From field crops to garden vegetables, various types of foods rely on soil for growth. The world population continues to grow, and one of the main challenges those involved in agriculture face is increasing the overall productivity of soils to meet elevated food demands.
“We have crops today with highly productive genetics that require productive soils,” said Dorivar Ruiz Diaz, associate professor of agronomy at Kansas State University. “I think our job as agronomists and farmers is to maintain and improve that productivity through proper management.”
The International Year of Soils is taking place in 2015, and it calls to mind the importance of soil for life to exist. Food production is necessary to sustain life, which is why March’s theme is “Soils Support Agriculture.”
Soils contain nutrients
In the K-State soil-testing lab, scientists routinely examine soil samples for many different nutrients; nitrogen, phosphorus, potassium, zinc and sulfur are among the most common, as these nutrients are all essential for plant growth, said David Mengel, K-State professor of agronomy.
Soils are an important source of nutrients for all crops produced in Kansas and beyond, he said. Scientists can make recommendations on what nutrient adjustments are needed, based on findings from soil tests.
“The nutrient concentration in soils can be replenished in a number of ways,” Mengel said. “There are a lot of natural processes that occur that provide nutrients for our crops through the soil. For example, free-living organisms and legumes grown in the field can produce nitrogen for crops. We also can get deposition of sulfur and nitrogen from the atmosphere.”
In addition to enhancing soil nutrients naturally, farmers can also apply nutrients in other forms, including using fertilizers, animal manure and waste products from cities and industries.
Ruiz Diaz said another important way to enhance soil nutrients naturally is through crop rotation. Especially in a state such as Kansas, which has a productive agricultural system that includes many different crops for both human and animal consumption, a systematic approach of deciding which crops to plant year-to-year becomes important. Different crops use different amounts of water and nutrients, which can affect the soil balance.
“Kansas is diverse in terms of its cropping system,” Ruiz Diaz said. “Some of the main crops are wheat for primarily human consumption, as well as corn, soybeans and sorghum. We have many other types of crops and vegetable production as well.”
“Producers use crop rotation as one key tool, as well use cover crops, to help with the cycling of nutrients in the soil.”
With the use of cover crops, which are crops planted specifically for erosion management and to enhance soil fertility, soil quality and water infiltration, farmers strive to increase soil and environmental health. Cover crops can add nutrients to the soil both at the surface and below the surface through their valuable root systems.
“Both agronomists and farmers are concerned and focused on not just maintaining, but also increasing the overall health and productivity of soils to secure food production,” Ruiz Diaz said. “We try to do a good job minimizing any potential nutrient losses and losses to surface water.”
Soils help supply water
Another important function of soils is to store water that plants need for growth. Although many areas of the United States, including parts of Kansas, don’t receive much rainfall annually, soils used for food production have the capacity to hold large quantities of water to help make up for rain shortfalls.
Mengel said farmers can help the soil accept and store water in many ways, including conservation tillage, which is used to keep the surface of the soil covered with crop residues to enhance the infiltration of water and reduce runoff.
An increasing number of farmers are using a no-till system, Ruiz Diaz said, which means they intentionally do not mix and disturb the soil prior to planting. This helps maintain residue on the soil surface and capture more water.
Another alternative to no-till is a minimum tillage system, sometimes called strip-till, where farmers only disturb a small amount of soil to place the seeds, nutrients and fertilizer. A strip-till system, although it does disturb the soil to some degree, can provide a balance between a good seedbed and soil protection with residue cover.
In addition to conservation tillage practices, farmers can also produce crops that are known to use less water, Mengel said. This is especially helpful for Kansas farmers who experience drier conditions, particularly those in western areas of the state.
“Crops differ tremendously in their ability to withstand drought stress,” he said. “So we use crops like sorghum, for example, that is drought tolerant. We use that in areas of western Kansas where there isn’t enough rainfall and stored water to be able to grow corn reliably.”
“The other thing is change the season in which the crop grows,” Mengel added. “A good example of that is wheat. Corn grows during the summertime when it is hot and dry. Corn may not survive well in some of our areas. However, we can grow winter wheat that we plant in the fall, it comes up early in the spring, and it’s done by the heat of the summer. It utilizes water a little more efficiently, and it’s much more capable of withstanding the stressful conditions in some areas.”