Conclusions
Agricultural land spreading of tank bottoms from Williston Basin oilfields may successfully grow crops in the same year as the application with a loading rate of 0.6%. If a loading rate of 6% is used, it is unlikely that the soil will grow crops, largely due to lack of water infiltration. Large, frequent applications of fertilizer may be required to maintain nitrogen concentrations that are favorable for the oxidation of oil by microbes. Application of manure appears to be beneficial due to its effect of increasing water infiltration and retention, and may promote plant growth within a few years following a 6% loading rate.
Although this study offers encouragement for future collaboration between farmers and oilfield operators in dealing with tank bottoms, additional research is necessary. Because the soil may be rendered hydrophobic by the oil, there should be assurance that the practice of spreading tank bottoms on agricultural land does not bring a legacy of poor crop performance.