Humification of Added Organic Materials in Some Typical Soils of Rajasthan

Humification studies in eight major soils of Rajasthan were carried out, using jowar, wheat and cowpea straws. After 30 and 60 days of incubation, there wos decrease in the organic carbon and variable effect on the humic and fulvic acid carbon content of different soils with these straws. However the process appears to be stabilizing after 60 days. Increase in humic acid carbon was observed after 120 days of humification in most of the soils, higher contents being in cowpea straw treatment. Humic to fulvic acid carbon ratio widened in all the soils with these straw treatments and generally was in the range: cowpea (0.48 to 3.81), wheat (0.85 to 3.08) and jowar (0.26 to 2.89). Accumulation of humic and fulvic acid carbon was related with soil organic carbon, while CaCO₃ content showed detrimental effect on humic carbon accumulation. Among the different straw treated soils, correlation coefficient values between humic acid and fulvic acid carbon were significant only in case of cowpea treatment and thereby suggested possible participation of N in humification process.