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When drilling canola a common strategy to improve seeding rate accuracy is to only use every other row which effectively doubles the rate of seed going through each meter. There are also many producers who utilize air seeders and just prefer the wider spacing. Every season I get several questions about determining total fertilizer rates if the seed is dropped every other row but fertilizer is dropped every row. Regardless of whether or not fertilizer goes down every row it is important that the amount of salts placed with seed does not exceed the limit. The table below provide the limits in terms of lbs of salt per acre. If using 18-46-0 (DAP) or 11-52-0 (MAP) this is equivalent to pounds of N per acre. However if the fertilizer you use contains potassium (K) or sulfur (S), those have to be considered. An easy rule of thumb for determining total salt level of a fertilizer is pounds of N + K + 1/2 S.
In a scenario in which canola is seeded in skip rows but every row will get fertilizer the total amount of fertilizer can be doubled. For example on a 15″ row spacing the max salt rate is 5 lbs per acre. If you were using DAP as your starter that maximum rate to place in furrow would be 28 lbs of DAP per acre. If using a drill set of 7.5″ spacing and putting fertilizer down every row the max rate would increase up to 56 lbs DAP per acre.
Some producers may have the capability of applying different rate in every other row. In this scenario it is important to maintain that safe rate in the seed furrow. In the opposite row, fertilizer rate can go as high as you wish or the equipment can handle.
Now the big question is, “Is between row fertilization a good idea?” While we do not have results on this style of application (trials will be going out this year) we can draw upon upon similar work in other crops. For me the best win would be the second scenario in which a higher rate could be place between the rows. In this row I would use a urea and DAP blend. Any time we can put urea below the soil surface its a win and in fields with very soil soil test phosphorus (P) it would create something similar to the deep P bands once popular in corn production. Now if the field had adequate soil test P, I would focus on urea between rows. Keep in mind it is never a good to place urea in furrow with canola seed. For the average producer who is using a box drill the first scenario is the only option. In this case the rate of the between row bands will be reduced however I still believe on fields with very low soil test P this is potentially a great way to get the rest of it on. Remember if on 15″ and using DAP max rate only gets 12.9 lbs of P2O5 down. If fertilizer is dropped down every tube that number increases to about 26 lbs P2O5, which is still not enough for fields with low soil test P, but is better. With hope we will have some good results to share from the 2015-2016 canola crop.
It is that time of year, every Co-op I drove by the other day had a line of trucks pulling anhydrous tanks and the spinner spreaders were being loaded. For those of you who haven’t applied your nitrogen yet lets discuss the options traditional and nontraditional.
Anhydrous Ammonia, 82-0-0: by far the most widely used N source is the southern Great Plains. While it is not the most enjoyable to work with it is the cheapest per pound of N and that leads to its wide spread use without Oklahoma wheat production. Just a few simple rules with NH3, get it in the ground and close the row behind you. In conventional till this is usually easier unless the ground is too wet or too dry. In no-till this may be a little more challenging but usually easily accomplished. With the rise in low disturbance applicators I am seeing more and more acres of no-till receiving NH3. Last year I was in a field of stripper stubble and I had a hard time finding where the rig had run, minus wheel tracks.
Urea, 46-0-0: is second on the hit list in nitrogen sales in our state. It is a safe source that is easily handled and applied. In a conventional till system where the urea can be worked in shortly after application it is a very efficient and effective source. Unfortunately when it is applied to the soil surface and rain is the method of incorporation we can experience between 5-60% N losses. The losses come from how urea is converted to plant available ammonium (NH4). For urea (NH2)2CO2, to be converted to plant available NH4 it needs the enzyme urease. Urease is present everywhere but in the highest concentrations on plant residue. The figure below shows the reaction, urease converts urea into NH3 as soon as the prill dissolves. In the presence of moisture the NH3 (gas) is turned immediately to NH4 (solid) and is absorbed onto the soil particle.
The problems come when there is no soil particle for the NH4 to bind with. It usually takes 0.50 inches of rain or irrigation to fully dissolve and incorporate urea into the soil. So if we only get a few tenths or hundredths, even heavy dews, some of the urea will dissolve, be converted to NH3 then NH4 and be left on the plant/residue. When the moisture dries, some or all of the NH4 goes back to NH3 and will gas off into the atmosphere. I have even seen this happen when urea is applied on a wet/damp soil, not incorporated and it doesn’t rain for significant period of time. If the temps are cooler the urease is slower so less of the urea is converted to NH4, but if the temps are warm 60+ degrees these little enzymes can act very quickly.
