Managing Nitrogen as a System in Corn

By Dale Cowan

Crop planning by customer by farm by field by crop by product continues on with even more urgency as spring like weather in late February and early March lingers. One of the input areas of interest with challenging crop prices is Nitrogen on corn. Determination of the “right” rate of nitrogen continues to be somewhat elusive as many factors compound the choosing of the right rate. Is the right rate something that is realistic? At some point we need a “number” to set up an applicator to apply the targeted rate of nitrogen. The reality is most decisions we make in farming are from a systematic process of trade offs with consideration given for risks associated with each decision step. Add in field variability the complexity increases.

One of the tools we can use to understand the complexity of making a nitrogen recommendation is the Ontario Nitrogen Calculator (ONC)( found on our website)

The calculator ask for input on soil texture, soil organic matter, yield goal, price of corn, price of nitrogen, any other nitrogen sources and previous crop. It is an interactive spread sheet so you can enter different scenarios to see how that impacts on the nitrogen rate. 

It allows for a pre-sidedress nitrate soil test to be used prior to side-dressing UAN as final check in adjusting N rates which overrides the preplant and side-dress application rates calculated previously. In this example a PSNT test of 11 ppm taken in early June adjusts the N recommendation to 180 lbs. of N. The spread sheet also provides for an interpretation of an ear leaf tissue sample.

Once you have the spread sheet filled in it is easy to change the price of corn and see how that changes the nitrogen recommendation.Under this scenario dropping the price of corn from $5.75 to $4.75 only drops the nitrogen rate by 12 Lbs. of actual N per acre.Changing soil texture from loamy sand to heavy clay increases N recommendation to 214 lbs. of actual N. Changing soil organic matter from 3% to 5% decreases N recommendation by 24 lbs. of N. Changing the previous crop from corn to red clover ploughed down decreases the N recommendation by 73 lbs. to 126 lbs. of actual N.

What’s the right rate of nitrogen?

It is situationally specific.

Download the spread sheet and contact your AGRIS Crop Specialists to learn more on managing nitrogen application risk. Including the use of nitrogen stabilizers to further protect the nitrogen investment and reduce any environmental risk of N loss.

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Nitrogen Management in Wheat 

By Kent Wolfe

Nitrogen management is a very critical part of winter wheat production. Spring N demand in winter wheat basically has two important functions, one is to help manipulate head count per square foot through the tillers and secondly it must supply nutritional needs to that plant through all stages of growth so that it can maximize both yield and protein content.

What is the right time, right rate, right source and right place? This approach is referred to as the 4 R’s of Nutrient Stewardship. We always take these factors into account when making crop plans for your farm. The whole Nitrogen system availability can be a very complex issue, so the more we look at these factors the more we learn, allowing use to make better recommendations.

What is the right time; Nitrogen application timing should be aimed at green up time with a onetime application by Zadok’s 30 (stem elongation) this spring it looks like we will be a couple weeks earlier than normal, so for our trade area the window will be over the next couple of weeks. It is from this stage to Zadok’s 58 (early flower) that the majority of N is required by the plant.

If going with a split application often times applying an initial amount based on tiller count at early green up then taking a plant tissue leaf sample prior to stem elongation can assist in determining the final split application timing and rate.

One of the key observations in determining both timing and rate is the crop condition and plant density or population of your crop, this involves doing both plant, stem and tiller counts in your fields. This is the only way to answer the questions of. Do you have full stand? What is considered a full stand? Is it well tillered or mostly single stems?

If plants are well tillered as it would appear a lot of fields are in our territory are due to earlier planting, above normal temperatures and an adequate amount of available N last fall, the recommendation would be normally timing by growth stage 30. In contrast a thin stand with very little tillering would suggest an earlier application at a higher rate to promote some more spring tillers.

The following table and diagrams below offers some guidelines on plant stand, how to determine tiller counts per plant, growth stages and then a general N timing recommendation.

What is the right rate of N that I should be applying to my wheat this year? There are 2 parts to this question. Are you pushing for maximum yield? Then that means higher N rates and higher N rates in turn mean a fungicide application to maintain plant health and allow the plant to utilize the additional nitrogen. Higher N rates, high yield and fungicide need to be a coordinated effort.

We have conducted trials over the last few years comparing rates of N, it would suggest that the average number is 120 lb/ac of actual N in normal crop conditions, this value can be adjusted by (+ or – 20 lbs) when looking at some of the other factors like expected yield, plant stand, plant health, application timing and wheat prices. Adding a fungicide at T1 or T2 & T3 will result in greater returns in high yield environments.

What is the right source of fertilizer to supply the wheat crop with its nitrogen requirements. In our territory basically it comes down to one of two sources Urea or UAN, each product comes with their own advantages and disadvantages.

