what causes low test weight in corn



Corn is one of the most widely grown cereal crops in the world. It is not only a crucial staple food but also a vital feed ingredient for livestock. Farmers have always aimed to maximize the quality and yield of their corn crops, and achieving high grain weight is a key component of this goal. However, low test weight in corn can have a detrimental impact on both the yield and quality of the crop. This article explores the various factors that can contribute to low test weight in corn and offers insights into how farmers can address this issue to optimize their corn production.

What is Test Weight in Corn?

Test weight is a measure of the weight of a specific volume of grain. In the case of corn, it is usually expressed as the weight of a bushel (56 pounds) of grain. The test weight of corn provides a valuable indicator of its quality, as it reflects the density and overall condition of the kernels. Generally, higher test weights indicate better-quality corn with fewer damaged kernels, while lower test weights can suggest lower-quality grain and potentially reduced market value.

The Impact of Low Test Weight on Corn

Low test weight in corn can have several adverse effects on both the yield and market value of the crop. Firstly, it can result in reduced grain yield per acre, ultimately leading to financial losses for farmers. Additionally, low test weight corn often contains a higher proportion of lightweight and shriveled kernels, which have lower feeding value for livestock. This can pose challenges for corn growers who rely on corn as a vital feed ingredient in animal production.

Furthermore, low test weight corn may face difficulties during transportation and storage due to its reduced density. Lightweight kernels are more susceptible to breakage, damage, and spoilage, resulting in increased aflatoxin formation and decreased shelf life. These factors not only affect the profitability of corn growers but also impact the overall quality and safety of corn-based products across the supply chain.

The Causes of Low Test Weight in Corn

Now, let's delve into the various factors that can contribute to low test weight in corn.

Drought or Water Stress

Drought or insufficient water availability during critical growth stages can significantly impact the test weight of corn. Adequate soil moisture is crucial for the proper development and elongation of corn kernels. When corn plants experience drought conditions, they may prioritize survival over grain filling, resulting in lighter kernels and reduced test weight. Furthermore, water stress can disrupt the proper functioning of the plant's reproductive system, leading to poor pollination and kernel set, further exacerbating the issue.

Poor Nutrient Management

Proper nutrient management plays a vital role in optimizing corn production. Nutrient deficiencies, imbalances, or inadequate nutrient uptake can lead to low test weight in corn. Some key nutrients that influence grain development and quality include nitrogen, phosphorus, potassium, magnesium, and zinc. Insufficient levels of these nutrients can impair the metabolic processes responsible for grain filling, resulting in reduced test weight. Soil testing, regular fertilizer applications, and crop nutrient monitoring are essential for identifying and addressing any nutrient deficiencies in corn fields.

Insect Pests and Diseases

Insect pests and diseases can cause substantial damage to corn plants and negatively impact test weight. Pests such as corn borers, armyworms, or corn rootworms can directly damage developing kernels, resulting in lightweight or shriveled grains. Diseases like gray leaf spot, southern corn leaf blight, or stalk rot can also hamper grain development and contribute to lower test weight. Early detection, integrated pest management strategies, and appropriate disease control measures are vital for minimizing the impact of insect pests and diseases on corn yield and quality.

Environmental Factors

Environmental conditions, including temperature and humidity, can influence the test weight of corn. High temperatures during the pollination period can disrupt the pollination process, leading to poor kernel set and reduced test weight. Similarly, excessive moisture or rainfall during the later stages of grain filling can result in kernel abortion, delayed maturity, and ultimately lower test weight. Understanding the local climate patterns and selecting corn hybrids that are well-adapted to the prevailing conditions can help mitigate the impact of these environmental factors on test weight.

Weed Competition and Crop Density

Weed competition can significantly affect corn growth and development, ultimately impacting test weight. Weeds compete with corn plants for vital resources such as sunlight, water, and nutrients. This competition can limit the growth and vigor of corn, resulting in smaller, lighter grains and lower test weight. Proper weed management practices, including timely herbicide applications and crop rotation, can help minimize weed pressure and optimize corn test weight. Additionally, maintaining appropriate plant populations and spacing can ensure optimal grain fill and improve test weight.


High test weight is a desirable trait in corn as it signifies good quality grain with higher market value. However, several factors can contribute to low test weight in corn, including drought, poor nutrient management, insect pests, diseases, environmental conditions, weed competition, and crop density. Addressing these factors requires a proactive and integrated approach that includes proper irrigation, nutrient management, pest and disease control, climate-adapted hybrid selection, and effective weed management. By considering these factors and implementing appropriate strategies, corn growers can enhance test weight, optimize yield, and ensure the production of high-quality corn for both feed and human consumption purposes.


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