SECTION II 



REC OMME ND AT I ON S 



Simple, reliable techniques are urgently needed for nutrient 

 assay in lakes and streams. This project was an initial 

 effort to develop and apply plant analysis as a nutrient 

 assay. The results suggest plant analysis is a promising 

 technique. However, additional work is recommended to 

 verify this promise and to further refine the technique. 



Critical concentrations and index segments should be 

 established in macrophytes other than the two species used 

 in the work on this project. It would be desirable to 

 know if the critical concentrations for Elodea occidentalis 

 and Ceratophylum demursum were generally applicable to 

 macrophytes. It also seems desirable to develop plant 

 analysis using aquatic organisms other than macrophytes. 

 A filamentous, green alga which is responsible for 

 nuisance conditions seems a suitable possibility. 



Determining whether analysis for the total concentration 

 of an element or for an extracted fraction more reliably 

 correlates with yield also would be desirable. In 

 agricultural applications, for some elements and in some 

 species extracted fractions have been found more reliable 

 than total concentrations. 



Further evaluations of the plant analysis technique should 

 be made using the organisms and critical concentrations 

 established on this project. This would involve additional 

 samplings of Elodea and C eratophylum from Wisconsin lakes 

 differing in fertility. Further tests with the assay 

 species isolated in floating, porous baskets and sampled 

 through the summer, as initiated on this project, also 

 seem highly desirable. An effort should be made to obtain 

 samples of natural populations of macrophytes from lakes 

 in other parts of the United States in which deficiencies 

 of specific elements have been indicated. Analyses would 

 be compared with critical concentrations established on 

 this project to verify the suggested deficiencies and the 

 usefulness of the plant analysis technique. 



Results on this project suggested macrophytes in some 

 northern Wisconsin lakes are copper deficient. Copper 

 becomes growth limiting. This must be verified. If 

 true, the copper requirements of other nuisance aquatic 

 plants should be studied. 



