Controlled-Release Diammonium Phosphate Alleviates Apple Replant Disease: An Integrated Analysis of Soil Properties, Plant Growth, and the Soil Microbiome

Exogenous application of nitrogen (N) and phosphate (P) has been demonstrated to alleviate apple replant disease (ARD). Yet, the effect of controlled-release diammonium phosphate (C-DAP), which continuously supply N and P for ARD control, is still poorly understood. Applying C-DAP markedly alleviated the typical symptoms of ARD. C-DAP maintained soil N and P at relatively high and stable levels during the entire growth period of the replanted seedlings, thus, limiting the copy number of the four key pathogenic Fusarium species that cause ARD. Particularly, continuously supplying N and P by C-DAP established a higher fungal diversity than that of conventional diammonium phosphate and induced the fungal community to be more similar to fumigated soil. The positive effect of C-DAP originated from the synergistic effects of regulating microorganisms and enhancing the resistance of the plant caused by a continuous nutrient supply. These findings provide a new perspective in the management of soil-borne diseases.