Below is a short video on using urea fertilizer.
While the recent rains are a blessing and will surely help germination, it is not aiding our N use efficiency especially in no-till. That is why in some parts of the state you may see some grain drills running right now. Some of those producers are not planting wheat they are actually applying there pre-plant urea. I have even been told in the SW part of the start some producers are using air-seeders to apply their urea. While this seems like a costly venture I have worked with the Ag Economist to create a calculator to figure up the break even for when it would pay to use an air-seeder over the traditional spinner spreader in no-till. We hope to put the finishing touches on it in the next few days. When it is completed it will be shared on this blog.
Liquid Urea Ammonium Nitrate, 32-0-0 or 28-0-0: while this is one of the more expensive forms of N many producers are utilizing this source because the can pre buy and store on site and as sprayer get larger they can cover a significant amount of ground quickly. For the most part UAN is used in no-till and is a great source. I always recommend that applicators use streamer nozzle or streamer bars to apply UAN. When UAN is applied via a flat fan nozzle it spreads the fertilizer across the residue allowing a significant portion to be tied up. The streamers concentrate the fertilizer into streams/bands reducing contact with residue and increasing the amount of UAN that reaches the soil surface.
Timing and Rates
The cost of anhydrous, about $0.1 to 0.12 less per pound N less than urea is driving its use this year. The lower price is also driving a significant about of producers to go with 100% of their N pre-plant. While this makes for sound economics now having all of your N upfront is like putting all of your eggs in one basket. If we do get that cold and wet winter as some are calling for this presents a great chance for the N to move down the soil profile and down the slope. I have always recommended split application. This allows a producer to judge the crop throughout fall, winter and even yearly spring and adjust his or her N plan accordingly. For those who plan to graze there is still a need to get enough N down to produce fall forage, this may be 50 to 80 lbs of N, but for grain only production planted later in the fall a typical crop may only need 20-30 lbs of N before going into winter. The old rules of thumb, 2 lbs N per bushel and 30 lbs N per 100 lbs of gain still work and are better than a guestimate but we have better ways. Right now is the time to plan to apply N-rich strip, a strip in the field with 40 to 50 lbs more than the rest of the field. These strips can be applied with a variety of applicators, but as long as the N goes down in at least an area 10 ft wide by 300 ft long it is good to go.
Below is a N-Rich Strip 101 video.
If you have got the N-Rich strips out you can set back and watch to see when and if they develop. If you can see the strip you know you need too fertilize.
While many are not ready to think about top-dressing yet, it is never too early. Don’t be afraid to think outside the box. Oklahoma’s springs tend to present the perfect conditions for N loss when urea is the primary N source. This year in a 4R Top-dress Nitrogen Application Demo, at Lahoma and Chickasha, we are going to apply just about every available commercial source in about every possible manor. Urea will be broadcast, coated with inhibitors, applied with a grain drill, NH3 will be knifed in, and UAN will be applied with flat fan nozzles, streamer nozzles and knifed in. As technologies improve and the cost of N remains relatively high the options for top-dress N application will continue to improve. The economics of wheat production don’t look great right now so don’t be afraid to think outside the box, even if it does raise the eyebrows of your neighbors. Fill free to contact myself or your local extension educator if you have any questions about N application.
Every few years I request the results of all soil samples submitted to OSU Soil, Water, & Forage Analytical Labs (www.soiltesting.okstate.edu) under the crop codes of winter wheat and winter canola. Within this data set I can look at trends occurring across the state over time. In this report I will focus on the 2013 results but make some comparison with the 2011 sample values.
As it pertains to mobile nutrients such as N, S, and B there is little that can be applied from the previous year’s soil samples because their levels in the soil change rapidly. Samples must be collected every year to determine the current status. However the soil test levels of immobile nutrients, P, K, Mg, ect are relatively stable over time and the recommendation is to take a close look at these values every three to five years.
In 2013 the number of sample submitted increase. There were nearly 1000 more wheat soil samples (2733 to 3574) and 200 more canola soil samples (33 to 231). If the distribution of nutrient levels of the two years are compared the only significant change is that the soil test NO3 level was significantly lower in 2013 (Tables 1 and 2). This is attributed to the extremely dry 2012 spring and summer which delayed the breakdown of wheat straw and immobilization of residual N.
