Climate change, imbalance in fertiliser use kill soil’s organic carbon: ICAR study

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

The study, coordinated primarily by ICAR’s Indian Institute of Soil Science in Bhopal, used 254,236 soil samples from 620 districts covering 29 States to arrive at the results. A research paper based on six years of research initiated in 2017 has been published in the UK-based international research journal ‘Land Degradation and Development’.

I’m talking Hindu Commenting on the research, Arvind K. Shukla, coordinator of the project, said that organic carbon is not just a part of the chemistry of the soil but also encompasses all aspects of the physics, chemistry and biology of the soil. He said this problem was flagged in a study published by the Food and Agriculture Organization of the United Nations about 25 years ago, but the examples were very low. “We sampled extensively in this study and the sample collection 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 if organic carbon is low, micronutrient deficiency in the soil is high, and if organic carbon is high, the deficiency is low. The team used an earlier study that said precipitation and temperature determine organic carbon. “We correlated this across the country. We found that organic carbon is highly correlated with elevation. If the altitude of the land is high, the organic carbon content is high. But if we move from the hills to the lowlands, the organic carbon content is low.”

Organic soil carbon is negatively correlated with temperature, Mr. Shukla said. “For example, in Rajasthan and Telangana, the temperature is very high and their organic carbon content is low,” he added. The study noted that temperature, precipitation and altitude are three important factors that determine soil organic carbon concentration, regardless of crops and cropping patterns.

The team of scientists developed an ‘agro-ecological basis’ map to assess the impact of cropping systems and fertilizer use on organic carbon. It covered 20 agro-ecological zones. “The cropping system is very, very important in determining the organic carbon content in areas. Wherever there are rice-based cropping systems or legume-based systems, the organic carbon content is slightly higher than in areas following wheat and coarse grain cropping systems. For rice, where we need to apply more water, the microbial activities are very high, which helps sequester more carbon in the soil,” Mr. Shukla added.

Scientists have prepared a map that can help make policy decisions, especially regarding the assessment of carbon credits and land degradation. They also addressed questions such as whether the rice food system degrades the land and the extent of degradation. “We have seen that wherever there is unbalanced application of fertilizers, organic carbon in the soil decreases. Haryana, Punjab and parts of Western Uttar Pradesh have intensified application of fertilizers, mostly shifting towards the scientific practice of urea and phosphorus, negatively affecting organic carbon in the soil. However, the situation is better in states like Bihar, where balanced application of fertilizers can be seen,” the scientist added.

The study stated that climate change will have an impact on organic carbon. Precipitation will not have a significant impact, but it has a rather negative relationship with temperature. “If the temperature is increasing, then there is a possibility that soil organic carbon will further decrease in the future and this will not only affect soil health but also affect carbon credit and heat emission from the soil. If there is more carbon in the soil, then the heat absorption will be more. If the carbon content is lower, the heat absorption in the soil will be less and more heat reflection from the ground will create a greenhouse gas effect. This will be dangerous,” warned Mr. Shukla.

Scientists suggested that the entire land of the country should be covered with crops and efforts should be made to establish many plantations in the country. The first policy measure they advocated was that wherever soils had less than 0.25% carbon, governments should encourage organic carbon sequestration so that farmers could develop some form of cropping system with increased irrigation opportunities. “The second is carbon credits. We must give incentives to those farmers who can sequester more carbon dioxide from the soil and convert it into organic carbon. Third, we must find different crop management options for climate change mitigation,” he added.