Static chambers are commonly used to provide in-situ quantification of nitrous oxide (N2O) fluxes. This research aimed to study the effects of static chamber bases on water and N distribution and the subsequent impact on N2O fluxes in drip irrigation. N2O emissions were measured in a drip-irrigated avocado orchard for two years, using bases with a dripper at their center (In) and bases installed adjacent to the dripper (Adjacent). During the irrigation/fertigation season, the measured N2OIn fluxes were 3.8±0.56 times greater than the fluxes from the chambers adjacent to the dripper (N2OAdjecent) (0.015 ± 0.003 vs. 0.006 ± 0.001 g m-2 d-1), and the cumulative N2O emission were 40% – 70% higher.
Three-dimensional simulations of water flow, nitrogen (N) transport and N transformations showed two opposing phenomena (a) increased water contents, N concentrations, and downward flushing when the dripper is placed inside the base, and (b) hampering of the lateral distribution of water and solutes into the most bio-active part of the soil inside the base when the base is placed adjacent to the dripper. It also showed that both “In” and “adjacent” practices underestimate the “true” cumulative flux from a dripper with no base by ~25% and ~50%, respectively.
A nomogram in a non-dimensional form corresponding to all soil textures, emitter spacings and discharge rates, was developed to determine the optimal diameter of an equivalent cylindrical base to be used along a single dripline.