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Tea (Camelia sinensis) a major cash crop in Kenya is normally grown on highly weathered and strongly acidic soils. Non-judicial use of the recommended inorganic compound fertilizer 25:5:5:5s acidifies the soil and pollutes water masses. Integrated soil fertility management, the combined use of organic and inorganic fertilizer is recommended for higher tea yield and soil health. An experiment was carried out in the Eastern Highlands of Kenya to determine the effect of different ratios and rates of enriched cattle manure on leaf nitrogen content, yield and quality of tea. Inorganic compound fertilizer 25:5:5:5s led to the highest N level in the mature leaf. Enriching organic manures with inorganic fertilizers increased the yield but reduced the quality. Tea quality parameters Theaflavins (TF) and Thearubigins decreased with increase in fertilizer rate irrespective of fertilizer type. Caffeine content however increased with increasing rate fertilizer especially in the case of inorganic compound fertilizer 25:5:5:5. Enriching organic manures with inorganic fertilizers increased the N content in the mature leaf and crop yield but reduced the quality. The study showed the beneficial effect of enriched manures in tea production.

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Russian wheat aphid Diuraphis noxia (Kurdjumov) is widely established in wheat-growing countries where it causes significant economic losses. The development and use of Russian wheat aphid (RWA)-resistant wheat varieties has been constrained by the variation in resident RWA populations and the evolution of virulent biotypes. An experiment was set up at the Kenya Agricultural and Livestock Research Organization (KALRO), Njoro, to characterize RWA populations based on phenotypic characteristics of reproduction, development and population dynamics. RWA populations from the regions of Eldoret, Mau Narok and Njoro were used in the study. A factorial experiment was set up in randomized complete block design replicated eleven times. A single day-old nymph was placed on a new, fully-open leaf in a 0.5 cm-diameter clear plastic straw leaf cage and observed daily for its entire lifetime. The results showed that there were variations in aphid lifespan, reproductive longevity and aphid fecundity between populations, indicating that the phenotypic markers used to determine biotypes were good enough to show distinct biotypes among populations of the RWA in Kenya. Further, the study concluded that the use of phenotypic life and reproductive markers was a valid way of characterizing biotypes of RWA worldwide.

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The traditional natural fallows are no longer practicable in sub-Saharan Africa and technologies to replace them are being popularised through management of short fallow systems. Dolichos [Lablab purpureus (L.) Sweet] is among the legumes used to improve such fallows and its residues are incorporated to improve yield of succeeding cereal. Two field studies were conducted to determine dolichos residue mineralisation schedule and response of maize to timing of the residue incorporation, to establish if the current residue incorporation practice maximises nutrient benefit to succeeding cereal. Dolichos residue was applied at 2 t/ha in litterbags, buried in the field at 15-cm depth and retrieved after 1, 2, 4, 8 and 16 weeks, and the remaining debris analysed for loss of weight, N, P and K. A parallel split-plot experiment was set up to determine response of maize to time of residue incorporation, with or without fertiliser nitrogen supplementation. The main plot treatments were nitrogen fertiliser applied at 0, 30 and 60 kg/ha at sixth fully opened leaf in maize. The subplot treatments were residue management regimes, which included four residue incorporation times of 2, 4, 6, and 8 weeks before sowing maize, residue removal off the field, residue mulched on surface and traditional weedy fallow. Results show rapid loss of N, with 50% being released within the first 2–4 weeks after burying. Residue incorporated at 2 and 4 weeks before sowing improved maize yield, while residue removal off-field reduced yield comparably with the traditional weedy fallow. However, there were no statistical differences among the timing of the dolichos residue incorporation. These results reflect poor synchrony of mineralised N and uptake by succeeding maize as currently practiced and suggest residue incorporation closer to sowing maize to benefit the cereal.