First-Cut Forage Considerations

For most areas, this means grass forages, and those mixed with legumes, but the alfalfa stands will not be far behind in terms of harvest date. These considerations will help improve stands for the subsequent harvests, but also help increase forage quality and stand longevity.

Forage Quality vs Forage Quantity

The decision is always: quality vs quantity. Do you delay harvest, for the under growth to come in and the plant to elongate, or do you cut short, harvesting a lower lignin, more digestible, higher protein forage? A lot of this decision will be determined on what type of livestock will consume the forage. If it is dairy animal or young stock, who has a high demand for protein, cutting for quality is very important. If this will be fed to leisure animals or brood cattle, targeting more quantity and a little less quality is acceptable. When determining the optimum cutting time for quality we rely on the plant’s physiological maturity for indicators. Table 1 lists different growth stages and corresponding forage digestibility. For a more in-depth look at forage quality, read Understanding Forage Quality.

Table 1. Growth Stage of Forages and Digestibility for Cool-Season Grasses

Source: Adapted from Ball,D.M.,M.Collins, G.D. Lacefield, N.P. Martin, D.A. Mertens, K.E. Olson, D.H. Putnam, D.J. Undersander, and M.W. Wolf. 2001. Understanding Forage Quality. American Farm Bureau Federation Publication 1-01, Park Ridge, IL.

Another factor that controls our timing and ability to make quality first cutting hay is the weather. Often, spring is either cool and wet or hot and dry leading to a first cut that is not as cooperative as desired. In many cases some species of grass will be fully headed and have set seed while others will just be in boot stage, making it next to impossible to cut for quality. Should the weather be uncooperative for making dry hay, producers now have the option to still make high-quality hay as silage or baleage. Baling at 45-65% moisture, rather than the typical 15-20% moisture, and wrapping in plastic will ensile the bale and make it more digestible for the livestock. For more information on this practice read Baleage – An Opportunity for High Quality First-Cutting Hay or watch a short video titled Baleage.

Fertility Management

Soil fertility is critical for growing a second, third, fourth, and potentially fifth, harvest within the season. Depending on if the crop is grass or legume, this may mean additional nitrogen, phosphorus and potassium after each harvest. The amount of N fertilizer recommended is proportional to estimated crop yields in each upcoming cutting, with a recommendation of 50 lbs N per ton of expected yield (dry hay yield). Phosphorus and potassium, however, are based on maintaining optimum soil levels and expectations for crop removal of nutrients in each cutting. For the most accurate recommendations, it is best to soil test every three years.  When soil test levels are below optimum, an additional quantity of fertilizer will be recommended to build soil nutrient levels into the optimum range.  When soil test levels are above optimum, no fertilizer is recommended, allowing the crop removal to draw down soil nutrient levels into the optimum range.

Nitrogen Management

To accurately assess nitrogen needs and application rates, the forage type must first be determined. That is, is the forage a legume, legume, and grass mixture, or grass?

Legumes, if properly inoculated, should not need any nitrogen for production, and applying nitrogen can actually decrease the life of the stand, by virtue of increasing competition from weeds. Purchasing nitrogen fertilizer for a legume forage does not make sense economically, however, if acreage to apply manure is needed and no other nitrogen demanding crops are available, manure can be utilized on legume forages up to the N removal rate (50 lbs N/ton of expected yield), while also supplying P and K fertility. Legume and grass stands require additional nitrogen if the stand is less than 50% legume. If greater than 50% legume, adding additional nitrogen will promote grass growth excessively and increase competition with the legumes, phasing them out.

Grass forages, or mixed stands less than 50% legumes, require nitrogen for optimum growth. A general recommendation is 50 pounds of nitrogen for each ton of forage harvested over the course of a year. One-third of this total quantity of N should be applied at green-up in the spring, and the remaining quantity should be split evenly between the cuttings. For example- if a field produces 3 tons/ acre, it will need 150 pounds of nitrogen (equivalent to 326 pounds of urea). Splitting the N applications between cuttings is recommended because N is subject to several types of losses, including leaching, volatilization, and immobilization. Further, having excessive N available to forage can lead to some luxury uptake of N by the forage (see luxury uptake of potassium, below, for more detail.)  In some situations, uptake of large amounts of N can lead to excessive nitrate in the forage, and contribute to possible nitrate toxicity issues when the forage is fed.  With these risks of loss, applying all 150 pounds in spring would not be a best management practice.  If the forage will be cut three times, 50 pounds of N should be applied at greenup, another 50 pounds N applied after first cutting and the last 50 pounds of N should be applied after second cutting. Apply 50 pounds for each ton/ acre expected in the subsequent cut. For more information on the nitrogen cycle and its movement, please read Nutrient Management to Improve Nitrogen Use Efficiency and Reduce Environmental Losses.

Phosphorus and Potassium Management

If forages need phosphorus fertilizer, but time did not allow it to be applied before the growing season, after the first harvest is an excellent time to apply it. Supplying additional P and K will help in tillering, root development, and drought tolerance throughout the season. Fall is the other ideal time to apply phosphorus and potassium fertilizers.

If current soil test K levels are optimal, or slightly below, application timing is of little consequence; K can be applied after harvests. Due to a phenomenon known as luxury uptake, heavy applications of K are not recommended.  Forages are known to take up more K than is required for high yields, when soil K levels are high, possibly resulting in insufficient K being available for growth later in the season. For this reason, it is suggested producers use the split application method. The split application method means just that, the recommended rates would be split into multiple applications during the season.

Manure Nutrients

Animal manure is an excellent source of nutrients for grass and grass mix crops. However, it is not as well suited for legume crops, as they do not need the nitrogen component and it can decrease the longevity of a legume stand. Often, applying manure during the growing season has more drawbacks than benefits.

A large concern of using manure during the growing season is the risk of smothering plants with large volumes of material. If using stacked manure or material with bedding or forage in it, high application rates mean material could lay on the crop and cause a lessened yield in the next harvest. Another concern is the amount of traffic on the field with heavily loaded manure spreaders. During the harvest season, compaction and plant damage should already be a concern, but by adding another heavy piece of equipment loaded with manure, more crop damage could follow. A last concern is that material will not break down before the next harvest. If conditions are not right, lack rain, sunshine, and microbial activity, the manure can remain on the surface, unincorporated, until the next harvest. While harvesting, this old manure can contaminate bales or forage meant for a silo. This contamination can lead to the transfer of disease or spoiled forages.

When treating forages with manure, they are best applied in the fall or spring, ensuring there is time for the nutrients and material to be incorporated into the soil. In situations where legumes will receive manure, this application should be made in the fall, a point in the growing season when the manure can provide a useful replenishment of P and K fertility if needed, while minimizing drawbacks.

For more information on forage maintenance fertility, read Penn State Extension: Soil Fertility Management for Forage Crops: Maintenance.

Weed Management

After first harvest is a good time to clean up some weeds that have lingered after fall or spring herbicide applications. If treating for annual grasses with Prowl H20 (pendimethalin), this is the time to make the second application for continued residual control. If broadleaf weeds have continued to persist, monitor the situation, but be prepared to make the proper application at the proper time. When controlling perennial weeds, application timing will be bud to bloom, typically mid-June into July, depending on the species, but scouting now for species identification and proper herbicide selection will ensure timing of application is correct.

Table 2.6-17, from the Penn State Agronomy Guide, shows the optimal time for foliar application of systemic herbicides for common weeds. For more information on selecting the proper herbicide and weed control options, read Spring Hay and Pasture Weed Issues and Alfalfa Herbicide Considerations by the Weed Management Specialists at Penn State.