ABSTRACT
The primary purpose of retaining or capturing snow by residue management in semiarid regions is to increase the supply of soil moisture for subsequent crops. Snow retention and capture are of major benefit in regions, such as the North American Great Plains, where blowing snow can result in considerable loss of moisture from the landscape. This moisture is often needed to supplement seasonal rainfall and to bolster spring crop production. In the Great Plains, rainfall during the growing season is typically low and is quickly lost from the surface or shallow depth in the soil due to high evaporative demand.[1]
Managing snow on the landscape is also beneficial for moderating soil temperatures and protecting dormant plants from freezing and desiccating. This is particularly important in cold regions where lethal soil temperatures can occur in the absence of snow cover during winter. Snow cover aids in reducing the depth of soil freezing which, in combination with duration of soil freezing, can affect hydrological processes such as infiltration and runoff. Snow retention or trapping also reduces the loss of water associated with sublimation of blowing snow. Sublimation can result in a substantial loss of precipitation in cold regions. Indeed, sublimation of blowing snow has been found to comprise 15-40% of the annual snowfall in the Canadian Prairies and up to 45% of annual snowfall in the arctic region of North America.[2]
POTENTIAL FOR SOIL WATER INCREASE
A relatively large portion of the annual precipitation occurs in the form of snow in the cold, semiarid regions of the United States and Canada. In the Northern
Great Plains of the United States, about 20% of the annual precipitation of 250mm to over 500mm occurs in the form of snow.[3,4] Steppuhn[1] indicated that in the Canadian Prairies, 20-30% of the annual precipitation of 300mm yr1 to over 500mm yr1 occurs as snowfall. Staple and Lehane,[5] Zentner et al.,[6] and Pomeroy and Gray[7] report somewhat different values for precipitation falling as snow on the Canadian Prairies. These studies suggest that from 30% to nearly 40% of annual precipitation occurs in the form of snow. The shortage of precipitation to sustain maximum crop production in cold, semiarid regions requires the use of management techniques that conserve winter precipitation. Conservation of winter precipitation is vital in the Great Plains where economical production of spring wheat requires the annual withdrawal of about 250-400mm of water from the soil.[8]
Indeed, Greb[9] suggested that sustainable crop production can only be attained in the Great Plains as a result of soil water recharge occurring from snowmelt.
