Productivity and Persistency among the Single and Mixed Swards Composed of Orchardgrass and Red Clover as Affected by the Isoxathion Application

Abstract

Red clover has a shortage, i.e. its yield greatly decreases within a few years in single or grass-red clover mixtures. We report here that the application of the insecticide isoxathion, lengthened the persistence of red clover included in the swards. Four single and mixed swards, i.e. O (orchardgrass single), R (red clover single), O-R (orchardgrass and red clover were sown in alternate rows) and O/R (orchardgrass and red clover mixture, broadcasted) were made in October of 1976. The forage was cut four times each year. The insecticide was applied from 1978 through 1980. The insecticide application increased the total dry matter yield for 4 years in every sward. This yield increment was greater in the swards which included red clover. It was also greater in the 3rd and 4th year. In the 4th year, the ratio of the forage yield of the swards applied with insecticide to that of the control swards (water application) was 1.1 in O, 2.7 in R, 3.1 in O/R and 1.6 in O-R, respectively. Insecticide application produced both a higher yield of red clover and a higher percentage of the red clover to the total yield in the swards. In the control swards, the red clover yield and the percentage of the red clover to the total yield were greatly decreased during the 3rd and 4th year. After the final harvest of the 4th year, the larvae of cupreous chafer (Anomala cuprea Hope) were counted. It was found that the larvae population was very high in the red clover control sward and very low in all swards applied with the insecticide.