Yield of sugar beet in relation to weather and nutrients

Data on sugar beet yields from a long-term experiment (1965-1993) at IACR B room's Barn are used, in conjunction with long-term weather data, to assess the degree to which weather affects yield and how this effect is modified by nutrient availability. Mean temperatures and rainfall during July and Au gust were strongly correlated with sugar beet yields, as well as mean tempe rature during April and the length of time between sowing and harvest. The data from July and August were entered into a factor analysis to generate t wo factors describing how hot and dry weather conditions are during July an d August. These two factors, as well as April temperature and the length of the growing season, were entered into a multiple regression. The regressio ns revealed strong effects of the principal axis factors on sugar beet yiel ds across treatments, as well as strong effects of the length of the growin g season, but weaker effects of April temperatures. The strength of respons e to weather was dependent on the nutrient regime, and was, in particular, greater with increased application of nitrogen. There was, however, no effe ct of nutrient regime on the strength of response of yield to the length of the growing season. These results indicate that weather-induced year-to-ye ar variability in sugar beet yields in unirrigated crops is primarily deter mined by conditions in July and August as well as the length of time betwee n sowing and harvest, and imply that drought limits yields in well-fertilis ed crops. The practical implications of these results are that the risk of yield losses due to drought may be minimised by maximising the length of gr owing season, and that there is the potential for developing simple measure s to forecast yields through monitoring of rainfall. (C) 1999 Elsevier Scie nce B.V. All rights reserved.