Any legume — such as peas, beans or lupins — can be harvested as fermented wholecrop. Legumes are good sources of quality protein for livestock. When protein is adequately preserved, legume silage can help reduce subsequent feed costs and improve animal performance.
In addition, these crops can provide residual soil nitrogen for following crops, cereal or grass. Wholecrop legumes can also be grown in conjunction with a whole-crop cereal or small-grain crop. More information is available on that practice in other sections.
As with all forages, one of the most important decisions is when to harvest. Harvest timing will affect crop yield and the quality of the resulting silage’s nutrients. For legumes, it is particularly important that protein yield is maximized.
The best time to harvest wholecrop peas occurs at the “pod fill” stage. The canopy will be turning green to yellow. Pods towards the middle of the plant will be fully formed. The peas inside the pods will also be fully formed and can be easily split between the thumb and forefinger. These features will occur about 14 to 16 weeks after sowing, although there may be some differences based on variety.
The harvest window for beans is longer than some legumes due to the lower risk of lodging. The recommended stage for harvesting beans occurs when the foliage is still green. The pods will appear fully developed, similar in appearance to garden broad beans. Beans can be harvested when the pods are still pliable, but turning black, and the bean has a rubbery texture.
The correct time for harvesting fermented wholecrop lupins will depend on the lupin species. In general, the crop should be harvested when the canopy is turning green to yellow. This could be 14 to 18 weeks after sowing. The pods will be swollen and at their full size.
Dry Matter and Harvest
The crop should be cut using a mower without a conditioner and left to wilt for two to three days. This will help raise dry matter (DM) to a target of 30%. The crop should be picked up with a forage harvester. A chop length of 1 inch, or 2.5 cm., will ensure good clamp consolidation and provide effective fiber for livestock.
Beans can be harvested using a conventional mower (without a conditioner) and left to wilt for three to four days. This will help elevate forage DM to around 30 to 35%. The crop should be picked up using a forage harvester or round baler. A chop length of 1 inch, or 2.5 cm., will aid in clamp consolidation and provide effective fiber for livestock.
Lupins should be cut using a mower without a conditioner. The crop should be wilted for one to two days to expand forage DM to around 25 to 30%. After wilting, the lupins should be picked up using a forage harvester. A chop length of 1 inch, or 2.5 cm, will ensure the woody stem is broken. This will aid in clamp consolidation and improve livestock-forage utilization.
Soil, or ash, contamination is common in legume silage. Excess ash can increase the risk of impaired fermentation and spoiled silage. Producers should aim to keep ash content below 10% DM for wholecrop legume by:
- Planting varieties that stand better
- Harvesting earlier
- Raising the cutter bar
- Using flat knives
- Keeping the windrow off the ground
- Keeping rake tines from touching the ground
- Minimizing movement of hay horizontally
- Using a windrow merger
- Storing silage on concrete or asphalt
Legumes generally have thick fibrous stems that are less digestible as the crop matures. Using a forage inoculant with enzymes can help spread the feed value of the legume stems. Learn more about inoculant formulations with enzymes here.
Legume crops with a high buffering capacity resist a drop in pH. Reduced pH is needed for good fermentation and to prevent secondary fermentation. Therefore, some legume crops are at a greater risk of being poorly preserved. A forage inoculant can help ensure a rapid drop in pH and improve silage stability.
To take full advantage of legume forages, protein yield must be conserved. Good silage practices that help drive fermentation can help lower protein losses.