Sunflower water productivity in four Great Plains soils

Sunflower (Helianthus annuus L.) is a drought-adapted crop whose short growing season reduces irrigation requirements which 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-adapted crop, maximum yields may be difficult to achieve due to the climatic conditions in the southern Great Plains.

► Irrigation increased crop yield by 0.22 g m−2 mm−1 in the fine sand and 0.63 g m−2 mm−1in the clay loam.
► Crops in sandy soils tended to produce larger yields with deficit irrigation compared with those in clay and silt loams.
► Beginning plant available water was important for crop yield in the clay loam under deficit irrigation.
► The crops in the fine sand had the largest water productivities and the crops in the clay loam the lowest.