Effect of leucaena leucocephala, cassia siamea and terminalia brownii leaf mulch on maize performance and soil nutrients under the semi-arid conditionsin Machakos, Kenya.

Abstract

The influence of three leaf mulches from three tree species on soil nutrients, maize performance and yield and N concentration of maize at various growth stag£~ was studied for two. very contrasting seasons (ven dry 1987 "short rains" and wet 1988 "long rains") in the semi-arid district of Machakos, Kenya. Fresh leaf mulches of Leucaena leucocephala, Cassia siamea and Terminalia brownii were burried in the soil at a depth of 15cm at 1 and 2kg/m 2 rates. The mulching materials were burried in furrows 90cm apart. The design of the experiments was randomised complete block replicated four times. After burying the mulches, KaLumani maize was planted on ridges (above the mulch layers ), at a spacing of 90x30cm. Analysis of the leaf mulches for their nutrient composition showed that Leucaena leucocephala had the highest concentration of nutrients while Terminalia brownii had the lowest concentrations but highest C content. I n terms of C/N rati 0 Terminal i e brown i i had the highest (average of 38.4) while Leucaena letlcocephala had the lowest (Average of 15.4) , indicating a lower ..decomposition of the former. Soil analysis showed that the mulches increased soil pH,organic carbon, exchangeable bases, lolal nitrogen and phosphorus during their decomposition xi and even cumulative over the trials. There was a progressive decline in the soil nutrient status in the unmulched plots, which is likely to be due to nutrient removal by the maize crop and leaching. Results on the mulched influence on maize indicated that mulch application significantly increased n i t r-o gen concentration of maize ear leaves (cobbing stage). Maize grain yield was higher In the mulched plots compared to the unmulched, however the differences were not significant (p=O.05). Maize grain yield w a s significantly and positively cor re 1ate d w iLh p 1ant he j gh t, p La n t bas e diarneter , leaf area index, cob weight, and grain size in the second trial.