Nitrogen Fertilizer and Irrigation Effects on Seed Yield and Oil in Camelina

Interest is growing in camelina (Camelina sativa L. Crantz) as a biofuel feedstock. However, there has been little camelina research in irrigated arid systems. A 2-yr field study in Maricopa, AZ, under an overhead sprinkler irrigation system determined the effects of 10 water levels (irrigation fraction 0.5–1.1) and five N fertilizer rates (38–150 kg N ha–1) on seed yield, seed oil content, and N use efficiency. Cultivar Robinson was planted in December 2012 and 2013. Nitrogen fertilizer (urea ammonium nitrate) was applied in three split applications. Irrigation amounts were from 125 to 380 mm, and in-season rain was 70 and 50 mm, in 2013 and 2014, respectively. Camelina seed yields were maximum at water level 7 (irrigation fraction 0.93) in 2013 at 1800 kg ha–1. Maximum seed yields were 1600 kg ha–1 at water level 6 (irrigation fraction 0.83) in 2014. These highest seed yields were achieved with 150 kg N ha–1 in both years. Oil content (maximum 41%) decreased with N rate but increased with water level. Seed N increased with N rate but decreased with irrigation level. Recovery efficiency of N fertilizer by camelina ranged from 12 to 72%. The results indicate that good high-oil camelina yields can be produced in the southwestern United States with 320 to 380 mm irrigation plus rain and N fertilizer rates of 150 kg N ha–1

Ecology of Urban Bees: A Review of Current Knowledge and Directions for Future Study

Urban bee ecology is an emerging field that holds promise for advancing knowledge of bee community dynamics and promoting bee conservation. Published studies of bee communities in urban and suburban habitats are fewer than those documenting bees in agricultural and wildland settings. As land lost to urbanization is predicted to increase in coming years the necessity of studying urban bee populations is growing. We reviewed 59 publications on urban bee ecology with the following goals, to assess current knowledge, to highlight areas in need of further research, and to suggest applications of study findings to bee conservation. Methodological variation between studies was discussed in the context of data interpretation. Identified trends in urban areas included the following, negative correlation between bee species richness and urban development, cavity-nesters increase in abundance in urban habitats, and floral specialists are scarce. Future directions for studying urban bee ecology include incorporation of landscape-scale assessments, conducting manipulative experiments and actively designing urban bee habitats. We include descriptions of plant and habitat management techniques derived from our research in northern and southern California urban habitats to promote development of bee-friendly habitats