Discerning Agronomic Best Management Practices for the Bioenergy Crop Camelina: A Focus on Water Requirements, Sowing Date and Method, and Nitrogen Application Rate in the Semiarid Environment of Northern Nevada
Environmental and Natural Resource Sciences
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The increasing global demand for food and energy has stimulated multiple innovations and adaptive strategies to optimize agricultural productivity in semiarid regions of the world. However, water availability for agricultural production is a growing challenge globally and has significant implications for long term sustainable agriculture production and associated food security. Camelina [Camelina sativa (L.) Crantz], a reemerging crop that has been grown for decades in different parts of the world, has drawn considerable attention as a viable feedstock for biodiesel and jet fuel production, and it has widespread environmental adaptations, because of its ability to thrive well under diverse climatic and soil conditions. Some competitive advantages of growing camelina as an alternative crop are its short growing cycle, low fertilizer, and water requirements, high oil content and unique oil characteristics and its ability to grow successfully on marginal lands. The objective of this study was to evaluate the best management practices (BMPs) for the bioenergy crop camelina such as water requirements, planting date and methods, and nitrogen application rate in the semiarid environment of Northern Nevada. A two-year study was performed at the University of Nevada, Reno Main Station Field Laboratory, and Reno, Nevada during the spring growing seasons of 2016 and 2017 ( for planting date and method, and nitrogen application rate), and 2017 and 2018 ( for irrigation rate). For irrigation rate study, treatments were three irrigation rates (IR) based on reference evapotranspiration (ET), 100% ET (full-IR), 75% ET (medium-IR), and 50% ET (low-IR) as the main plots and five camelina cultivars (Blaine Creek, Calena, Columbia, Pronghorn, and Yellowstone) as subplots arranged in a randomized complete block design experiment with four replications. Plot size was 7.62 m long × 1.83 m wide, and camelina cultivars were seeded at a rate of 5 kg PLS seed ha-1 to a depth of 1 cm on April 11, during both years of the study. Nitrogen fertilizer was applied at a rate 80 kg N ha-1 using urea (46-0-0) and based on soil test results, 40 kg P ha-1 was applied using triple superphosphate (0-45-0) but no potassium (K). Irrigation treatments were applied three weeks after germination using reference ET and crop coefficient for camelina at different growth stages. Similarly for planting date and method study, treatments were two sowing dates (SD) of March 18, (early SD) and April 17, 2016 (late SD) and April 11, (early SD) and May 11, 2017 (late SD), two sowing methods (SM), and three cultivars of camelina (Blaine Creek, Columbia, and Pronghorn) arranged in a 3 × 2 × 2 factorial randomized complete block design experiment with four replications. Further, for the nitrogen source and rate study, treatments included two sources of urea fertilizer [conventional urea (CU) and polymer coated urea (PCU)], four N rates (0, 40, 80, and 120 kg N ha-1), and two cultivars of camelina (‘Blaine Creek’ and ‘Pronghorn’) arranged in a 4×2×2 factorial combinations with four replications each in a RCBD experiment. Data collected included plant height, leaf area index (LAI), SPAD chlorophyll index, light interception (LI), and grain yield for all three studies. Treatment means were considered different at P < 0.05.The results of the irrigation study revealed that grain yield increased linearly from low- (770 kg ha 1) to full- IR (1013 kg ha-1) but significant difference was achieved only betweeen low- and full IR. Grain oil concentration was greater at medium-IR (333.2 g kg-1) compared to low- (317.7 g kg-1) and full-IR (321.6 g kg-1). However, cultivar had no influence on the measured parameters in this study. Based on the results of grain yield, oil, and biodiesel production, camelina requires a medium irrigation rate of 75% of reference evapotranspiration (ET) for its optimum production in Nevada. In addition, the results of planting date and sowing method (SM) showed that camelina grain yield was affected by sowing date (SD) and was greater for early (921 kg ha-1) compared to late SD (503 kg ha-1) in 2017, and SD × SM interaction in 2018. There was no significant difference in grain yield for early SD between SM, however, for late SM, it was greater for drill (676 kg ha 1) than broadcast (130 kg ha-1). The result also examined the effect on oil concentration and found that there was an influence of SD on oil concentration in both years, and it was greater for early (295 kg ha-1) than late (284 kg ha-1) in 2017. Overall results show that early SD and drill sowing methods are best practices for farmers growing camelina in Nevada. Likewise, from an evaluation of nitrogen source and rate, we observed a linear increase in grain yield (ranges from 534 to 1010 kg ha-1) and potential biodiesel production (ranges from 51.2 to 94.2 L ha-1) with increasing N application rate from 0 to 120 kg ha-1. In 2016, it was detected that Blaine creek (898 kg ha-1) produced greater seed yield compared to Pronghorn (464 kg ha-1). But it was found that there was no competitive advantage of using controlled release PCU over conventional urea in this study. Based on our observations, an optimum nitrogen application rate of 80 to 120 kg ha-1 produced maximum yield of camelina in water-scarce environments such as Nevada.