Effects of soil and foliar applications of sodium borate to sugar beet

Abstract

AbstractThe effects were examined of liquid and solid applications of sodium borates, used at the rate of 20 lb. borax equivalent/acre, to sugar beet at seeding, mid‐June and late August. The trials were conducted at twelve sites on light‐land farms in East Anglia, selected as far as possible as having a previous history of boron deficiency.Treatments were effective in controlling, but not always entirely eliminating, boron‐deficiency symptoms, and had no detrimental influence on germination, population or growth. Nevertheless yields of roots and sugar, and sugar content, were increased significantly only at severely deficient sites; juice purity was not improved nor was noxious nitrogen reduced even at such sites; and these trials lend no support to theories that boron addition has some specific value in increasing sugar content, even where soils have a normal supply of the element. Leaf weight was increased more consistently, even where boron had no effect on root yield and there were no noticeable deficiency symptoms. Climatic and soil influences were very marked, serious deficiency being more prevalent in drier years and on lighter soils, where temporary attacks in intermittent dry periods were also liable to occur. No consistent differences could be observed between liquid or solid applications whether to the seed bed or to the growing crop, but August treatment in neither case gave good results.Boron analyses were made on soils and leaves. Results suggest that soil analysis (either for total or available boron) is an unreliable means of diagnosing boron requirement, that roots neither reflect boron contents of soils or plants, nor the results of boron addition. The analysis of blades of older leaves in June when it is not too late to take the necessary corrective action, is the best procedure for sugar beet. The available boron content of soils and the total boron content of plants were highest in late summer, and even where boron had been added in August, residual effects were small and well below the safety margin for crops less tolerant than beet. In view of climatic hazards, the uncertainty of soil analysis as a means of diagnosis, the low residual effects of boron addition, and the damaging losses from serious deficiency, a routine application of borate to all sugar beet crops grown on lighter soils seems a wise precaution. These trials indicate that for this purpose a foliar spray applied in June, or after singling, is just as effective as a fertiliser applied to the seed bed.