The effect of sowing date and harvesting date on the yield of sugar beet

SUMMARYA field experiment in each year 1963 to 1967 in Suffolk, England, tested the effect on yield of sugar beet of sowing dates ranging from 13 March to 11 May and harvest dates ranging from 20 September to 8 December. Sowings in March or early April gave similar yields of sugar but with later sowings yield decreased progressively faster. The relationship is represented by the equationy = 106·3 (±2·24) + 0·212 (±0·184)x-0·009 (±0·003)x2,y = yield as percentage of mean (60·1 cwt/acre of sugar), x = number of days after 12 March.Delayed harvest increased sugar yield; the relationship is represented by the equationy = 80·22 (±1·51) + 0·836 (±0·09)z-0·006 (±0·001)z2,z = number of days after 19 September. This represents an increase of 0·247 cwt/acre/day of sugar in October and 0·083 cwt/acre/day in November, equivalent to about 2½ tons/acre of roots in October and 1 ton/acre in November.The effect on sugar yield of different lengths of growing period, which ranged from 138 to 271 days, is represented by the equationy = 38·7 (±26·6) + 1·045 (±0·267)a-0·0017 (±0·0007)a2,a = number of days between sowing and harvest.On average, sowing date had negligible effect on sugar percentage at harvest. In 3 years sugar percentage increased after the first harvest to a maximum and then decreased; in 2 years it decreased with consecutive harvests.