| Abstract: | Accumulation and Mobilisation of Phosphate in Haplic chernozem of the Static Long-Term Experiment at Lauchstädt - Consideration of the P-Balance after 84 Years Phosphate balance was calculated and various soil P parameters of a long-term field experiment at Lauchstädt were determined in which mineral fertilizer and farm yard manure were applied in rates of 0 to 54 kg P/ha/year. The various fertilizer treatments resulted in a considerable variation of the P balance sheet ranging from -738 to 2652 kg P/ha. This implies that 59 % of the applied P (cumulated maximum 4477 kgP/ha) remained in the soil, the rest was taken up by crops. Assuming a balanced P supply in which crop P uptake equaled the P fertilizer rate, a rate of 12, 9 kgP/ha/year would be required. This rate was approximately calculated for the various treatments having received farm yard manure. Phosphate mobilized from the soil (up to 738 kg P/ha) was related to factors which had an impact on crop yield. The decrease of total P in the upper soil layer (0 to 25 cm) was lower than the cumulative P uptake of crops. It is therefore assumed that a considerable proportion of P taken up by crops came from the subsoil. The change in the P balance sheet obtained during 84 years was clearly reflected by various soil parameters including the maximum P adsorption capacity which was highest in the treatment with the largest P deficit (NK treatment). |
