Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/8/2011
Publication Date: 1/14/2012
Citation: Tolk, J.A., Howell, T.A. 2012. Sunflower water productivity in four Great Plains soils. Field Crops Research. 120(1):120-128. Interpretive Summary: Sunflower is a drought-adapted crop whose seeds are used to make oil and whose short growing season reduces irrigation requirements. This makes it ideal for regions with limited irrigation water supplies. We evaluated the yield potential of sunflower under full and limited irrigation. We also wanted to determine if the differences in types of soils (clay loam, silt loam, sandy loam, and fine sand) affected how efficiently the sunflower crops could use irrigation water. We grew sunflower in 2008 and 2009 with irrigation treatments were 25%, 50%, 75% and 100% replacement of full crop water needs. At the lowest irrigation levels, the crops grown in the fine sand and sandy loam soils had the largest yields. Irrigation increased the seed yield of the crops in the fine sand more than that of the crops in the silt loam and clay loam. When comparing our yields to those from around the world, our yields were as much as 30% lower, even at the highest irrigation levels. Our smaller yields are probably due to the hot, dry conditions of our climate. The climate causes us to lose our irrigation water to evaporation and puts additional water stress on our crops, which results in yields being reduced.
Technical Abstract: Sunflower (Helianthus annuus L.) is a drought-adapted crop whose short growing season reduces irrigation requirements, makes it ideal for regions with limited irrigation water supplies. Our objectives were to a) evaluate the yield (Y) potential of sunflower under full and deficit irrigation (IR) b) determine if water productivity (WP) and irrigation water productivity (IWP) of sunflower were affected by soil textural class differences and c) compare the WP relationship to a benchmark maximum productivity relationship for consideration of limitations to crop yield in a semiarid environment. Sunflower was grown in 2008 and 2009 in 48 weighing lysimeters under an automated rain shelter containing soil monoliths of four regional soils - clay loam, silt loam, sandy loam or fine sand (12 each) - at Bushland, TX, USA, a semiarid region of the southern Great Plains. Irrigation treatments were 25%, 50%, 75% and 100% replacement of evapotranspiration. The regression of IR:Y for all soil textural classes showed that irrigation increased yield by 0.47 g m**-2 mm**-1 in 2008 and 0.51 g m**-2 mm**-1 in 2009. Averaged across irrigation treatments, the WP of the crops in the fine sand (0.54 kg m**-3) was larger than that of the crops in the silt loam (0.46 kg m**-3) and clay loam (0.44 kg m**-3). The IWP of the crops in the fine sand (1.0 kg m**-3) and the sandy loam (0.96 kg m**-3) were significantly larger than the IWP of the crops in the clay loam (0.72 kg m**-3). Yields were as much as 30% lower at full irrigation levels compared with benchmark maximum yields. Probable limitations to increased yield include high evaporative deficits and soil water evaporation. Although sunflower may be a drought tolerant crop, maximum yields may be difficult to achieve due to the climatic conditions in the southern Great Plains.