Soil moisture and soil frost regimes under annual, perennial and agroforestry Crops in Waseca, Minnesota.

Abstract

The potential for agroforestry and other perennial crops to provide hydrologic benefits is of interest in the Minnesota River Basin, where the landscape is dominated by annual row crops and the river is plagued by water quality and quantity issues. Perennial herbaceous and woody crops are thought to have higher annual consumptive use of water than annual corn-soybean crops, influencing antecedent water status, creating more water storage, potentially decreasing discharge, and reducing the duration of soil frost and prevalence of concrete soil frost in the early spring. Quantification of potential hydrologic benefits is needed to provide support for more sustainable agroforestry and other alternative cropping practices in the basin. To this end, in the summers of 2004 and 2005, biweekly measurements of soil moisture under one annual crop (corn/soybean rotation), two perennial herbaceous crops (perennial flax and Illinois bundleflower) and two woody crops (hybrid hazelnuts and hybrid willow) were taken on replicated experimental plots at the University of Minnesota’s Southern Research and Outreach Center in Waseca, Minnesota. Similar measurements were taken in a stand of mature hybrid poplar and a field planted in a corn/soybean rotation. Likewise, soil frost depth, duration, and type were measured under the same crop types during the intervening winter. Analysis of soil moisture data showed few significant differences in soil moisture between the various crop types on the experimental plots, perhaps due to a combination of the perennial and agroforestry crops being in the establishment phase and unusually wet weather. The mature poplar stand had consistently drier soils than the cornfield during the 2004 season, although these differences disappeared during the course of the 2005 season, likely due to a change in management of understory plant cover in the poplar stand. During the winter, no significant differences in soil frost duration or type were observed, likely due to uniformly wet fall soil conditions, a lack of snow during the coldest part of the winter and rapid spring warm up. Thus, agroforestry and herbaceous perennial crops appear to provide little hydrologic benefit during the establishment phase or in winters with low snowfall, but when mature or in winters with heavier snowfall, could have the potential to provide such benefits.