Sugar beet response to the application of slow-release nitrogen fertilizers

Urea is the most common form of nitrogen fertilizer used in sugar beet cultivation. Urea has a high solubility and its losses are high and consequently its efficiency is low. It is supposed that urea solubility can be limited and its efficiency can be increased by using slow-release nitrogen fertilizers. By conducting an experiment in three important sugar beet cultivation areas of Khorasan Province, the effects of Urea (soluble form of N-fertilizer) and Urea formaldehyde (slow-release N-fertilizer) application in sugar beet cultivation were investigated. In each area, by using a randomized complete block design replicated three times, effects of six fertilizer treatments including three levels of 75, 100 and 125 percent of nitrogen requirement calculated based on soil test from two sources of Urea and Urea formaldehyde were evaluated. Soil samples were taken before cultivation and three times during the growing season and their NO3-N and NH4-N content were determined. During the growing season, leaf samples were taken three times and their NO3-N content was determined. In addition, the quantity and quality of roots were determined after harvesting. The results showed that application of 250 kg N.ha-1 from Urea formaldehyde (equal to 650 kg. ha-1 Urea formaldehyde), with mean root and white sugar yields of 48.836 and 6.544 t.ha -1 respectively, improved the root and white sugar yields for 1500 and 300 kg.ha -1 respectively as compared with the control treatment. Application of Urea formaldehyde as compared with urea increased the NO3-N and NH4-N content of the soils. In two out of the three sites, the increase in white sugar yield due to this treatment was more than one ton per hectare. This finding necessitates more research concerning the application of Urea formaldehyde in sugar beet production.