Furrow irrigation of grain sorghum in a tropical environment. I. Influence of period of inundation and nitrogen fertilizer on dry matter production, grain yield and soil aeration

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Abstract
An experiment was conducted during the dry season in monsoonal tropical Australia to determine the influence of applied nitrogen (N) and period of inundation during furrow irrigation on the growth and yield of grain sorghum. Water was run in the furrows for 3, 6, 12 and 24 h at all irrigations, which were applied every 7-10 days throughout the season. A sprinkler irrigated crop was used to represent zero inundation. Increasing the period of inundation from 0 to 24 h at each irrigation reduced grain yield by 43.8, 49.5 and 43.2% for crops supplied with 0, 80 and 170 kg N ha-1 respectively. This yield reduction was associated with fewer grains per plant, grain weight having only a small influence on final yield. Air-filled porosity of the soil recovered more slowly as the period of inundation increased. The time taken to reach an air-filled porosity of 0.10 at the 10-20 cm depth interval was highly correlated with grain yield. The results indicate that grain yield is strongly influenced by the duration of waterlogging associated with flood irrigation. To minimize yield losses crops should be irrigated and drained rapidly to reduce the duration and severity of soil anaerobiosis.