The main objective of this study was to examine the effects of intraspecific competition on the growth and reproduction of yellow nutsedge. A field experiment was conducted to examine twelve tuber densities of yellow nutsedge, ranging from 1 to 1000 tubers/m$ sp2$. Results indicate that spring tuber populations of 100 tubers/m$ sp2$ and lower require close to 100% control of the infestation in order to prevent the yellow nutsedge population from increasing. Yellow nutsedge spring tuber population does not appear to influence tuber distribution in the soil profile. All tuber densities examined produced the greatest proportion of tubers in the top 20 cm of the soil profile. Tuber and shoot production increased as initial yellow nutsedge tuber populations increased from 1 to 1000 tubers/m$ sp2$, as did tuber and shoot biomass. Consequently, intraspecific competition does not appear to come into effect at tuber populations of 1000 tubers/m$ sp2$ and less. / Predictions were made to determine the spread of yellow nutsedge based on an infestation of a single tuber. A single yellow nutsedge tuber could grow to infest an area of 50 m$ sp2$ in 5 years. Information concerning the effect of spring tuber density on the reproduction and spread of yellow nutsedge should be used in formulating control strategies for this weed.

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Cropping systems were: corn + atrazine + EPTC/dichlormid; corn + atrazine + metolachlor; corn + atrazine + bentazon; corn + EPTC/dichlormid intercropped with red clover as green manure or managed as forage crop in the following year; alfalfa + EPTC; soybean + metalachlor + metribuzin; sorghum as green manure followed by winter wheat; and spring barley + diclofop-methyl + bromoxynil. Control treatments were yellow nutsedge growing in a pure stand and complete yellow nutsedge control. After two growing seasons in experiment #1, the tuber population had decreased in all cropping systems. Yellow nutsedge was reduced to 9% of the initial population under perfect control while it tripled in the pure stand. After the first growing season in the second experiment, only corn intercropped with red clover significantly reduced yellow nutsedge population by 17%. When the systems were not treated with herbicides, the yellow nutsedge population increased between 41 to 180% in all cropping systems. There was a significant relation between yellow nutsedge, broadleaf weed and grass densities and yellow nutsedge tuber production. Corn was the most profitable cropping system. The least economically advantageous cropping system was barley.

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