Many farmers in the black and gray soil zones of Saskatchewan are concernedabout making a direct seeding system work in the wetter springs. The pasttwo springs there have been many comments about the trouble those withstanding stubble are going to have. In spite of the concerns many directseeders have developed solutions and systems that have achieved their goalsof reduced tillage and given them many of the associated benefits.
For some this has meant not adopting a "true" low disturbanceone pass seeding system. They have stayed with a two pass system in whichthey band fertilizer and seed in two separate operations. If they can bandin the fall they move some stubble and open up the ground to get some dryingearly in the spring. One of the most popular banding methods is applyinganhydrous ammonia with knives on 12 in. row spacing. Some have even goneto using every other shank on 8 in. spaced machines. Either of these systemsleaves much of the stubble standing and maintains many of the efficienciesof direct seeding.
For many direct seeders in those areas with concerns about wet fieldsin the spring there has been more reliance on harrows to break up and spreadstraw evenly and to expose the ground to more drying. Heavy harrows canbe used very aggressively but regular tine and diamond harrows at fasterspeeds can also do a lot to breakup straw on hot afternoons.
A number of direct seeders have included other adaptations that allowthem to seed in wetter conditions. One of these is developing seeding unitsthat reduce compaction in moist soil and can travel and seed on wettersoil. To accomplish this they must reduce slippage and be able to transferweight to the ground over a larger surface area. Reed Turner with the AlbertaFarm Machinery Research Center says a principal to keep in mind is thata tractor with tires will pull about half its weight. Triples increaseflotation but reduce ability to pull. So if you want to increase flotationand ability to pull you must increase weight and increase tire size. Triplesis one way to do that but weight may have to be added to maintain traction.
Another easy way this can be done is to run lower tire pressures. Thisin turn reduces the pressure on the ground surface because the tire deflectsto the point where tire pressure equals pressure on the ground. Dr. Wulfsohnat the Agriculture and Bioresource Dept. of the U of S College of Engineeringsays that most manufacturers of agriculture radial tires are reducing theirrecommendations to 8 - 10 . from the older bias ply tire recommendations.Besides reducing surface compaction, fuel efficiencies are improved andtire wear is reduced. Individual recommendations depend on the weight eachtire is carrying. Reed Turner stresses that is important to have ratedinflation pressures in all tires on each axle. Ask the dealer to show youthe load inflation table for your tires and then set pressures accordingto the weight on each axle.
One of the tire manufacturers claims that their radial gives 17% moredrawbar pull on tilled ground and 41 % more on untilled ground as compareto their bias ply tire. This radial tire should cost you less than 30%more than the bias ply tire. A more conservative figure in PAMI's researchupdates indicates that properly inflated radials are 6 - 8% more efficientthan bias ply tires.
Another tire that some direct seeders have turned to is the Trelleborgtire designed in Switzerland. Ed Wiebe of Eds Ok Tire Store in Morris Manitobadistributes these tires. He says they have a flatter surface and run 7to 12 psi. They have very good cleaning characteristics and deep lugs.Trelleborg makes different tires designed for a wide range of applicationsincluding tractors, air carts and the cultivator seeder. Interestinglythe cost can vary from about 1/3 to double the price of other radials butsome 4 wheel drive owners testify that one wide Trelleborg out performsduals.
Instead of utilizing tires some manufacturers have gone to rubber belttracks. Reed Turner has put out a good summary on the differences betweentires and tracks. Tractors with tracks can develop about 20% more pullingforce. In other words the rubber belted tractor can pull about 70% of itsweight. They also have less slip at lower speeds so they perform to theiroptimum at a wider range of speeds than the tired tractor. Ground pressureis about 6 psi depending on the width of track. Steering control and costare the disadvantages of the belted tracks. Tracks for a 270 Hp Challengercost $12,000 but their salesmen suggest they have twice the life of tireson a comparable tractor with tires..
Soil compaction on Saskatchewan soils is not thought to be a seriousproblem because our freeze thaw and wet dry cycles nullify any of the effectsof compaction from agricultural equipment. There are two types of compactiondamage to soils. One of these is at the surface and depends upon tire pressures.We all know that if a soil is too wet we get balling or crusting especiallyin the wheel tracks. The other type of compaction is to deeper levels ofthe soil and depends more upon the total weight of the machine. Bettersoils with more organic matter have more ability to withstand compaction.Also the wetter the soil and the finer the texture the more damage compactioncan do. Dr. Wulfsohn suggests that if compaction was a problem it shouldshow up in visible differences in crop growth. If you think that you areseeing crop damage that relates to wheel tracks consider compaction asa possible cause.
We all hope for a more reasonable spring next May but we should probablybe prepared to overcome some of the difficulties of direct seeding in wetsoils.