Canola Discovery Forum 4R panel – more Q&A

Canola Discovery Forum had a 4R fertilizer management theme. The 4R principles are Right Source at the Right Time, Right Rate and Right Place. The program included a panel with Lyle Cowell with Nutrien in Saskatchewan, Mario Tenuta with the University of Manitoba, Dean Nelson, who farms in Alberta, and Adam Gurr, who farms in Manitoba.

The panel emphasized the importance of placing fertilizer into the soil. Mario Tenuta said, “I think subsoil banding is absolutely critical. The concentration of nutrients results in less interaction with the soil and means more availability to the plant. It is one of things farmers have some ability to control.” Dean Nelson talked about the importance of soil sampling so he knows what rates to use. Logistically, he says it’s easier to have one blend for canola for the farm, but with soil tests he can adjust the rate based on needs for each field. Adam Gurr talked about phosphorus rates that match crop removal, and added that farmers would really benefit from an accurate economic evaluation of phosphorus fertilizer rates. Lyle Cowell says the first thing farmers should do is figure out the appropriate rate based on the potential of the soil. The whole panel is captured in this Canola Watch podcast.  

The panel generated a lot of interest among attendees, which meant a lot of questions went unanswered. Fortunately, the panelists agreed to answer the questions after the fact. Here are answers to the unanswered questions:

For producers: Which changes in fertilizer programs should take place to increase yield to 52 bu./ac. in the next five years as planned for CCC? 

Adam Gurr: On our farm we have been able to achieve average yields in excess of the CCC goal for several years now. Some of this is no doubt related to our region and growing environment, but I will list off some things I feel has perhaps helped us along the way. 

1. Don’t seed too early. We prefer to target the last half of May for our canola and most years our best yields come from the last crop we seed, which is often into the last week of May or first few days of June.  I used to seed early, even in April, but always found that I ended up dealing with frost-damaged canola and flea beetles. Mortality was higher of course and the stand was patchy and uneven, which makes it difficult to properly time fungicide applications and swathing/dessication.  In our area, if we have an outbreak of sclerotinia it is most often on the early-seeded canola and losses can be high even with a fungicide application. 

2. We still swath most of our canola as we feel it is a lower cost option for us, but we use only varieties with pod shatter resistance as it allows us to swath later ensuring that the entire field area has reach an acceptable level of seed colour change (SCC) prior to swathing, which can be a challenge in our variable landscapes. 

3. If you struggle to get adequate stand establishment on a regular basis, do yourself a favour and invest in a terrain-following drill.

4. I feel that many producers still do not apply enough nitrogen (N) fertilizer to achieve maximum yields, except maybe for a year where yields are limited by drought.  We have been running a long-term trial on our farm for eight years now where we have been comparing three different fertilizer regimes applied to the same plots each year.  I have been surprised at how responsive both wheat and canola have become as time has progressed. This has been a real eye-opener as it has made it clear to me that we have been under-fertilizing canola and wheat on our farm and I suspect we are closer to the upper range for nitrogen fertilizer in our area. 

5. With regards to phosphorus (P), for most I suspect it is much the same story as it is with N where the rates applied to canola and other crops in rotation are simply not high enough to maintain optimum levels in the soil.  Experts like Don Flaten, John Heard, Cindy Grant and others have stressed the importance of maintaining adequate P levels to achieve maximum yields in all crops, not just canola.  If a producer is in it for the long haul then it makes perfect sense to at least match P removals with additions. There is plenty of data to support this.  Also in the year of application, P fertility rates are important, especially in soils testing low in available P.  We have taken steps over the last three seasons to address our own P deficit and it is something we will continue to manage in the years ahead. The recent years of low P fertilizer prices has made this decision an easy one especially when combined with data we have collected on our farm showing how responsive our soils can be to P fertilizer additions.   

6. We don’t see responses to potassium on our soils and we feel our sulphur applications are adequate, so I won’t speak about them. 

Dean Nelson:  I think we have all the tools we need to reach those goals.  We have been hitting a 49 bu./ac. average for the last couple of years on our farm, with the top field getting 55 bu./ac. The most significant factor now is taking the time to do the little things to get that extra five to 10 bushels we need.  We need to take that 10 minutes to double check how the seeder is seeding in each field.  Take the time to double check that our combine is set the best we can, not just that first day of combining. Plug the holes on our combine that are leaking a little bit of canola.  We are always rushing to get the field done before the rain comes, but we need to stop and ensure all our equipment is running at the optimum. As Lyle says in question 10 (below), “Only seed genetics and nutrients can increase yield.  Everything else a farmer does is to preserve that yield.”  Are we taking the steps to preserve that yield? 

