Why Is Soil Organic Carbon in USA Considered So Important for Crop Health?

Soil organic carbon or the SOC is the carbon that stays in the soil after partial decomposition of any substance produced by the living organisms. It is present as a central component of soil organic matter. It is believed to be crucial for many soil functions and ecological properties. Carbon makes up approximately 58% of the soil organic matter, revealing just how significant it is for maximizing soil health and crop production. Without adequate amounts of soil organic carbon in the USA, crops cannot reach their genetic potential, resulting in lower yields, less profit, and higher costs to the farmer. 

Soil organic matter is essential in integrating many aspects of soil health. It can be divided into labile and stable pools, each with different characteristics and functions in the soil. In agricultural soils, organic matter can ranges from 1 to 8%, depending on climate, soil type, and soil management practices. 

How Does SOC Relate to Soil Function? 

Soil organic carbon impacts the soil's biological, physical, and chemical functioning. Total Carbon and SOC are more precise indicators for a soil sample's organic matter or soil organic matter (SOM). Carbon is the main element in soil organic matter, comprising 48-58% of its total dry weight. SOM acts as a long-term carbon sink and a slow-release pool for nutrients. Therefore, soils with higher SOC, Tot C, or SOM require fewer off-farm inputs and are more resilient to drought and extreme rainfall. 

Improving Soil Carbon:

Adequate soil organic carbon is essential for soil health (the capacity of soil to function). It has a direct impact on crop production and an indirect effect on water quality. Unhealthy soils with less soil carbon are more likely to erode and have a higher potential for runoff during storm events. Soil erosion can carry sediments, nutrients, and pesticides to surface water bodies, degrading water quality. Healthy soils can absorb and supply water, retain nutrients, suppress pests and weeds, and produce high crop yields. 

How Do We Manage Soils to Increase Soil Carbon? 

Minimizing Soil Disturbance:

Tillage contributes the most to soil disturbance, which has implications for soil erosion. It also leads to the soil organic matter losses. However, many farmers use tillage to prepare seeds for cultivation and manage the crop residue by mixing it with soil. 

A best management practice that relies on soil conservation is minimizing till or completely using no-till. No-till practices have been found to have 71% lesser greenhouse gas intensity than the conventional tillage. 

Covering the Soil:

Soils require protection, and it makes sense that farmers find soil conservation techniques like using a cover crop and leaving the straws in the fields beneficial. The added inputs of organic matter can minimize losses and also help prevent the soil from eroding away while improving the soil structure. 

Cultivating Crops in Rotation:

Adopting the crop management practices that increase soil carbon inputs helps improve productivity and soil condition. Crop rotation methods like seasonal cover crops or continuous cropping, which minimizes fallow frequency, are some ways to boost soil organic carbon stock.