Our farm is a dryland grain farm in the thin black soil zone. This past year we received about 2.5" of rainfall, from the completion of seeding to the beginning of harvest. Our definition of "Direct Seeding" is placing the seed and fertilizer in the field with one operation.
Our current system has evolved over a number of years. It began with a concern over soil erosion due to both wind and water, hence we started continuous cropping. In the '80's we had been deep-banding dry fertilizer in the fall or spring. We found this practice to be time consuming and costly. There were a number of years where spring moisture was a concern. For these reasons, in 1990, we started direct seeding as an experiment on one quarter using an air seeder with 16" sweeps. The seed and dry fertilizer were placed in a spread pattern into the unworked soil. The field was then harrow-packed shortly after seeding, but in a separate operation. We felt that we had not lost any germination or appreciable yield with the change in seeding method. Based on the success of our "experiment" we used the same system on five quarters the following year. At this stage only cereal crops were being direct seeded in this manner since they could withstand the rates of nitrogen that we were applying. The oilseeds were broadcast with a Valmar attachment on the air seeder cultivator and fertilizer was applied as the seed was incorporated. This was direct seeding by our definition however there was no direct contact between the seed and fertilizer.
As quackgrass became more of a problem for us, we began to use pre-seeding burnoff control with glyphosate rather than pre-working as the method for weed control. This change meant that we were direct seeding into unworked ground. This caused a problem with depth control. The roots from the grass and the previous year's crop would only clear through the shovels at a depth of 2 to 2.5". This was deeper than we needed to go for good moisture, causing slower emergence and uneven germination due to cold soil.
We wanted to continue with one pass seeding, but dry fertilizer costs were increasing rapidly. For this reason we began to look at using anhydrous ammonia. It became clear that our current system would require major adaptations and therefore we started considering new machines that were available.
The benefits of air drills with on-row packing had been apparent for a few years, however we had not found an opener that we felt would work in our situation. With the development of the Swede opener we became more interested. During the winter we spoke with several people that had used the new opener and were encouraged by what we were told. We decided that with a few changes, the Swede opener would work for anhydrous ammonia application. We ordered the new system to arrive in the spring of '95. We chose 7.5" spacing for two reasons: we felt that this would allow us to swath even in short crops, and the increased number of openers resulted in less anhydrous ammonia per outlet thus reducing the possible risk of germination problems.
Rather than gamble with direct seeding and anhydrous ammonia, we used a rented cultivator with 12" spacings in the fall to apply anhydrous ammonia on a number of quarters. After the drill arrived in the spring, to get used to it and to check for any problems in the system, we applied anhydrous to one quarter prior to seeding. This left about half for direct seeding using anhydrous ammonia. The fields which received fall applied anhydrous ammonia showed early signs of striping caused by uneven availability of nitrogen due to the 12" spacing on the rented cultivator. Meanwhile, the two different methods of applying anhydrous ammonia for wheat and canola showed no differences in plant emergence. We could see no visible benefit for making the extra field operation either in spring or fall. Because of the differences in expenses between the three operations, the direct seeding method using anhydrous ammonia netted more dollars per acre for the farm.
Every implement has its advantages and disadvantages. One distinct advantage of the air drill is the on-row packing. It results in better seed to soil contact and quickly seals in the anhydrous ammonia. A side benefit is the reduction in weed population since weeds only grow where the packers have gone and not between the rows in the loose soil.
The major disadvantage that we have encountered with 7.5" spacing and the Swede opener is that soil is pushed aside as it travels. The first two ranks open alternate rows and as the back two ranks open the rows in between. This tends to crowd the soil over, causing uneven depth of coverage over the seed on every other row. This results in uneven packing and consequently, uneven plant density, especially in oilseeds. The unevenness in canola is not a yield robbing concern, as canola seems to be able to compensate for the lack of plants. We have tried to correct this problem by installing shank mounted tine harrows on the back two ranks. At 5 miles/hour they appear to do a reasonable job. However, this year's experience showed that as the season got later, we could seed at 6 miles/hour with similar seed coverage to last year and get more acres done in a day.
Another concern with our current system is the limited amount of dry fertilizer we can seed place with oilseeds. It appears that we might have to move to a triple shoot system for adequately fertilizing oilseeds.
Overall we have been pleased with our end result. This appears to be a reasonably cost effective seeding operation. It allows us to do what we set out to do; seed shallow into moist soil at an acceptable acre/day rate using one pass seeding and the less expensive form of fertilizer while leaving the soil less vulnerable to wind and water erosion.