THE EFFECTS OF SHOOT REMOVAL ON THE RHIZOME CARBOHYDRATE RESERVES OF COUCH GRASS (AGROPYRON REPENS (L.) BEAUV.)

Summary. Three box experiments examining the effects of shoot removal on rhizome carbohydrate reserves are reported.
During summer in England the optimum frequency of hand defoliation for maximum loss of carbohydrate was 10–14 days. As in previous experiments, high levels of soil nitrogen sometimes increased the rate of carbohydrate loss from 9-in. rhizome pieces. This result was obtained when nitrogen was supplied as a nitrate, an ammonium salt, or urea.
Repeated applications of 2 or 4 oz/ac paraquat over a period of about 60 days reduced carbohydrate reserves to about 50% of the level obtained with the same number of hand clippings. It is suggested that paraquat may have been translocated to the rhizomes, the carbohydrate content of which may have been reduced by an effect of the paraquat on the respiration rate.
When plants which had been subjected to different methods and frequencies of defoliation were uprooted and buried beneath 2 in. of soil, there was a connection between the rhizome carbohydrate content at the time of burial, the ability of the plants to regenerate, and the rate at which new carbohydrate reserves built up during the following two months.     

INCORPORATED VERSUS SUBSURFACE VERNOLATE FOR WEED CONTROL TN PEANUTS*

Summary. Under dry field conditions, vernolate (S-propyl dipropylthiocarbamate) incorporated by conventional methods controlled less yellow nutsedge (Cyperusesculentus L.) and injuied peanuts (Arachis hypogaea L., groundnuts) more than when injected in lines under the soil or subsurface-applied through sweep applicators. In glasshouse studies, vernolate eliminated production of new nutsedge tubers if it was applied below the soil surface either 1 in. above or 1 in. below the parent tuber. Method of placement was less critical in determining control of most annual weeds. When averaged over two soil types and 2 years, peanuts yielded 14% more after subsurface applications than after incorporated treatments of vernolate. In comparison with the optimum subsurface placement, the yield from incorporation was significantly lower in three of four field studies, the reduced yields probably resulting from a combination of herbicide injury and poor weed control. Factors affecting the distribution of vernolate vapours (such as method of placement, soil type and amount of rainfall after treatment) apparently determine the differential toxicity of this herbicide. Neither market quality nor germination of peanut seed was adversely affected by vernolate treatment.