Fertilizer Management on Hay Fields

Richard Taylor, Extension Agronomist; rtaylor@udel.edu

For those producers very worried about the impact of the shortage of rainfall so far this year, I suggest a two-pronged approach. First, soil test your fields to determine if any phosphorus (P), potassium (K), or limestone (to adjust soil pH) will be needed this year. If P is required, all of it can be applied at this time as well as limestone to both correct soil pH and to make nutrients such as P more available to the forage plants. If K is also required, it should be applied either all at this time, if less than 100 lb/acre is recommended, or should be applied in two equal applications when the recommendation is for more than 100 lbs/acre. For K, the second application should occur in late August or early September and is designed to help the forage grasses and legumes better tolerate winter weather.

Unless you are using manure or compost on your hay fields, you will not be using a soil test to check on nitrogen (N) recommendation rates. In general, the suggested rates for nitrogen range from 40 to 60 lbs of N per acre for each expected ton per acre of hay produced. Especially in drier years when drought may be a serious concern, the lower suggested rate should be used to avoid the possibility that high levels of nitrates will accumulate in the grass. My suggestion for N fertilization is to apply it very sparingly between each hay harvest or to evaluate the soil moisture levels and if they are adequate for a good period of growth the N can be applied at that time. A number of folks have recently completed their first hay harvest and in the fields I’ve check the soil moisture level is severely limited. The rain earlier this week was insufficient to refill the soil moisture holding capacity and I would suggest waiting a bit longer to see if more rain will come out way before applying N to stimulate grass growth. In the past few years, we’ve seen damage to grass hay fields when N was applied during hot, dry weather. Finally, don’t forget to consider fertilizing with N in a fashion similar to the turf industry and by that I mean applying N in early and mid-fall to encourage fall root growth to help the grass be in better shape for growth during the following spring and summer.

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