Rhizosphere soil properties and banana Fusarium wilt suppression influenced by combined chemical and organic fertilizations

Combining chemical fertilizer with organic fertilizer is an important management strategy for maintaining soil fertility and disease suppression. Banana is an important cash crop in tropical regions and is severely threatened by Fusarium wilt disease. Little is known about the effects of combined fertilization on rhizosphere soil properties and disease suppression in tropical regions in China. In this study, the effects of combined fertilization on rhizosphere soil properties and the development of banana Fusarium wilt disease were assessed based on key components of soil chemical and biological properties. With chemical fertilization (CF) only, the soil urease, SOC and available nutrients contents were increased continuously, while the soil bacterial diversity, pH, and acid phosphatase activities were initially increased, and then decreased with increasing NPK application rate. Under low NPK application rate (25% CF), the OM addition was more effective in increasing soil bacterial diversity, pH, available nutrients, urease and acid phosphatase activities than NPK fertilization only. However, excessive OM addition had negative effect on soil available P and K content under high NPK application rate (100% CF). The T6 treatment of 50% CF + 500 organic matter (OM) had the highest integrated score among the treatments. Path coefficient analysis revealed that soil bacterial diversity plays the most important role in improving soil integrated score. The disease index was significantly and negatively linear correlated with the integrated score (r = −0.92, P < 0.01). These results demonstrate that an appropriate combination of organic and inorganic fertilizer application is effective at improving soil fertility and reduced disease incidence of banana.