Selection of flow rate and irrigation duration for high performance bay irrigation

• Published in: Agricultural water management Vol. 228; p. 105850
• Main Authors: Smith, RJ, Uddin, MJ
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 20-02-2020
• Subjects: Application efficiency; Border-check irrigation; Infiltration; Optimization; Simulation; Surface irrigation; Time to cut-off; Simulation; Border-check irrigation; Infiltration; Time to cut-off; Application efficiency; Optimization; Surface irrigation
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2019.105850

•A guidelines for high performance bay irrigation.•Higher flow rates and lower irrigation duration can deliver higher application efficiencies.•Preferred flow rates for the major soil groups are recommended.•A simple linear function can be used to estimate the irrigation duration at constant soil moisture deficit.
The maximum efficiency attainable by surface irrigation in any particular situation is determined largely by the soil infiltration characteristic and the flow rate onto the field. Performance evaluations have suggested that higher flow rates than those traditionally recommended can lead to increases of about 20% in the application efficiency of bay irrigation across the dairy regions of southern Australia. However, substantially reduced irrigation durations are required to realise these efficiency gains and greater precision is required in the selection and management of these shorter durations.
In this paper, infiltration characteristic curves representative of the predominant (cracking and non-cracking) soils of the region are used in the surface irrigation simulation model SISCO, for a range of bay lengths and soil moisture deficits, to determine: (i) the flow rates required to achieve the maximum efficiency on the bay irrigated soils of southern Australia; and (ii) the means for real-time estimation of optimum irrigation durations. The aim is provision of guidance to irrigators seeking higher efficiency through the use of higher flow rates.
Real-time estimation of optimum time to cut-off must recognise the substantial variations in infiltration within a soil type and with time due to changes in antecedent moisture content, and hence must be adaptive to the conditions prevailing at the time of any irrigation. A method for estimating time to cut-off (previously developed for furrow irrigation), is extended to the hydraulically more complex case of bay irrigation. The method is based on simple linear relationships between the advance time to a nominated point part way down the field and the time to cut-off. Its application to the management of irrigations is demonstrated using data from multiple irrigations of a single bay under varying soil moisture conditions.