The use of corn bulk density detectors indicates two common reasons for low bulk density caused by the environment: firstly, in the field, natural disasters such as frost, hail, or diseases and pests hinder the process of grain filling and ripening, leading to dehydration of starch molecules inside the grains and hindering the natural process of grain volume shrinkage. Although the manual drying process removes excess moisture, the starch molecules no longer contract, the grain size remains unchanged, and the bulk density decreases. The second is that the seeds naturally mature and dry in the field to a certain moisture content, but sometimes due to rain, humidity, or fog, they regain moisture, causing the seeds to start brewing and germinating before harvest, digesting and absorbing energy and nutrients such as fat, starch, and protein in the seeds. This process occupies most of the internal space of the grain. Although the grain can still dry in the field, its size does not change, and the small remaining space inside leads to a decrease in bulk density. The large capacity weight value is obtained during the formation period of secondary dry weight of grains while still maintaining high water content. Temperature has little effect on bulk density (when the moisture content is low), but when the moisture content is greater than 18%, the bulk density decreases more significantly. Temperature has a particularly significant impact on high moisture corn, and the situation is complex and variable. There are also reports abroad that the late drought during the corn growing season has to some extent caused a decrease in maize bulk density by affecting grain filling.

Research has shown that the size of wheat bulk density is closely related to various ecological conditions and the determination of wheat amylose. The bulk density is positively correlated with latitude, daily average temperature from heading to maturity, and total sunshine hours, reaching a significant level. Research by Joe Lauer and others abroad has shown that delaying the corn harvest period does not increase bulk density. Gan et al. also found that humid weather in Canada often delays the harvest period of spring wheat, resulting in a decrease in bulk density and affecting grade quality.

The bulk density, specific gravity, and weight of corn kernels decrease with increasing planting density, while the fragility rate increases. There are also studies in China that show a highly significant negative correlation between planting density and bulk density (r=-0.9807). Oikeh et al. (1998) showed that the response of bulk density to nitrogen application varied with inter year and variety changes, and the impact of variety on corn grain bulk density was greater than that of nitrogen fertilizer.

In addition, the measurement methods and rules of bulk density also affect the changes in bulk density. The unit weight index detection stipulates that when the sample temperature is below 0 ℃ (inclusive), the actual unit weight of corn with a moisture content below 23% (inclusive) is the measured unit weight, which also brings some problems to farmers. Wang Hong et al. conducted experiments showing that the bulk density values measured using Chinese inspection methods are 24-30g/l higher than those measured using American standard methods, which is one level higher. Low moisture corn can be tested at any temperature, while high moisture corn (over 18%) requires testing under thawing conditions, i.e. between 0 ℃ and 5 ℃. When the moisture content reaches about 23%, the grains freeze at low temperatures, the surface is smooth, and the embryo bulges. When the temperature rises to 0 ℃, the surface of the particles quickly condenses, affecting the measurement. When the water content is 23%, the critical point for free water to free and the saturated free water