All Things Organic - Lessons learned from direct-seeding experiment

By Ian Cushon
December 4, 2003

In the past, we have experimented with direct-seeded peas with some success on our organic farm. This year we decided to try it again. We rented a John Deere 750 no-till disc drill with 71/2 inch spacings. These expensive drills are rare on the Canadian Prairies, but are more common in North and South Dakota and Montana. It is an impressive-looking unit, but after having used an air seeder for many years, filling the 750 drill was annoying. It was especially annoying because we bought a used end-gate drill fill specifically for the job, only to find out it would have been better used as a pea splitter. Unfortunately, the CDC Montero green pea seed we bought was unusually fragile because the wet 2002 harvest had weakened the seed coat, making it too dry. But even less-fragile peas would have suffered badly in that coffee grinder. We quickly went to plan B.

With only 100 acres of peas to direct seed, we unhappily decided that filling with a pail was a better option. When sowing peas at 3.25 bushels per acre, pailing 100 acres of peas into a drill is just plain hard work. The drill appeared to operate fairly well, but the high volume of peas caused plugging in the seed cups on some runs. I also suspect that the overfull seed cups caused additional seed cracking. At 3.25 bu. per acre, we were close to the drill's maximum feed rate, which was below the target seeding rate of 3.85 bu. per acre to adjust for lower seed germination.

As is the case with some drills, there was significant seeding rate variation between the two 15-foot units. It appeared that the disc openers were cutting and packing a good seed trench, but there were a significant number of stray peas on or near the surface. In the end, emergence was poor and the target plant population was below normal. It was a sad reminder that I had broken the cardinal rule of organic crop production - carefully plant good quality seed at increased seeding rates to establish the most competitive crop stand possible.

Field selection was the second major problem. We seeded into what was 2002's best yielding and cleanest wheat field. Unfortunately, in 2003 it produced a lot of wild oats. Early May was wet. As a result, the direct-seeded green peas, which went into the ground on May 14, was our first crop to be seeded. The wild oats came with a vengeance, especially in low spots. There were too few peas to provide effective competition. Green peas are poor competitors anyway, because varieties commonly available are semi-leafless types that do not cover the ground well. I have never found a variety of green peas that was competitive. In contrast, our more competitive long-vined and normal-leaf type Grande yellow peas would have done much better.

In the next 30 acre field we tried direct-seeding yellow peas, but we used 16-inch sweeps on 12-inch spacings with our conventional air seeder. Overall, these yielded much better, at around 20 bu. per acre, although some parts of that field were also inundated with wild oats. The direct-seeded green peas yielded less than 10 bu. per acre. Summer drought caused some of the yield loss, but poor stand establishment and wild oats were the primary causes. This year's experience with direct seeding was disappointing. The one bright spot was fewer wild mustard plants than normal, but whether overall weed emergence was lower with direct seeding, I am not sure.

The one major advantage of using conventional seeding methods in organic production is you can still use pre-emergent and post emergent tillage for weed control. Both these practices have proven to reduce weed competition in peas. With direct seeding, you lose these options. By its nature, soil that is direct seeded is cooler and delays wild oat germination. Delayed seeding is still needed on fields infested with wild oats. Conventionally tilled soil will bring wild oats and other weeds on earlier and allow for earlier seeding. We clearly saw this in 2003, where wild oats emerged early on fallow and were easily wiped out before we seeded our cereal crops. There was little problem with wild oats in these fields.

For 2004 I would like to try direct seeding peas again but with fewer acres and a better direct-seeding tool. Direct-seeded peas should be sown as early as possible to increase their early competitive advantages. I would also like to revisit inter-cropping oats and peas, a technique that several organic farmers use. On weedier fields, we need to use late conventional seeding andpre-emergent and post emergent harrowing if necessary. The complication is that a dry spring makes pre-seeding tillage risky. Aside from reduced soil erosion, moisture conservation is the other major advantage of direct seeding. A dry spring will quickly prove the value of direct seeding.

Organic farmers need more competitive pea varieties. Unfortunately, almost all plant breeding is done with the expectation that weed control will be accomplished with herbicides. Variety selection and breeding is one of the most important agronomic issues for organic production. Organic farming is often criticized for low yields, but those criticisms are unfounded, considering that there has been little investment in organic agronomic research or plant breeding. Varieties that improve weed competition will help narrow the yield gap between organic and non-organic farmers.

Ian Cushon
Moose Creek Organic Farm Inc.
P.O. Box 85
Oxbow, Saskatchewan
Canada, S0C 2B0

Tel. 306-483-5034
FAX 306-483-2799
Cell 306-483-8257
E-mail: coldridge@sasktel.net