Studies On Ecological Weed Control in Pasture

1. Effects of Shading Treatment on the Growth and Chemical Composition of Weeds

Abstract

In order to obtain the basic information of ecological weed control in pasture, the experiment dealt with the effects of shading treatment on the growth and chemical composition of weeds. The weeds examined were Chenopodium album L. var. centrorubrum Makino, Commelina communis L., Artemisia vulgaris L. var. vulgatissma Bess. and Rumex obtusifolius L.
Three levels of shading treatments used in this experiment were non-shading, 70% and 85% of shading of solar radiation.
The results obtained were summarized as follows:
1. The growing rate of plant height was intensified or lowered by the shading treatments in Chenopodium album and Artemisia vulgaris respectively. On the other hand, the growing rate was not affected in Rumex obtusifolius.
2. The number of the plant leaf was decreased by the shading treatments in each weed, especially in Chenopodium album, Artemisia vulgaris and Commelina communis.
3. The leaf area of Artemisia vulgaris was remarkably decreased by the shading treatments, especially of higher level of shading, while that of Rumex obtusifolius increased with shading.
4. The fresh weight and the dry weight of the plant were considerably decreased by the shading treatments in Chenopodium album, Artemisia vulgaris and Commelina communis. But both of these weights were not decreased in Rumex obtusifolius.
5. The TAC% of the plant tended to decrease in proportion to the increase of the shading rate, but the T-N% of the plant tended to increase. Therefore, TAC: T-N ratio of the plant was lessened in proportion to the increase of the shading.
From these results, it is concluded that the effects of shading treatments on the growth of weeds vary with the kinds of weeds, namely, Chenopodium album, Artemisia vulgaris and Commelina communis remarkably respond to the shading treatments, whereas Rumex obtusifolius do not much respond to them.