Browsing by Author "Kungu, James"

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    Effect of plant biomass, manure and inorganic fertilizer on maize yield in the central Highlands of Kenya
    (2007) Mugwe, Jayne; Mugendi, Daniel N.; Kungu, James; Mucheru-Muna, Monicah
    Soil fertility degradation remains the major biophysical cause of declining per capita crop production on smallholder farms in sub-Saharan Africa. Appropriate soil fertility regimes, are therefore, critical for improved crop productivity. This study investigated the feasibility of using sole organics or their combinations with inorganic fertilisers to improve maize (Zea mays) production in the highlands central Kenya. Sole application of Calliandra calotyrsus, Leucaena trichandra trichandra, Mucuna pruriens, Crotalaria ochroleuca, Tithonia diversifolia and cattle manure at 60 kg N ha-1 or combined application of the organic materials (30 kg N ha-1) plus inorganic fertiliser (30 kg N ha-1) gave significantly (P < 0.05) higher maize grain yields than the recommended rate of inorganic fertiliser (60 kg N ha-1). These treatments maintained maize yields at 4 to 6 t ha-1. Farmers had their own innovations where they combined organic resources and generally appreciable yields (3.0 to 5.6 t ha-1) were obtained from these innovations. However, there was a maize yield gap between on station and on farm trials with on station yields having on average 65% more yields than the on-farm yields. This was mainly attributed to differences in management practices arising from partial adoption of recommended rates. There is need therefore to develop and implement mechanisms tailored to ensure that farmers’ modications recommended soil amendment regimes and other agronomic practices are appropriate for enhanced crop productivity. Further studies are needed to establish the optimum mixture of different organic materials.
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    Impacts of vegetative contour hedges on soil inorganic-N cycling and erosional losses in Arable Steep-lands of the Central Highlands of Kenya
    (Springer, 2007) Mutegi, James; Mugendi, Daniel N.; Verchot, Louis V.; Kungu, James
    Moderate to steep landscapes and severe soil, water and nutrient losses characterize over 40% of arable land in the central highlands of Kenya. To study the effectiveness of biological methods in management and enhancement of productivity of these arable steep-lands, we established contour double row hedges of sole Calliandra, Leucaena and napier and combination hedges of either Calliandra or Leucaena with napier. Hedges were established on slopes exceeding 5%, pruned regularly and the resulting biomass cut into fine pieces, which were then incorporated into the plots they served. We then evaluated these plots for inorganic-N changes with depth, soil conservation and soil loss/crop growth relationships. We observed accumulation of inorganic-N in the sub-soil in the control and napier plots but a reduction of sub-soil inorganic-N and its re-accumulation in the top-soil in the leguminous hedge plots after 20 months of trial. The first season on average, registered higher soil losses (P = 0.004) than the second season for treatments with hedges and vice versa for the control. During the first season there were significantly lower (P < 0.001) soil losses in plots with hedges relative to the control on slopes exceeding 10% but with the exception of napier, no significant differences among different types of hedges. We observed higher soil loss reduction in the combination hedge relative to individual tree hedges across the two seasons (P = 0.012). The relationship between cumulative soil loss and any of the four crop growth parameters i.e., grain weight, plant height, stover weight and total above ground biomass was negative, linear and highly significant (P < 0.0001), indicating decreased crop growth with soil loss. We conclude that there are heavy productivity losses as a result of soil erosion in arable steep-lands of the central highlands of Kenya and that well spaced, managed and combined contour hedges of leguminous trees and napier can reduce soil and nutrient losses from steep arable landscapes while simultaneously enhancing soil fertility