Water use profiles across the rooting zones of various pulse crops

Knowledge of crop water use at various soil depths is key to improving water use efficiency (WUE) for cropping systems in semiarid areas. The objective of this study was to characterize soil water extraction profiles across rooting zones for various pulse crops in a semiarid environment. We tested the hypothesis that water use profiles across the rooting zone vary between pulse species and among individual cultivars. Six dry pea (Pisum sativum L.), six chickpea (Cicer arietinum L.), 11 lentil (Lens culinaris Medik.) cultivars, along with fababean (Vicia faha L.), dry bean (Phaseolus vulgaris L.) and lupin (Sundial lupine L.) were grown in southwest Saskatchewan, 2008–2010. In the low-rainfall year, pulse plants extracted water mainly from the top 60 cm soil layer, and no water was extracted from the soil below 90 cm. In the moderate-rainfall year, pulses extracted an average of 9 mm water from the top 15 cm layer, 10 mm from the 15–30 cm layer, and <5 mm from each of the 30–60, 60–90, and 90–120 cm layers. In the high-rainfall year, pulse plants extracted about 4 mm of water from the top 30 cm layer, and extracted little to none below 30 cm soil depth; in the 30–120 cm layers, the soil under dry pea stored >85 mm of water and the soil under kabuli chickpea and fababean stored about 20 mm. Dry pea had the highest WUE among the pulses evaluated, averaging 8.3 kg ha−1 mm−1, and chickpea the lowest WUE especially in the wet year. No difference was found in water use profile or WUE among individual cultivars in dry pea or chickpea and only small differences existed among lentil cultivars. In semiarid areas, pulse plants extract soil water mostly from shallow depths, and the water in the deeper soil layers is left unused which could benefit deep-rooting crops the following year. Alternatively, improved pulse cultivars should be bred to utilize soil water that is available in the deeper rooting zones.