ผลของการไถกลบหญ้าแฝกและระดับน้ำในนาข้าวต่อสมบัติของดินและการปลดปล่อยก๊าซมีเทน / อรรถพล โสภาพงศ์ = Effect of vetiver grass plough and water levels in rice field on soil properties and methane gas emission / Attapon Sophapongse
This research aimed to study the effects of vetiver grass plough and water levels on soil properties and methane emission from organic rice production in Cha-am District, Phetchaburi Province. The studies were conducted in four plots of approximately 800 m2 each. The factors studied were (1) soil improvement i.e., plot with vetiver plough (cultivated vetiver grass for approximately 500 days before ploughing) and plot without vetiver plough (cultivated rice for 3 consecutive crops; and after each harvest, sunn hemp was used as green manure for soil improvement) and (2) floodwater levels i.e., 5 and 10 cm. The rice Oryza sativa L. cultivar Chainat1 was cultivated using broadcasting technique for 117 days. The methane emissions were measured 6 periods during growth stages of rice i.e. germination, seedling, tillering, booting, milk grain and harvest using static closed chamber technique. The results indicated that soil in plots with vetiver plough had significantly higher pH (7.38-7.42 and 6.74-6.82), electrical conductivity (0.45-0.52 and 0.19-0.27 dS/m), Eh (-106.93 to -110.21 and -109.29 to -113.38 mV), bulk density (1.33-1.36 and 1.21-1.24 g/cm3) and exchangeable K (72.96-74.39 and 46.70-58.04 mg/kg) than soil in plots without vetiver plough. For methane emission, the values from plots with vetiver plough with both 5 and 10 cm. water levels (15.79 and 18.19 mg/m2/hr) were lower than plots without vetiver plough (25.29 and 29.96 mg/m2/hr). The methane emission trends were increased with rice growth stages i.e., lowest in germination stage (0.60-2.83 mg/m2/hr) and highest in milk grain stage (52.22-86.86 mg/m2/hr). According to the correlation between soil properties and methane emission, the results indicated significant correlation (p<0.05) between soil pH, electrical conductivity, Eh, temperature, organic matter, organic carbon; and methane emission. In addition, shoot height and total biomass of rice were significantly correlated with methane emission. Whereas floodwater level showed non-significantly correlated with methane emission (p>0.05). However, there was the tendency that plots with 5 cm. water level emitted lower methane. For rice production, the production in plots with vetiver plough with both 5 and 10 cm. water levels (421.47 and 401.35 kg/rai) were higher than plots without vetiver plough (374.72 and 366.72 kg/rai). In conclusion, overall results suggested that soil improvement by vetiver grass plough emitted lower methane while yielded higher rice production.
