Effect of chemical weed management practices on soil microbial population and yield in direct seeded rice

The use of herbicides in direct-seeded rice may affect the biological properties of the soil and thus influence the nutrient status, health and productivity of the soil. To study the effect of herbicides on soil microbial population and yield of direct-seeded rice. A field experiment was conducted RBD with eleven treatments at Agriculture Research Farm, Bihar Agricultural University, Sabour, Bhagalpur, Bihar, India during Kharif 2018. The results revealed that viable microbial population was influenced to varying degrees with different weed control treatments. The maximum bacterial count (14.86 X 106 CFU g-1 soil) was observed under the treatment T4 (Pyrazosulfuron @ 25 g a.i. ha-1 PE fb Bispyribac sodium @ 25 g a.i. ha-1 POE) and minimum bacterial count was found under the treatment T9 (Halosulfuron @ 67.5 g a.i. ha-1 + Azimsulfuron @ 30 g a.i. ha-1 POE) (11.46 X 106 CFU g-1 soil). the maximum actinomycetes count (17.82 X 105 CFU g-1 soil) was observed under the treatment T1 (Pyrazosulfuron @ 25 g a.i. ha-1 PE) and the minimum actinomycetes count was observed under the treatment T6 (Bispyribac sodium @ 25 g a.i. ha-1 POE) (14.05 X 105 CFU g-1and , the maximum fungi count (10.55 X 104 CFU g-1 soil) was observed under the treatment T9 (Halosulfuron @ 67.5 g a.i. ha-1 + Azimsulfuron @ 30 g a.i. ha-1 POE) and the minimum fungi count was observed under the treatment T10 (hand weeding) (7.60 X104 CFU g-1 soil).The maximum grain yield (5.50 t ha-1) was observed in T10 (hand weeding) and it was followed (5.41 t ha-1) by T5 (Pyrazosulfuron @ 25 g a.i. ha-1 PE fb Bispyribac sodium @ 20 g a.i. ha-1 + Pyrazosulfuron @ 20 g a.i. ha-1 POE). T5 fb T4 (5.08 t ha-1) and T9 (4.67 t ha-1) and which was significantly superior over rest of the treatments. The minimum grains yield was recorded (2.70 t ha-1). in T11 (weedy check) as post-emergence were safe for soil microbial populations at recommended rate application of herbicides.