Organic lentil production – optimum seeding rate, row spacing

E. Johnson - Scott Research Farm


Problem
Pulse crops such as lentils compete poorly with weeds. Post-emergence harrowing may be used; however, this can cause damage and result in higher levels of disease such as Ascochyta blight. This study’s objective was to assess various row spacings (11, 22, 33, and 44 cm) and seeding rates (30, 60, 120, and 240 kg ha ) to improve competitiveness of organically grown lentil.

Background
Farmers attempting to minimize negative effects of uncontrolled weeds often consider using narrower row spacings and higher seeding rates. Spring barley seeded in 33 cm rows and not treated with herbicides had 46% and 55% higher wild mustard biomass compared to barley seeded in 11 and 22 cm rows, respectively. Increasing barley seed rate from 85 kg ha to 200 kg ha reduced wild oat dry matter and seed production. Increasing field pea seeding rate reduced weed densities and improved crop yield at Melfort. Research conducted in Alberta shows that increased canola seeding rates can reduce the competitive effect of tartary buckwheat. We anticipate that narrower row spacings and higher seeding rates will improve the yield of organically grown lentil.

Study description
The study was conducted in both 2000 and 2001 on a tilled fallow site that received an early spring cultivation. Glamis lentil was seeded with a hoe-drill plot seeder equipped with on-row packing. In the 2000 trial, weeds were seeded into the test area prior to seeding lentil. In 2001, lentil was seeded into a location known for its high natural density of annual weeds. Wild oat, wild mustard, lambs quarters and stinkweed made up most of the weed population in both years. The experiment was conducted according to a split plot design with row spacings (11, 22, 33, and 44 cm) as the main plot factor and seeding rate (30, 60, 120, and 240 kg ha ) as the subplot factor. Treatments were replicated four times. Subplot size was 2 m x 5 m. No post-emergence herbicides were applied. Data collected included only lentil seed yield.

Major findings
Extremely high weed populations severely reduced lentil yield in 2000, while 2001 yields were much better under natural weed populations. In spite of low yields in 2000, yield trends were similar for both years and data were combined. Lentil yield increased as seeding rate increased at the 11, 22 and 33 cm row spacings (Figure 1). At the 44 cm row spacing, increased seeding rate above 60 kg ha had no effect. Optimum seed rate for lentil grown in the presence of weeds approached 150 to 200 kg ha.

Conclusions
Organic producers should consider seeding in a narrow row spacing combined with increased seeding rates. If narrow rows are not practical, then producers should use a seeding implement that distributes seed in a wide row band. Optimum seed rate for lentil under weedy conditions was approximately 1.5 - 2.0 times the current recommended seeding rate for conventional producers.

Funding
Provided by the Canada-Saskatchewan Agri-Food Innovation Fund


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