Fertilizing Pastures

As I write this, it is late-May. The temperature is having a hard time getting up to what is referred to as “seasonal”. This backward type of weather makes for slow plant growth and very little pasture available for the grazing livestock. What options do you have to stimulate the grass to grow? Heat is the first requirement and that one you can’t do anything about. The other consideration is fertilizer application.

Can You Manage More Grass?

With warm weather there will be rapid grass growth that will need to be managed. Do you have the number of livestock and the fencing that will allow you to manage this growth? If you can rotate livestock from pasture to pasture, then you have the main requirement for taking the best advantage of the grass growth and optimizing its use.

Legumes Provide Nitrogen

If the pasture has greater than 35% legume in it, there will likely be adequate nitrogen produced by the legumes to meet the requirements of the grasses. When estimating the amount of legume, keep in mind that there needs to be an even distribution of the legumes across the pastures. Legume plants are often more visible than the grass plants in the stand. As producers, we often overestimate the amount of legume present. Take a careful look and even harvest a small square sample. Separate the grasses and the legumes to see how much of each are actually present.

Nitrogen Application - Rate & Timing

Grass responds very well to nitrogen fertilization, provided there is a reasonable level of phosphorous and potassium available in the soil. You will see a response to nitrogen about 2 weeks after application, and this increased growth will carry on for about 5-6 weeks.

To get an economic response to nitrogen, a minimum of 40 lbs per acre of actual nitrogen should be applied. Because of the high solubility of nitrogen, a maximum application rate of 75 lbs per acre is suggested. If you have a very productive pasture that you want to put on more nitrogen, then increase the number of applications.

Timing of application will depend on a number of factors, but mid-June will generally give the optimum results. By mid-June, the lush spring growth will have slowed and the nitrogen will give the grass another boost. Once we are into July the risk of not getting enough rainfall to take the nitrogen into the root zone is a concern. The other consideration is that grass growth may slow in the heat of the summer, especially if there is a shortage of moisture.

| Top of Page |
| OMAFRA Newsletters |