| Abstract: | Phosphate fertilizer requirement of cereals and sugar beets on “loess soils” in the Southern part of Lower Saxony (F.R. of Germany) In the years 1984 to 1986 105 P-fertilizer experiments with winter wheat, winter barley and sugar beets were carried out on “loess soils” in the Southern part of Lower Saxony (F. R. of Germany). The mineral P fertilization applied as “Triplephosphat” varied between 0 and 250 kg P2O5/ha. Soil test values (P-H2O method) of the sites ranged from 6 to 38 and were on the average 18 ± 8 mg P/kg. Besides the P-H2O-extraction the following methods were used: CAL, DL, NaHCO3 and EUF. In no case P-application increased yields of cereals and sugar beets, although in 1986 there was no P fertilization for three years. Results of plant analysis (0.3–0.6% P i. dm) also showed a sufficient P-status. Furthermore an increase of P content of soils (+20 mg P-H2O/kg on average) by a fertilizer rate of 1500 kg P2O5/ha did not effect yield in the following years. Thus, on these fields with P levels of 5 mg P-H2/kg soil (5 mg P2O5-CAL/100 g) and more a P fertilization corresponding to the P removal by the crop rotation of sugar beets and 2x cereals of about 180 kg P2O5/ha in three years is recommended, if crop residues remain on the field. At P levels higher than 12–14 mg P-H2O/kg soil P fertilization can be below P-removal or omitted. |
