Seasonal Water Withdrawal Patterns of Spring Safflower Under Growth Stage Based Irrigation Managements.

In the semi-arid Southern High Plains, limiting water resources are influencing selection of crops. More drought hardy and deep-rooted crops are needed for sustainability of agriculture in the region. Safflower is regarded as a drought tolerant, deep rooting crop. Our objective was to investigate soil water extraction and water use efficiency (WUE) of spring safflower cultivars under different growth stage based irrigation managements. Field experiments were conducted at Clovis, NM during 2013 and 2014 seasons. Four irrigation treatments, i.e. stress at vegetative stage (Vst), stress at reproductive stage (Rst), non-irrigated or rainfed (Rfd) and fully irrigated (Irr) were randomized into a split plot design with four replications. Water content to the depth of 1.5 m was measured by neutron attenuation. Soil water extraction depth was not affected by cultivars and irrigation treatments; safflower extracted water to 1.5 m soil depth in both years. Net seasonal water extraction was highest in Rst treatment as compare to Irr, Vst and Rfd treatments in both years. During stress at vegetative stage, stressed treatment Vst extracted 45% and 20% more water as compared to Rst treatment in 2013 and 2014, respectively. When stress was applied at reproductive stage, stressed treatment Rst extracted 177% higher water than Vst treatment in 2013; however, in 2014, water was stored in the soil profile in all treatments at this stage and stored water in Rst treatment was 84% less than Vst treatment indicating more water use/extraction in Rst treatment. The WUE and seed yield did not differ significantly between Rst and Vst treatments; but these traits were higher in Rst treatment as compared to Vst treatment. Results support the cutting of irrigation at reproductive stage of safflower to obtain higher water extraction, WUE and seed yield under limited water conditions. In general, rooting depth of safflower did not change much in response to water stress, but water extraction during stress periods was increased to support the crop.