Answers can sometimes be inadvertently found to questions that weren’t asked in the first place. It’s like looking for a lost glove and finding a hat that you didn’t know was missing.
That’s the situation Dennis McIntosh found himself in last year. The farmer and researcher from Melfort, Sask., made an unexpected discovery while reviewing a large volume of GreenSeeker data gathered by the Saskatchewan VRT Project during the past three growing seasons.
GreenSeeker measures the normalized difference vegetative index, or NDVI, of a crop. In simple terms, NDVI is a direct indicator of the vegetative biomass at each spot the instrument snaps at the moment the reading is taken.
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A high NDVI reading indicates a healthy crop and the potential for high yield. Sick or under-nourished plants give a low biomass reading. Exposed soil gives an extremely low biomass reading, indicating no vegetative cover.
The data involve a high degree of detail and accuracy because Green
Seeker works at a resolution of about 0.2 sq. metres.
By analyzing the variability in NDVI data, crop uniformity can be assessed and described in numerical terms. Strong and weak areas can be pinpointed and the reasons for the differences can be analyzed.
Although the VRT Project is primarily focused on nitrogen management issues, McIntosh noticed that the NDVI data showed distinct differences
from one drill to the next. Some drills consistently produced a more uniform crop canopy than others.
Running the data again, he began to see that certain engineering characteristics in the basic design of each drill had an impact on the crop performance numbers.
“The average NDVI values on fields seeded with the top performing drill were almost always higher than the NDVI values on fields seeded with other drills,” said McIntosh, project manager for the research group.
He said it’s not important to mention the drill brands because only three drills were used in the field trials, which is not a broad-scale comparison.
“We weren’t looking for drill data,” he said.
“We were looking at nitrogen utilization. We came across this drill variance quite by accident. What we see is that drill design is very important. We found a strong correlation between the mechanical characteristics of a drill and crop uniformity. And crop uniformity is a key factor in overall crop performance.”
McIntosh decided the uniformity data required further investigation. With engineering and technical support from Morris Industries and Paragon Ag Services of Melfort, which are founding members of the Saskatchewan VRT Project, he pursued a new approach to evaluating air drill performance.
The result was an experimental set of software he calls the crop uniformity index, or CUI, with higher CUI values representing better crop uniformity. The system is based on the three years of NDVI crop density readings already taken by Green-
Seeker.
He used the new index to compare results from fields seeded with different air drills. All drills in the VRT Project had a five-frame design with on-row packing. Most were equipped with fertilizer banding coulters.
The CUI pointed to a strong relationship between crop uniformity and drill design. GreenSeeker documented major variations between drills, with CUI values ranging from 3.5 to 14.2.
These findings put the focus on fundamental differences in air drill component designs, particularly seed metering and air distribution, which McIntosh organized into a table so that comparisons would be easier to make.
Comparing the NDVI-based CUI data to the table, McIntosh noticed that momentary breaks in seed flow at the metering point can create seed spacing fluctuations within the rows at the start of the seed’s journey.
Another cause of irregular seed metering might be a metering system that is sensitive to changes in the frictional properties of seed and metering body surfaces.
Every metering unit has a limited range of flow rates with predictable and reproducible performance. Pushing the flow rate to either the high or the low extreme creates a metering compromise. Any perceived time saving benefit from not changing metering components is negated by poor drill performance.
Greater crop uniformity was statistically linked to a multi-flex frame, plus a number of other design features. The metering system on this particular drill was continuous flow without momentary on-off cycling. There were no abrupt 90-degree directional changes. These findings, based on comparisons of actual field CUI values, are consistent with the results outlined by the drill ranking table.
“11783 is the international communications and control standard for agricultural equipment, much like the ISO standard for hydraulic couplers,” McIntosh said.
“Equipment that does not have ISO compatibility forces the farmer to make redundant purchases of electronic control boxes and it just complicates life for the operator.”
McIntosh said uniformity is only one issue. The other problem is the violent beating that seeds must take.
“Soil and seed borne diseases have become a major problem with our widespread adoption of continuous cropping, zero tillage and short crop rotations,” he said.
“Violent seed collisions in air distribution systems can damage seeds both visually and microscopically. Seed damage provides an infection pathway for seedling disease at an early date. That damage is irreversible. There is no treatment for these diseases once they establish.”
McIntosh said seed damage increases with the number of times they sustain impact energy by sudden changes in direction.
“A drill salesperson might refer to the process as ‘gentle.’ However, the basic laws of physics predict the outcome of these torturous events.”
McIntosh said seed violence can be better understood by counting the number of abrupt directional changes the seed undergoes in its path to the seed boots.
“Tests for seed damage indicate that the amount of cracked flaxseed can go up by 20 percent with an 800 rpm increase in fan speed on certain drills. As the fan speed is increased further, nearly 100 percent of the flaxseed is cracked.”
When calibrating the drill, seed is typically collected at the metering assemblies or the seed delivery boots and the weight of seed is measured as a basic check on uniformity, but McIntosh said this procedure provides no information about the distance between individual plants.
“All things considered, there is no simple means of assessing or predicting the eventual field outcome in a laboratory setting. This is a burdensome challenge for air drill engineers.”
The relationship between crop performance and plant spacing has been thoroughly researched in corn. Yield losses are substantial with only small variations in plant spacing, explaining why corn growers invest in corn planters rather than drills.
Annual recalibration of each seed row wheel on a corn planter returns an extra $20 per acre through increased yield created by uniformity in the seed row.
McIntosh said that, although the consequences of non-uniform seeding are not as well understood for other field crops, producers do know that a large percentage of the expensive canola seed they plant every year never grows.
Canola seed tolerates violence about as well as flaxseed. It’s generally accepted that slightly more than half the canola seeds that are seeded actually grow to become productive plants.
“Uniformity studies in canola indicate a threshold below which yields are seriously reduced,” he said.
“But rather than fix the problem of non-uniform crop establishment at the source, our commonly applied practice is to simply increase the seeding rate.”
McIntosh said recommended canola seeding rates are typically about two pounds per acre higher than those required for optimal yields if the seeds were not damaged and the plants were uniformly established.
The extra two lb. of seed compensate for the poor drill performance that producers have come to accept. He thinks a high precision seeding system could slash canola production costs by $5 to $12 per acre through reduced seed costs.
Wheat, often considered to be an easy crop to grow, has some of the same uniformity issues as corn and canola, McIntosh said.
Plot scale yields in wheat are up to 40 percent higher than whole-field results with the same varieties on the same soil. The exact causes of these yield losses in field-scale production have yet to be determined, but McIntosh thinks crop uniformity is a leading suspect.
“We simply do not know the amount of yield loss due to variability in soil quality as compared to loss caused by seeding methods on commercial farms. But we do know that the seeding procedure on research plots is much more precise than the seeding of real fields.”
He said when spot yields are measured on small areas of a sq. metre, some of them yield as much as double the average for the whole field. That indicates wheat yields can increase dramatically if seeding methods are improved.
“More than 80 percent of the total energy supply for a crop comes in the form of radiant energy from the sun,” he said.
“Total plant energy collection is much better if a uniform crop canopy with total ground cover is developed early in the season. There is no magic here: just a small dose of common sense.”
McIntosh said precision seeding is a way to achieve better yields without increasing production costs.
“More appropriately, in an era of depressed commodity prices, precision seeding reduces production costs while maintaining yields. In short, it reduces financial risks associated with crop production.”
McIntosh’s research focuses on more effective combinations of technology to grow more grain with lower input costs.
Unlike many private and publicly funded research programs where the first goal is patent protection, McIntosh continues to place his findings in the public domain, freely available to all farmers.
