Effects of different manuring levels on some quantity and quality factors of sugar beet in wheat-sugar beet rotation

The use of organic fertilizer brings about an increase in the organic matter of soil and the microbiological activities. Generally as the soil in many parts of Iran is poor, the use of manure is suggested for improvement of soil structure and physical and chemical properties to increase yield and to reach a sustainable agriculture. This investigation was conducted during 2001-2004 in Karaj at the experimental station to study the effects of different amounts of manure on quality and quantity of sugar beet. The experiment was carried out in a complete block design with three replications in permanent plots for no-manure, 30ton manure/ha and 60ton manure/ha treatments. A cereal-sugar beet rotation for two cycles was followed in the experimental field. Manuring was done in autumn before wheat planting in order to avoid any detrimental effect on beet quality. Beet quantitative and qualitative traits along with physical and chemical properties of the soil were recorded. The results showed that the use of manure increased the grain weight (of wheat) and total yield significantly. Wheat crop yield of 4.17t/ha in the no-manure increased to 5.41t/ha in 30t manure/ha treatment. The white sugar yield increased significantly from 5.78 to 6.78 t/ha using manure, although the sugar content suffered a decrease. The 60t/ha treatment increased the organic carbon of the soil from 0.81 to 0.94 percent. Furthermore, manuring improved the soil physical condition with apparent specific weight of soil at 0-20 cm depth which decreased from 1.46 g/cm3 in no-manure treatment to 1.38 g/cm3 in 30ton manure/ha, while the water capacity of soil improved significantly by the increase of soil organic matter. Moreover, crop nutrition was improved by manuring of the soil and diminished the need for chemical fertilization. Manuring with 30ton manure/ha before wheat cultivation is justified