Curious on liquid nitrogen stabilizers…use, success, trials? Recommendations from some fertilizer 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're 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're 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.