How do roll timing and seeding rate affect lentil yields?

Lentil (Lens culinaris Medik.) production has increased exponentially in Montana in the last two decades. However, there are important gaps in knowledge on best management practices for lentil. Agronomic recommendations are based on performance of old cultivars outside of the area for seeding rate, and on anecdotal evidence for proper roll timing, particularly since the widespread adoption of no-till farming. Replicated field experiments were conducted at three sites during the 2019, 2020, and 2021 growing seasons in Montana to determine the impacts of roll timing and seeding rate on lentil yield and identify best practices. Overall, rolling at emergence and at the 10-leaf stage decreased yields by 5% and 8%, respectively, but rolling just after planting or at the early vegetative stage (two- to four-leaf stage) did not decrease yields. Higher yields were achieved at higher seeding rates, with yields increasing between 6 and 52 lb ac(-1) for each additional plant established per square foot, but emergence rates were variable and relatively low, so a higher seeding rate may be necessary to achieve plant densities above 12 plants ft(-2) in this region. In five out of nine site years, the largest partial economic returns were achieved with 22.5 or 30 live seeds ft(-2) seeding rate, corresponding to achieved plant densities of 12 to 16 plants ft(-2). It was generally economical to increase seeding rate from 15 to 22.5 live seeds ft(-2), thus increasing average achieved plant density from 8 to 13 plants ft(-2), except when seed costs were high (>$0.45 lb(-1)) combined with low market prices (< $0.20 lb(-1)). Lentil production has increased exponentially in Montana in the last two decades. However, there are important gaps in knowledge on best management practices for lentil regarding the correct timing for rolling lentil and what seeding rates to use. We conducted an experiment at three sites in Montana during the 2019, 2020, and 2021 growing seasons and found that rolling immediately after planting and at the -two-to four-leaf stage was safe, but rolling at emergence or later in the season (10-leaf stage) led to reductions in yields. In addition, we found it was generally economical to increase seeding rates up to 22.5 live seeds ft(-2) to ensure a target plant population density of 12 to 16 plants ft(-2), as emergence rates in semi-arid areas can be low and variable.