Soybean Protein Gains Achieved Without Reducing Oil Quality
Researchers at Kentucky State University are exploring new ways to address declining soybean protein levels, an issue that affects the nutritional quality of soybean meal used in livestock feed.
Findings showed that applying nitrogen fertilizer during the seed-filling stage improved soybean protein concentration by 1.2% to 2.8% across both growing seasons. Researchers also noted that oil levels remained unchanged, indicating that higher protein content did not reduce oil quality.
The research, led by Deepak Khatri with guidance from Dr. Anuj Chiluwal, evaluated the impact of biochar and late-season nitrogen applications on soybean performance and seed composition.
The two-year field study took place at the university’s Harold R. Benson Research and Demonstration Farm and involved two soybean varieties representing different maturity groups.
“Declining soybean protein concentration is a major concern because it directly affects the quality of soybean meal used in animal feed,” Khatri said. “Our research provides evidence that lower nitrogen applications during the seed-filling period can help reverse this trend.”
The researchers explained that soybean plants require large amounts of nitrogen during seed development, and natural nitrogen sources may not always meet crop demand under high-yield conditions.
“Previous studies aimed at increasing soybean protein through late-season nitrogen applications relied on extremely high rates — ranging from more than 200 to 870 kilograms per hectare — making them neither economically viable nor environmentally sustainable,” Dr. Chiluwal said.
“In contrast, this study takes a different approach by testing lower nitrogen rates of 40 to 120 kilograms per hectare, applied in three split applications during the seed-filling period. The findings demonstrate that even modest nitrogen applications can improve seed protein concentration, offering a more practical and scalable solution to a significant industry challenge.”
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