Effect of Organic and Mineral Nitrogenous Fertilizers and Plant Density on Yield and Quality of Sugar Beet (Beta vulgaris L.)

TWO FIELD trials were conducted during 2008/2009 and 2009/2010 seasons in the Agricultural experiment and Research Center, Fac. Agric., Cairo Univ., Giza, Egypt, to study the response of sugar beet to mineral N rates (60, 80 and 100 kg/fed¹), compost rates (0, 1 and 2 tons/fed of plant compost 15% N) and plant density (40 x 10³ and 46 x 10³ plants/fed). Results revealed that increasing N rate up to 100 kg significantly favored beet growth in terms of leaf area index (LAI) at 145 and 175 days from sowing as well as relative growth rate (RGR) and individual root weight. LAI decreased as plants advanced towards maturity. On the other hand, juice quality traits, sucrose, purity and sugar recovery were decreased as N rate increased, while sucrose loss to molasses was gradually increased as N rate increased. A substantial increase in root yield (24.9% and 21.5%) and recoverable sugar yield (16.7% and 11.3%) was recorded as N rate increased from 60 to 100 kg/fed in the first and second season, respectively.
Application of 2 tons of compost/fed significantly produced the highest LAI and RGR as well as the heaviest roots, and improved juice quality traits (sucrose, purity and recoverable sugar %). 1 and 2 tons of compost were significantly different in most of quality traits. Increasing compost rate from zero to 2 tons/fed increased root yield by 16.4 and 14.0% and sugar yield by 27.8 and 20.2% in the first and second seasons, respectively.
Increasing plant density from 40000 to 46000 plants/fed depressed beet growth in terms of LAI, RGR and root fresh weight, while sucrose, purity and recoverable sugar % were increased with increasing plant density. On the other hand, sucrose loss to molasses decreased as plant density increased. 46000 plants maximized root and sugar production per feddan. All interactions between the studied factors were significant with respect to the studied traits in both seasons. The highest root yield 41.57 and 41.02 ton/fed and sugar yield 6.30 and 5.87 ton/fed resulted from 100 kg N + 2 tons of compost with 46000 plants/fed.