Hay and Pasture Fertilization This Spring

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

In many areas of the state, pastures and hay fields are either just beginning to green-up (northern sections) or while having started the process of greening-up several weeks ago are making slow growth with the cool, often cloudy and rainy weather. Now that calendar-wise, we are into mid-April, it’s time to apply nitrogen (N) fertilizer to hay and pasture grasses to boost production.

With fertilizer prices still high and the threat of frequent showers in the forecast, growers will want to limit their application rates of N to ensure maximum plant uptake and minimum loss to leaching or denitrification (wasted fertilizer dollars). The slow start to forage growth this year suggests that at least some N will be useful in encouraging forage (grass) production for grazing animals and reducing the need for supplemental hay or grain.

For pastures or hayfields that contain a significant proportion of legumes (clover, alfalfa, Birdsfoot trefoil, or lespedeza), N application rate should not exceed 30 lb N/acre/application. Otherwise, the N-fixing value of the legume will be lost to the grower.

On pure grass pastures not fertilized with N last fall, an application of 30 to 50 lb N/acre will be sufficient to boost grass productivity. On pastures fertilized with N last fall, the N stored in the plants should be adequate for much of the early grazing season but watch the pastures carefully for the first sign of slowing growth and then apply additional N at that time, probably in mid- to late-May.

For hay fields, research from The Pennsylvania State University and Dr. Marvin Hall suggests that an application of 40 to 60 lb N/ton of expected yield will maximize production of most forage grasses while minimizing the risk of nitrate toxicity. I would suggest going with the lower rate this year because of the growing conditions we’ve experienced so far this season.


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