With the adoption of direct seeding, finding the right package of opener, row spacing, and packers that will seed and fertilize through standing stubble in a one-pass system, no matter what the conditions are at seeding time, has been a bit of a challenge. Recently, there has been some controversy regarding row spacing on seeding implements. This is not a new issue and there are many factors to consider when deciding what row spacing to choose when purchasing equipment or retrofitting. Unfortunately, there has tended to be more emphasis on the "perfect" row spacing; one that will be ideal for all seeding conditions, soils and soil zones. Results concluded from research in one soil zone, has in some cases, been assumed that the results will be the same in other soil zones. As we have learned from openers, what works well in one area of the province, may not work well in another for a variety of reasons.
There is a surprisingly large amount of research on the matter, but all too often the parameters of the studies were different, such as row spacing and openers used, seeding rates, border effects on small plots, or problems with fertilizer placement. There are still many issues that need researching with respect to row spacing. Interactions between a number of variables such as stubble height, amount of residue on the soil surface and the impact of weed densities still needs research to better understand their effect on row spacing.
As I see it, the whole issue of row spacing is important only when using narrow openers with low seedbed utilization, such as a knife or disc. The issue is moot if higher seedbed utilizations are achieved using openers like a spreader tip, paired row, spoon, mini-sweep or even a full sweep, because the negative impacts associated with row spacing generally occur only when narrow seed rows are being used.
In Saskatchewan, the trends from research have indicated that wider row spacings (i.e. 12-inch) perform as well or better than narrower row spacings in the Black, Grey, and Moist Dark Brown Soil Zones with respect to yields in most crops. However, research from Swift Current indicates that for some crops, the 8 or 9-inch row spacings provide a yield advantage compared to the 12-inch spacing. At Swift Current, results indicated that for flax, lentils and spring wheat, there was a 10-20% yield reduction when using 12-inch row spacing compared to 8-inch spacing. Durum and chickpeas had a 5-10% yield reduction on 12-inch rows. However, reduced seeding rates had more of an effect on field peas than row spacing. In addition, row spacing had little effect on canola and mustard yields. Once canola and mustard bolts, they create a full canopy very quickly.
So, why the difference in results from the Parkland regions and southwestern Saskatchewan? Granted, results can differ somewhat from year to year, but there are several factors that occur between these regions that can account for these differences. In the Black Soil Zone, cereal crops develop quickly and can create a full canopy, which makes for very unfavourable growing conditions for weeds. In the Brown and much of the Dark Brown Soils, crops like wheat, lentils and chickpeas usually don't create a full canopy with 12-inch spacings. This has several consequences. First of all, when a full canopy is not achieved, weeds have an opportunity to become established and compete with the crop. In addition, because of the higher moisture limitations in these areas, even light weed pressure will have much more of a negative impact on yield as compared to the Black Soil Zone. In the southwest, less soil moisture is lost to evaporation and the moisture use efficiency is better with the narrower rows."
There is an argument that with wider rows, one can leave taller stubble for better snow trapping. However, in the southwest, the last couple of years did not exactly provide much snowfall and taller stubble will not overcome the increased evaporation from wide row spacing. Wider row spacings make a lot of sense in the Black Soil Zone, where very heavy residue conditions exist.
If the producer has to swath, 12-inch rows can create problems, particularly with thin stands or normally short cereals such as Harrington barley. Seeding on an angle can reduce some of this problem, but in our farming operation, I don't have time for this and it will also make it much rougher for the sprayer. Producers should also be aware that with the majority of the hoe type openers, there will be higher ridging when used with 12-inch row spacing versus 9-inch. It is not a big issue, but the wider row spacing do make a rougher surface.
What about plant disease in this issue? There needs to be much more research in this area, but studies conducted at the Saskatchewan Irrigation Development Centre in Outlook found very little difference in sclerotinia levels between wide or narrower rows. Studies at Indian Head and Brandon indicated that root diseases were less on wider row spacings. It has also been suggested that there could be some benefits with wider row spacings with crops like chickpeas. The idea is that it would allow the surface of the soil to dry out quicker and there would be less humidity under the canopy, which promotes ascochyta development. However, although this can be an advantage with heavier textured soils, there still remains a problem in that wider rows may allow for more rain splash to occur from the soil, which is a major source of ascochyta infection.
There are certainly advantages to using wider row spacing. There is less capital cost for the seeder and openers needed. There is also less draft when using wider row spacings. One can use a wider machine using the same horsepower with wider rows, which will speed up the seeding operation. There certainly is better residue clearance with hoe type openers on wider row spacing. On heavy clay soils, especially when wet, the wider row spacing can make a major difference.
So what is the farmer to do when faced with sometimes contradictory information on the same issue? In my opinion, farmers need to evaluate what conditions, soil types and amount of stubble that he/she might encounter on the farm on an average year. The next decision is what opener is going to be used on the seeder. If using single shoot openers, then fertilizer becomes an issue. Less fertilizer can be seed-placed on wider rows than on narrow. Therefore, the producer must do a banding operation, a split application, mid-row band, or use liquid fertilizer that is offset to the side of the seed row. Sidebanding openers can generally handle as much fertilizer as your wallet can provide. If your are in the Black, Grey or Moist Dark Brown Soil Zones and have large amounts of stubble and surface residue to get through, then wider row spacing is a very good option. If in the Brown or Dark Brown Soil Zones, then the narrower row spacing, in the 8 to10-inch range tends to be more appropriate. However, it should be stressed that there are farmers quite happy with their row spacing that may be contrary to these suggestions. Row spacing is but one factor that needs to be considered when making equipment decisions. I'll conclude this article with a quote from Dr. Brian McConkey at the Swift Current Research Station; "Use as wide a row spacing as possible until you can't sleep at night."