To study the effect of different levels of potassium humate and boron fertilization, two field trials were carried out in a private farm at El-Nubaria region, (latitude of 30.86° N, longitude of 31.16° E and altitude of 21 m above sea level) El-Bahira Governorate, Egypt in 2018/2019 and 2019/2020 seasons. This work included sixteen treatments, represent the combinations of four levels of potassium humate as a soil application (0, 2.5, 5 and 7.5 kg/fed) and four levels of boron (zero, 70, 140 and 210 ppm/fed) as a foliar application in the form of boric acid 17% boron), which sprayed thrice at 50, 65 and 80 days from sowing and their effect on growth, yield and quality of sugar beet (Beta vulgaris var. saccharifera, L.). A split-plot design in three replications was done.
The results revealed that fertilizing sugar beet with 7.5 kg potassium humate resulted in higher values of leaf area index (LAI), photosynthetic pigments, root diameter, fresh and foliage weights/plant, sucrose, sugar lost to molasses, extractable sugar percentages, quality index, root and sugar yields/fed in both seasons. However, the sodium content of roots was insignificantly affected by the studied potassium humate levels in both seasons.
It was found that higher values of leaf area index (LAI), root diameter, fresh and foliage weights/plant, sucrose, sugar lost to molasses, sugar extractable percentages and quality index, as well as root, top and sugar yields/fed, were obtained with increasing boron application to 210 ppm/fed. otherwise, photosynthetic pigments, K, Na and alfa-amino N contents were insignificantly affected by the applied boron levels in both seasons.
Fertilizing beet plants with 7.5 kg potassium humat/fed + 210 ppm boron resulted in a significant increase of LAI, chlorophyll (a), (b), root diameter and yield/fed compared to other combinations in both seasons.
Under conditions of this work, the maximum root and sugar yields/fed were obtained by fertilizing beets with 7.5 kg potassium humate/fed as a soil application and spraying beets with 210 ppm boron/fed at three times (50, 65 and 80 days) after sowing.