Sugar beet take up and utilise large quantities of potassium (K) and sodium (Na) - uptakes of 300-400 kg K/ha and over 100 kg Na/ha are common. Potassium and sodium have similar effects on the growth and productivity of sugar beet and have been generally thought to be interchangeable when used as fertilisers. Many plant use K and Na ions as solutes to maintain tissue osmotic and turgor potentials for growth. Most use K because they cannot tolerate high concentrations of Na but sugar beet, being a derived halophyte, can readily use sodium. In sugar beet, the concentrations of K and Na in the shoot are particularly important during the early growth for the rapid expansion of the leaf canopy to maximise radiation interception 1 . Unlike K, sodium is not particularly mobile within the plant and is largely retained by the shoot and very little is translocated to the storage root. The concentrations of K and Na are more important in the shoot than the storage root because, in the latter, the sucrose accumulated during the growth acts as the primary osmotic solute. However, recent BBRO-funded experiments on the K requirement of sugar beet, done on plots at Rothamsted with long-established differences in exchangeable soil K, showed that sugar beets use K as the main shoot osmoticum in preference to Na and use Na only when insufficient K is available.
Outcomes / Key Message For Growers And Industry
Triazole fungicides physiologically delay canopy senescence during the autumn. They were applied to sub-plots in the Rothamsted experiments to test whether they also altered the accumulation of translocated shoot K and N in the harvested beet. Table 4 shows responses to the fungicide averaged over the different levels of soil K and the Na treatments. The fungicide had few effects on yield, the N, K and Na content of the crop or beet quality, apart from a small decrease in the amount of K in the beet in 2004 and a small increase in clean beet yield and decrease in the N content of the beet in 2005. The experiments were harvested toward the end of September in both years, so there could have been greater effects had the beet been harvested late.