Seasonal and long-term dynamics of phosphorus in leached chernozem as affected by rates and methods of fertilizer application.

摘要

The effects of applications of NPK fertilizers (with or without animal manures) on P content of a clay loam leached chernozem in the southern forest steppe region of Bashkortostan, Russia were investigated for a rotation of clean fallow, winter rye,spring wheat, maize, spring wheat and oats, over a period of 2 complete rotations [dates not given]. Comparisons were also made between broadcasting and placement application methods and their effects on soil fertility and yields of spring wheat. Application of NPK fertilizers increased mobility of phosphates by 2.5-4.0 times, with highest values for mobility being achieved with treatments which included animal manures. A significant multiple correlation was established between soil P soluble in aceticacid and meteorological factors (moisture content of soil, rainfall and average combined daytime and night-time temperature) over the entire experimental period, with r=0.69?.11. The significance of this multiple correlation was subject to seasonal variation, being most pronounced at the beginning of the growth period, with r=0.79?.16, and becoming insignificant during the summer months. Contents of P in soil also varied more (by 19-21%) during the summer months. When fertilizers were used, increasing soil moisture content was accompanied by decreasing contents of mobile P, both at the beginning and at the end of the growth period. All treatments with fertilizers had a positive effect on P dynamics in soil. A stable increase of soil P soluble in acetic acid was achieved by the application of ?5 kg P2O5/ha. Crop yields increased by 11.3-45.7% compared with control plots. Broadcasting and localized placement of fertilizers increased yields of spring wheat by 22.9 and 42.7% respectively.