Effect of Chemical Fertilizer Applications on Soil and Rice Yields in Pappy Fields of Nong Harn Area, Sakon Nakhon Province

Abstract

     The study of the effect of fertilizer application on the qualities of soil and rice yields in paddy field, Nong Harn area, Sakon Nakhon province. The experiments were conducted with six different treatments, by using chemical fertilizers (16-16-8 and 46-0-0 or urea): (1) 35 kg/rai of 16-16-8 fertilizer on 30^th day and 15 kg/rai of urea fertilizer on 60^th and 90^th day by broadcasting (T1), deep placement at 10 cm (T2) and 20 cm (T3); (2) fertilizer 16-16-8 70 kg/rai and urea 30 kg/rai by broadcasting (T4), deep placement at 10 cm (T5) and 20 cm (T6).
     The results of soil qualities revealed that pH was highest (8.44) in T5 on 90^th day and the lowest pH was 8.44 in T1. Additionally, the highest and lowest of OM were found in T1 (0.98%) and T4 (0.57%), respectively. At the same fertilization rate, the oxidationreduction potential was highest in T1 (-130.00 mV), the lowest NH₄⁺-N concentration was 103.96 mg/L and NO₃^--N concentration of 8.30 mg/L was highest. For deep placement at 10 and 20 cm, the oxidation-reduction potentials were -161.00 and -215.20 mV; the NH₄⁺-N concentrations were 230.42 and 314.23 mg/kg; NO₃^--N concentrations were 7.39 and 5.91 mg/kg, respectively. The soil qualities in different treatments were significantly different (P < 0.05). The highest and lowest of PO₄^3--P concentrations were 29.17 in T3 and 10.03 mg/kg in T1, respectively. It was noted that the available phosphorus was very low and the results showed the same as two times of fertilization rate.
     The results of rice yield presented significantly difference (P < 0.05). The highest rice yield was found in treatment of deep placement at 10 cm at the same fertilization rate. The highest rice yield was 360.2 kg/rai in T5 and lowest was 215.0 kg/rai in T3. However, 245.3 kg/rai of rice yield by fertilizer application by T2 was produced which is less affecting the aquatic environment than that by T5. Therefore, the fertilizer application of T2 was suggested for farmer practice.