Chapter 16 - Simulated effects of land use, soil texture, and precipitation on N gas emissions using DAYCENT

Abstract

This chapter discusses simulated effects of land use; soil texture; and precipitation on N gas emissions using DAYCENT. The chapter describes the N gas flux submodel used in the DAYCENT ecosystem model and demonstrates the ability of DAYCENT to simulate the low N gas emissions observed from native soils, the intermediate emissions associated with dryland agriculture, and the high emissions observed for irrigated agricultural soils. DAYCENT has been used to compare N gas emissions from soils for native range grass, winter wheat conventional till and no till, winter wheat/corn/fallow no till, irrigated corn and irrigated silage cropping. NOx made up the majority of N gas fluxes in all cases followed by N2O and N2. Soil water inputs, tillage, timing of crop/fallow periods, and fertilizer application interact to control N gas emissions so generalizations regarding land use are difficult to make. Switching to no till without changing the winter wheat cropping schedule resulted in higher N2O emissions because the increased soil water content induced by no till supported higher denitrification rates. Finally, the soil water savings associated with no till also allows a reduction in the fallow period and the 3-year winter wheat rotations had lower N2O and NOx emissions than the 2-year winter wheat/fallow systems considered.