Reviewing the 2013 values the most concerning aspect is that 72% of the 3800+ soils samples had a Mehlich 3 P value below optimum soil test phosphorus (STP) of 65 (Figures 1 and 2). That adds up to 109,000 acres needing phosphorus, if you assume each sample represents 40 acres. There is no way to determine how much P2O5 if any was applied to these particular fields. However, an estimated impact of not fertilizing can be calculated. Based on the Oklahoma typical average yield of just below 40 bpa, it would cost the state approximately 575,000 bushels if the land went unfertilized. At $5.00 a bushel that is $2.8 million in revenue. To remedy the low STP it would take approximately 2.76 million lbs P2O5 at a cost of $1.5 million ($0.50 per lb).
In the NPKS response study wheat fields across the state were evaluated for a response to additional (in addition to producer’s standard practice) nitrogen, phosphorus, potassium, and sulfur. Phosphorus was the most limiting nutrient at 7 of the 59 harvest locations. A response to P occurred more often than any of the other nutrients tested. It is important to note at all seven fields had been fertilized with P that season, however each time it was below the OSU recommended rate. The response study was a great reminder that it is important to have a good soil test and to follow the recommendations.
Soil pH on the other hand showed a slight improvement from 2011. The percent of samples under 5.5 decreased by 4%, 25 to 21. Of the samples <5.5 the majority fall within the 5.0-5.5 category, which for winter wheat is still within the optimum growth window (Figures 3 and 4). These numbers are a good sign however two points should be made. There is a significant amount of winter wheat acres that is not sampled; much of this is likely to fall below 5.5 soil pH.
Additionally grid soil sampling and variable rate lime should consider on any field which the composite soil sample pH ranges from the high 4’s to the high 5’s. For example a 75 ac field near Deer Creek had a composite soil sample test pH of 5.3 and buffer index of 6.5. The OSU lime recommendation, for a wheat crop, was 2.2 ton per acre for a total of 166 tons to lime the entire field. However the producer grid soil sampled the field himself at a 2.5 acre resolution (31 samples). Figure 5, shows that the pH of the field ranged from 4.4 to 7.9. Only 33 tons of lime would be required if the field were limed using a variable rate technologies. Cutting the total amount applied by 133 tons would save the producer approximately $4000.
Oklahoma wheat and canola producers must take advantage of the weather when it goes their way. Yet if the crop does not have the proper soil pH and nutrients under it, it will never reach its potential. Take the time to collect a soil sample and send it in to a lab. The hour it takes to collect the sample a few dollars you spend on analysis will help ensure that crop you are producing has the best chance of hitting maximum yield in the most economically and environmentally sound manner.
OSU Soil Test Interpretations
Fertilization Based on Sufficiency, Build-up and Maintenance Concepts
With all things holding constant the last canola trials of our project should be picked up by the plot combine Thursday 6-20-13. Before the first yield results comes to my desk I can tell you that we are learning a great deal from the trials this year. In particular the DAP (18-46-0) placed with seed trail that was supported by the Oklahoma Oilseed Commission. This past year at the no-till site in Perkins, which has a low soil pH, the check plots that did not receive any fertilizer, preplant or banded, did not survive the winter. Additionally at both of our locations, Lahoma (low soil test P) and Perkins, we have documented that oil content was reduced when phosphorus was left out of the treatment.
Additionally out of the four site years, that is two locations over two years, the addition of DAP with the seed in-row reduced stand. The graph below shows just how much stand was reduced on a relative basis. Relative stand is a way to compare the DAP treated to the Check (no DAP) which we assume is 100%. So if we look at the graph below the plots were at 75% relative stand (i.e. 25% loss) at approx 5 lbs N per ac. By about 15 lbs N the stand was down to 50%.
There are a few things to keep in mind first, in the case of these trials stand loss did not always mean yield loss. Canola is a great compensatory crop, if there is open space it will grow into it. I will have to run the final yield data to get more answers. These trials were planted on 15″ rows putting down 5 lbs seed per ac, or at least that was the target rate. Many have shown that the seeding rate does not have to be that high if sown properly. I believe in a few cases we may have actually benefited from thinning the stand. However if you were planting 2.5 lbs seed per acre a small loss of stand may be a bigger yield loss. This is one of the question we will have to answer in the future.
And finally it should be noted that canola is planted on a wide range of spaces 6″,7.5″, 12″, 15″, 30″ are some of the most common. As the row width changes the amount of N placed with the seed changes. In other words if the goal is 50 lbs DAP per acre you will put twice as much in a 15″ row than you do a 7.5″ row. The Table at the bottom provide a guide for equivalent rate based on 15″ rows. For example if your target a excepted stand loss of 25% (5 lbs N according to the Figure) but you are planting on 6″ row spacing the recommendation would be apply no more than 13 lbs N per ac in the row or 72 lbs DAP/ac (13/.18)