| Lentil trial at seedling stage in 2008: The trial at Brooks, Alberta, compared various row spacings and seeding rates for three types of lentils. Photos courtesy of Alberta Agriculture and Rural Development.
Until now, Alberta’s recommendations for lentil row spacing and seeding densities have been based on a large-seeded green lentil, the first commercially grown lentil in the province. But lentil varieties have come a long way since commercial production started on the Prairies in 1978. Today, large-, medium- and small-seeded green lentils and medium- and small-seeded red lentils are all grown in Alberta, so researchers have updated the recommendations. “We now have many types of lentils, but we had only one seeding density recommendation, which was 12 seeds per square foot, or 132 seeds per square metre for large-seeded lentils. And for row spacing, lentil growers have been using eight, nine, 10, 12, 14 inches, all kinds of different spacings, and they were claiming ‘my spacing is better than your spacing’,” says Dr. Manjula Bandara, pulse and special crops research scientist with Alberta Agriculture and Rural Development. “With that kind of variation and the different yield responses to seeding rates and row spacings, southern Alberta farmers started saying, ‘We need recommendations for seeding rates combined with row spacings for small lentils, medium lentils and large lentils’.”
| Lentil trial at podding stage in 2008: When moisture conditions were good, the plants were able to quickly close up the spaces between rows.
So the Alberta Pulse Growers Commission funded a three-year project led by Bandara to develop those recommendations. The trial was set up at Brooks in southern Alberta and started in 2006. The researchers used three varieties: a large-seeded green lentil (CDC Sovereign); a medium-seeded red lentil (CDC Redberry); and a small-seeded green lentil (CDC Viceroy).
They compared three row spacings of 20, 25 and 30 centimetres (eight, 10 and 12 inches), in combination with three seeding rates of 121, 143 and 165 seeds per square metre (11, 13 and 15 seeds per square foot).
Bandara gives examples of how row spacing and seeding density can influence lentil yields and/or quality. “Row spacings that are too wide can have effects like increased weeds and moisture loss. And if you start doing inter-row cultivation then you are breaking the soil and losing more moisture, so the crop will suffer.”
And if the plants are too close together, then the risk of disease, poor pod set, and other problems can increase. He says, “When you have a higher seeding rate and higher moisture, then vegetative growth is going to be very high. Those conditions create microclimates favourable for fungal diseases, like anthracnose and ascochyta, which can reduce seed quality and yields. In addition, with high moisture conditions, you can get indeterminate growth, which can cause late flowering and immature seed.”
The project was conducted under weed-free conditions, using herbicides, mechanical weed control methods, and hand weeding. Bandara notes that the development of Clearfield lentil varieties (non-genetically modified, herbicide-tolerant varieties) for Western Canada is making weed-free lentil production easier for growers. “With Clearfield lentils you can spray imazamox-based herbicides and get rid of most weeds from the lentil field.”
Not surprisingly, the results from the various treatments were influenced by year-to-year differences in precipitation. For instance, for CDC Redberry, in 2006 and 2008 when moisture conditions were satisfactory, yields increased with wider row spacings. But under the hot, dry conditions of 2007, yields decreased with wider row spacings.
Bandara explains, “If the moisture conditions are pretty good and you have a wider row spacing, the crop growth will be good enough that it can close the spacing very quickly, so weed competition won’t be that great, and the crop can produce a good yield. But if it is a dry season and you have wider spacing, then you have a place for weed growth and you also lose moisture because of the ground exposure.”
Although the treatment results varied, the overall trends were strong enough for Bandara to make recommendations under weed-free conditions, for each of the three lentil types. For large-seeded green lentils, like CDC Sovereign, he recommends a narrower row spacing, like 20 centimetres (eight inches), and a higher seeding density of 165 seeds per square metre (15 per square foot). For medium-sized red lentils, like CDC Redberry, he recommends a 30-centimetre (12-inch) row spacing and a seeding density of about 165 seeds per square metre (13 per square foot). And for small-seeded green lentil varieties, like CDC Viceroy, he recommends a narrower row spacing of 20 centimetres (8 inches) with a seeding density of 143 seeds per square metre (13 per square foot).