The Weed Seed Population of Arable Soil: II. Influence of Crop, Soil and Methods of Cultivation Upon the Relative Abundance of Viable Seeds

Abstract

The weed seed population is greatly influenced by the type of crop grown, and although the composition of the flora on land carrying continuous wheat or barley is very similar, the numbers are lower in the latter case owing to the spring cultivation. The effect of fallowing or cultivation processes on weeds varies with the different species, and although most weeds are reduced by fallowing, either a reduction or increase may be brought about by cultivations on cropped land according to the species. Some weeds respond similarly to both operations, whereas others show a difference in behavior in the two cases. The results depend on the correlation between the times at which the operations are carried out and the period of maximum germination of the species coupled with the length of its natural dormancy. Unless fallowing operations can be carried out with a much greater degree of thoroughness than is usual, reduction of many weeds can be effected almost as well and more economically by intensified cultivation while the land is under crop. Other species, however, which tend to increase in some seasons under crop conditions, may be more effectively dealt with by fallowing if their predominance justifies the expense.