PARENT SESSION
Poster Session 24: Agro-Ecology
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Interaction between organic and mineral resource inputs on emissions of CO₂ and N₂O from different soil textures and residue qualities.

Gentile, Roberta^*,1, Nhamo, Pauline¹, Vanlauwe, Bernard², van Kessel, Chris¹, Six, Johan¹, ¹ University of California, Davis, CA² TSBF-CIAT, Nairobi, Kenya

ABSTRACT- Increasing concern about the long term sustainability and high environmental costs of agroecosystems supports the need for increased understanding of ecosystem nutrient use efficiency and C cycling. Combining mineral with organic resource inputs of certain residue quality classes may benefit plant N uptake, reduce N loss, and promote C stabilization. This study examines the controls of resource inputs on C and N cycling across a range of soil textures. We hypothesized that combining organic and mineral resources would enhance C stabilization and potential N availability relative to either input alone, due to their controls on residue decomposition and soil aggregate turnover. Organic and mineral resources labeled with ¹³C (1300-1700 ¹³C) and ¹⁵N (40 atom% ¹⁵N) were incubated with 200 g soil in a microcosm experiment. Input treatments consisted of organic residue, mineral N, and a combination of both with either the organic or mineral resource ¹⁵N-labelled. Inputs were added to four different textured soils: clay, clay loam, sandy loam, and sand. Additionally, organic inputs characterized by three residue quality classes differing in N, lignin and polyphenol contents were applied to the clay soil. Emissions of CO₂ and N₂O and their isotopic signatures are reported for the first 90 days of the experiment to assess the mineralization and system losses of C and N. Preliminary results have supported our hypothesis of reduced C and N losses with combined inputs compared to sole applications of either resource. The application of this relationship across all soil textures and with different residue quality inputs is discussed.

Key words: residue quality, mineralization, carbon dioxide, nitrous oxide