Transformation, interaction, and bioavailability of nutrients in the fertisphere

In the interface of soil and fertilizer, the concentration of nutrients is several times that in bulk soil, resulting in strong and special reactions between nutrients or nutrients and soil fractions. It’s important to study the transformation, transference, and reactions of nutrients in this micro-zone to better understand their effect on the enhancement of fertilizer use efficiency and in designing new fertilizer products. Study on the effects of interactions of N and K, or N and P, and the application sites on K or P use efficiency, could help design better fertilization strategies and enhance K and P use efficiencies. The effects of ammonium and K interaction on the transformation and transference of K in the paddy soil-fertilizer interface were studied in 2011 by the Nanjing Institute of Soil Science, CAS. In addition, the effects of N and P interaction on the transformation and transference of P, and the influence of N and P fertilization on the uptake and bioavailability of N and P on wheat in the alluvial soil were also explored.

The use efficiency of K fertilizers could be increased by reducing the fixation of K in soil fertisphere. When potash was applied together with ammonium, the contents of soil water soluble and exchangeable K were increased in the paddy soil fertisphere, while the non-exchangeable K content was decreased. The increase of water soluble P and Ca₂-P contents and the decrease of Ca₈-P content was found in the co-application of Ca(H_-2PO₄)₂ and (NH₄)₂SO₄ treatment. But when Ca(H-₂PO₄)₂ was co-applied with urea, these effects of N fertilizers on the P availability of co-applied P fertilizer were not expressed in the wheat pot experiment. Maximum N use efficiency was observed when N was applied 5 cm below wheat roots in the soil. When P fertilizer was mixed thoroughly with soil near roots, the best P use efficiency was obtained. Nanjing-11