Transformation, interaction, and bioavailability of nutrients in the fertisphere

In the interface between soil and fertilizer, the concentrations of nutrients are several times that of bulk soil, resulting in strong and unique reactions between nutrients or nutrients and soil fractions. It is of great significance to study the transformation, transference, and reactions of nutrients in this micro-zone, or “fertisphere”, to better understand the effect of nutrient reactions on the enhancement of fertilizer use efficiency, and the design of new fertilizer products. The effects of soil, temperature, time, and moisture on the transformation of P in the soil-fertilizer interface were studied in 2010. In addition, the influence of fertilization measures on the bioavailability of P on rice was also investigated.

Pot study results showed that monoammonium phosphate (MAP) and mono-calcium phosphate (MCP) fertilizers were mainly transformed into Al-P and Fe-P complexes in black soil, Ca₂-P and Ca₈-P in alluvial soil, and were kept mainly as water soluble P in paddy soil. An increase in temperature significantly increased the fixation of P in black soil, and accelerated the formation of Al-P. An increase in incubation time promoted the gradual transformation of water soluble P into Al-P and Fe-P. The transformation of water soluble P into other forms of P was inhibited by flooding during a short incubation period, but the transformation was promoted during longer incubation periods. Surface broadcasting resulted in the highest concentration of total soil P in ground water. By mixing the fertilizer with soil, the availability of P fertilizer was the highest, providing rice roots more absorption sites. Therefore, mixing of P fertilizer with soil that is closely associated with roots could be recommended for P application in wet or flooded lands. Nanjing-11