larger area to forage for plant nutrients.