4R nutrient stewardship has been around for a while but according to the presentation (from Fertilizer Canada at CDF), the basic 4R nutrient stewardship is followed by about 50-60 per cent of farms. Do we know what is the difficulty for growers to apply 4R widely?  

Dean Nelson: Several things come to mind. What is in it for me?  Other than a pat on the back saying, “we are doing the right thing”, and it is good for future generations.  Is there a payback?  If we can see that, maybe there is some extra benefit, it does make it easier. Payback could be an additional premium for our crops when we sell them, or a better price for our land when we sell it in the future.  How much time does it take?  The average farmer has so many hats they are wearing – agronomist, marketer, mechanic, livestock manager, human resources, etc. – and now one more thing is not what we want to do.  But show us that it is easy to do.  We are already doing 80 per cent of the work, and the next 20 per cent is not that hard.  If someone could hold our hand for the first time, it would make a world of difference.  Those are a couple that comes to mind. 

Adam Gurr: This one really puzzles me.  We have been using 4R practices on our farm for as long as I can recall. With the use of 4R nutrient stewardship we are more profitable than we would be if we didn’t use it, simple as that.  It makes perfect sense to band your fertilizer as close to seeding as possible and at rates that will maximize profitability.   

Is there a benefit to putting down a source of phosphorous at herbicide timing for canola? (If not enough was put down at the time of seeding to reach yield target?)

Lyle Cowell: No. In terms of 4R management, this is both the wrong time (far too late for efficient uptake and use by an annual crop) and the wrong place (foliar uptake is very limited). It is also probably the wrong rate (rates of both application and certainly uptake will be too low).   

Even though the soil tests say we have a high level of potash in our soil, should we still be adding this nutrient, and what are the pros and cons of adding potash? 

Lyle Cowell: Probably not, but this will depend a bit on what is called ‘very high’, the crop species and yield, and field history.  Keeping in mind that the potassium soil test should be regarded as an index of available K (not an absolute number), the test is fairly accurate.  There is some grey area on response potential though.  For example, if the soil test indicates more than 200 ppm K, I very much doubt added K will lead to a response.  If it is 150 ppm K, perhaps some crops will have a small response to added K (barley first), and in particular there may be parts of a field that will respond.  Once you are in the range of 100 ppm K or lower – you need to give serious thought to K fertilizer addition.  This still leaves some grey area, so consider crop, portions of the field that may respond (sand or peat) or field history.  One added note: Long term hay stands may become K deficient due to high rates of K removal with hay, and no fertilizer use. If in a hay crop or hay rotation, you may see a larger response to added K, despite the level of soil test K.

How do you account for fall manure application when you are trying to estimate your nitrogen needs that spring? 

Lyle Cowell: Use soil tests and know what type of manure was applied (liquid hog, cattle manure with bedding, etc.), what rates were applied, and if application was uniform.  By and large most fields with manure applied in fall will need little or no addition of N or P, and likely not other nutrients.  Again, a soil test is better than a guess, and manure testing is also available.

Is there increased risk of volatilization of N when seeding shallow (canola) and applying high rates of UAN as a sideband? If so, under what circumstances are risks higher? I’m talking about placing fertilizer in a band at the same depth as the seed but 1.5 inches to the side. 

Mario Tenuta: We have no evidence of substantial volatilization of ammonia in shallow side-band urea or shallow side-dress UAN in clay and sandy loam soil in Manitoba. A very important consideration is to ensure cover of the band with soil to limit losses.  

Lyle Cowell: The key is good closure over the N fertilizer.  In most canola seeding systems, the seed and side-band are well covered and adequately packed to seal in moisture, and also seal the fertilizer band.  UAN includes urea, ammonium and nitrate, and your risk is gaseous loss from the urea.  If in conditions where the soil is not fully sealing the band, it may be a good idea to add a urease inhibitor – NBPT/Agrotain or similar products – to reduce this risk. 

