Crust management factors for some soils of the mid Western United States

A study was conducted to identify soil physical properties that best describe crust strength of three Illinois soils under vary¬ing rainfall intensity and mulch rate. Different rainfall intensities having the same drop diameter, used to supply the same rainfall amount to soil did not create different crust strengths in the three soils. Surface mulch rate differences significantly reduced crust strengths of the soils but was ineffective when the effects of moisture content and bulk density were removed. Increased soil water content after rainfall significantly controlled the variation in crust strength of the Blair soil but had no influence on crust strength of the Cisne and Drummer. High bulk density resulting from raindrop impact increased crust strength across all soils but the effect was mild at high mulch rates. High organic matter content in Cisne and Drummer resulted in increased cracking upon drying, an effect which greatly masked treatment effects. Crust strengths of Drummer and Cisne soils, both containing higher organic matter than the Blair, were slightly greater for "seed-surface up" than for "rain-surface up" orientations. The dependence of crust strength on briquette orientation in Cisne and Drummer soils indicates that in the absence of cracking, seedlings may experi¬ence greater crust resistance than is often measured by a downward force, e.g. by use of a penetrometer in situ. The regression equations revealed that for Cisne and Drummer soils, bulk density and orienta¬tion are the major factor controlling crust strength. Regression accounted for only a portion of the variation in crust strength in all soils, indicating that there were other unstudied factors controlling soil crust strength. This points to a need for a careful evaluation of the effects of soil physico¬chemical and mineralogical properties on crust strength.