SUGAR-BEET PERFORMANCE AND INTERACTIONS WITH PLANTING DATE, GENOTYPE,AND HARVEST DATE

Producers and processors have lengthened the sugar beet (Beta vulgaris L.) factory campaign by beginning harvest about 1 mo earlier. Agronom ic practices may need to be adjusted to maximize yield and quality of sugar beet harvested earlier. The objective was to describe yield and quality relationships between dates of planting and harvest among 18 s ugar beet genotypes. The experiment was conducted at the University of Wyoming Research and Extension Center near Powell, WY, during 1992 an d 1993 on a Garland clay loam (fine-loamy over sandy or sandy-skeletal , mixed, mesic Typic Haplargids). Treatments consisted of five plantin g dates between 30 March and 8 June, and four harvest dates every 2 wk beginning 10 September. When averaged across all years, genotypes, an d harvest dates, a delay in emergence of 46 d decreased root yield 38% (from 52.5 to 32.3 Mg ha(-1)), sugar content 4% (183 to 175 g kg(-1)) , and recoverable sucrose 42% (9.25 to 5.34 Mg ha(-1)). Delaying plant ing 46 d increased loss to molasses by 21% (7.75 to 9.41 g kg(-1)). Ro ot yield varied 18% among sugar beet genotypes (40.9-50.1 Mg ha(-1)), sugar content varied 6% (173-185 g kg(-1)), loss to molasses varied 13 % (7.90-9.10 g kg(-1)), and recoverable sucrose varied 14% (7.14-8.33 Mg ha(-1)). Over the 43-d harvest period, root yield increased 22% (fr om 41.1 to 50.2 Mg ha(-1)), sugar content 15% (165 to 190 g kg(-1)), a nd recoverable sucrose 45% (6.41 to 9.28 Mg ha(-1)). Over the harvest period, loss to molasses decreased 21% (from 9.10 to 7.12 g kg(-1)). T he relationships for both yield and quality between planting and harve st dates was linear and nearly parallel. Genotypic differences for yie ld and quality were greatest on early planting dates as compared with later planting dates. Recoverable sucrose ranking of genotypes at the beginning of harvest was similar at the end of harvest. Producers shou ld consider planting high root yield genotypes in early planted fields that are harvested late, thereby taking advantage of the entire growi ng season, and genotypes with average root yield and above-average sug ar content should be used for late planted or early harvested fields.