How to Determine the Quality of Soybeans?

The seed quality from the 2021 harvest was below average in the bulk of the US soybean-producing regions. Wet weather throughout the fall and the consequently postponed harvest were some of the most significant variables contributing to low-quality soybean seed.

The rainy weather put off harvesting while fostering the growth of various seed diseases, including Purple seed stain and Phomopsis seed decay. Phomopsis seed deterioration can cause seeds to become broken, fade, and have a chalk-white appearance on their surface.

On the other hand, purple seed stain causes purple spots on seeds or the whole seed to be purple. 

Outlined below are methods on how to determine the quality of soybeans.

1. Seed Treatment

Fungicide seed treatment is advised for the seed planted early in the growing season. When pathogens are present on the seed, fungicide seed treatments can help protect the seed and young seedlings from seed-borne and soilborne diseases, and seed treatments have been proven to boost warm germination scores by 10-15%. 

Seed treatments can also help protect seeds and seedlings from identified pests, resulting in more uniform plant stands and increased soybean value production potential.

Wet, poorly drained soils, frequent during spring planting and crop emergence, promote the growth of fungal and water-mold pathogens that cause soybean seedling disease. These diseases have the potential to delay germination and plant growth. 

2. Appearance of Soybean Seed

Some soybean seeds may have a bad appearance due to environmental and disease concerns from the previous growing season and a few storage challenges since harvest. Drought, aphids, bean leaf beetles, viruses, and a rapid harvest dry-down can all lead to poor seed appearance. 

Low harvest moisture levels can increase the possibility of mechanical damage during conditioning and packaging. Also, rapidly shutting down soybean plants during harvest can result in immature green seeds, and excess moisture in bins might contribute to seed surface mold.

3. Urease Test

Urease, an enzyme found in soybeans, is of little interest in monogastric feeding. However, like trypsin inhibitors and lectins, cooking reduces its activity. Because urease activity determinations are significantly more straightforward to perform than trypsin inhibitor assays, urease activity is widely employed as a “marker” to indirectly represent the presence of antinutritional substances in soy products. 

Historically, urease activity greater than a 0.15 pH unit increase indicated under processing, whereas activities less than 0.05 indicated overprocessing. However, over the last several decades, a change in soybean processing has resulted in the manufacture of meals with pH changes much more minor than 0.05, with no apparent adverse effect on animal performance.

Furthermore, the previous maximum allowable level of 0.15 pH units is no longer regarded as absolute. Older birds, particularly laying hens, can easily handle meals with urease values of 0.25 or higher. Because turkey starting diets commonly contain more than 40% soybean meal, turkey poults may be the most sensitive. 

4. Planting Date

Farmers should plant the highest quality seed first and the lowest quality seed last. Planting low-quality seeds into cold, wet soils, inadequate seed beds, or high residue conditions that impede seed-to-soil contact should be avoided. 

Early planting of late-maturing cultivars can assist maximize output potential, while early planting of early-maturing kinds can help spread out the harvest window.

5. Protein Solubility

The amount of heat treatment affects how soluble soybean protein is in potassium hydroxide solution. While meals that have been roasted to a dark brown tone may have PS as low as 30 or 40%, raw soybean flour has PS that approaches 100%. 

It is reasonable to assume that protein solubilities in the range of 78–84% reflect ideal soybean processing, even though precise numbers are complex. Meals containing 84-89% protein may be appropriate for laying hens and older broilers, less sensitive to antinutritional elements. 

In contrast, values less than 78, and notably less than 74% PS, indicate a gradual decline in lysine availability for all animals.

6. Clean Seed if Possible

Soybean seed producers utilizing seed cleaning equipment should clean their seed lots to obtain lots with fewer than 20% damaged seeds. This reduces the amount of damaged seed you sow and produces uniform lots that you can check for germination.

7. Protein Dispersibility Index

The protein dispersibility index is another method for assessing the sufficiency of soybean meal processing (PDI). Although the protein dispersibility index has been used in the feed business for nearly a quarter-century, it has only lately acquired popularity as a tool to differentiate soybean meal quality for feed application.

The protein dispersibility index calculates the quantity of protein disseminated in water after blending a sample with water in a high-speed blender. According to the findings of Batal et al. (2000), PDI is a more consistent and sensitive indicator of adequately heat processed soybean meal than urease index or protein solubility in KOH. 

Soybean meal with a PDI of 45% or below is heat appropriately processed. This figure is slightly higher than the National Soybean Processors Association’s recommended range of 15% to 30%. More research is needed to find the best PDI range and maximum level in commercially processed soybean meals. Combining the PDI and urease tests could help soybean processors and poultry nutritionists better monitor the quality of soybean meals. 

Bottomline 

To improve germination rates and avoid seedling infections, many farmers will choose to have their seeds treated with a fungicide. Significantly, it is essential to consider altering planting on the low-germination seed to achieve the desired final stand.

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