Smart Crop Nutrition With Dr. Cristie Preston

Dr. Cristie Preston, Senior Agronomist with Nutrien, discusses sulfur and Smart Nutrition™ MAP + MST® in this episode of Inputs by Top Crop Manager. Listen to the interview or read Dr. Preston’s answers below.

What are some of the benefits of sulfur fertilization on your crops?

Not all crops respond to sulfur application, so a lot of times it’s not on the forefront of our nutrient management plans. The reason why we soil sample for phosphorus and potassium is because the crops have more potential to be responding to those nutrients. When we talk about sulfur it’s a pretty common practice to apply it to your canola crop, because canola is one crop that does respond great to sulfur application, but there are others within the rotation that need sulfur as well. Whether that’s a spring wheat or some type of lentil, we need to make sure that those crops have enough sulfur, or yield could potentially be limiting.

 

Can you explain the difference between Smart Nutrition MAP+MST and traditional forms of sulfur?

There are two main types of sulfur when we think about fertilizer products. You have the sulfate form, which most commonly is found in ammonium sulfate and is readily plant available. As soon as you apply it the plant can begin taking it up. The other form is elemental sulfur, and that form has to be oxidized to sulfate before it can be taken up by the plant. A lot of times when we are choosing between the two different forms, it has a lot to do with timing and crop uptake. The overall goal is to apply these nutrients at the time that the plant is taking them up so that we maximize production and reduce losses. The sulfate form of sulfur can also be leached from the environment so it’s not necessarily ideal to apply a sulfate fertilizer in the fall. This new product Smart Nutrition MAP+MST contains sulfur in the elemental form. So it’s not in that sulfate form, it’s not subject to leaching losses, but it does have to be oxidized to become plant available.

 

Are there different forms of elemental sulfur?

Traditional granular elemental sulfur has a really big particle size, so when we think about oxidation rates, the smaller the particle size of the sulfur within the fertilizer, the quicker the oxidation. Smart Nutrition MAP+MST has a smaller elemental sulfur particle size and that increases the oxidation rate, allowing for sulfur to be plant-available quicker compared to traditional granular elemental sulfur. It also allows for a slow release because that elemental sulfur does have to be oxidized to sulfate to be plant available.

 

What are the key benefits of this from a crop production standpoint?

Smart Nutrition MAP+MST is a very nutrient-dense fertilizer. It has a fertilizer grade of 9-43-0-16, so it’s high in phosphorus and high in sulfur. When we talk about oxidation rates of elemental sulfur we also need to consider the distribution of that sulfur within the fertilizer product. Even distribution within the MAP granule allows for maximum soil to fertilizer contact, maximizing oxidation rates. Since the sulfur is present in the elemental form it carries a low salt index, which means you’re not going to see the seed burn or the seedling burn as the plant begins to grow. You’re able to apply higher rates in-furrow.

One scenario that we’re running into is when farmers are applying Smart Nutrition MAP+MST in-furrow with the seed, they’re applying fertilizer at rates to not exceed phosphorus recommended rates. Since Smart Nutrition MAP+MST carries such a high phosphorus concentration we’re not able to meet the sulfur needs of, say, the canola crop. Now that is requiring us to look at a blend of sulfur products within the sulfur nutrient management plan of that canola crop. We are suggesting that farmers apply Smart Nutrition MAP+MST in-furrow with the seed to meet those phosphorus needs but then apply additional sulfur with ammonium sulfate to get that early sulfur uptake and have the extended availability from the sulfur from the Smart Nutrition MAP+MST.

 

Can Smart Nutrition MAP+MST be applied in the seed row?

Yes, because Smart Nutrition MAP+MST has the lower salt index compared to other products like ammonium sulfate. We’re still doing trials on what rates we can push in-furrow and it does depend on the soil conditions for that year. This year we’ve seen drought conditions and that is not ideal for high rates of fertilizer being applied in-furrow. A lot of times we can navigate around that because many of the prairie soils are thicker in texture and that allows for the fertilizer to not necessarily cause germination issues as long as a little bit of moisture is present at planting.

 

Is there a seed safety trial that Nutrien has done that you can share some data on?

Yes. We had one trial this year with Antara Agronomy in Manitoba where we looked at in-furrow applications and really tried to push those in-furrow rates to see what the maximum amount would be. Of course those rates were based on phosphorus rates with an additional sulfur application needed afterwards to meet those sulfur recommendations for the canola crop.

 

Are there certain crops that you’re seeing good results from using Smart Nutrition MAP+MST?

In general, canola is one crop that we consistently see respond to sulfur. But I’d like to add in that a lot of times we may not see a response to sulfur application due to several reasons. One is there’s not a good soil test to make recommendations from, so a lot of times we focus on crop removal rates (what’s actually being removed in the grain) to make those fertilizer recommendations. Historical data – if we’ve seen sulfur efficiency, if we’ve seen the canola blooming or those flowers are aborting, then maybe you need to think about an in-season application to potentially salvage those yields. A lot of times are soils warm up we get a breakdown of organic matter that can supply enough sulfur to the crop, so we don’t actually see a response to supplemental sulfur applications.

 

Are there any other crops that would benefit from using Smart Nutrition MAP+MST?

Traditionally farmers haven’t made sulfur applications to other crops within the rotation because canola is the crop that responds the most to sulfur application, but there are some reasons why we may not see a yield benefit from sulfur application. A lot of times that comes back down to soil conditions. If there is residual sulfur in the soil from that canola crop to the next crop, we may potentially not need to apply sulfur there. Any time we have high organic matter soils we can see a breakdown of that organic matter to the sulfate form and plants can take that up. For the most part canola is the main crop that we see Smart Nutrition MAP+MST showing the greatest benefit. Again, that comes back to the low salt index, being able to apply it in-furrow and since it is the most responsive crop in the rotation, making sure that we have enough sulfur availability out there to maximize that crop.

 

What’s the impact of a drought or dry soil conditions on a fertilizer application?

In general, if fertilizer is applied in-furrow with the seed and you have drought conditions, that fertilizer has a higher potential to suck the moisture from the seed and the seedling as it begins to grow and that causes damage. Now Smart Nutrition MAP+MST, since it has a lower salt index and doesn’t have high amounts of ammonia like ammonium sulfate, you’re not going to see that seedling burn under those drought conditions. Even though fertilizers do need some moisture to dissolve, the tiniest bit of soil moisture can allow that Smart Nutrition MAP+MST fertilizer to dissolve.