By Jim Hoorman, Hoorman Soil Health Services

Farmers consistently attempt to increase crop yields but may not know which factors are important.  Yield is influenced by climate and temperature, plant and water management, and soil nutrient management factors.  Good genetics plus the ability to manipulate and optimize the plant’s environment generally result in the highest yields.

Climate and temperature factors are critical to achieving high yields.  Warmer temperatures maximize crop growth including cell division, cell growth, and crop metabolism while cold temperatures inhibit plant growth.  Ideally, soybeans grow the best at air temperatures of 770F. A string of temperatures below 600F reduces soybean pod set.  Corn is a warm season plant that germinates best at 60-650F soil temperatures and grows best between 72-850F.  Iowa and Illinois benefit from dark soils, high in soil organic matter (SOM) which absorbs heat and warms soils better than light-colored sandy soils.  Ideally, try to plant both corn and soybeans when soil temperatures reach 550F to optimize yields.  With large acreage that may not be possible but avoid planting early if conditions are poor.

Larger differences in day and night temperatures reduces plants respiration and allows more carbohydrates to be stored, important in wheat yields.  Temperatures above 800F tend to cause wheat to mature quicker, reducing yields. Longer day lengths stimulate solar radiation and increases photosynthesis in plant leaves. Plant growth rates increases up to June 21st then starts decreasing after that date.  Alaska, with it’s long day length, can produce bumper crops of cold tolerant plants like cabbage even though they have a short growing season.

Farmers often manipulate plant management factors to increase yield.  Wide plant spacing or planting fewer plants in an area reduces competition among plant roots and enhances canopy growth.  Last year, I had a single corn plant in the open by itself produce 9 ears, with 2.5 viable ears.  Most farmers increase plant populations to maximize yield, but it is possible to get higher yields with lower population because solar energy is affected by plant spacing.  With more exposure to sunlight, photosynthesis increases and there is more aeration in the canopy. Precision Ag Technology ReviewsPlanting soybeans in 15-inch or 30-inch rows may produce similar yields to drilled beans while producing healthier plants. Twin row corn with 60-inch spacing also produce good yields.

Orienting crops leaves relative to the path of the sunlight reduces weed pressure and increases crop photosynthesis. The impact of row orientation varies with latitude and the seasonal tilt of the earth’s rotation.  The further North, planting East-West is preferred; while the further South around the equator, North-South is better.

Water management factors include soil moisture and soil aeration.  Increasing SOM allows soils to store water for plant growth and improves a plant’s water efficiency, reducing water needs.  Intermittent irrigation provides water to meet plant needs while non-flooding conditions contribute to soil aeration.  In the humid, wet Midwest states; soil drainage is critical for good root growth.  Good drainage, soil aeration, and oxygen availability support root growth and the soil microbe’s ability to recycle soil nutrients.

Soil and nutrient management factors involving soil structure, nutrient supply, and SOM are critical to achieving higher yields.  Permeable friable soils allow good root growth and optimal soil microbial activity due to optimal oxygen and water availability.  Poor soil structure and compaction often are a result of over tilled soils. Abundant SOM supports a diversity and abundance of soil microbes that improve plant nutrition and protects plants from pests.  When soil become constrained by poor soil structure and compaction, plant root growth and microbial levels decline causing a reduced nutrient supply, reducing crop yields.  Limited plant growth can be affected by too much inorganic fertilizer and/or too little organic nutrients. Organic nutrients are needed to stimulate plant growth and reproduction.

Adding compost and building SOM creates many soil benefits.  Root growth increases 2-3X, tillers 3-4X, and stalks are stronger (higher silicon and calcium) with less lodging.  Plants have more upright leaves for higher photosynthesis and less pest pressure. Healthy abundant microbes produce heathy plants that stay green longer, optimizing yields.  Compost and SOM chelate and provide many plant available micronutrients like copper, zinc, manganese, molybdenum, iron, nickel, and sulfur; resulting in higher grain nutrient levels.  Compost and SOM hold water and tend to moderate soil temperature extremes (warmer in winter, cooler in summer).  Building soil health enhances the environmental factors that influence crop yield and allows genetics to more fully express its yield potential.

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