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 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 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 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.

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 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, 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 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 less than 50% legumes, require nitrogen for optimum 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 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, the 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 the best management practice.  If the forage is cut three times, 50 pounds of N should be applied at green-up, another 50 pounds of N after the first cutting, and the last 50 pounds of N should be applied 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, after the first harvest is an excellent time to apply. 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 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 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, which can decrease 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 mean material could lay on the crop and cause a lessened 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, 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 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 is a good time to clean up some lingering weeds after 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 continue 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. However, scouting now for species identification and proper herbicide selection will ensure the application timing 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.