| Abstract: | Influence of long-term application of different nitrogen sources on the dynamics of phosphate in an arable brown earth In a long-term field experiment parameters of the soil phosphate status were determined after 53 years. Soil characteristics of the arable brown earth are: sandy silt loam; pH 5,9–6,6; total carbon 0,9%; CEC 13–15 meq/100 g soil; effective field capacity 160 mm unto 150 cm. The following results were obtained: Total P content was slightly higher in the plots without mineral N and with farm manure (90 and 93 mg P/100 g soil resp.) than in the plots with mineral N supply (Ø 85 mg P/100 g soil). Application of farm yard manure and ammonium sulfate caused higher proportions of ?Fe and Al phosphates”? (56–57% of inorganic phosphate) whereas calcium cyanamide, calcium nitrate and ammonium sulfate with annual liming led to higher a content of Ca-phosphate (52–56% of inorganic phosphate). When pH was brought to 6,5 by liming, P uptake of rye grass and green oats/green rape-seed in a pot experiment depended on the soil content of ?Fe- and Al-phosphates”?. Without liming, P uptake was lower in the plot with ammonium sulfate, however, in the calcium cyanamide plot P uptake was higher than expected from the content of ?Fe- and Al-phosphate”?. |
