EFFECT OF SOWING AND HARVESTING DATES, PLANT POPULATION AND FERTILIZERS ON SEED YIELD AND QUALITY OF DIRECT-DRILLED SUGAR-BEET AND SEED CROPS

Sixteen field experiments made between 1963 and 1967 on direct-drilled sugar-beet seed crops comparedthe effects of cultural practices on the yield and quality of seed. Sowing in July gave earlier flowering and ripening than sowing in August and usually increased yields, cluster size and percentage germination. Downy mildew was sometimes more prevalent in late sowings. Seed yields increased as the crop changed colour from greento yellow and percentage germination increased greatly as more clusters contained ‘mealy’ rather than ‘milky’ perisperm. Because of natural shedding and bird damage, seed yields then decreased and losses of 0.6 cwt/acre/day were recorded for early ripening treatments. Cluster size and percentage germination continued to increase while yield was decreasing. Crops ripened a month earlier in 1967, the ‘earliest’ year, than in 1965, the latest year. Crops grown in rows 10 in apart lodged less than those sown 20 in apart, ripened earlier and produced, on average, 3 cwt/acre more seed, which was slightly smaller. In one experiment rows 5 in apart gave similar yields but smaller clusters than rows 10 in apart. Row width had little effect on percentage germination. Increasing the distance between plants in the row gave smaller yields with wider spaced rows, but with narrow rows plants 6 in and 12 in apart yielded more than those 2 in apart. Yields from a plant population of 52,200 plants/acre were 4 cwt/acre greater when plants were 12 in apart in narrow (10 in) rows rather than 6 in apart in wide (20 in) rows. Spacing further apart in narrow rows increased seed size. In wide rows many plants 12 in apart lodged, made secondary growth and produced small, late maturing clusters, of which few germinated. Response to fertilizer nitrogen applied in spring was less, and less was needed for maximum yield on the thin Cotswold soils than on the silty clay loam in Lincolnshire, where it doubled yield in 1966. Phosphate and potash applied in spring had little effect on yield. Usually fertilizers had no effect on cluster size or germination percentages, but 1.6 cwt/acre N given to a late-ripening crop in 1965decreased seed size and germination. Ramularia leaf spot, which defoliated crops in the Cotswolds, was worst on early sown and closely spaced plants, and was unaffected by fertilizer. © 1969, Cambridge University Press. All rights reserved.