Optimal seeding rate for organic production of lentil in the northern Great Plains

Baird, J. M., Shirtliffe, S. J. and Walley, F. L. 2009. Optimal seeding rate for organic production of lentil in the northern Great Plains. Can. J. Plant Sci. 89: 1089-1097. Organic lentil (Lens culinaris Medik.) producers must rely upon the recommended rate for conventional production of 130 plants m(-2), but this seeding rate may not be suitable, as organic and conventional production systems differ in management and inputs. The objective of this study was to determine an optimal seeding rate for organic production of lentil considering a number of factors, including yield, weed suppression, soil nitrogen and phosphorus concentrations, plant uptake of phosphorus, and economic return. A field experiment was conducted for 4 site-years at locations near Saskatoon, SK. Treatments included seeding rates of 15, 38 94, 235 and 375 seeds m(-2). Seed yield increased with increasing seeding rate up to 1290 kg ha(-1). Weed biomass was reduced by 59% at the highest seeding rate as compared with the lowest seeding rate. Post-harvest soil phosphorus and nitrogen levels were similar between seeding rate treatments. Economic return was maximized at $952 ha(-1) at the highest density of 229 plants m(-2), achieved with a seeding rate of 375 seeds m(-2). Organic farmers should increase the seeding rate of lentil to achieve a plant density of 229 plants m(-2) to increase profitability and provide better weed suppression.