Study on the effects of different manuring levels on soil physical conditions and water consumption in wheat-sugar beet rotation.

The use of organic fertilizer brings about an increase in organic matter of the soil and microbiological activities. In our country the soil is poor in organic matter, and the use of manuring is suggested for improvement of soil structure and its physical and chemical properties for increase yields and arrive at a sustainable agriculture. This investigation was conducted during 2000-2004 at Karaj experimental station in order to study the amount of manure to be used and its effects on qualitative and quantitative yield of sugar beet crop. The experiment was carried out in a complete block design in permanent plots with three replications for no-manure, 30t of manure/ha and 60t/manure/ha treatments. A cereal-sugar beet rotation for two cycles was followed in the experimental field. Manuring was done in autumn before the wheat culture 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 of the study showed that the use of manure increased the wheat grain weight and yield significantly. Wheat crop yield of 4.17t in the no-manure increased to 5.41t in 30t manure/ha treatment. The 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 level 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 gr/cm 3 in no manure treatment to 1.38 gr/cm 3 in 30t manure/ha/.While water capacity of soil improved significantly by the increase in soil organic matter. Moreover crop nutrition was improved by manuring of the soil and diminished the need for chemical fertilization. Manuring with 30t manure/ha before wheat cultivation in wheat-sugar beet rotation is justified.