The first product is Urea (46-0-0) this is a dry product that is popular in some areas because it is the most economical form of N. It can be also be applied easily with pull type spreaders or custom applied with airflow units and can also have other dry fertilizer products blended with it for a one pass program.

The main disadvantage of Urea is that it can be subject to losses from volatilization, this occurs during the conversion process to ammonium nitrogen. These losses can be as high as 30% under the right conditions which are dry soil surfaces, higher ph soils, warmer soils, windy days and high trash cover.

The other N source is UAN 28% which is a combination of Urea & Ammonium Nitrate in a liquid form. This form of N has shown a slight yield advantage when compared to the dry forms of N over the last couple of years. It does however require special sprayer tips to apply the product (jet or streamer tips are what they are referred to) These tips get less product on the leaf surface of the plant which greatly reduces the leaf burn that we would see with tradition fan or flood jet nozzles.

Whatever the N source always remember to add Sulphur at 20 lbs/ac actual. Field trials conducted by your co-operatives over the past 4 years shows on average a 6 bushel yield response to S. Another consideration would be treating your nitrogen with Anvol, this product is a urease inhibitor that blocks the urease enzyme thus reducing volatilization loss, if you are applying your nitrogen in dry conditions and no rain is in the forecast this treatment will protect your nitrogen investment and maximize full nitrogen availability for wheat crop.

What is the right place? For the majority of us a spring top dress application of N at green up is the only option. Make sure application equipment is calibrated to ensure uniform application, this is very important in maintaining uniform, consistent maturity, reduce lodging and maximize the yield.

Efficient nitrogen fertilization is crucial for economic wheat production. Over applying N not only could cause environmental concerns, it will also increase your cost of production and could possibly reduce your yield by increasing the chance for lodging and the risk of increased disease pressure. Lowering N rates to address these situations can lead to insufficient N being available to the plant at critical stages such as flowering and grain fill, which would significantly reduce your yields and profits. If you have any questions regarding your wheat N management call your local Crop Specialist. As always, we are pleased to help. 

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Choosing Your Herbicide Program 

by Chris Snip

As glyphosate resistant weeds continue to be more prevalent and new seed technologies come to market herbicide programs can change and be more complex. Glyphosate resistant Waterhemp is continuing to spread while glyphosate resistant Canada Fleabane and Giant Ragweed are ever present. These weeds may be making growers look to new herbicide options they are not used to using, to match this, new seed technology have continued to come to market allowing the use of different herbicide programs. This combination creates other situations a lot of growers haven’t had to deal with in several years or decades in certain cases.

In the soybean world we basically have 4 different herbicide platforms that can be used, some of them have cross over with other platforms while others do not so knowing what seed technology you have ordered is imperative to making appropriate herbicide plans. The platforms used in Southwestern Ontario include, Roundup Ready 2 Xtend, Roundup Ready Xtend Flex, Enlist E3 and Conventional/IP. When using different platforms on your farm there are several considerations to make, the first starting with planting. Seed cleanout is extremely important when switching between technologies simply dumping the new seed on the other seed results in frustration and limiting the herbicide portfolio in a field that has mixed seed technologies, this cleanout includes planters, seed wagons and any seed conveyance equipment used. The seed needs to be cleanout out before and after switching these technologies and everyone that may be running the planter or handing the seed needs to understand the importance of this exercise.

In corn the herbicide platforms are a little simpler for the most part having basically 3 different platforms. The problem in corn seed is that different seed companies have different trait messaging like SmartStax, SmartStax Pro, VT Double Pro, AcreMax, Qrome and the list goes on. With all of these trait portfolios there are basically three different herbicide programs, the hybrids that are Roundup Ready only, the ones that are tolerant to Roundup as well as Liberty herbicide and then conventional corn. Like soybeans it is important for you to know what herbicide tolerant package your hybrids have and plan your planting accordingly to maximize your herbicide options and illuminate any mix ups.

When choosing and using herbicides it is extremely important for you to know what technology is used in which field on your farm operation and just like planting proper sprayer cleanout going into and coming out of some of this technology is critical to ensuring herbicide success while reducing any negative consequences. Along with your own farm it is important to understand what technology your neighbour is using while nobody likes to see 2 feet of weeds between you and your neighbor spraying the wrong herbicide into your neighbours field and killing his crop is less desirable so communicate what technology you are using and inquire about what your neighbours are using to reduce any potential conflicts.

We continue to have great seed and technology choices in Ontario understanding the herbicide platforms that we can use with this seed is an important part of these choices. When working on your herbicide programs this year please make sure your crop specialist knows what seed you are using so we can help you make the best weed management decisions for your farm operation.