The Effect of the Digestive Tract of Farm Animals and the Fermentation of Manures upon the Viability of Certain Weed Seeds

Weed seeds are scattered over the farm artificially and naturally. Many times man distributes weed seeds when he plants his crop by using crop seeds which contain weed seeds. Again he may scatter many weed seeds when he manures his land. Animals distribute seeds by carrying them in their hair as they do the cockle bur and sand bur, or they may eat certain seeds and pass them through the digestive tract unharmed and viable. Nature has provided many ways in which to distribute seeds but the two most important natural agencies are wind and water. Annual weeds can be quite easily controlled by cultivation, thereby keeping them from going to seed. The perennial weeds, especially those propogating vegetatively by rhizomes and rootstocks are very difficult to eradicate when once started on a farm. Therefore, the greatest precaution should be taken to avoid introducing noxious weed seeds on the land. The prevalent belief that weed seeds pass uninjured through the digestive tract of farm animals and still remain viable is based mostly upon observation and to some extent upon experimental results. The purpose of this investigation is to determine the percentage of weed seeds that will pass uninjured through the digestive tract of different farm animals, the percentage of recovered seeds which are viable, and how long they will remain viable in a manure pile which is going through the process of fermentation and decomposition. The seeds of eleven common species of noxious weeds were selected to be used in this investigation: velvet weed, bindweed, sweet clover, smart weed, peppergrass, smooth dock, horse nettle, cockle bur, puncture vine, foxtail and wild rose. Advisor: F. D. Kei