Effect of Potassium Budget on Evolution of Soil Potassium in Different Crop Sequences and Site Conditions
2015
Madaras, Mikuláš
The influence of six different crop sequences on the dynamics of topsoil available and fixed potassium (Kₐᵥₐᵢₗ and Kfᵢₓ) was studied within a 4-year period at 6 sites of different soil and climatic conditions. The highest K off takes were recorded for 3-year alfalfa / clover cropping followed by winter wheat (-151 kg K/ha/year) and for the crop sequence including one year of sugar beet / potato (-0124 kg K/ha/year). Kₐᵥₐᵢₗ and Kfᵢₓ were significantly decreased especially at crop sequence with alfalfa / clover cropping, compared to other crop sequences. At three sites of lower Kfᵢₓ content (340-830 mg K/kg), differences in Kₐᵥₐᵢₗ and Kfᵢₓ between crop sequences were more frequent, whereas almost no significant differences between treatments were observed at sites of higher Kfᵢₓ content (1,000-1,380 mg K/kg). Changes of both K forms and K budget correlated significantly at sites of lower Kfᵢₓ content. At these sites, Kₐᵥₐᵢₗ decreased at the rate of 0.045 mg K per 1 kg/ha of K offtake; the rate of Kfᵢₓ decrease was 0.059 mg K per 1 kg/ha of K offtake. At sites of higher Kfᵢₓ, no significant relation between K forms and K budget was observed. The results show an importance of Kfᵢₓ as a K source in intensive agricultural systems with low or no K inputs.
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