The effects of grass strips on crop growth, yield and terrace development
Kinoti, Kaburu Franklin
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Investigations were carried out during the rainy seasons of 1996 on humic nitisol at Kabete Steepland Research Site, University of Nairobi to study the effectives of grass strips as a means of soil and water conservation and on crop performance. The study assessed the performance of seven different grass species on terrace development, moisture conservation, fodder production, crop growth and yield. Measurements on moisture, crop growth and crop yield were made on the lower, middle and upper slope position of each terrace formed by the individual strips. The results obtained indicated that Donkey grass was the best in promoting bench development with 6.2 % mean slope. This was followed by Creeping signal (5.1%), Bana (4.7%), Tall signall and Guantamala (4.2%), Tall guinea (4.0%) and lastly Makarikari with only 1.8%, which was due to its poor ground cover. The corresponding embankment heights increased with increased slope reduction. Bana Tall guinea and Guatamala grasses depleted more moisture on the lower slope position during dry spells but conserved more in the 60 cm depth during rainy periods mainly due to their deep rooting depths. Generally more moisture was conserved by all the grasses on the lower slope position compared to the upper slope position during rainy periods. Bana and Tall guinea grasses had significantly (p=0.01) decreased maize plant heights and yields on the lower and upper positions due to their competitive effects. The yield of Bana was 1190kg/ha and 1420kg/ha in the lower and upper terrace positions respectively compared to 2400kg/ha in the middle terrace position. Tall guinea yields were 925 and 999kg/ha for lower and upper positions respectively compared to 2030kg/ha for the middle. Yield differences among positions for Makarikari, Creeping signal, Donkey and Guatamala grasses were not significant. There was general poor crop performance on the upper terrace position for all the grass strips. On fodder production bana grass tall guinea produced the highest yields (16.96 and 12.23 tons per hectare respectively) although they put more land out of cultivation due to their growth characteristics. Makarikari performed poorly in both fodder production and terrace development and therefore deemed not suitable in the area. Of those grasses evaluated, Bana and Tall guinea would be more appropriate for farmers who are confronted by conservation needs and require fodder for animals. On considering better crop performance without need for fodder the other grasses would be more appropriate.