Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate

Department name when degree awarded

Plant Science

Committee Chair(s)

John O. Evans


John O. Evans


Howard B. Peterson


DeVere McAllister


The following herbicides were evaluated for their effect on perennial grasses and water pollution in El Salvador, Central America: MSMA (monosodium methanearsonate), DSMA (disodium methanearsonate), cacodylic acid (hydroxydimethylarsine oxide), paraquat (1 ,1 'dimethyl- 4,4'-bipyridinium ion), dalapon (2,2-dichloropropionic acid), amitrole (3-amino-s-triazole), atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)- s-triazine), diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea), and karbutilate (m-(3,3-dimethylureido)phenyl-t-butylcarbamate), The herbicides were sprayed on drainage channels at different dosage levels, Some plots received one application, others received two, and still others received three applications.

All herbicides except atrazine effectively controlled perennial grasses, Cacodylic acid was the most effective contact chemical, with dosage levels of 7 and 10 kg/ha achieving 77 percent control of the grasses after two applications, Four and 6 kg/ha of amitrole produced 67 percent during the same period, but control of amitrole then increased while control of cacodylic acid decreased.

After three applications, 5 kg/ha of MSMA yielded 88 percent control, MSMA was more effective than DSMA or dalapon, No significant increase in control was obtained by alternating dalapon and organic arsenicals.

A single application of 12 kg/ha of diuron and karbutilate effectively controlled perennial grasses for 6 weeks.

During the dry season, a single application of MSMA at 5 kg/ha, cacodylic acid at 10 kg/ha, and paraquat at 2 kg/ha each yielded over 70 percent control after 8 days.

Water samples were taken during rainstorms that occurred shortly after application of diuron, MSMA, and cacodylic acid, The highest concentration of diuron was 1,8 ppm, Samples containing MSMA and cacodylic acid were analyzed for arsenic, and in no case was the concentration greater than .5 ppm, These low concentrations likely would not be hazardous to crops, animals, or fish.