Diversity in our agricultural and food production systems is integral in varying structure, reducing risk, and bringing new ideas and perspectives. In the context of soil, diversity is vital to be healthy and productive. The five principles of soil health are to keep soil covered, minimize disturbance, plant diversity, continual living roots, and livestock integration. Crop and plant diversity have such an impact on maintaining and improving soil health, it is one of the principles. Although our current agricultural system can prove challenging for crop diversity, the benefits far outweigh the challenges. Improved water infiltration, reduced risk of pests and diseases, nutrient cycling, new markets, and livestock feed make looking at a broad crop portfolio worth considering.
There are many different plant families around the world. In the Midwest, we commonly plant in the Poaceae, or grass, family (corn) and Fabaceae, or legume, family (soybean). Ultimately, this crop rotation is popular because it protects yield by changing families. When you change families, the root structure is different, which creates various underground pathways that help increase water infiltration. Water infiltration is vital to reducing erosion rates because water runs across the field when it cannot be soaked up by the soil. With the ability to soak into the soil deeper, the water reaches the root structure and can be taken up easier, nourishing the plant.
Diseases and pests are also less prominent when a crop rotation is utilized. The change in crops reduces the available food for pest larva, or young, to feed on and, in turn, disrupts their reproductive cycle. Without a solid food source, or host, the population can’t build up. For example, when corn, grasses or small grains are used in the crop rotation with soybeans, soybean cyst nematode issues are reduced.
Grown since early spring, this cereal rye cover crop stands 8-12 inches tall adjacent to a recently planted and emerging corn crop. [May 2020]
Each crop has different nutrient needs. Macro-nutrients such as nitrogen, phosphorus and potassium dissolve in the water attached to and surrounding soil particles. The availability of these nutrients is dependent on the crops planted. Legumes, as an example, fix nitrogen from the air, making it accessible to the crop. Corn, on the other hand, requires nitrogen to be taken up by the roots, intensively relying on nitrogen already available in the soil. When legumes are planted prior to the corn, they add nitrogen to the soil, in turn crediting the corn’s nutrient needs. By utilizing the additional nutrients leftover in the soil from the legumes, a smaller fertilizer application is required and nutrient loss to leaching and erosion is reduced.
Prior to instituting crop diversification, it is important to establish a goal. This can range from entering additional markets or providing livestock feed to improving soil health. When looking to diversify cash crops, it is important to research if there is a local market or the crop will not be economically viable. A primary local market option is livestock feed, which enables additional cover crops to be planted. The cover crop can be harvested and fed, or with permanent or portable fencing in place, can be grazed by livestock, making for a resourceful feed option.
The soil health benefits from cover crops can be justified economically as well. Incorporated into a rotation, cover crops build organic matter and decrease commercial fertilizer needs. Through the use of our EcoPractices® platform we can quantify the erosion control and carbon benefits, as well as return on investment, resulting from the use of cover crops. Overall, the additional markets can make or break adding an additional crop.
Crop diversity, incorporated as cash or cover crops, is important in protecting soil health. Planting different families improves water infiltration, breaks the pest cycle, and reduces nutrient depletion. Crop diversity is beneficial in the context of biodiversity but also can have an economic benefit if planned for. This practice can be implemented around the country and the world to have a positive effect on soil health and the pocketbook.
Mahdi Al-Kaisi Professor of Soil Management/ Environment Mahdi Al-Kaisi is a professor of agronomy and extension soil and water specialist at Iowa State University. His current research and extension in soil management and environment focuses on the effects of crop rotation, M. A. (2001, April). Value of crop rotation in nitrogen management. Retrieved November, 2020, from https://crops.extension.iastate.edu/encyclopedia/value-crop-rotation-nitrogen-management
Conservation Crop Rotation Effects on Soil Quality. (1996, August). Soil Quality - Agronomy - Technical Note No. 2, 2, 1-3.
Soybean cyst nematode management guide. (2018). Retrieved November, 2020, from https://extension.umn.edu/soybean-pest-management/soybean-cyst-nematode-management-guide#how-to-use-crop-rotation-to-manage-scn-1497862