Studies on the Damage to Upland Crops Caused by Weeds

I. Competition between Upland Crops and Weeds

Abstract

From 1968 to '70, we have carried out experiments to clarify degree and pattern of the damage to upland crops due to the competition with weeds under non-weeding condition.
The results are summarized as follows:
1. Growth of weed was more influenced by the weight of large crabgrass and goosegrass than kinds of crops and its planting density.
2. Number of emergence of weeds was affected remarkably by kinds of crops, but the total number of weeds was decresed in late stage.
3. Patterns of weed damage to each crop-plants are as follows. Growth of sorghum was not affected by weeds, and this crop suppressed the growth of weeds very strongly.
Growth of upland rice and peanut was affected by weeds from middle stage.
In soybean (summer soybean) the ratio of crop weight to total community weight was largely reduced at late stage, caused by the defoliation before havesting time.
Corn showed the habitat segregation and it grew normaly together with weeds in the same field.