Hay and Pasture Fertilization Options

Richard Taylor, Extension Agronomy Specialist; rtaylor@udel.edu

With a very unusual wet weather pattern in place over the MidAtlantic, it is possible to alter the usual nitrogen (N) fertilization practices if more forage is needed for grazing animals or to stimulate more hay crop growth. Normally, it is not recommended to apply N during the middle of the summer, due to the combination of heat and drought which can put significant stress on the typical cool-season grass species used in hay and pasture fields. Nitrogen, of course, stimulates top-growth, often at the expense of root growth, especially in late spring and summer; and this, combined with the impact of the usual mid-summer dry soil and high temperatures, can stress the tolerance of cool-season grasses causing them to go dormant or even cause some stand loss.

The current weather pattern has left many fields with soils at or near field capacity and for those producers who need extra forage production, application of N fertilizer now can boost yield potential on hay and pasture fields. Since no one can predict how long the current rain pattern will last, growers should limit any N application to 30 to 50 lbs N/acre which should be enough to stimulate top-growth using the current soil moisture without elevating the risk to stand health if the rain pattern changes drastically soon.

Another factor to keep in mind when deciding which fields might benefit from an unusual mid-summer N application is the dominant species present and its maximum temperature for good growth. Species such as Kentucky bluegrass, ryegrass, and timothy (if not one of the new varieties with greater heat tolerance) have relatively low temperature optimums, do not respond well to even irrigation at high temperature, and are not the best candidates for N application in mid-summer. Tall fescue, reed canarygrass, and possibly orchardgrass are your best choices for a mid-summer N application.

Those harvesting for hay have another worry with the current rainfall pattern, which is finding a period of time when hay can be adequately cured without having rain damage the mowed hay. Increasing the yield potential for a harvest will not necessarily be helpful since the increase in the amount of hay to cure will slow the drying process and increase the risk that rainfall will damage the windrowed hay. Hay producers will have to balance the increase risk with the potential benefits if they are successful in harvesting a larger crop and getting it into the barn.

Whether you have hay or pasture fields if you do consider a mid-summer N application, be sure to contact your nutrient management consultant before adding N so that the consultant can make the change to your nutrient management plan. Few producers either add any N or add as much N as is generally recommended by universities; so for most of you, total N applications will remain below the maximum recommended level. If the consultant requires justification for the change in N application timing/amount, pass along this article, indicate your need for additional forage production, and cite the high amount of rainfall received to date.

Finally, if your fertilization budget is limited and won’t stretch to an extra summer N application, you should remember that your pasture and hay fields will benefit the most from a fall application of N. This application is made once the air temperatures begin to decline in the fall, soil temperatures remain high, and top-growth has significantly slowed. The N applied at the fall application (mid-October to mid-November) stimulates root growth which can significantly benefit the grass next spring and summer since it increases the total rooting zone available to the grass for moisture and nutrients. You should plan on the fall N application since it will be the most important N application you can make. Again, make sure any changes you intend to make are incorporated in your current nutrient management plan.

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