The Chunky Soup Debate

By Tim Nerbas, PAg

Conservation Agrologist

Do you remember the old TV commercial for chunky soup? It depicted two people arguing over whether the soup should be eaten with a spoon or a fork. The commercial never picked a winner; it was simply a personal preference.

Over the last decade producers and researchers have pondered, and in some instances argued adamantly, a similar "chunky soup" question - how do we get all the fertilizer down in a one-pass seeding system? Some feel that side-banding is the best way while others argue in defense of mid-row banding. Should we be using anhydrous ammonia (AA) or urea as our nitrogen source? Is it simply a matter of personal preference? Recent research hopes to shed some light on the subject.

Studies were completed on this subject by Masters student Dil Thavarajah under the direction of Dr. Schoenau at the University of Saskatchewan. Field experiments were conducted at four sites within Saskatchewan during the 2000-growing season: Star City, Indian Head, Scott, and Swift Current. Moisture conditions were above normal at Star City and Indian Head compared to the 16-year average, and below and much below average for May and June at Swift Current and Scott, respectively, with above normal precipitation for July. These field experiments are part of a three-year study (2000-2002). The remaining two years of data are still being compiled and should be released in 2003.

Seeding was completed by PAMI. The plot seeder was configured to apply AA and urea in addition to seed and phosphorus requirements. Openers were located at 10-inch row spacing. Side banding openers placed the nitrogen fertilizer 1-inch below and 1-inch to the side of the seed-row at the time of seeding. The mid-row banding component involved using spoons to open up the seed-row with mid-row coulters for the nitrogen fertilizer. The coulters were between every second seed-row. Travel speed was 4 mph.

So what did the research find? The Swift Current site was the least responsive to added N because of the higher available soil N associated with the previous year's fallow period.

At Star City, maximum wheat yields occurred at the 120 kg/ha rate (Table 1). The different N fertilizer forms and placement methods had no significant effect on wheat yield. The canola yield plateau occurred between 80 to 120 kg/ha (Table 2). However, for canola there was a significantly higher grain yield for mid-row banded urea versus side-band placement. The researcher hypothesized that early supplies of N to the seed row may have provided some level of toxicity that was not evident by early season plant counts.

In this project, two check treatments were done to compare the effect of opener type (side-band vs mid-row). At Star City, the mid-row band treatment (0 kg/ha) had significantly greater canola yield when compared to the side-band treatment. The difference could be from better placement of the P fertilizer. The side-band treatment had the P fertilizer banded below and to the side of the seed row compared to the mid-row which had the P fertilizer seed placed. The difference could also be an effect of the opener configuration on the seedbed quality. Wheat was not affected.

At Indian Head the N fertilizer rates, forms, and placement methods had little effect on the research parameters. This is attributed to the high inherent N fertility at this site.

Under the dry conditions at Scott the N fertilizer rates, forms and placement method were the most evident. Yield responses for wheat continued at the high rate or 90 kg/ha. The greatest yield reductions were often the AA trials for both wheat and canola. The lower yields are likely due to the dry conditions that will have favored NH₃ losses during seeding.

For both wheat and canola, side-banding produced significantly higher yields. It also increased the protein percentage of wheat (Table 3). However it was not the focus of this research to determine the most economic rate of fertilizer.

The study also looked at the nitrate and ammonium supply rates. Thavarajah concluded that the early supply of N to the seed-row was more pronounced with side-band placement than with mid-row placement. At rates below 80 kg/ha, no evidence of significant seedling damage was evident using either placement. It should be noted though, that these openers were new with very little wear. At higher rates (120 kg/ha) some injury may occur that may not be expressed in reduced plant counts the researcher hypothesized.

The first year of the three-year project concludes that the rate of N has a more pronounced effect on agronomic characteristics than different N forms and placement methods. Under dry conditions, N forms and placement can have the greatest impact. When soil moisture is good or soil N levels are high, the position of the band in relation to the seed-row is much less important.

So the debate of side-band vs mid-row will likely continue. Like the chunky soup debate, it comes down to your personal preference and your perceived level of risk. But remember that opener wear and air velocity and speed can be disastrous to your potential seed and fertilizer separation.

Table 1: Wheat grain yields for the 2000 crop year (adapted from Thavarajah, 2001).

* - Fertility rates at Scott were as follows: 0, 30, 60 and 90 kg/ha.
** For the Indian Head site, no mid-row (no N) check treatment was used in the plot design
SC - Star City; IH - Indian Head; S - Scott; SB - Side-band; MR - Mid-row

Table 3: Wheat protein percentages for the 2000 crop year (adapted from Thavarajah, 2001).

* - Fertility rates at Scott were as follows: 0, 30, 60 and 90 kg/ha.
** For the Indian Head site, no mid-row (no N) check treatment was used in the plot design
SC - Star City; IH - Indian Head; S - Scott; SB - Side-band; MR - Mid-row

Table 2: Canola yields for the 2000 crop year (adapted from Thavarajah, 2001)

* - Fertility rates at Scott were as follows: 0, 30, 60 and 90 kg/ha.
** For the Indian Head site, no mid-row (no N) check treatment was used in the plot design
SC - Star City; IH - Indian Head; S - Scott; SB - Side-band; MR - Mid-row