Effect of the 35-years fertilization on the agrochemical prpperties of two-meter soil profile of leached vertisols. III. Content of available potassium in the soil
2005
Panajotova, G. (Institut po Pamuka i Tvardata Pshenitsa, Chirpan (Bulgaaria))
The changes of available potassium for a 0-200 cm soil profile of a 35-year fertilizing trial were studied on leached vertisols with cotton-durum wheat crop rotation. It was estabished that after 35-yr fertilization with low potassium levels the content of available potassium the 0-30 cm layer increased with 31,2%, and in the subsurface -with 23,3% compared to the unfertilized (30-32 mg/100 g soil). Al-k2O went up to 49 mg in the 0-30 cm layer and to 42 mg/100g soil in the 30-60 cm soil layer at moderate K levels. The potassium fertilization influenced the available potassium at 0-200 cm depth and the content decreased at higher depth values. In the 180-200 cm layer K2O was 24-28 mg/100 g soil.Periodical balanced potassium fertilization in rates of 60-70 kg/ha is necessary to support the soil fertiility.
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