Soil health changes from grassland to row crops conversion on Natric Aridisols in South Dakota, USA

Abstract

In the northern Great Plains vast amounts of native grassland have given way to crops, mostly small grains and corn, over the past half century. It is well understood that over the long-term, grassland conversion accelerates erosion and generally decreases many soil functions. It is less clear, however, what short-term effects occur to the soil from grassland conversion; after the first or second year of conversion. The objectives of this study were to assess the short-term (first year) effects of converting land that is considered long-term grassland to small grain production through either conventional tillage (CT) or no-till (NT) practices using various indicators of soil health and to demonstrate how tools such as the Comprehensive Assessment for Soil Health (CASH), can be used to document soil health indicator decline immediately upon conversion from grassland to small grains. The CASH offers a suite of chemical, physical and biological soil tests to broadly assess soil health. In general, these indicators showed a more rapid decline in soil health under CT than NT. After the first year of grassland conversion, aggregate stability declined by 7% and 19% in the NT and CT plots, respectively when compared to the grassland control. Likewise, CT produced significantly greater declines in permanganate oxidizable carbon (POX-C) and soil protein (ACE-Protein), particularly under reduced precipitation. This study highlights how the CASH can provide an intuitive framework for monitoring the effects of land use change and can be used by land managers to identify potential soil constraints and formulate potential interventions.