Impact of Cropping Systems on Soil Organic Carbon Levels and Enzyme Activity

Monocropping makes agriculture more susceptible to the adverse effects of climate change. Resilient agriculture systems that can buffer crops against various agricultural vulnerabilities is the need of the hour. In this context, a study was conducted to assess the impact of various rice based cropping systems on soil health.

Aims: To study the effect of different rice based cropping systems on soil enzyme activity and organic carbon.

Study Design: Randomized block design, Replications – 3.

Place and Duration of Study: Integrated Farming System Research Station (IFSRS) of Kerala Agricultural University located at Karamana, Thiruvananthapuram, during kharif, rabi and summer seasons of 2019-2020.

Methodology: The experiment consists of eleven cropping systems (T1 : rice - fallow - fallow, T2 : rice - rice - fallow, T3 : rice - daincha - cowpea, T4 : (rice + daincha) - rice - green gram, T5 : rice - cassava - amaranthus, T6 : rice - cassava - cowpea, T7 : rice - para grass - fodder cowpea, T8 : rice - fodder cowpea - fodder maize, T9 : rice - okra - culinary melon, T10 : rice - okra - yard long bean and T11 : rice - rice – amaranthus).

Results: Soil organic carbon and enzyme activities were found highest in the cropping system (rice+daincha) – rice – green gram during kharif. During rabi, soil organic carbon and activity of urease and acid phosphatase were highest in rice- daincha- cowpea while dehydrogenase activity was highest in rice- fodder cowpea – fodder maize. During summer, rice- okra – yard long bean, rice- cassava- amaranthus and rice- cassava – cowpea recorded the highest urease, acid phosphatase and dehydrogenase activity, respectively. The organic carbon was highest for the sequence rice – okra –culinary melon. The soil organic carbon and enzyme activities were least in rice- fallow-fallow cropping sequence during all the three cropping seasons.

Conclusion: Brown manuring, use of leguminous crops and cover crops in the crop sequence instead of leaving the land fallow and addition of organic sources of nutrition increase the soil organic carbon and enzymatic activity of microbes. The increase in soil organic carbon and activity of enzymes in soil owing to crop rotation of rice with arable crops relies on the crop species which are cultivated.