Determining ideal soil conditions for rearing alkali bees (Nomia melanderi)

The alkali bee (Nomia melanderi Cockerell) is the world’s only intensively managed ground-nesting bee and a highly efficient pollinator of alfalfa (Medicago sativa L.) grown for seed. Since 2008, the price of an alternative pollinator, the alfalfa leafcutting bee (Megachile rotundata F.), has more than quadrupled, increasing growers’ reliance on alkali bees. Natural alkali bee beds are found in wet soils with a salty surface contributing to capillary rise. Growers build alkali bee beds by installing subsurface irrigation and heavily salting the topsoil to deter weeds and draw water to the surface. Unlined beds are irrigated constantly and use a substantial amount of water. In previous studies, soil moisture content, soil temperature, and soil salinity were demonstrated to influence the establishment of alkali bee nests and larval development rates. However, no previous study has related alkali bee nesting rates with all three factors. Additionally, no study has followed these alkali bee bed characteristics over the course of an entire season. This study uses lined beds to manipulate soil moisture with the goal of increasing the populations of alkali bee pollinators in alfalfa seed fields.