Evaluation of Effect of Sowing Date and Nitrogen Fertilizer Application on Nitrogen Productivity of Camelina (Camelina sativa L.)

Introduction Currently, more than 90% of the edible oil needed in Iran is supplied through imports from other countries. This amount of oil import is not suitable for a country with high potential and capacity to produce agricultural products. Therefore, it is necessary to increase the production of oilseeds in the country. Camelina (Camelina sativa L.) is a new and unique oilseed plant for Iran. This oil plant is part of the Brassicaceae family, and it has been shown in various tests that it has much less water needs and more resistance to spring cold than other oil plants, especially canola. Therefore, considering the importance of self-sufficiency in oil production in the country and the introduction of crops that can have a good yield in the dry climate of most parts of the country, this research aims to evaluate the effect of sowing date and nitrogen fertilizer application on the nitrogen productivity of camelina as a new crop was implemented in the crop rotation with most of the rainfed crops. Materials and Methods This study was conducted in order to investigate the effect of sowing date and nitrogen fertilizer application on the nitrogen capture and use efficiency of camelina under the conditions of rainfed fields in the climatic conditions of Kermanshah city in 2018-2019. A split plots experiment was conducted based on the randomized complete blocks in three replicates at the research farm of the Campus of Agriculture and Natural Resources at Razi University. The main factor was the sowing date (October 25, November 9, and November 21), and the secondary factor was nitrogen fertilizer application (0, 50, 100, 150 kg.ha-1). The implementation of the sowing date treatment was based on the occurrence of effective rainfall, and the source of nitrogen fertilizer application was 46% urea fertilizer. The nitrogen fertilizer was applied at three stages (at the end of the six-leaf stage, at the end of the stem elongation stage, and at the beginning of the grain filling stage). The plant was harvested on each sowing date according to the physiological maturity (browning of 90% of pods). The evaluated traits were grain protein percentage, grain protein yield, nitrogen harvesting index nitrogen capture and use efficiency, and nitrogen productivity. Results and Discussion The results showed that the treatments of sowing date and nitrogen fertilizer application had significant effects on the evaluated traits. In the maximum fertilizer application treatment, compared to the control condition, the grain protein percentage and grain protein yield increased by 39.0% and 128.8%, respectively. The highest nitrogen capture efficiency (0.81 kg of total plant nitrogen.kg-1 of soil nitrogen) and nitrogen use efficiency (11.4 kg of grain.kg-1 of nitrogen) was observed on the November 9 sowing date and the lowest of these belonged to the November 21 sowing date. The increase in the amount of nitrogen fertilizer application decreased the nitrogen capture efficiency (64.8 %), nitrogen use efficiency (63.7 %), and nitrogen productivity (51.3 %) in the treatment of 150 kg of nitrogen application per hectare compared to the treatment of no nitrogen application. Conclusion The results showed that most of the investigated traits of camelina were observed in the sowing date of mid-November, and the delay in the sowing date led to a decrease in these traits. The highest nitrogen capture efficiency, nitrogen use efficiency, and nitrogen productivity were observed in the treatments with the lowest amount of nitrogen fertilizer application and the control treatments. In general, the results of this research showed that under the climatic conditions of the Kermanshah region, it is better to sow the camelina in the rain-fed fields in the middle of November, and because of the undeniable effects of using nitrogen fertilizer on improving the grain yield, but if the environmental risks of excessive use of chemical fertilizers are considered, it is better to application nitrogen fertilizer in the minimum amount the plant's needs.