High prices of fertilizer have many beef producers reconsidering their pasture fertility programs. Dr.’s Rob Kallenbach and John Lory at the University of Missouri offer the following suggestions for fertilizing pastures.
The core rules for making nitrogen fertilizer pay in forage systems have not changed: (1) Fertilize when the plant has a capacity to respond and (2) Maximize forage utilization. Fertilizer only pays if it increases the amount and/or quality of beef, milk or hay sold from your farm. High fertilizer prices favor farmers who harvest high quality hay and maximize forage utilization on pastures.
Another nitrogen option is inter-seeding a legume such as red clover, birdsfoot trefoil, or lespedeza. Legumes fix nitrogen from the atmosphere providing the nitrogen needed for their own growth and sharing some their nitrogen with neighboring grass plants.
Legumes transfer up to 20% of the nitrogen they fix to the surrounding grass. Legumes have the capacity to fix 50 to 300 pounds of nitrogen per acre so the potential contribution can be significant. Grass doubly benefits from the legume, it gains fixed nitrogen from nitrogen transfer and the grass benefits from reduced competition for the limited nitrogen already in the soil.
Tips for success with inter-seeded legumes include paying attention to soil nutrients. Phosphorus and pH are important! Legumes need a higher soil test values to succeed than do most grasses. In low fertility pastures legumes will germinate but fail to establish.
Do not apply nitrogen! Fertilizer nitrogen increases the competitive advantage of grasses hurting establishment of inter-seeded legumes. Missouri research demonstrated that as little as 25 lbs/acre spring nitrogen reduced lespedeza in a mixed sward and 100 lbs/acre essentially eliminated it. Low rates of nitrogen (up to 50 lbs/acre) may be considered in August to promote fall grass growth on established mixed stands.
Options for seeding include frost seeding and no-till drill. Optimum seed depth is ¼ inch and it is better to be too shallow than too deep. Recommended seeding rates are 4 lbs/acre for red clover, 6 lbs/acre for birdsfoot trefoil and 10 lbs/acre for lespedeza and alfalfa. The objective is a stand that is about 30% legumes. Minimize grass competition during establishment by keeping grass short when legumes are germinating. This can be accomplished through flash grazing or clipping in early spring.