Die Bodenkultur - Journal for Land Management, Food and Environment

Th. Lindenthal, H. Spiegel, M. Mazorek, J. Heß, B. Freyer und A. Köchl:

Results of three long-term P-field experiments in Austria

2nd Report: Effects of different types and quantities of P-fertiliser on P-uptake and P-balances

Summary

The effects of different types (super-phosphate, basic slag and rock-phosphate) and quantities (0, 44 and 175 kg P ha-1a-1) of P-fertiliser application on P-uptake by crops and P-balances were evaluated in three long-term field experiments lasting 40 years. The omission of P-fertiliser during the whole 40-year-period resulted in P- uptakes of Ø 649–694 kg P ha-1 and considerable negative balances. The fertilisation of 44 kg P ha-1a-1 as basic slag and superphosphate showed higher P-uptake than zero P-fertilisation in 40 years, these differences were statistically significant at all three experimental sites for the last 20 years. When discontinuing P-fertilisation after 20 years of application the annual P-uptakes by crops remained at a high level and differed in the majority of cases not significantly compared to continuous fertilisation. But an annual fertilisation of 44 kg P ha-1a-1 had already caused an accumulation of 371–562 kg P ha-1 in the soil during the first 20 years. After 40 years a balanced P supply in which crop P uptake nearly equalled the P fertiliser rate was assessed at the variants where the fertilisation of 44 kg P ha-1a-1 as basic slag and super-phosphate was terminated after 20 years. The different P-fertilisation during 20–40 years affected the P-uptake more strongly than the yields at all three sites. In the majority of cases also the correlations between PCAL/DL-contents in soils and P-uptake were closer compared to the crop yields. Key words: P-fertiliser, long-term field experiment, P-uptake, P-balances, crops.