Crop continuity and prediction of maturity in the crisp lettuce variety Saladin

Abstract

SummaryThe dates of transplanting and maturity of twenty-four experiments between 1980 and 1986 with the lettuce varieties Saladin and Saladin R 100 were used, together with meteorological data for each crop, to study the planning of crop continuity and the prediction of crop maturity. The interval in days from transplanting to maturity was shown to be a minimum for crops transplanted around the middle of June and was described by a fitted quadratic relationship which accounted for 34·6% of the variance. When expressed in accumulated day-degrees >0 °C the interval increased with later transplanting but a linear relationship accounted for only 22·2% of the variance. However, when expressed as accumulated solar radiation the interval decreased with later transplanting and a linear relationship accounted for 82·2% of the variance. When expressed in effective day-degrees (EDDs) the interval was relatively stable at 589 EDDs (S.D. = 39·5).Predictions of commercial crop maturity based on these relationships and using a combination of average and observed meteorological data showed that EDDs gave the most accurate prediction. Differences between actual and predicted maturity appeared to be associated with the site of production, suggesting that a ‘site’ factor needs to be incorporated to take account of local differences in temperature, solar radiation and soil type. The use of long-term average day-degree and EDD data was less consistent than estimates of maturity based wholly or predominantly on observed day-degree and EDD data though with solar radiation the reverse was true.