Response of Three Irrigated Crops to Deep Tillage of a Semiarid Silt Loam
1979
Cary, J. W. | Rasmussen, W. W.
The growth and water relations of winter wheat (Triticum aestivum L.), sugarbeets (Beta vulgaris L.) and corn (Zea mays L.) were studied after deepening the root zone in the Portneuf silt loam soil (Durixerollic calciorthid). Roots of annual plants are largely restricted by a hard layer that lies between the 0.4- and 1-m depths. This layer was disrupted to a depth of 1.2 m by complete mixing, by chiseling, or by trenching on 0.6- and 1.2-m centers. The treatments included two irrigation levels to show any advantage in crop water relations due to deeper rooting after deep tillage. Deeper rooting did develop on the deep-tilled treatments, but the water supplied through net soil moisture depletion below 0.6 m was increased by < 4 cm, even when the crop was stressed for water late in the season. Deep soil water extraction was not always proportional to rooting density. Trenching on 0.6-m centers was the most favorable treatment. Completely mixing the soil decreased yields, due in part to a lighter surface color and lower soil temperatures. Deep tillage seldom had a measurable effect on stomatal resistance or plant water potential. Management of this soil should be concentrated on providing the best possible root environment in the top 0.5 m of soil as this is the basis for maximum production in irrigated agriculture.
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