Fertility and Nutrients
Maximizing economic return in oat
By Donna Fleury
Target 89 lb. N per acre for most consistent economic return.
As demand for quality milling oats continues to expand, oat growers are looking for ways to increase yields and maintain better quality oat production. Some growers have expressed interest in combining higher nitrogen (N) rates with a fungicide application, even when disease intensity is low, as a way to help maximize economic returns in oat.
Bill May, crop management agronomist with Agriculture and Agri-Food Canada in Indian Head, Sask., led a two-year study to evaluate the effect of fungicide application and N rate on the grain yield and oat quality. The project also included an economic analysis to provide growers with information on the economic benefits of these inputs.
“Overall, if growers are using an oat cultivar with good disease resistance and there is little or no disease present in the crop, then there doesn’t seem to be a benefit to using a fungicide,” May explains. “The results of our study showed that an application of fungicide did not benefit the grain yield at the disease levels measured in this experiment. Disease was not high enough to affect grain yields significantly, and fungicide showed no benefits to improving key quality variables such as test weights and groat percentage. At the low levels of leaf disease, fungicide was not warranted and would have resulted in a negative economic return in our study.”
The research trials included three fungicide treatments: a control, pyraclostrobin (Headline) and propiconazole plus trifloxystrobin (Stratego), applied after the flag leaf had fully emerged at Zadoks 45. Eight N rates were compared, ranging from 4.5 to 125 pounds per acre (lb./ac, or five to 140 kilograms per hectare), plus 20 lb. phosphorus pentoxide (P2O5) per acre (23 kg P2O5 per hectare), all side-banded during seeding. The study also included an economic analysis that calculated the change in gross return at three oat prices: $2, $2.50 and $3/bushel ($130, $162 and $194 per ton) and three N fertilizer prices, $0.45, $0.68 and $0.91/pound ($1, $1.5, and $2/kg).
“Although there are some growers who like to use a fungicide even if they don’t have disease pressure, we still haven’t been able to figure out the benefits so far,” May says. “However, if an oat cultivar is susceptible to crown rust and if there is crown rust disease pressure, then using a fungicide is recommended. It will depend on what level of crown rust disease is present in the crop and the type of cultivar being grown. In Saskatchewan, most cultivars with moderate resistance have good enough resistance in most situations. In Manitoba, further east and south, there tends to be heavier disease pressure and growers will want to be growing a variety with crown rust resistance. For Alberta, crown rust is not really an issue for oats at this time.”
Another important finding of the study is that fungicides and N can be managed independently. There is no beneficial interaction between fungicide and N for growers using higher N rates at low disease intensity and resistant genotypes. “The study shows that although we can push the N rate up, economically it doesn’t always make sense,” May says. “The price of the crop is more sensitive than the price of N for picking an appropriate N rate. We found that a nitrogen fertilizer rate of 89 lb. N/ac provided the most consistent economic returns when oat prices were between $2.50 and $3 per bushel. This rate met most of the needs of the crop without pushing the test weights down very much.”
The study results showed oat yield was highly responsive to increasing fertilizer N at low rates but less responsive to higher N rates, with the 18 lb./ac N rate yielding 144 bushels/ac, while the 89 lb. N rate yielded 174 bushels/ac and the 125 lb. N rate yielded 177 bushels/ac.
May emphasizes that higher N rates beyond what yields require can push test weights down. Using enough N to optimize yields is important, but don’t use too much. Lodging is also an important factor and can really knock the quality of the product. Not only do growers need to be concerned about the N rates lowering test weight, if it is in excess of what the crop needs, higher levels can start to lodge the crop through excess growth. Lodging multiplies the negative impacts onto the test weight, and this risk needs to be considered when deciding on an N rate. If the crop lodges, other quality parameters go down as well, such as poor colour, more thins and less plumps, and disease pressure may increase due to a tighter, denser canopy with less airflow.
Other studies have compared seeding rates for oat, and the recommended rate is 300 plants per square metre (/m2). However, if the field has heavy wild oat infestations, then a higher seeding rate of 350 plants/m2 is recommended. Currently there are no in-crop herbicides registered to control wild oat in tame oat, therefore growers must rely on using other agronomic practices. May completed another study comparing the effect of phosphorus (P) and seeding rate on wild oat. The objective of this research was to determine if side-banded P in combination with seeding rate would increase the competitiveness of tame oat with wild oat, increasing yield and quality. The trials included two wild oat strips of either low or high wild oat density. The tame oats were seeded across the wild oat strips using seeding rates of 150, 250, 350, and 450 plants/m2 and compared three side-banded P rates of 0, 15, and 30 kg P2O5/ha.
The results showed that seeding rate and P fertilizer can be managed independently of each other to improve oat yields. Although increased seeding rate did improve tame oat competitiveness, wild oat competition still decreased grain yield. At the highest seeding rate, the tame oat biomass was lower in the high-density wild oat treatment than in the wild oat free treatment, indicating that the wild oat is still competitive enough to impact the development of the tame oat even at a high seeding rate. The effect of seeding rate on wild oat is strongly influenced by the environmental conditions during the growing season. Both plump seed and thin seed were affected by seeding rate and year, but not by P rate.
“Our results did show that with increasing P rates, the competitiveness of tame oat with wild oat was also improved,” May explains. “We saw a reduction in wild oat seed production by 38 per cent with P fertilizer application, likely due to an increase in tame oat biomass. The application of P increased the competitiveness of tame oat by increasing crop biomass by 7.6 per cent and grain yield by 3.4 per cent. The side-band supplies the fertilizer preferentially to the tame oat over the wild oat, and the wild oat did not interfere with the uptake of side-banded P. Therefore, using P fertilizer is recommended especially in dry years because it has a benefit with improving competition with wild oat. A good practice is to use a seeding rate of 350 plants/m2 and at least 13.4 lb. P2O5/acre to improve wild oat competitiveness and increase tame oat yield.”
Oats are generally a good crop to have in rotation – they fit well with no real negative impacts to other crops around them in rotation. “For oats, test weight is still king for markets, so managing agronomics and inputs to maximize test weights and economics is key,” May adds. “Although most variables seem to be independent of each other, using recommended seeds rates, balanced fertility, disease-resistant cultivars and other good agronomic practices can help maximize economic return on oat.”