Soil factors that affect yield variability in corn production

Soil factors that affect yield variability in corn production

Updated Aug 1, 2020 

As the most important crop in North America, corn production has been growing steadily from 1930 until today. There are two periods where the yield of American farmers has increased significantly. The first is the last years of the Dust Bowl and the Great Depression, where farmers begin to adopt double-cross hybrids with a yield increase of 0.8 per bushel per acre per year. The second period, significant for US corn production, started in the mid-1950s due to intensive modification of genetic potential, increased use of nitrogen fertilizers and chemical pesticides, and the use of more sophisticated agricultural machinery. The yield increased by 1.9 bushels per acre per year. From that point, the yield increased consecutively, where the most significant credit goes to the genetic improvements and the advancement of agricultural production technology.

Soil factors that affect yield variability in corn production
Figure 1 Annual U.S. Corn Grain Yields and Historical Trends Since 1866. Data derived from annual USDA-NASS Crop Production Reports

Every farmer's dream is to have a field that contains fertile soil, sufficient nutrient content, and a right balance between beneficial and harmful microorganisms and insects. The ideal field, with all its characteristics, enables optimal growth and development of a particular crop. Hypothetically, if every segment of the "ideal field" were the same, producing a specific crop would result in uniform plants and equal yields. But unfortunately, if we take into account the real conditions and the different topography that changes from place to place, uniform plants and equality of yield is a real challenge for every farmer. Therefore, a better understanding of the factors contributing to unequal plant development enables proper decision-making regarding all undertaken agricultural technological measures to balance the differences in the field.

For easier understanding, the variability itself is dividing into two parts: temporal and spatial yield variability.

Temporal variability refers to the difference in yield in different years and is usually due to changes in weather conditions.

Spatial variability refers to the difference in the yield of certain areas in the same field due to unequal characteristics of soil, plants, and terrain.

Factors affecting corn yield variability:

Soil texture

The percentage of sand, gravel, and clay in the soil determines its texture. With the help of a simple manual technique, one can quickly identify the soil texture in a specific field.

Different texture in spatial distribution differently affects corn yield through variations in nutrient capacity and availability, water capacity and transport, binding or decomposition of pesticides, as well as soil stability itself to different destructive forces. The spatial variation of the soil texture in the field itself contributes to the final variability of the corn yield.

Soil structure

The structure can clearly be explained as the arrangement of the different particles that make up the soil and the distribution of air space between the particles. Soil structure affects the penetration, growth, and attachment of the root system of corn. It also regulates the balance between air and moisture, water retention capacity, and drainage and affects the erosion potential. Soil can be degraded through introducing mechanical force by agricultural machinery, improper cultivation, soil wetting and drying cycles, loss of organic matter and salinity. Degraded soil reduces the availability of oxygen needed to carry out metabolic processes, restricts the root system's volume, and elongation of the roots. Also, poorly structured soil has reduced infiltration, increased pond formation capacity, and reduced plant available water capacity (PAWC).

Soil depth

Soil depth is defined as the depth that a root system can penetrate. It is a significant parameter, and the amounts of absorbed nutrients and water depend on it. Depth may refer to the distance between the surface and the bedrock, the surface and the first subsoil that the plant cannot penetrate, or the creation of a plow pan as a result of the soil's prior management.

Organic matter in the soil

It is most often a proof of soil fertility. Organic matter plays a major role in the positive characteristics of good soil. It binds the particles and determines the storage and release of nutrients. The type and amount of organic matter in the soil affect the microbial activity and the availability of nitrogen, phosphorus, and sulfur. Also, the amount of organic matter contributes to the degree of absorption and degradation of agrochemical compounds.

Soil water

One of the most significant limiting factors for corn yield is the available soil water. The variability of the yield from one field largely depends on the spatial distribution of soil moisture. The total amount of water that can be retained in a soil profile is called PAWC and that PAWC is determined by soil characteristics such as structure, texture, and depth of the soil profile. The most sensitive component of the soil that can easily be subjected to changes is its structure. The structure is often disrupting through intensive tillage and penetration of the root system into the soil profile.

Soil pH

On a scale from 1 to 14, the soil's pH is a measure of soil acidity or alkalinity, where below 7 the soil is acidic, and above 7, the soil has an alkaline reaction. With the help of this measure, we can see the degree of adoption of individual elements found in the soil, which are useful for corn. The optimal pH value in which the corn grows intensively is from 5.8 to 7. If the pH value varies more than 1 unit in the field, it will contribute to the incorrect absorption of nutrients even if we have a uniform application of mineral fertilizers.

Soil Nutrients

The type and amount of nutrients in the soil largely depend on the soil's physical characteristics. These characteristics dictate the distribution, quantity, availability, and mobility of the individual elements found in the soil itself. The primary macronutrients (nitrogen, phosphorus, and potassium) have different mobility in the soil (nitrogen is more mobile than potassium, while potassium is more mobile than phosphorus). The consequence of this mobility makes the spatial variability in the field, and as a result, there is variability in corn yield.