Effects of rates and ratios of nitrogen and potash fertilizers on seedling tea at Kericho. 1. Soil pH, soil available calcium, magnesium and extractable manganese
1998
Kamau, D.M. | Owuor, P.O. | Wanyoko, J.K.
In a field trial lasting 14 years, different rates and ratios of nitrogen and potash fertilizers were applied annualy as sulphate of ammonia (S/A) and muriate of potash (MOP) at rates 0, 90, 180 and 270 kg. N /ha/year and 0, 45, 90 and 135 kg. K2O/ha/year respectively. Intial soil chemical properties showed that soil available potassium, calcium and magnesium and extractable manganese decreased linearly with soil depth. Soil pH for the top 20 cm depth increased by 0.2 - 0.3 pH units for the nil-nitrogen treatment during the 14 years of continous cropping while it decreased by 0.6 pH units for the nil-potassium treatments at the top 30 cm depths. After 14 years, potassium fertilizer application did not cause variations in the soil pH, soil available calcium and magnesium and extractable manganese at all the four depths sampled (0-10, 10-20, 20-30 and 40-60 cm). At the upper three soil depths, soil available fertilizer rates reduced soil available calcium and magnesium. The results indicated that long term continous tea cropping with high rates of nitrogen leads to soil nutrient imbalances which may impair future crop production.
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