In our area, moisture can vary significantly. I prefer to fertilize based on what is required to get the yield I am shooting for.  If it is dry, the fertilizer is still there for next year.  If it is wet, the fertility in the soil enables the higher yield than expected.  Even if I tested regularly, the moisture variability would lead me to stay with my theory. 

Mario Tenuta: I can see this approach working where N losses are not significant and in conjunction with soil N testing to two feet. If N was added for a yield target and the target wasn’t reached, the residual N should be taken into account in next year’s fertility plan to recapture the money investment in fertilizer the previous year. 

Lyle Cowell: This seems more of a statement than a question, but in general I would be OK with this.  It sounds like you are in an area of often dry conditions with low risk to loss of nutrients.  If you take this strategy and subsurface apply the fertilizer, then this strategy may be OK for your farm.  However you should include soil tests to confirm residual nutrient levels.  You may want to avoid this idea on some fields that are low lying and subject to spring flooding or runoff. 

What do you think will be the next breakthrough fertility research or management for crop production in Western Canada? 

Lyle Cowell: I don’t think there is a new “breakthrough” on the horizon. I have been hearing about the “next great fertilizer product” for 30 years and it hasn’t arrived.  Instead we need to look behind and be sure we are not forgetting the breakthroughs of the past.  The simple 4R ideas will gain most farms added yield. Perhaps the next step is to target the 4R practice per field or per landscape. Too many farms are now applying the same rate of N nutrients per crop across every acre. This is very 1990. We can do better with more accurate 4R practices. 

Mario Tenuta: Precision 4R nutrient management. For crops that respond to side-dressing, a distributed network of soil sensors for nitrate. Maps showing soil properties, moisture and temperature for yield potential and prediction of N mineralization. And canopy sensing at side-dressing to estimate variable N application rates. If the promised expansion of irrigation networks happens, the reduction in drought stress will shake up yields and crop options for parts of Saskatchewan and Alberta. But if it is economical to irrigate will depend if access and rights to water are costly or not. 

I’m curious to understand the opinions of the panelists regarding organic amendments and biostimulants and if or how much that should factor in to fertilizer rates, being that they are often positioned as products that replace the need for synthetic fertilizers? 

Lyle Cowell: A crop will require a minimum of each nutrient to produce each bushel of seed.  These nutrients can come from the soil or from the air (N fixation) or from fertilizer.  There is no replacement.  If a canola crop needs 40 lb./ac. of P2O5, applying a niche biostimulant does not change this. It will not need only 20 lb./ac. of P2O5.  You can replace synthetic N with rhizobial fixation in legume crops.  And if you apply enough biosolid waste (manure or sewage waste), then you can replace fertilizer.  But that’s it. If you want to remove nutrients from the soil bank, then you have to replace them with the same nutrients. 

Mario Tenuta: My opinion and experience is the typical organic amendments supplements and biostimulant products that have been marketed have no value. There is increasing investment and purchase of startups by some of the larger ag input companies, so in the future there may actually be products that are useful. Scrutinize the data of product efficacy. If AAFC and university researchers have peer-review published studies showing that products work, then you can believe there is efficacy. But the research needs to be peer-reviewed. Be leery of trial data that is not peer-review published. 

To what extent can crop rotation help to get to 52 bu./ac. canola yield in addition to proper use of fertilizers? 

Mario Tenuta: Crop rotation is shown to increase yield compared to following the same crop. For Manitoba, yield of canola is lowest following canola and then sunflower, neutral following cereals, flax, peas, soy, and higher following corn, potato and navy bean.  See crop insurance data.

Lyle Cowell: A step back first.  Only seed genetics and nutrients can increase yield.  Everything else a farmer does is to preserve that yield.  A crop rotation does not “increase yield”, it preserves the yield potential that you have created.  Poor crop rotations lead to yield loss due to disease or insects or water use or other factors.  But if the potential is not present to start with, it will not get you to a goal.  Do we need to be careful to preserve yield goals with better crop rotations? Yes, in most cases we do need to do this.  In canola we play with fire when it comes to loss of potential due to disease (blackleg, clubroot and other) and insects (flea beetles and others).  The yield factor will vary per the risk. A poor rotation in a field with compromised disease levels in the soil can have a huge impact on yield potential. 

What is boron bringing to the crop?

