Tillage and Fertilizer N: Temporal Change in Corn Yield Response.

Temporal changes in the pattern of crop yield response to tillage and fertilizer input are common in long-term research. Changes in yield responses in two long-term (40 and 25 yr) monoculture corn (Zea mays L.) tillage by N rate trials were evaluated. There was a tillage by N rate interaction on corn yield, and the nature of the interaction has changed with time. The yield response to tillage became increasingly negative with time, though more slowly with adequate N nutrition. The response to fertilizer N became increasingly positive, especially at higher N rates in tilled systems. No-till corn yields are greater, at lower N rates, demonstrating the superior agroecosystem functions (water and nutrient storage capacity) of soil under no-tillage soil management.