Studies on the Damage to Upland Crops Caused by Weeds

II. The Effects of Weed Competition on the Growth and Yield of Crops

Abstract

In upland rice, peanut, corn and soybean field, non-weeding, once-weeding and twice-weeding treatments were done, for the purpose to know the effects of weed competition on the growth and yield of crops.
1) The composition of weed community was changed after weeding, namely, in weeding plot smaller broadleaf weeds, umbrella sedge and later emerging gramineous weeds grew much than non-weeding plot. But the aspect of this change was differented between wide spacing and dense spacing of crops.
2) Effect on growth of crops by weed competitive stress was appeared as decreasing stem or branch number of upland rice, peanut and soybean, and also plant height of corn.
Yield decrease of crop was resulted from the poor ripening more than decreasing of panicle or pod number.
3) Degree of damage to crops due to weeds can be estimated by measuering the ratio of crop weight to total community weight at 50 days or later after sowing.