Lyle Cowell: Like any nutrient, boron increases yield if it is deficient.  That’s it, nothing else.  In nearly 30 years I have seen boron deficiency four times – always on very sandy low organic soils.  If your soil is not B deficient, do not think that adding a bit will have a benefit. 

Curious on liquid nitrogen stabilizers…use, success, trials? Recommendations from some fertilizere dealers is to apply on all N for canola blends? 

Mario Tenuta: Urease inhibitors are useful when it can’t be avoided to leave urea at the soil surface with spring or top dressing additions. For UAN the benefit is less because there is less ammonia to volatilize from UAN than urea. In regions with good snow packs and spring waterlogging, urease inhibitors with fall-applied surface urea is likely not a benefit. 

For nitrification inhibitors, use these with subsurfac-placed nitrogen if there is a concern with loss of fall-applied N and loss of spring-applied N before crop uptake kicks in. There is a benefit with nitrification inhibitors with banded urea in fall. Our research hasn’t found a commercial product yet effective to limit nitrification of fall banded anhydrous. We are looking into the new available products now and different methods of application of the older inhibitor products to anhydrous. The benefit of nitrification inhibitors depends on soil moisture and temperature. If both are high and there is no crop to take up the nitrate, they are helpful. 

Lyle Cowell: These can be helpful, depending on your placement of N fertilizer.  If you carefully apply N in a subsurface band with good closure of soil over the band, then I see little value in adding a stabilizer.  If you broadcast N with no incorporation at the wrong time of year – you should use a stabilizer.  But as an agronomist, I would first ask you to consider better 4R placement of N fertilizer.  This question is about liquid N.  If you apply the UAN in a subsurface band, the same answer applies.  If you decide to topdress some N with fertilizer nozzles on the soil surface, you should add a urease inhibitor if you are not confident it will l rain in the next one to three days.

How about using lime on low pH soils to improve fertilizer efficiencies? 

Lyle Cowell: To increase fertilizer efficiency? Probably not.  First – if you have acidic soils that that actually lead to lower yields, then liming may help you.  But liming does not mean applying few pounds of pelletized lime in a seedrow application.  To be truly effective, lime must be applied at high rates (likely tonnes per acre) and in a finely divided product. 

How could we slow down acidification in agricultural soils? 

Mario Tenuta: Acidification occurs from rain, root growth, root uptake of ammonium (uptake of nitrate increases pH) and nitrification of urea (46-0-0), anhydrous ammonia (86-0-0) and ammonium (including 28-0-0) fertilizer products and reaction of phosphates in soil water. MAP (11-52-0) fertilizer can acidify basic soils. It does not acidify neutral and acid soils. There isn’t information on the pH reaction of ammonium polyphosphate (10-34-0). However, the product itself is at around a pH of 6.0 and nitrogen is in ammonium form, so it should acidify neutral to basic soils. A pound of ammonium sulphate (21-0-0-24) can acidify soil more than a pound of anhydrous ammonia or urea because the sulphate reacts in soil water to form sulfuric acid. Unless pH is below 5.5, there may be no benefit to increasing pH. Agricultural lime or Ag Lime can be added to increase pH in those most severely acid soils. I’d be only concerned for acidification in soils with low pH buffering capacity. These are soils dominated by sand and have low organic matter and pH below 7.  DAP (18-46-0) instead of MAP can be used, though DAP is not readily available in the Prairies. As well, calcium nitrate (15.5-0-0-19) won’t acidify and can be used instead of urea, and anhydrous ammonia fertilizers. However it is very expensive and not readily available. Seek advice from CCAs and extension agents if you are concerned about acidification. 

If you’re wondering about pH variability in a field, nothing beats testing within a field. A map and SKSIS are good preliminary tools to ball park pH to see if management is possibly warranted, but these can’t be relied on for actual pH. Many decades have passed since soil surveys were done, so pH values in the data base are often a bit higher than actual in the field now. 

Lyle Cowell: If your soil is acidic then you will need to lime it.  It’s really the only solution. Production and removal of crops and application of most fertilizers will lead to acidification, plus it is a natural soil forming process.  Our choice is really to not grow crops or to lime acidic soils, following the 4R principles of lime application.  We are at least fortunate in Western Canada as our relatively young glacial soils very rarely require additions  of lime.  In fact by the time that acidity limits production on most of our land, there will be much more significant nutrient deficiency problems. 

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