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 harvest date. These considerations will help improve stands for subsequent harvests and increase forage quality and stand longevity.

Forage Quality vs. Forage Quantity

The decision is always: quality vs quantity. Do you delay harvest to allow the undergrowth to come in and the plant to elongate, or do you cut short, harvesting lower-lignin, more digestible, higher-protein forage? This decision will be largely determined by what livestock will consume the forage. If dairy animals or young stock are the targeted group, 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 optimal cutting time for quality, we rely on the plant's physiological maturity as an indicator. Table 1 lists different growth stages and the corresponding forage digestibility. For a more in-depth look at forage quality, read Understanding Forage Quality.

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 less cooperative than desired. In many cases, some grass species will be fully headed and have set seed, while others will be in the boot stage, making it next to impossible to cut for quality. Should the weather be uncooperative for making dry hay, producers can 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, watch this 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 whether 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 expecting 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, more fertilizer will be recommended to build soil nutrient levels into the optimum range. No fertilizer is recommended when soil test levels are above optimum, allowing crop removal to draw down soil nutrient levels into the optimum range.

Nitrogen Management

The forage type must first be determined to assess nitrogen needs and application rates. Is the forage a legume, legume-grass mixture, or grass?

Legumes, if properly inoculated, should not need any nitrogen for production, and applying nitrogen can 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-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 with less than 50% legumes require nitrogen for optimal growth. A general recommendation is 50 pounds of nitrogen for each ton of forage harvested over 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 across cuttings is recommended because N is subject to several losses, including leaching, volatilization, and immobilization. Further, having excessive N available for forage can lead to some luxury uptake of N by the forage (see luxury uptake of potassium below for more detail.) In some situations, the uptake of large amounts of N can lead to excessive nitrate levels in forage and contribute to nitrate toxicity when the forage is fed. With these risks of loss, applying all 150 pounds in spring would not be the best management practice. If the forage is cut three times, apply 50 pounds of N at green-up, another 50 pounds after the first cutting, and the last 50 pounds after the second cutting. Apply 50 pounds for each ton/ acre expected in the subsequent cut.

Phosphorus and Potassium Management

If forages need phosphorus fertilizer but time does not allow it to be applied before the growing season, the first harvest is an excellent time to apply it. Supplying additional P and K will help 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 required for high yields when soil K levels are high, potentially leaving insufficient K available for growth later in the season. For this reason, producers are advised to use the split application method. The split application method means the recommended rates are applied in multiple applications throughout 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 require nitrogen, which can shorten the longevity of a legume stand. Often, applying manure during the growing season has more drawbacks than benefits.

A large concern about 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, high application rates could cause the material to lie on the crop and reduce yield in the next harvest. Another concern is the traffic on the field with heavily loaded manure spreaders. During the harvest season, compaction and plant damage should already be a concern, but adding another heavy piece of equipment loaded with manure could lead to even more crop damage. A last concern is that the 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, it is best applied in the fall or spring, allowing 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 the first harvest, it's a good time to clean up lingering weeds following fall or spring herbicide applications. If treating annual grasses with Prowl H20 (pendimethalin), this is the time to make the second application for continued residual control. If broadleaf weeds persist, monitor the situation and be prepared to apply the proper treatment at the proper time. When controlling perennial weeds, application timing is bud-to-bloom, typically mid-June to July, depending on the species. However, scouting now for species identification and proper herbicide selection will ensure the application timing is correct.

Additional Information as Podcast

An episode of the Agronomy Highlights Podcast covered this topic. The episode, titled Forage Fertilization After First Cutting, covers harvest timing, fertilizer cost analysis, and more. This episode, along with hundreds more, is available on your preferred podcast platform. Just search Penn State Agronomy Highlights.