Tail‐drain sediments are a potential hotspot for nitrous oxide emissions in furrow‐irrigated Vertisols used to grow cotton: A laboratory incubation study

Abstract

The impacts of soil properties and urea fertigation on nitrous oxide (N2O) emissions from uncropped areas of furrow‐irrigated Vertisol paddocks are unknown. We sampled soils from the head‐ditch end (upslope) and sediments from the tail‐drain end (downslope) of 10 Vertisols under irrigated cotton (Gossypium hirsutum L.) production in northeastern Australia. Four replicates of each sample were incubated in open‐top polyvinyl chloride (PVC) chambers at 25 ± 2°C for 25 d. Nitrous oxide emissions were measured periodically after simulated irrigations on Days 0 and 15 with either water or, for soils, urea solution. Compared with the soils, sediments were enriched in silt, total organic carbon (TOC), total nitrogen (TN), ammonium N, and dissolved organic C (DOC) but had lower pH and sand content. Sediments emitted more N2O than soils from the same paddocks after water irrigations. Nitrous oxide fluxes varied by two orders of magnitude between paddocks, with most variation explained by baseline nitrate N, TOC, pH (inversely), and sand content. Urea solution applied to soils at 30 kg N ha−1 irrigation−1 increased N2O emitted, but more so after the second irrigation. In irrigated cotton systems, tail‐drain sediments are a potential hotspot for N2O emissions that has not previously been documented.

Cause of Death: Phytophthora or Flood? Effects of Waterlogging on Phytophthora medicaginis and Resistance of Chickpea (Cicer arietinum)

“…Soil moisture probes (EP100GL-80, Eviropro ® , Golden Grove, Australia) were inserted into representative control, early and late waterlogging treatments to determine the timing of manual watering (2-3 L rainwater) at approximately 80% field capacity 20 cm below the soil surface. Water holding capacity of potting media was determined using a modified version of the Schwenke et al [25] method to calibrate moisture probes. All bins were initially flooded for 24 h then drained for 48 h prior to sowing.…”