Soil fertility technologies for increased food production in Chuka, Meru South district, Kenya
Mucheru, Monicah Wanjiku
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The high population pressure in Chuka has led to continuous cultivation with minimal additional of inputs, leading to soil nutrient depletion. Research work has reported positive results from the use of manure and biomass from tithonia, calliandra, leucaena, mucuna and crotalaria for soil fertility replenishment. In relation to this a multidisciplinary farmers participatory trial was established in Chuka Division, Meru District, to offer small-scale resource poor farmers feasible soil nutrient replenishment technologies. The experiment was set up in a randomized complete block design with 14 nutrient replenishment treatments (technologies) replicated thrice. At the beginning and at the end of the study soil was sampled at 0-15 cam depth and the samples analysed for pH, Ca, Mg, K, C, N, and P. At the end of the 2000/2001 short rains season and 2001 long rains season soil samples were taken at 0-30, 30-100 and 100-150 cm, for nitrate and ammonium analysis. All the treatments received an equivalent of 60 kg N ha-1 except the herbaceous legume treatments where the among of N was determined by the amount of the biomass harvested and incorporated and the absolute control treatment that received no inputs. Net benefit and benefit-cost analysis were conducted using farm gate prices. The results indicate that soil fertility increased slightly in all the treatments (except the control) over the two years of the study period. The average maize grain yield across the treatments was 1.1, 5.4. 3.5 and 4.0 Mg ha-1 during the 2000 long rains, 2000/2001 short rains, 2001 long rains and 2001/2002 short rains seasons respectively. The poor yields in the 2000 long rains and 2001 long rains seasons were attributed to the poor rainfall received in these two seasons. On average tithonia with half recommended rate of inorganic fertilizer recorded the highest (4.8 Mg ha-1) maize yield followed by sole tithonia (4.7 Mg ha-1). The highest average concentration (144.8 and 115.5 kg N ha-1) of mineral N was recorded at the 30-100 cm soil depth at the end of both the 2000/2001 short rains and 2001 long rains respectively. The lowest average concentration (67.1 kg N ha-1) was recorded in the 100-150 cm soil depth during the 2000/2001 short rains while during the 2001 long rains the 0-30 cm depth recorded the lowest concentration (52.3 kg N ha-1). The residual mineral N in the 100-150 cm soil depth doubled at the end of the long rains 2001 compared to what was present at the end of short rains 2000/2001 season in all the treatments. This shows that there is a substantial amount of mineral-N that is being leached below the rooting systems of maize. Sole tithonia was ranked as the best treatment, while, the control was ranked as the poorest treatment by both the farmers and future farmers (students). The treatment ranking by both groups was closely related to the actual maize grain yields attained later at the end of the season. Out of the 171 farmers who attended the 3rd field day, 153 farmers (90%) indicated willingness to take the technologies to their farms. Sole leucaena and calliandra were the most cost effective technologies with a benefit/cost ratio ratio (BCR) of 7.3 while sole tithonia followed closely with a (BCR of 6.9) through out the four seasons.