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White Spot, Deep Tillage and Water Infiltration of the Portneuf and Related Silt Loam Soils

Rasmussen, W.W. and Cary, J.W. (1979) White Spot, Deep Tillage and Water Infiltration of the Portneuf and Related Silt Loam Soils. University of Idaho Current Information Series No. 460. University of Idaho College of Agriculture. 4 pp.


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The Portneuf silt loam and related soils of southcentral Idaho have formed from wind-laid material (loess) deposited over the thick lava of the Snake River Plains. Extensive areas of these soils are irrigated cropland. They are considered some of the most valuable and productive soils in Idaho. The soils have a lime (calcium carbonate) cemented hard-pan layer beginning about 14 inches below the surface and extending to depths of 30 or 40 inches in the soil. The hard layers allow irrigation water to move down but restrict most plant roots. Because of this, the water and nutrients that move through and below the hard layers are only slowly available to most annual crop plans. These high silt soils are extremely susceptible to erosion, especially under the common methods of furrow irrigation. Land grading has further depleted the valuable topsoil on many fields. If the fields are cut and graded, or severely eroded, material from the hard layers may be brought to the surface by tillage. Because of the hard layers' high lime content and low organic matter, the surface color becomes lighter and is known as a white spot. Crop yields from white spots are reduced. The loss of valuable topsoil and the resultant depleted soil fertility are considered the most important soil problems in this region of Idaho. Methods for eliminating soil erosion caused by irrigation and for improving the already eroded and denuded white spot soils are urgently needed.

Item Type: Technical Bulletin
NWISRL Publication Number: 0438
Subjects: Irrigation > Furrow irrigation > Infiltration
Soil > Tillage
Mass Import - autoclassified (may be erroneous)
Depositing User: Dan Stieneke
Date Deposited: 20 Nov 2010 21:58
Last Modified: 27 Oct 2016 15:21
Item ID: 1162

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