Start Date: 2008
Principal Investigator: Michael Russelle
Organization: USDA Agricultural Research Service
Status: Complete
Background Info
Soil fertility affects alfalfa yield and quality. Potassium (K) plays a critical role in yield by moving sugars from shoots to roots, and then back again during regrowth. Additionally, K availability is crucial for optimum stress tolerance, including winter survival. However, because K fertilizer is expensive and forage with excessive K can cause problems as dry cow feed, it’s imperative that producers apply the most economic rate in order to maximize profit. As corn grain and cellulosic biomass production become more important in Minnesota, growers must be educated as to what minimum rates of fertilizer inputs will support maximum economic yields. Considering that corn stover likely will become a significant source of cellulosic biofuel, do the same fertilizer N and K recommendations apply as for corn grain?
Objectives
Determine alfalfa yield, forage quality, and final plant population in response to top-dressed K applied in spring of the last production year
Determine the fertilizer N requirement for corn after alfalfa that received different K rates
Determine the apparent fertilizer K carryover for corn when K is top-dressed on alfalfa
Calculate the net marginal economic returns for topdressing K on alfalfa during its last production year
Key Findings
There was no alfalfa yield response to potash.
Corn grain and silage yield did not respond to previous potash treatments or to fertilizer N, confirming that alfalfa provided sufficient N to the first corn crop. Corn yield was increased, however, by the addition of fertilizer K in spring.