In Western Canada, winter wheat is a high-yielding, profitable crop, and it is good practice to match your fertility rates with your yield goals. Managing the health of winter wheat is important for its success, and fertility is a key player in crop health. Here are some guidelines for winter wheat fertility management.
Every area is different when it comes to soil types and nutrient contents in soil. Soil sampling and testing can show you the plant available nutrients and other soil chemical factors important for winter wheat production.
Nutrient levels in soil also vary from year to year, so it is important to perform soil sampling and testing prior to planting any new crop. It is important for farmers to follow certain recommended steps for soil sampling and testing to develop a fertility management program.
To ensure accurate results, standards must be set for performing soil sampling and testing. Here are some guidelines set out by Alberta Agriculture:
Nitrogen (N) fertility is an important consideration in winter wheat production, and can be one of the most challenging factors for producers planning winter wheat. The 4R Nutrient Stewardship approach: Right Source at Right Rate, Right Time, Right Place can be helpful in assessing the merits of various nutrient management options. By adopting the 4R Nutrient Stewardship approach producers maximize the productive capacity within their operation without adversely affecting the other pillars of sustainability; environment and social.
Selecting the right source will help ensure your soil has a balanced supply of essential plant nutrients. Performing annual soil tests and applying nutrients to meet crop requirements will assist in deciding on the right rate. Applying nutrients at the right time will ensure nutrient uptake when the demand is high. Lastly, the right place helps minimize the risk of loss while increasing the availability of nutrients to the crop.
The 4Rs of Nutrient Stewardship is a site-specific, integrated approach that considers source, rate, time, and place decisions for the cropping system. These decisions work towards the economic, social, and environmental sustainability goals for the farm.
To learn more about 4R practices and programs in Canada, visit Farming4RFuture.ca.
There are several advantages of applying N at planting time. Typically, the price of N is more cost-effective in the fall than in the spring of the following year. If the nitrogen requirements of the crop can be applied at the time of seeding, the additional time and expense of a second pass over the field can be eliminated. Also, it ensures that there are nutrients available to the crop early in the spring, a critical time in establishing yield potential. Spring applications can get delayed due to poor weather or adverse field conditions, thus limiting the roots’ access to available N.
In a study done by Alberta Agriculture, it was discovered that when planting winter wheat in stubble fields low in soil N, the additional N fertilizer that was applied improved stand establishment and overwintering ability and did not reduce winter hardiness, plant populations, or yield. In this same study it was determined that N applied at the time of seeding was generally as effective and often more effective than spring broadcasting.
Possible disadvantages of N applications at seeding time are risk of seedling damage and risk of significant N losses. If placing N in the seedrow, safe rates of up to 30 lbs/ac can be applied, but may vary with moisture conditions, soil type, type of opener, and row width. Seedling damage can largely be overcome with openers, which place fertilizer away from the seedrow. If warm and moist soil conditions persist for a long period following seeding, risk of N losses due to denitrification or leaching can be substantial. Slow release N products can create more options for producers wishing to place higher rates of N with the seed and can also decrease the risk of these N losses.
Topdressing in late fall has also attracted the attention of some growers. With the cooler temperatures that the Prairies typically experience in late fall, N losses are usually minimal. Applying urea to cold (temperatures below 10°C approximately), but not frozen soils is the primary way to minimize losses. Precipitation, either as rain or wet snow, is always needed to move surface-applied urea into soil so it does not volatilize. On warm soils having temperatures above 15 degrees C, it is essential that precipitation occur within a day or two of application to minimize losses. On cold soils, the critical window for rain or snow is a little wider at five to seven days after application. To minimize N losses, spread urea fertilizer when rain or snow is in the forecast or when the chances are good for substantial showers soon after application.
The key to a successful spring broadcast N application is to apply early when soil conditions are still cool. A healthy winter wheat crop will resume growth early in the spring. Cereal crops use 70 per cent of their N by late tillering, and late applications of N will hinder the plant’s ability to convert this into yield. As a rule of thumb, spring N applications should be made as soon as it is dry enough to operate equipment without making too many ruts. Some growers will even apply very early when they can still travel on the frost; however, it is not a good idea to apply N on frozen soils.
Liquid UAN (28-0-0) and ammonium sulfate (including sulfur fines) are less susceptible to volatilization losses then urea (46-0-0), but under ideal conditions, spring topdressing can occur on cool soils and/or just before a significant precipitation event. Under these circumstances, any of these products will perform equally well. However, if warm and humid conditions persist for a period of time, some N losses will likely occur. To minimize volatilization losses associated with these products, the use of commercial urease inhibitors, such as Agrotain, can be considered. The amount of trash on the soil surface may affect liquid N efficiency by immobilizing applied N.
Some producers prefer to split their N fertilizer application between the fall and the spring. The value of this option depends on how practical it is for individual growers. For example, this may be a good fit for producers who do not have side or mid-row banding capabilities but want to make sure their crop has enough N to make it through the first few weeks of growth in the spring before they can get out and topdress the balance. In the spring, the producer can then apply the remaining N requirement based on soil moisture and crop conditions. This helps manage nutrient losses in wet soil conditions.
Winter wheat nitrogen management is different than spring wheat; therefore, when considering how to adopt the 4Rs into your farm operation, it may involve different choices than a spring sown crop. For example, choosing the right source/lowest risk product (i.e. a urease inhibitor) based on best management practices may help reduce risks associated with broadcasting if this is the best choice to achieve the desired nutrients to the crop at the right time and right rate.
Regardless of the option chosen to apply N, there is one component that is critical: be certain to use adequate rates. Winter wheat yields up to 40 per cent more that CWRS wheat and therefore requires more nitrogen. Using a soil test and the assistance of a local agronomist to determine proper rates is advised.
Regardless of the option chosen to apply N, there is one component that is critical. Be certain to use adequate rates. Winter wheat yields up to 40 per cent more that CWRS wheat and therefore requires more nitrogen. Using a soil test and the assistance of a local agronomist to determine proper rates is advised.
Nutrients and micronutrients (not just nitrogen), specifically phosphorus (P), potassium (K), and sulfur (S), are required in similar fashions and levels as spring-seeded wheat varieties. Manage these appropriately and you will have a well-established winter wheat crop in the fall.
It is important to pay particular attention to phosphate applications. In addition to a potentially good yield response, adequate seed-placed phosphate will aid in the establishment of a healthy winter wheat crop in the fall and increase winter hardiness. The general recommendation is to apply 20-25 lbs/ac of actual phosphate with the seed. Not unlike other cereals, maintenance amounts of nutrients such as sulfur, potassium, and copper are required.