Safflower Oilseed Production Under Deficit Irrigation and Variable N Fertilization.

The production of oilseed crops represents a unique opportunity for PNW producers to provide a biodiesel feedstock for an emerging renewable energy industry.  The inclusion of oilseeds in rotation offers producers an alternative strategy to improve farm economies and gain additional benefits that improve soil and water conservation, reduce pest cycles, and diversify cropping systems.  Safflower (Carthamus tinctorius) is considered a low input and drought tolerant crop, but responds well with irrigation and fertilizers.  The objectives of this study were to determine: 1) Varietal responses of safflower to deficit irrigation and N fertilization under center pivot irrigation, 2) oil production and quality under deficit irrigation and N fertilization. Three safflower varieties S334, S345 and CW99OL were planted in April 2009-2011 under center pivot irrigation.  The experimental design was a strip-split plot with four replications. Standard irrigation and deficit irrigation were 725 mm and 555 mm, respectively. Safflower oilseed yields averaged 3100 kg ha-1 among years in for all treatments under center pivot irrigation. Safflower oilseed yields were significantly higher (+224 kg yield ha-1) under the 112 than 162 kg N ha-1 fertilizer rate in 2008. Indicating low N rates (<112 kg ha-1) are viable. Safflower oilseed yields were not significantly different between the 90 and 70% ET treatments. Indicating a potential 12 - 17 cm water savings using a deficit irrigation strategy. Deficit irrigation (70% of ET) had a positive effect on WUE with an average increase of 10 kg seed yield ha-1 cm-1 of water applied. Oil contents of the seed were 1.5 – 2.2% higher under deficit irrigation than under full irrigation following the higher yields and greater water use efficiencies.