SOIL-MOISTURE CHANGES AND MAIZE PRODUCTIVITY UNDER ALLEY CROPPING WITH LEUCAENA AND FLEMINGIA HEDGEROWS AT CHALIMBANA NEAR LUSAKA, ZAMBIA

Soil moisture changes and maize yield were studied in 2-year-old alleys of Leucaena leucocephala and Flemingia macrophylla at Chalimbana, Zambia. Field tensiometers were installed at 15, 30 and 45 cm depth, in fertilized and unfertilized alleys within the double hedgerows, and the first, second and third rows of maize, and were monitored throughout one maize growing season in 1989/1990. In general, maize growth (indicated by height and dry matter measured at roughly fortnightly internal) was higher (P < 0.01) in fertilized alleys than in unfertilized alleys, and there were no differences between Leucaena and Flemingia alleys. In both fertilized and unfertilized alleys, the maize plants were 20% shorter (P < 0.01) in the first row (nearer the hedgerows) than in the second and third maize rows. Maize dry matter yield was 30% more (P < 0.01) in unfertilized Flemingia alleys than in corresponding Leucaena alleys. The grain yield was similar in the fertilized alleys of Leucaena and Flemingia. However, in unfertilized alleys, the grain yield in Flemingia alleys was 50% more than that of the corresponding Leucaena alleys. The fertilized alleys produced twice as much grain as unfertilized alleys when hedgerow prunings were added to the plots. The prunings as a source of nutrient did not appear to have any noticeable effect on crop productivity. The soil moisture content under both Leucaena and Flemingia hedgerows was higher than under the maize rows in the alleys throughout the growing season. The study shows that, under conditions of low fertility and no addition of fertilizers, Leucaena is twice as competitive, as Flemingia for soil resources, and reduces yield of alley-cropped maize from 2.2 t ha-1 to 0.7 t ha-1. If, however, fertilizer is added, there are no short-term differences between the two hedgerow species.