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Title: Validating potassium fertilizer guidelines in alfalfa-corn rotations

item YOST, MATT - University Of Minnesota
item Russelle, Michael
item COULTER, JEFF - University Of Minnesota
item SHEAFFER, CRAIG - University Of Minnesota
item KAISER, DANIEL - University Of Minnesota

Submitted to: North Central Extension Industry Soil Fertility Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/22/2011
Publication Date: 11/16/2011
Citation: Yost, M.A., Russelle, M.P., Coulter, J.A., Sheaffer, C.C., Kaiser, D.E. 2011. Validating potassium fertilizer guidelines in alfalfa-corn rotations. In: Proceedings of the North Central Extension-Industry Soil Fertility Conference, November 16-17, 2011, Des Moines, Iowa. 27:20-27.

Interpretive Summary:

Technical Abstract: From 2008 to 2010, on-farm research was conducted on 10 fields with medium soil test K (STK) to validate Minnesota K fertilizer guidelines by determining the effect of K fertilizer applications on alfalfa yield and quality in its last production year and estimating the carryover of excess fertilizer K to first-year corn. We were surprised to find that no K fertilizer was needed to maximize alfalfa yield or overall forage feed value and quality. Luxury consumption of K occurred because as K application increased, alfalfa K concentration and K uptake increased. Even though 60 to 75% of the fertilizer K was not utilized by the alfalfa, this carryover K did not increase corn grain yield as efficiently as K applied directly to the corn. When K was applied to the corn, stover and silage yield were 10 and 8% higher, respectively, than corn that relied on carryover K alone. These results do not support the current medium soil test K (STK) range and demonstrate that applying K to first-year corn rather than last-year alfalfa may be more economical on medium- to fine-textured soils with medium STK.