Soil Health, Micronutrients and Macronutrients. (Part 1)

By Dusty Sonnenberg, CCA, Ohio Field Leader, a project of the Ohio Soybean Council and soybean check-off.

There are a handful of reasons micronutrients are important in agriculture, and they all relate to soil health. “When there is a nutrient deficiency, it is important to make changes to help plants maximize photosynthesis,” said Jim Hoorman of Hoorman Soil Health Services. Healthy soils lead to maximized photosynthesis and healthy plants, which lead to higher yields and greater sustainability.

The soil organic matter is an important component of healthy soils. “Most micronutrients are associated with organic matter. If there is a loss of organic matter, there is a loss of micronutrients as well. When you loose organic matter, you lose both micronutrients and soil microbes.” The loss of microbes can lead to less mineralization of nutrients in the soil making those nutrients less plant available.

The loss of livestock on many farms, and the inherent loss of livestock manure being applied to fields is also an issue. “A lot of micronutrients are associated with livestock manure,” said Hoorman. “If livestock manure is not used, farmers may be lacking the benefit of the associated micronutrients.”

Commercial fertilizer has changed over time. “The fertilizer we used in the past had a lot of impurities in it, which were things like zinc and copper,” said Hoorman. “In the past, we got those for free. Now that the fertilizer is more pure, we don’t get those with our fertilizer applications anymore.”

Changes in the weather also impact micronutrient availability. “The weather has changed,” said Hoorman. “That makes an impact on what nutrients are available to the plants.”

“Increased crop yields also impacts the nutrients available in the soil,” said Hoorman. “As yields have increased, the amount of nutrients removed from the soil has increased. We have higher yields and more nutrient dense crops, which leads to more nutrients being removed from the soil at harvest.”

Healthy soils are a function of several natural cycles. “In soils that are not healthy, we have broken cycles; such as broken water cycles, carbon cycles, nitrogen cycles, and phosphorus cycles,” said Hoorman. “We need increased photosynthetic volume in plants that enhances the amount of sugars delivered to the roots, which enhances the microbial activity, which in turn enhances the nutrient uptake in the plant.”

Healthy soils impact plants and final crop yields in many other ways. “We know that increased plant photosynthesis is dependent upon healthy soils . Healthy soils lead to healthy plants that lead to fewer weeds because the crops out compete the weeds. Healthy plants also fight off insects. Insects can detect incomplete photosynthesis in unhealthy plants, which send out signals and insects attach them. The insect attacks also makes the plants susceptible to diseases.”