Effects of Organic and Inorganic Nitrogen Sources on Seed Yield of Some Rapeseed (Brassica napus L.) Varieties and Soil Properties

In order to assess the effects of organic and inorganic nitrogen sources on yield of some winter rapeseed (Brassica napus L.) varieties, soil physicochemical properties and available nutrient elements such as nitrogen, potassium, phosphorus, iron, manganese, zinc, copper and sulphur, two field experiments were carried out during 2008 - 2010 cropping seasons as factorial arrangement in randomized complete blocks design in three replications at the Agricultural and Natural Resources Research Center of Markazi Province, Arak, by using two factors of nitrogen sources at three levels of Azocompost, 50% Azocompost plus 50% urea, 100% urea and three rapeseed varieties including Okapi, Modena and Licord. Nitrogen sources were utilized such that a net quantity of 150 kg N/ha was added to the soil. The results showed that there were significant differences between the nitrogen sources for seed yield and soil properties including moisture weight, bulk density, soil electrical conductivity, pH, organic matter, saturation percentage, porosity percentage and infiltration velocity at 1% probability level. The rapeseed varieties had significant differences for seed yield and soil properties such as bulk density, electrical conductivity, organic matter, porosity percentage and also for the availability of nitrogen, potassium, iron, zinc, manganese and sulphur elements in the soil. In these experiments, the Licord variety showed a greater yield (3847 kg/ha) at integrated nutrition system compared to the other treatments. In addition, the availability of Fe, Mn, Zn and S in soil solution were increased, but the availability of K was decreased. In this research, the integrated application of Azocompost and Urea fertilizers, increased seed yield of Licord cultivar and improved the most of soil properties. Therefore, the integrated nutrition (50% Azocompost plus 50% urea) and extension of Licord variety cultivation area could be recommended for the rapeseed yield enhancement.