Irrigation of Dwarf Wheats in the Yaqui Valley of Mexico

SUMMARY The response of the latest wheat cultivars to irrigation regimes was studied between 1970 and 1975 in a heavy soil of the Yaqui Valley of north-west Mexico. Yield showed greatest sensitivity to water shortage in the period 65–110 days after seeding (spike emergence around 90 days), due largely to responses in grains/m 2 . More frequent irrigation increased yields 5–10% over the average of 7 t/ha obtained with the commonly-adopted five irrigation regime. Various irrigation criteria were tested: potential evapotranspiration calculations seemed the most useful. Measurement of leaf permeability (with an air flow porometer) showed more promise than the use of plant water potential (measured with a pressure chamber).