Forage Focus 2019: Agronomic Considerations For Forage Production and Quality
Joe Lawrence, of the Department of Animal Science at Cornell University, was the keynote speaker at Ontario Forage Council’s Forage Focus 2019 Conference. He gave two talks during the day. This article will focus on his first talk, which was entitled “Agronomic considerations for Forage Production and Quality.”
Lawrence started his presentation by outlining the six most important factors that influence the quality of a forage in the field. These factors are maturity of the forage at harvest, crop species, harvest and storage practices, environment, soil fertility, and variety of forage species. Some of these factors are things that farmers can control, others are not, but all of them combine to determine the quality of a forage crop.
He first addressed soil fertility, which is the grassroots base of forage quality (if you will). Often strategies for improving soil fertility in forage fields have negligible benefits when compared to the costs, but there are a few exceptions. Adding nitrogen to grass fields, for example, “is a no-brainer” as it increases yield and protein content. Lawrence believes that soil fertility requires further research to determine what the best way to foster forage growth is while still being economically feasible.
Lawrence then addressed the species of forage crop. The usual school of thought for forages is that corn is a source of energy while hay is a source of protein, but that has been changing in recent years. A new metric for the value of a forage crop is total digestible fibre and nutrients. This metric gauges the amount of matter within a forage feed source that is actually digestible, and therefore useful to the animals.
On the graph above it can be seen how the percentage of digestible matter vary widely across the different forage types and overlap quite a bit. Lawrence points out that grass hay and silage have the widest range on the chart. That means that grass has a lot of potential to be a high quality feed source, but on the other hand it is also less forgiving, and its quality can fall well below that of corn and legumes, which are more reliable.
In terms of variety of forage crop species, each variety has its own features that must be considered. Lignin in alfalfa, for example, affects its quality. Alfalfa varieties with reduced lignin often have a higher quality at a higher yield. Similarly, starch content in corn affects its digestibility and type of grass affects its quality. The variety of forage depends on the needs of the individual farmer as well as the ground that the crop will be growing in.
Environmental factors are often out of the hands of the farmer, but proper field drainage certainly helps the farmer with planting and harvest timing. Additionally, proper drainage can let a farmer select a crop species or variety that may be less resistant to water but have a higher yield or feed quality. Lawrence noticed that corn silage seems to be more susceptible to weather conditions than other forages. Poorly drained fields generally show lower levels of digestibility. Extreme heat, especially around the time when the corn is tasseling, also has a negative effect on digestibility. The interaction of rainfall, drainage, and heat can combine to significantly effect digestibility.
Lawrence has a technique for ensuring that a farmer has enough high quality forage which he calls a Dynamic Harvest Scheduling. This is an idea for dairy cattle that require high quality feed, but can be applied to other animals. Often, in the spring farmers have already decided which fields are going to be high quality feed for lactating animals, and which are going to be lower quality feed for heifers or other non-lactating animals. What often happens in this scenario is that weather delays harvest or there are other issues, and harvest in the high quality fields is pushed back and the forage loses its quality. This results in the farmer having less high quality feed than is needed. Lawrence’s solution, the Dynamic Harvest Scheduling, is to initially plan for every field to be good enough quality to feed the animals that require high quality feed. As harvest progresses some fields may be delayed, and they can be harvested later as lower quality feed, while a field that’s dryer can be harvested with high quality feed instead. This way the farmer can decide at harvest which fields will be high or low quality, rather than making the decision in the spring and then trying to adjust when its too late.
During harvest, a way to maintain quality of forage is the cutting height. If forage is cut too low, it takes more energy for the plant to regrow than if cut at a higher length. If the farmer is hoping to get multiple cuts over the growing season, leaving the stem a little bit longer is a good practice. Additionally, leaving longer stems gives the cut forage a bit of an insulating layer and keeps it off the ground. The forage will lie on top of the stems which allows for better airflow underneath and if the ground is wet it will soak up less water. A final benefit of higher cutting is that it keeps the mower away from the ground. This means that the mower won’t be digging into the dirt and spreading dirt and ash into the feed, which can have negative effects on animal health.
Overall, there are many management practices related to maturity, crop species, harvest and storage, environment, soil fertility, and variety that can benefit forage crops. Lawrence closes his presentation by pointing out that its important to identify things that you can control, and things that are important. Where those two concepts overlap are important and controllable things, and that’s what a farmer should focus on.