Effect of Burning Rice and Wheat Crop Residues: Loss of N, P, K and S from Soil and Changes in the Nutrient Availability

The effect of simulated buring of rice and wheat crop residues on loss of N, P, K and S was measured and the influence of soil heating on the availability of macro and micronutrients in the soil was studied. Complete buring of the rice straw resulted in 100, 20.1, 19.8 and 80.2 per cent loss of N, P, K and S, respectively. Corresponding losses due to burning of wheat straw were 100, 22.2, 21.8 and 75.0 per cent. The loss of each nutrient was less due to incomplete buring of the crop residues as compared to complete buring. There was no loss of micronutrients such as Fe, Mn, Zn and Cu due to incomplete burning of the rice and wheat straw. To study the effect of soil heating on nutrient availability, temperatures of 50, 100 and 150°C for one, two and four hours were imposed. As the temperature increased the NH₄-N, NO₃-N, available K content of the soil increased. Similarly, DTPA-extractable Fe, Mn and Zn content of the soil also increased but DTPA-extractable Cu level decreased with increasing temperature. Heating up to 150°C showed no significant effect on soil organic carbon content. The results also showed that temperature of heating was more important than duration of heating.