. Training Project In Pedology, Kisii Kenya Soil Fertility Aspects Of The Kisii Soils

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Ministry Of Agriculture
Within the framework of the "Training project in pedology", that is executed at Kisii under the leadership of the subdepartment of Tropical Soils of the Wageningen Agricultural University, soil fertility has been studied since October 1974. The work is being done by post graduate students and consists of - multivariate analysis of the results of chemical analysis of samples of leaves of maize, coffee and tea, and the results of soil studies in the field and chemical and mineralogical analysis of soil samples, - pot experiments in greenhouses at Wageningen, - field trials in Kisii and South Nyanza, Phosphorus was most often the yield limiting nutrient. Classical soilP- tests had only a limited value in characterizing P availability. Factors of importance proved: soil parent material, pH, P-sorption, and climatic conditions during growth. In the field trials no response to P fertilizers was obtained if control yields and P-withdrawal were more than 2200 kg of grains and 6 kg P per ha, respectively. Probably the ease of phosphorus uptake between 7 weeks after planting and harvest was decisive for yield and P withdrawal. Nitrogen supply was via soil organic matter related to altitude, parent material, rainfall and drought intensity. Potassium supply waS mostly sufficient; in soils containing volcanic ash it was abundant. Zinc availability proved influenced by parent material; severe zinc deficiency was found in a soil from relatively young volcanic ash