ROULEAU, Sask. – Fertilizer misses generally show up in the field as pale, stunted, low-yielding patches, but farmers in northeastern Saskatchewan were surprised when strips of unfertilized crop yielded only slightly less than adjoining areas that received the full application.
The strips were part of the Variable Rate Technology project, a farmer-driven research exercise in the Melfort area. Farmers and researchers investigating nitrogen management and precision farming included unfertilized strips in certain fields and used combine yield monitors to compare yields with fertilized areas.
Stacy Moskal of Brooksby, Sask., said all farmers have unintentional misses with the anhydrous applicator. When he was approached to do a zero nitrogen strip trial, his initial reaction was, “no way. I have enough of them already.”
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But with rising fertilizer costs and the continuing search to be more profitable, he and his father decided to try it, with one goal being to better understand nitrogen mineralization in soil.
In 2002, the Moskals seeded 46A76 canola on a 160-acre field. They applied 50 pounds of an 8-25-6-8 blend, as well as 70 lb. of anhydrous ammonia on 155 of the acres.
“We had a five-acre check strip with the 50 lb. rate of the blend, with zero ammonia. In the middle of this check strip were six geo-referenced points with soil tests taken earlier,” Moskal said.
What he expected to see was a paler green colour in the zero nitrogen trial at some point after emergence. He thought the plants would be much shorter during flowering, and thinner, with fewer pods, when he swathed. Overall, he expected a 10-15 bushel an acre yield reduction in the zero nitrogen trial.
“What we actually saw was even emergence from both trials. We couldn’t see any colour difference. Both trials flowered at the same time and there didn’t seem to be a significant height difference at flowering,” he said.
“There was a distinct difference in the final stages of flowering. The normal application trial had significant second growth that was not noticeable in the zero nitrogen trial. When I was swathing I could tell the difference plain as day.
The zero nitrogen trial seemed to be thinner and a shorter stand than the rest of the field. It was also a lot riper and there was a little more shelling.”
At harvest, the seed in the zero nitrogen trial appeared larger and darker in colour. On their yield maps, the zero nitrogen plot actually outyielded the average of the whole field.
“Our zero nitrogen strip yielded 31.4 bu. per acre. The average of the whole field was just under 30. We tested plots to the north and south and found yields of 35.75 north and 32.5 south, with an average of the north and south plots around 34 bu.,” he said.
“We can say the plots with 70 lb. of nitrogen outyielded the zero nitrogen trials by only 2.75 bu. per acre.”
With further yield analysis, Moskal said he was able to determine the ratio of which of the three forms of nitrogen contributed to the crop yield at each of the six specific soil test points.
He concluded that most of the nitrogen supply for this crop came from nitrogen mineralized from soil organic matter, while little came from soil nitrates and applied fertilizer.
“We will continue to use zero nitrogen trials until we are able to have a legitimate test to predict the amount of nitrogen produced by soil mineralization,” he said.
Vince Walker, who included a similar strip trial in one of his fields southeast of Brooksby, said his objective is to make more money on his farm by improving productivity and maintaining or lowering input costs.
He said this trial was designed to help him learn more about field variability as it relates to nitrogen fertilizer response. He had a number of expectations, including lower yields in the unfertilized area, plus a high degree of yield variability within the check strip.
A soil test the previous fall gave the nitrate analysis as 40 lb. per acre, with a recommendation to apply 45-55 lb. based on a 29 bu. per acre canola yield. That yield projection was low, based on zero subsoil moisture that fall.
In the spring, Walker applied 50 lb. per acre of nitrogen with anhydrous, plus eight more lb. with a granular phosphate blend. For the check, he went down and back with a 55-foot air seeder, to give a 32.5 metre zero nitrogen strip.
“The yield in that zero nitrogen strip was 30.19 bu. per acre. West of that was 28.7 and east was 30.45. There was no significant yield increase due to nitrogen application,” he said.
From snowmelt to the end of July, the field received only 100 millimetres of rain.
“That’s probably got something to do with it. On the other hand, if someone told me I could grow 30 bu. of canola with no nitrogen, I wouldn’t have gone along with that, either.”
Yield monitor analysis revealed that most of the zero nitrogen check strip yielded 30 bu. per acre, so there wasn’t a lot of yield variability.
“With one year’s data, very little is totally conclusive,” Walker said.
“However, achieving full yield potential does appear to be possible with reduced application of nitrogen in certain areas.”
