Tuesday, November 14, 2006 - 4:00 PM

Soil-Plant N Resiliency - What is It and What Produces It?.

John J. Meisinger, BARC-East, 10300 Baltimore Ave, Bldg 163F Room 6, Beltsville, MD 20705-2350, James Schepers, Univ of Nebraska, 113 Keim Hall, Lincoln, NE 68583-0915, Larry Bundy, Univ of Wisconsin, Dept of Soil Science, 1525 Observatory Dr, Madison, WI 53706-1299, William Raun, 044 N Ag Hall, OK State Univ, Dept of Plant & Soil Sciences, Stillwater, OK 74078-0507, and Gyles W. Randall, Univ of Minnesota, Southern Research and Outreach Center, 35838 120th St, Waseca, MN 56093-4521.

A common observation in multi-year or multi-location N-response studies is the capacity of the soil-plant system to vary plant available N with growing conditions, this characteristic is termed soil-plant N resiliency.  Soil-plant N resiliency is not a newly discovered attribute, it has been observed by several generations of soil scientists, but its importance in N management schemes has not been fully appreciated. Nitrogen resiliency is a general biological characteristic of the soil-plant N cycle that is thought to be caused by soil and crop factors that interact with each other, and the environment, to produce higher grain yields on N-stressed plots in years with high-yield potentials and lower yields on the same plots in low-yield potential years. Some possible soil factors contributing to N resiliency are higher organic-N mineralization rates in good years, and/or higher N recovery efficiencies resulting from lower leaching and/or lower denitrification losses. Potential crop factors contributing to resiliency include a higher percentage distribution of fixed C into the grain compared to the roots in good years, or simply a greater total production of dry matter. The weather in high-yield years also interacts with N resiliency components with high solar radiation and ample rainfall contributing to higher photosynthesis vs. respiration rates, and/or higher transpiration rates that would transport more nitrates to the crop root surfaces. These explanations are necessarily speculative, because soil-plant N resiliency has not been systematically studied. Hopefully, a renewed interest in this characteristic will encourage future research studies that will expand our understanding of this characteristic.  An increased comprehension of soil-plant N resiliency would improve its application to N recommendations, could identify management practices to enhance resiliency, and would permit improved communication of this characteristic to producers.