INFLUENCE OF VARIETY AND POPULATION-DENSI TY ON YIELD AND QUALITY OF SUGAR-BEET - A CONTRIBUTION TO COMPETITION FOR LIGHT

In field populations of sugar beet the competition for the growth fact or light becomes more important with increasing population density. In which way varieties with different leaf formation could influence thi s fact should be investigated under field conditions. For this purpose a field trial including 5 varieties and 5 population densities (65,00 0 to 125,000 plants/ha) was carried out in 1991 and 1992 at Gottingen. Root yield, leaf yield and the standard parameters of technological q uality were determined at harvest. In addition leaf area index was mea sured in 1991. The components of variance were calculated for the fact ors variety, population density and year as well as for their interact ion terms to describe their influence on the determined parameters. Th e influence of year on yield characters and sugar content was dominant . Variety and population density had a clear influence on the paramete rs of the technological quality. The interaction year . population den sity, which was significant at the majority of the determined paramete rs, showed the different effect of population density in both years. A lthough the interaction variety . population density was not significa nt in most cases, root yield indicated a different reaction of variety depending on population density. The variety with the lowest leaf yie ld did not show a decrease in root yield with increasing population de nsity. Root yield of varieties with a higher leaf yield decreased as p opulation density exceeded 95,000 plants per ha. It was assumed that c ompetition for light, which occurred in high population densities, cau sed an increased leaf/root ratio, so that root yield was reduced.