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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Genetics Research » Research » Publications at this Location » Publication #312695
Title: Potassium and phosphorus have no effects on severity of charcoal rot of soybean

Author
item Mengistu, Alemu
item YIN, XINHUA - University Of Tennessee
item Bellaloui, Nacer
item MCCLURE, ANGELA - University Of Tennessee
item TYLER, DON - University Of Tennessee
item Reddy, Krishna

Submitted to: Canadian Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2016
Publication Date: 4/25/2016
Citation: Mengistu, A., Yin, X., Bellaloui, N., Mcclure, A., Tyler, D.D., Reddy, K.N. 2016. Potassium and phosphorus have no effects on severity of charcoal rot of soybean. Canadian Journal of Plant Pathology. 38:174-182. doi:10.1080/07060661.2016.1168869.

Interpretive Summary: The effects of potassium (K) and phosphorus (P) fertilizers on charcoal rot of soybean are unknown. Therefore, the severity of charcoal rot was studied at five levels of K (0, 37, 75, 111 and 149 kg K ha-1) and a level that was equal to the recommended fertilizer application rate based on annual soil K testing; and five levels of P (0, 10, 20, 30 and 40 kg P ha-1) and a level that was equal to the recommended P fertilizer application rate based on annual soil testing under field conditions in 2008, 2009 and 2010 at Jackson and Milan, TN, USA. Analysis of variance showed no significant effect from treatments or treatment-by-year interactions. However, analysis of colony forming unit of the charcoal rot fungus from soil showed a significant effect from P but not from K application. Analysis using treatment as a trend indicated that tissue colony forming unit as a function of K rates showed a positive but moderate significant slope at both Jackson and Milan in 2009 suggesting a modest increase in disease severity in that particular year. Further increase in K rate however, resulted in a negative slope at Milan in 2010. The CFU from soil also showed a similar positive significant slope for P in Milan in 2009 and 2010 but not for 2008. Our results showed that increasing the K and P application rates over both the recommended rate did not result in any consistent increase or decrease in disease severity of charcoal rot.

Technical Abstract: The effects of potassium (K) and phosphorus (P) fertilizers on charcoal rot of soybean [Glycine max (L.) Merr.] are unknown. Therefore, the severity of charcoal rot was studied at five levels of K (0, 37, 75, 111 and 149 kg K ha-1) and a level that was equal to the recommended fertilizer application rate based on annual soil K testing; and five levels of P (0, 10, 20, 30 and 40 kg P ha-1) and a level that was equal to the recommended P fertilizer application rate based on annual soil testing under field conditions in 2008, 2009 and 2010 at Jackson and Milan, TN, USA. Analysis of variance showed no significant effect from treatments or treatment-by-year interactions. However, analysis of colony forming unit (CFU) of Macrophomina phaseolina level from soil showed a significant effect from P but not from K application. Analysis using treatment as a linear trend effect indicated that tissue CFU as a function of K rates showed a positive but moderate significant slope at both Jackson (P=0.10) and Milan (P=0.08) in 2009 suggesting a modest increase in disease severity in that particular year. Further increase in K rate however, resulted in a negative slope at Milan (P=0.08) in 2010. The CFU from soil also showed a similar positive significant slope (P=0.03) for P in Milan in 2009 and 2010 (P=0.10) but not for 2008. Our results showed that increasing the K and P application rates over both the recommended rate and control (0 Kg-1ha) did not result in any consistent increase or decrease in disease severity of charcoal rot.