Weeds as Indicators of Soil Conditions


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By Jessi Cinque

Advised by Dr. Mark Boudreau
presented 11 Nov 1996

Anecdotal information and farmer’s folklore suggest that weeds are indicative of specific soil conditions. However, little research has been done to evaluate these claims. The purpose of this study was to methodically test two suggestions: Chenopodium album (common lamb’s quarters) will indicate phosphorus levels; and presence of Polygonum persicaria (common lady’s thumb) will indicate low pH. A greenhouse study was conducted to test the hypothesis that there is a positive correlation between the growth of C. album and the amount of available phosphorus. Potted plants were grown with different levels of available phosphorus. Average weight gained was determined for each treatment; ANOVA and Turkey Multiple Comparisons were performed. The data from this study support the hypothesis, (p<0.01). A field study was conducted to test two other hypotheses. One, that there is a positive correlation between populations of C. album and available phosphorus; and two, test weeds, as well as all other weeds, were identified and counted. Simple linear regression was performed on plant populations versus soil parameters. The data collected do not support either hypothesis; however, a positive correlation between P. persicaria and pH was found (p=0.0543). Correlation was also determined between other weeds and available phosphorus and/or pH. There are countless variables in the field which likely account for variation in the data.