Climate change, imbalance in fertilizer use kill soil organic carbon: ICAR study

A detailed study by eight Indian Council of Agricultural Research (ICAR) scientists, including its director general Mangi Lal Jat, found that unscientific use of fertilizers and climate change are contributing to the degradation of organic carbon in the country’s arable areas.

The study, largely coordinated by the Indian Institute of Soil Science ICAR in Bhopal, used 254,236 soil samples from 620 districts covering 29 states to draw its conclusions. The research paper, based on a six-year study that began in 2017, was published in the English international research journal Land Degradation & Development.

Talking to Hindu About the study, project coordinator Arvind K. Shukla said that organic carbon is not only part of soil chemistry, but it encompasses all aspects of soil physics, chemistry and biology. He said that a study published by the Food and Agriculture Organization of the United Nations about 25 years ago showed this problem, but the samples were very low. “In this study, we sampled widely and the sampling was well designed. We covered both arable and barren land, mostly arable land,” he said.

Effect of Altitude on Organic Carbon

The study found that when organic carbon is low, the micronutrient deficiency in the soil is high, and when organic carbon is high, the deficiency is low. The team used earlier research that said rainfall and temperature determine organic carbon. “We correlated it across the country. We found that organic carbon correlates closely with altitude. If the land elevation is high, organic carbon is high. But as we move from the hills to the lowlands, organic carbon is low,” he added.

Mr. Shukla said organic carbon in soil is negatively correlated with temperature. “For example, Rajasthan and Telangana have very high temperatures and low organic carbon,” he added. The study noted that regardless of crops and cropping patterns, temperature, rainfall, and elevation were the three most important factors determining soil organic carbon concentrations.

A team of scientists developed an “agroecological base” map to assess the impact of cropping systems and fertilizer use on organic carbon. They covered 20 agro-ecoregions. “The cropping system is very, very important in determining the organic carbon content of the regions. Wherever there are rice or pulse cropping systems, the organic carbon content is slightly higher than in areas that follow wheat and coarse grain cropping systems. For rice, where we need to use more water, the microbial activity is very high, which helps to absorb more carbon in the soil.” added Mr Shukla.

Scientists have prepared a map that can help in making policy decisions, in particular, for carbon emissions and assessment of land degradation. They also touched on issues such as how the rice food system has degraded the land and the extent of its degradation. “We found that where there was unbalanced fertilization, soil organic carbon declined. Haryana, Punjab and some parts of western Uttar Pradesh had intensified fertilization towards urea and phosphorus, which was mostly science-based, and this had a negative effect on soil organic carbon. But in states like Bihar, where balanced application of fertilizers is seen, the situation is better,” the scientist added.

The study notes that climate change will affect organic carbon. Precipitation will not have a significant impact, but it is strongly negatively correlated with temperature. “If temperatures rise, there is a chance that soil organic carbon will decline even further in the future, and this will not only affect soil health, but also impact carbon credit and soil heat release. If there is more carbon in the soil, more heat will be absorbed. If the carbon content is lower, there will be less soil heat absorption and more heat reflection.” from the ground, creating the effect of greenhouse gases. This will be dangerous,” warned Mr. Shukla.

Scientists suggested that the country should cover all soils with crops and try to create a large number of plantations in the country. The first policy measure they advocated was that where soils are very low in carbon, less than 0.25%, governments should promote organic carbon sequestration so that farmers can develop some kind of cropping system with enhanced irrigation capabilities. “Second is the carbon credit. We need to incentivize those farmers who are able to capture more carbon dioxide from the soil and convert it into organic carbon. Third, we need to find different options for managing agricultural plants to mitigate the effects of climate change,” he added.