Assessing the relationship between soil health and water quality in the St. Joseph River watershed
Soil health has become a popular topic of interest amongst researchers, conservationists, policy makers, and producers. It is believed that a healthier soil can improve both productivity and water quality. The objectives of this two year study were to (1) evaluate soil health under two management systems, a no-tillage system under a two year rotation (NT-2yr) and a conventional tillage system under an eight year rotation (CT-8yr) at the landscape scale (summit, backslope, footslope) using a specific set of physical, chemical and biological soil parameters to detect short-term changes in soil conditions and processes which could lead to water quality concerns and (2) determine if relationships exist between soil health and water quality in agricultural landscapes. Composite soil samples from two depths (0-5cm, 5-20cm) were collected after harvest from fifteen sites in five fields located in the St. Joseph Watershed in northeastern Indiana. Fields 1 and 2 were managed under continuous no-tillage and were in an annual corn-soybean rotation. Fields 3, 4, and 5 were managed under conventional tillage and were in an eight year rotation between corn, soybean, oat, wheat, and alfalfa. To determine the overall soil health for each of these fields, a series of physical (bulk density, porosity, aggregate stability, particle size distribution, water filled porosity), chemical (pH, EC, TN, CEC, extractable nutrients), and biological (SOM, SOC, PNM, respiration) were conducted. Water quality sensors installed in three of the five fields collected both surface runoff and tile drainage, which were analyzed for sediment and nutrient loads and concentrations. The water data results were used in conjunction with the results from the soil quality tests from these fields, to determine if soil health has an impact on water quality. The CT-8yr treatment had an overall healthier soil as compared to the NT-2yr treatment, indicating that the influence of crop rotation on overall soil health was much stronger than the influence of tillage operations, in this study. In comparing the landscape positions the FS position showed evidence of having the healthiest soil properties. In evaluating the effects of soil health on water quality, there were no direct links observed. Overall the relationship between soil health and water quality was observed as very complex, influenced strongly by many external factors that are highly variable. Additional years of research are required to better understand the interactions that are occurring between soil parameters and water quality at the field scale.
Smith, Purdue University.
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