Depletion and movement of water beneath cereal crops grown on a shallow soil overlying chalk

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Abstract
SUMMARY: Changes in water storage and gradients of water potential were measured beneath cereal crops grown on Andover soil series for three seasons. The measurements showed that depletion of water from the soil (0‐0.3 m) was 20–29% of the total profile depletion and that from the chalk/soil and chalk layers was 71–80%. Rain showers rewet the soil so that depletion from the non‐soil layers contributed about 35% of the total water use despite containing only 12% of the roots.Water in the chalk/soil and chalk layers was held at matric potentials between – 200 and – 800 kPa and gradients of hydraulic potential indicated upward movement from depths of almost 3 m. Comparisons of measured water depletion beneath the root zone with estimates of upward movement to the rooting zone indicate that substantial upward movement is possible, although the estimates were generally larger than the measured depletion.The estimated contribution of the water moved to the root zone for shoot dry matter production was 8% and 22% for winter and spring cereals respectively.