Effect of alkali-enhanced biochar on silicon uptake and suppression of gray leaf spot development in perennial ryegrass

Silicon (Si) is known to alleviate biotic and abiotic stress, and to reduce the development of fungal diseases in a number of different pathosystems. Biochar-based Si fertilizers, especially highly efficient alkali-enhanced biochar for recycling phytolith, has been recently proposed as a stress-alleviating amendment but its evaluation on plant disease development has not been investigated. In this study, several biochar-based Si fertilizers including raw biochar without alkaline enhancement (0 KB), alkali-enhanced biochars with KOH (10 KB), CaO (10CB), and K2CO3 (10K2B) along with commonly-used mineral Si fertilizer wollastonite (WO) and calcium silicate slag (SL) were evaluated in a controlled potting study for their potential to suppress gray leaf spot (Magnaporthe oryzae) development in perennial ryegrass (Lolium perenne L.). Application of 10 KB (at 0.22% rate) increased tissue Si content by 57% compared to the control. The 1% application rate of biochar enhanced ryegrass tissue Si content by 11, 8, 34 and 27% in 0 KB, 10 KB, 10K2B and 10CB compared to 0.22% rate correspondingly. Analysis of area under disease progress curve (AUDPC) showed that gray leaf spot development was reduced by 65-77% with treatments of 0 KB, 10CB and 10 KB, 10K2B at 0.22% rate, and 58-67% for treatments of 10 KB and 10CB at 1% rate compared with the control. At the same application rate (0.22%), 10CB and 10K2B showed better performance in suppressing disease severity than commonly-used wollastonite and calcium silicate slag. Overall, soil amendments with alkali-enhanced biochar-based Si sources increased Si tissue concentration and reduced gray leaf spot development in perennial ryegrass.