Richard Taylor, Extension Agronomist; rtaylor@udel.edu
Nitrogen (N) fertilization is not recommended after June and before mid- to late-August in most years. This growing season has been an exception to the general recommendation. Usually by late-June or early July, we begin to see summer dormancy begin for the cool-season grasses since drought and/or heat conditions have limited growth. A majority of hay and pasture fields in the state have an abundance of soil moisture available. Although air temperatures have been warm this month, temperatures have not been extreme so grass growth has continued. A limitation to growth with the environmental conditions we’ve experience this year is the lack of N. Excessive rainfall leads to nitrate leaching or the loss of nitrate from a process called denitrification.
Nitrogen is required by grasses to produce top growth. Present conditions would encourage more top growth if N fertilizer were added. There are two concerns to address before making the decision on whether to fertilize a pasture or hay field. Both concerns involve economics and are somewhat related. For pastures, the question that would need to be addressed is whether higher pasture productivity will be used by the grazing animal such that gains will offset the cost of the N fertilizer. If the animals will not be able to make use of the additional production, will it allow you, the grower, to use a portion of the pasture to produce extra hay (assuming the weather at some point allows hay making). Will the extra hay harvested have enough economic value to offset the cost of the N fertilizer?
For the hay producer, the question involves whether the producer has been successful in removing the first hay harvest or not. If the first harvest did take place, N fertilizer will help grow additional hay that if successfully cured and stored will more than pay for the cost of the fertilizer. If the first harvest is still in the field due to the lack of hay making weather, addition of N fertilizer will lead to new vegetative growth. This could complicate the hay making process when hay making conditions allow harvest since the total biomass present will slow the hay drying process. However, the increase in leaf content can improve the quality of the ultimate hay crop.