Integrated organic amendments and plant growth-promoting rhizobacteria improve soil fertility and sugarcane growth and yield components under rainfed conditions in Northeast Thailand
Sandy soils and unpredictable rainfall are the primary constraints on sugarcane productivity in the Tung Kula Ronghai region of Northeast Thailand. This field study examined the effects of integrated organic amendments combined with plant growth-promoting rhizobacteria (PGPR) on soil fertility, sugarcane growth, and yield components under rainfed conditions. Seven treatments were arranged in a randomized complete block design with three replications during the 2023–2024 growing season (June 2023–March 2024). The integrated treatment (T4) combining poultry manure (3 t/ha), rock phosphate (500 kg/ha), rice bran (100 kg/ha), agricultural lime (200 kg/ha), leonardite (200 kg/ha), and indigenous PGPR inoculant (presumptive Bacillus isolate BS-01 and presumptive Azotobacter isolate AZ-03 at 108 CFU/ml; genus-level identification only; see Section 4) achieved an estimated theoretical yield of 69,911 kg/ha in variety Suphanburi 50. A key finding was a twofold difference in PGPR-associated yield response between the two manure substrates: yield was 91.0% higher with PGPR than without in the chicken manure system (T4 vs. T5, p < 0.001, Cohen’s d = 10.35), compared with a 45.3% increase in the buffalo manure system (T6 vs. T7, p = 0.015, d = 3.36). Notably, PGPR-associated soil chemistry improvements were nearly identical across both manure systems (available nitrogen: +22.6 vs. +22.0 mg/kg; pH: +0.333 vs. +0.433), suggesting that the differential yield response may be related to substrate-dependent differences in how soil fertility gains were converted into biomass, rather than from differential soil chemical effects of PGPR. Soil chemical properties also improved substantially under T4: pH rose from 4.20 to 5.53, organic matter from 4.10 to 4.73 g/kg (pre-treatment plot mean), available phosphorus by 115%, and available potassium by 56%. The estimated theoretical yield under T4 (derived from stalk density and mean stalk weight) was 13.6% greater than that with chemical fertilizer (61,553 kg/ha) and 185.5% greater than that with the unfertilized control (24,490 kg/ha), supporting further evaluation of this integrated treatment under degraded tropical sandy-soil conditions. Confirming economic viability and regional applicability across the broader 3,370 km² Tung Kula Ronghai area will require multi-location, multi-season validation and formal cost-benefit analysis.
Sehawong W, Subepang S. Integrated organic amendments and plant growth-promoting rhizobacteria improve soil fertility and sugarcane growth and yield components under rainfed conditions in Northeast Thailand. J Appl Biol Biotech 2026. Article in Press. http://doi.org/10.7324/jabb.2026.313352
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