Evapotranspiration, daily water use, and soil water depletion by Feekes scale (7) growth stages of N‐fertilized winter wheat (Triticum aestivum, L. ’Winalta’) were measured under dryland field conditions. Fall‐applied N (NH4NO3) rates were 0, 67, and 268 kg/ha (0, 60, 240 lb/a). Soil water measurements were made at weekly intervals with a neutron moisture meter. Soil NO3−N to 183 cm (6 ft) in early spring was 21 kg/ha 19 lb/a). ET for the spring‐summer growth period was 22.1, 27.2, and 31.5 em (8.7, 10.7, and 12.4 in.) for the respective N treatments. Daily ET reached maximum values at the headed‐to‐flower stage. Soil water extraction was largely limited to the upper 91 cm (3 ft) with no N. With N, the wheat extracted water to 183 cm. Stored soil water supplied 6.1, 11.2, and 15.5 cm (2.4, 4.4, and 6.1 in.) of water to the wheat grown on the three N treatments. This was 30, 55, and 76% of the plant available water to 183 cm. At maturity, there was 18.0. 13.2, and 9.6 cm (7.1, 5.2, and 3.8 in.) of plant available water remaining in the soil to a depth of 183 cm. Grain yields were 1,610, 3,090, and 3,630 kg/ha (24, 46, and 54 bu/a). In addition to increasing ET, N increased water use efficiency by an average of 56%.
No takes yet. Share an insight, caveat, or question.
Paul L. Brown (1971) studied this question.