IMPROVING ALFALFA AND OTHER FORAGE CROPS FOR BIOENERGY, LIVESTOCK PRODUCTION, AND ENVIRONMENTAL PROTECTION
Location: Plant Science Research
Title: First-year corn after alfalfa showed no response to fertilizer nitrogen under no-tillage
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 2012
Publication Date: January 1, 2013
Citation: Yost, M.A., Coulter, J.A., Russelle, M.P. 2013. First-year corn after alfalfa showed no response to fertilizer nitrogen under no-tillage. Agronomy Journal. 105(1):208-214.
Interpretive Summary: The alfalfa-corn rotation is widely used by farmers because it is highly productive, it reduces the need for purchased fertilizer nitrogen, and it helps preserve soil quality. In the past, alfalfa has been killed by herbicides and intensive tillage, but many farmers have adopted reduced or no-tillage systems to reduce both costs and soil erosion. However, there are questions about how much fertilizer nitrogen is needed by corn grown after alfalfa in a no-till system. We conducted research to answer this question on six Minnesota farms and found that corn required only a small application of fertilizer nitrogen in this system. When we analyzed all the published information about this rotation, we discovered that no-till corn after alfalfa needs no additional fertilizer in two-thirds of the cases, which is similar to what occurs when the fields are tilled more intensively. Therefore, farmers can use the fertilizer nitrogen recommendations in both systems, which will save money and reduce environmental damage by excess nitrogen. Two tests that are used to predict fertilizer nitrogen need in continuous corn and soybean-corn rotations were not as reliable in our research, so these tests need to be revised for alfalfa-corn rotations. What remains to be discovered is how to identify which fields will show a response to added fertilizer, and this is the focus of our current research.
To determine the rate of fertilizer N required for first-year corn (Zea mays L.) after alfalfa (Medicago sativa L.) in a no-tillage system, on-farm experiments were conducted at seven locations in southern Minnesota and southwestern Wisconsin. The accuracy of the presidedress soil nitrate test (PSNT) and basal stalk nitrate test (BSNT) to identify the need for fertilizer N in first-year, no-tillage corn was also evaluated. Across the seven locations, no yield response to fertilizer N was observed for corn grain, cob, stover, or silage yield, confirming that alfalfa N credits can supply the entire N requirement of no-tillage corn following alfalfa. Soil NO3-N concentrations, according to the PSNT, were =18 mg NO3-N/kg at six locations where measured, indicating that sidedressed fertilizer N would increase yield according to the scale used in other U.S. Corn Belt states. The BSNT concentrations in non-fertilized corn were in the marginal range at two locations (between 250 and 700 mg NO3-N/kg) and optimum to excessive at the other four locations. Thus, both tests incorrectly predicted responses to fertilizer N, suggesting that the critical PSNT and BSNT concentrations may need to be lower than accepted levels for no-tillage corn following alfalfa.