|Loecke, T -|
|Liebman, M -|
Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 14, 2012
Publication Date: April 26, 2012
Citation: Loecke, T.D., Cambardella, C.A., Liebman, M. 2012. Synchrony of net nitrogen mineralization and maize nitrogen uptake following applications of composted and fresh swine manure in the Midwest U.S. Nutrient Cycling in Agroecosystems. 93:65–74. DOI:10.1007/s10705-012-9500-6. Interpretive Summary: The major soil nutrient limiting crop production in upper Midwest corn-based cropping systems is nitrogen (N). Plant available forms of N are released through mineralization into the soil after application of fresh or composted animal manure and/or chemical fertilizer. Ideally, corn uptake of N should be synchronized in space and time with availability of soil inorganic N in order to insure maximum crop productivity and minimal loss of N to the environment. We conducted experiments for two consecutive years to test the hypothesis that spring application of composted swine manure results in greater synchrony between soil N supply and corn N demand than spring application of fresh swine manure. We found that corn plants accumulated 23% more N after application of composted manure compared to fresh manure even though seasonal patterns of N mineralization and inorganic N were similar for composted and fresh manure. This suggests that soil N availability may not be the only factor determining corn plant N uptake in these cropping systems. Results of this research will impact producer decisions about nutrient management in farming systems that utilize manure.
Technical Abstract: Understanding how the quality of organic soil amendments affects the synchrony of nitrogen (N) mineralization and plant N uptake is critical for optimal agronomic N management and environmental protection. Composting solid livestock manures prior to soil application has been promoted to increase N synchrony; however, few field tests of this concept have been documented. Two years of replicated (r = 4) field trials were conducted near Boone, Iowa to determine the effect of composted versus fresh solid swine manure (i.e., hoop house manure) on Zea mays (maize) N uptake, in-situ soil net N mineralization, and soil inorganic N dynamics. Composted manure amended soils increased maize N accumulation 23% more than fresh manure (application rate of 340 kg N ha-1). Seasonal total in-situ net N mineralization was similar with composted and fresh manure applications. Net changes in soil N budgets (mineralization and soil inorganic N) in the surface 20 cm accounted for an average of 39% of the total plant N accumulation from manure amended soils. The timing of treatment differentiation in maize N uptake differed greatly between years, yet it did not indicate that soil N availability caused the maize N accumulation differences in either season. This finding was not possible without intensively and simultaneously studying the temporal dynamics of plant and soil N processes. The implications of this non-N effect on plant N uptake and whole system N cycling are unknown, yet warrant further investigation.