Effects of rates and rations 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.G. | Wanyoko, J.K.
In a fields trial lasting 14 years, different rates and rations of nitrogen and potash fertilizers were applied annually 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. Initial soil chemical properties showed that 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 treatmens at the top 30 cm depths. Ater 14 years, potassium fertilizer application did not cause variations in soil PhH, soil available calcium and magnesium anbd extractable manganese. Nitrogen fertilizer rates significantly reduced soil PH while a positive significant quadratic trend was shown by extractable manganese at all the four depth sampled ( 0-10-29, 20-30 and 40-60cm). At the upper three soil depths, nitrogen fertilizer rates reduced soil available calcium and magnessium. The results indicate that long term continous tea cropping with high rates of nitrogen leads to soil imbalances which may impair future crop production
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