A crop water stress index and time threshold for automatic irrigation scheduling of grain sorghum

Abstract

a b s t r a c tVariations of the crop water stress index (CWSI) have been used to characterize plant water stress and schedule irrigations. Usually, this thermal-based stress index has been calculated from measurements taken once daily or over a short period of time, near solar noon or after and in cloud free conditions. A method of integrating the CWSI over a day was developed to avoid the noise that may occur if weather prevents a clear CWSI signal near solar noon. This CWSI and time threshold (CWSI-TT) was the accumulated time that the CWSI was greater than a threshold value (0.45); and it was compared with a time threshold (CWSI-TT) based on a well-watered crop. We investigated the effectiveness of the CWSI-TT to automatically control irrigation of short and long season grain sorghum hybrids (Sorghum bicolor (L.) Moench, NC+ 5C35 and Pioneer 84G62); and to examine crop response to deficit irrigation treatments (i.e. 80%, 55%, 30% and 0% of full replenishment of soil water depletion to 1.5-m depth). Results from automated irrigation scheduling were compared to those from manual irrigation based on weekly neutron probe readings. In 2009, results from the Automatic irrigation were mixed; biomass yields in the 55% and 0% treatments, dry grain yields in the 80% and 0% treatments, and WUE in the 80%, 55%, and 0% treatments were not significantly different from those in the corresponding Manual treatments. However, dry grain yields in the 55% and 30% treatments were significantly less than those in the Manual control plots. These differences were due mainly to soil water variability in the beginning of the growing season. This conclusion is reinforced by the fact that IWUE for dry grain yield was not significantly different for 30% and 55% treatments, and was significantly greater for Automatic control at 80%. In 2010, there were no significant differences in biomass, dry grain yield, WUE, or IWUE for irrigation control methods when compared across the same amount treatments. Similar results between irrigation methods for at least the highest irrigation rate (80% of soil water depletion) in 2009 and among all irrigation treatment amounts in 2010 indicate that the CWSI-TT method can be an effective trigger for automatically scheduling either full or deficit irrigations for grain sorghum in a semi-arid region.Published by Elsevier B.V.

Irrigation Decision-making Methods Based on Multi-source Irrigation Information Fusion

“…Based on the measurement of cotton irrigation index (CWSI, soil moisture (gravimetric water content), and stomatal conductance) and its critical value [29][30][31][32][33][34] , membership functions were constructed. Using CWSI as the fusion factor, the membership functions were built.…”

Advanced Monitoring and Management Systems for Improving Sustainability in Precision Irrigation

“…Closed-loop irrigation strategies aim to irrigate: when the soil moisture content reaches a certain threshold [103][104][105]; when plant sensors indicate a certain stress threshold [93,106,107] or with feedback from crop simulation models with the aim of attaining a certain yield, crop physiological response or economic objective [108]. These closed-loop irrigation strategies have been shown to improve water use efficiency in the production of horticultural crops under protected environments.…”

Wireless Sensor Network Effectively Controls Center Pivot Irrigation of Sorghum

“…However, the largest mean WUE (2.04 kg m -3 ) resulted in I 55A% treatment plots. The automatic scheduling algorithm was a CWSI and time threshold method (O'Shaughnessy et al, 2012b). In 2010, the largest mean dry grain yields were similar to those in 2011, with yields of 0.71 and 0.63 kg m -2 produced in the automatic and manual I 80% treatment plots, respectively.…”

“…The integrated CWSI was based on the theoretical approach developed by Jackson et al (1981;1988). These calculations were thoroughly detailed by O'Shaughnessy et al (2012b). When triggered, 80%, 50%, 30%, and 0% of twice the daily peak crop water use (2 × 10 mm = 20 mm), designated I 80A% , I 50A% , I 30A% , and I 0A% , was applied to specific plots within the automatic sectors.…”