Submitted to: American Journal of Plant Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 10, 2013
Publication Date: May 20, 2013
Citation: Bellaloui, N., Yin, X., Mengistu, A., Mcclure, A.M., Tyler, D.D., Reddy, K.N. 2013. Soybean seed protein, oil, fatty acids, and isoflavones altered by potassium fertilizer rates in the midsouth. American Journal of Plant Sciences. 4(5):976-988. Interpretive Summary: Potassium is an essential nutrient for crop yield and seed quality, and its deficiency in soil results in yield loss and reduction in seed quality. Information on the effects of potassium fertilizer on soybean seed protein, oil, fatty acids, and isoflavones (a plant estrogen thought to have health benefits for human and play a role in plant defense mechanism against diseases) is limited and controversial. The source of this controversy could be due to genetic differences in the cultivars used, environments under which the cultivars were grown, and their interactions. In a three-year experiment conducted in two locations in TN for three years using five rates of potassium, it was shown that increasing the potassium fertilizer rate did not result in consistent effects on yield. However, increasing potassium rate increased protein, oleic acid, and total isoflavone concentrations at both locations in two of the three years. This new knowledge demonstrated the feasibility of obtaining desirable seed constituents such as high protein, oleic acid, and isoflavones (desirable by seed industry) by potassium fertilizer management. This information allows growers to optimize potassium fertilizer practices while maintaining high seed quality in the midsouth. The information on seed composition variability in different locations benefits soybean breeders in seed composition germplasm development.
Technical Abstract: Previous research has shown that the effect of potassium fertilizer on soybean ([Glycine max (L.) Merr.] seed composition (protein, oil, fatty acids, and isoflavones) is still largely unknown. Therefore, the objective of this research was to investigate the effects of potassium application on seed protein, oil, fatty acids, and isoflavones under Midsouth environmental conditions. A three-year experiment was conducted in two locations (Milan, TN and Jackson, TN). Potassium (K) rates were applied in the form of K2O at a rate of 0 (Control, C), 45 (T1), 90 (T2), 134 (T3), and 179 (T4) kg/ ha in a randomized complete block design. The results showed that increasing the K application rate did not result in consistent effects on yield. However, increasing K application rate did increase protein, oleic acid, and individual and total isoflavone concentrations at both locations in 2008 and 2009. In Jackson in 2010, the increase of K rate did not change oleic acid, but resulted in an increase in glycitein and genistein isoflavone concentrations. In 2010, increasing K application rate increased protein concentrations, decreased individual and total isoflavones, and did not change oleic acid concentration at Milan. At the highest rate of K, 179 kg/ha, yield and some seed composition constituents were negatively impacted. Generally, K concentration in leaves at V5, R1, R3, and seed at harvest maturity stage (R8) increased with the increase of K rate applications. The research demonstrated that K application can alter seed composition, but this alteration depended on location. Higher rates of K application may negatively impact seed composition constituents.