Study on Replacement Probability of Organic with Chemical Fertilizers in Canola (Brassica napus) under Two Deficit and Full Irrigation Conditions

In agricultural ecosystems, organic fertilizers play an important role in producing sustainable agricultural production. Considering this Sajjadi Nik et al (2011) reported that with increasing of vermicompost inoculation with nitroxin biofertilizer, capsule number per sesame plant increased, so that the most of capsule number per plant (124.7) was observed in 10 t/h vermicompost with nitroxin inoculation. Seyyedi and Rezvani Moghaddam (2011) reported that seed number per plant and the thousand kernel weight in treatment of 80 t/h mushroom compost in comparison with control were increased by 2.98 and 1.56 fold. In another experiment, Kato and Yamagishi (2011) reported that seed yield of wheat in application of manures equal to 80 t/h/ year more than 10 years in comparison with application of nitrogen fertilizer at the rate of 204 kg/h, showed significant increasing from 725 to 885 gr/m2. In another study, Rezvani Moghaddam et al (2010) reported that the most (74.08) and the least (60.94) seed number per capsule in sesame was obtained in the treatments of cow manure and control treatments respectively. The aim of this experiment was evaluation the effects of municipal waste compost, vermicompost and cow manure fertilizers in comparison with chemical fertilizer on yield and yield components of canola under two levels of deficit and full irrigation.
In order to evaluate the replacement probability of organic fertilizer with chemical fertilizers in canola cultivation, an experiment was conducted at research farm of Mashhad Faculty of Agriculture in year of 2013. Treatments were fertilizer and irrigation. Irrigation treatments included full and deficit irrigation. Fertilizer treatments included municipal waste compost, vermicompost, manure and chemical fertilizer. Chemical fertilizer included Nitrogen and Phosphorus. Experiment was conducted as split plot in randomized complete block design with three replications. Organic fertilizer was scattered in plots and mixed completely with soil. After that in each plot, six rows with distance of 25 cm were designed and canola seeds were placed into the rows and were covered by 3 cm of soil. Through cultivation season and after harvesting the treatments of plant height, pod number per plant, seed number per pod, thousand kernel weight, seed yield and biological yield were recorded. Data were analyzed by MSTAT-C and mean comparison was performed using Duncan's multiple test range.
The highest seed yield was obtained in irrigation treatment and application of chemical fertilizer (1284 kg/h). In all of vermicompost treatments in full irrigation compared with deficit irrigation, seed yield was more but the trend of changes in seed yield was the same in both conditions. It means that seed yield increased with increasing vermicompost application from 7 to 11 t/h, but seed yield decreased with increasing vermicompost from 11 to 15 t/h. In treatment of manure application in both conditions of deficit and full irrigation, increasing the manure fertilizer, increased seed yield. Seed yield reaction in treatments of municipal waste compost in both conditions of full and deficit irrigation was the same as vermicompost. It means that increasing the application of municipal waste compost from 7 to 11 t/h, increased seed yield and increasing the application of municipal waste compost from 11 to 15 t/h, decreased seed yield. Biological yield reaction to fertilizer treatments was the same as seed yield. Overlay application of 50 t/h cow manure in deficit irrigation produced the most seed yield compared with all other fertilizer treatments including chemical fertilizer at the rate of 6%. This yield increment was due to higher pod number per plant and higher seed number per pod. In full irrigation, chemical fertilizer produced the most seed yield compared with all other fertilizer treatments.
Generally, it is concluded that canola in deficit moisture conditions showed a better reaction to using organic fertilizers and their replacement possibility in same condition with chemical fertilizer is considerable but organic fertilizers in full irrigation condition are not able to produce yield equal with chemical fertilizers in canola cultivation.