Influence of Climate, Management and Previous Field History on Decomposition and Litter-C Accretion in No-till Maize-Based Agroecosystems.
Amy Kochsiek, University of Nebraska-Lincoln, University of Nebraska-Lincoln, 848 Manter Hall, Lincoln, NE 68588 and Johannes Knops, School of Biological Sciences, University of Nebraska-Lincoln, 348 Manter Hall, Lincoln, NE 68588.
Post-harvest, the litter carbon (C) pool of maize-based no-till agricultural systems comprises about 15-20 % of the system's overall C pool. Therefore, understanding the dynamics of the litter-C pool and the controls on decomposition of this pool is very important in determining the overall C dynamics of the system and potential of a system to sequester C. Litter decomposition and buildup of litter can be impacted by past field history (amount of litter-C remaining from past litter cohorts), present field management, and climate and these factors can directly influence decomposition by creating hospitable environments for soil decomposers or indirectly influence decomposition through changes in initial litter tissue quality. In order to understand the influence of these factors, we investigated initial litter tissue quality and in situ decomposition of maize and soybean litter using four annual litter cohorts (2001-2004) in three no-till management regimes: irrigated continuous maize, irrigated maize-soybean rotation, and rainfed maize-soybean rotation. We found that climate and field management interact to impact initial tissue quality. Dry years can lead to over-fertilization in the rainfed field, which then leads to increased % N in plant tissues. Our data also point to the fact that climate alone can impact initial tissue quality as we saw differences among years for the irrigated continuous maize site. Ultimately, changes in initial tissue quality among management regimes or years did not impact long-term decomposition rates. While indirect impacts on decomposition and litter pool build up through enhanced litter tissue quality seem unlikely, direct impacts of climate and management are plausible. Because maize-based agricultural systems have been identified as having high C sequestration potential, identifying the important factors controlling the dynamics of litter-C pools in these systems will help in understanding litter-C pool accretion and the probability of overall C sequestration.