Effects of Integrated Methods of Fertilization on Soil Nitrogen, Phosphorus, Biological Properties, and Canola Traits

In order to study the effects of crop rotation and different systems of fertilization on soil chemical and biological properties and grain yield of canola (Brassica napus L.) Talayeh cultivar، an experiment was conducted at experimental farm of Agricultural Research Center of Sanandaj during 2007 - 2010 growing seasons. Experimental design was arranged in split plots based on randomized complete blocks design with three replications. Main plots contained three crop rotations including (R1): chickpea، sunflower، wheat، canola; (R2): green manure، chickpea، green manure، wheat، green manure، canola; (R3): canola، wheat، canola. Sub plots were allocated to five strategies for provision of the basal fertilizers requirement and included (N1): farm yard manure; (N2): compost; (N3): chemical fertilizers (Urea، triple super phosphate and ammonium phosphate); (N4): farmyard manure + compost and (N5): farmyard manure + compost + chemical fertilizers; and control (N6). Results showed that simultaneous application of manure، compost and chemical fertilizers increased soil mineral elements (N، P، and K). Application of legume green manure in R2 rotation effectively increased nitrogen، phosphorus، and potassium of soil، number of bacteria، microbial carbon biomass، and also dehydrogenase and protease enzymes activity in comparison with the other rotations. The greatest number and biomass of microbial community was observed in the N4 treatment (farmyard manure + compost). The highest enzyme activity (phosphatase، protease، urease and dehydrogenase) occurred in N4 treatment. The lowest activity of dehydrogenase and protease was achieved from the R3 treatment. Green-manure crop rotation (R2) increased activity of these enzymes significantly. Most urease activity (48. 6 µg urea g-1dry soil) was achieved in the R2N4 treatment. The highest grain yield was observed in R2 and N5 treatments. The R2N4 treatment was selected as the best treatment in this experiment.