Irrigating-continuous cropping with Bacillus subtilis D9 fortified waste water could control the Fusarium wilt of Artemisia selengens

Abstract

Waste water from the animal production industry contains large amounts of nitrogen, phosphorus and organic matter, which can easily cause water pollution. Continuous-cropping of Artemisia selengens causes the accumulation of the serious soil-borne pathogen Fusarium oxysporum, resulting in serious disease in cutting seedlings. For the containment of organic matter and the flowability of waste water, the experiment to assay the biocontrol capacity of the waste water fortified with the biocontrol agent Bacillus subtilis D9 against F. oxysporum was performed. The results showed that the population of soil D9 significantly (P<0.05) affected the Fusarium wilt disease incidence of A. selengens and a higher population of D9 in the soil was correlated with a lower disease incidence of A. selengens. The effects of factors such as the irrigation quantity of treated waste water (TWW), the irrigation quantity of tap water, the percentage of D9 spores, the soil bulk density and the additive ratio of adsorbent in the soil population of Bacillus spp. were determined.The irrigation quantity of TWW, the irrigation quantity of tap water and the additive ratio of poly-γ-glutamic acid were selected as significant factors and were optimized using Central Composite Design. The optimal factors were a TWW irrigation quantity of 2.35mlcm−2, a tap water irrigation quantity of 3.21mlcm−2, and a poly-γ-glutamic acid additive ratio of 1.11gL−1. Validation of the predictive gained population of soil Bacillus was 1.92×108cfug−1, which was close to the predicted value of 2.0×108cfug−1. Compared with the control (soil not irrigated with waste water) and WW (soil irrigated with waste water) treatments, the disease incidence with the TWW (soil irrigated with treated waste water) treatment was significantly decreased. The biocontrol efficacy of TWW treatment was 92.5%. TWW significantly decreased the population of F. oxysporum by 47.1% in the rhizosphere soil and by 87.7% in the stem of A. selengens (P<0.05). These findings support a new value-added application method for waste water from the animal production industry.