Effect of long-term phosphorus fertilization on the phosphorus accumulation and distribution in black soil and its availability

Successively oversupply of phosphorus fertilizers brought about the accumulation of phosphorus in the black soil. The results showed that soil nutrients were unbalanced, and the fertilizer efficiency was low. The status of accumulated phosphorus, transform of inorganic phosphorus and bio-availability of accumulated phosphorus in black soil were studied in this paper by the means of long-term fixed site field trial. The results were as follows:1. Total P content decreased by 37.4% due to long-term no fertilization. Phosphorus fertilization remarkably increased total P content, especially the treatment with 2 times phosphorus fertilization, which was 53.9%65.7% higher compare with the treatment of no fertilization. Application of manure alone could not supply enough P to keep phosphorus balance in soil. And the P was exhausted.2. Available P in black soil decreased by 60.0% and 23.2% for the treatments of no fertilization and long-term applying manure, respectively. But available P in P fertilization treatments enhanced which was 615 times higher than that of no fertilization treatment. The more P fertilizer was applied, the more available P was accumulated.3. As to the accumulated P in black soil, Ca10-P is highest, then is O-P, Ca8-P and Ca2-P content was lowest. P (fertilization) could increased Ca2-P, Ca8-P and Al-P content which had higher availability to crop, while it had little effect on the content O-P and Ca10-P which had lower availability to crop.4. The phosphorus was depleted in black soil under the condition of long-term no P fertilization, so the effect of the P fertilizer was significant for the treatment of long-term no P fertilization, while, for the treatment of long-term P fertilization, the response is quite low. The accumulated phosphorus has an after effect on crops. It needn't to applying a mount of P fertilizer to soil every year under the condition of P accumulation in soil.