Reports indicate widespread alfalfa winterkill due to several thaws that reduced snow cover and created ice cover in fields. Producers need to scout their hay fields to assess the damage, then develop a plan to ensure they will have the forage they need.
Keep it, patch it, or start over?
Plant counts should be done in the spring and fall each year (Table 1). These can be done when the alfalfa is dormant. The spring count is a good time to dig up some plants and assess root health. Stem counts are useful for predicting yield potential, and these should be done when there is 15-20 cm (6-8 in.) of growth (Table 2). If the number of plants or stems per square foot is too low, consider patching to improve yields or rotating that field out of alfalfa.
Table 1. Assessing alfalfa stands using the plant count method
| Age of Alfalfa Stand | Desired plant count per square foot |
| New Seeding | 20+ plants |
| Year 1 | 12 to 20 plants |
| Year 2 | 8 to 12 plants |
| Year 3 | 5 plants |
Table 2. Assessing alfalfa stands using the stem count method
| Stems per square foot | % of Maximum Yield |
| 55 or more | 100% |
| 40 to 50 | 75 to 92% |
| Less than 40 | Stand is too weak to keep |
Alfalfa is autotoxic, which means mature plants produce chemicals that prevent new alfalfa plants from establishing. Stands planted in 2018 will not have this autotoxic effect; however older stands will and cannot be patched with or followed by alfalfa.
In fields with less than 50% damage, growers could patch with red clover and/or grass (Italian ryegrass or typical perennial forage grasses). For best results, use a no-till drill. Once the alfalfa is over 15 cm (6 in.) tall, the established plants are generally too competitive for new seedlings to establish well. In this case growers may have better success taking a first cut and then over-seeding into moisture. Plan to terminate and rotate patched stands in 2020.
With the 2019 planting season barely started, producers have plenty of options to establish alternative forage crops to replace winterkilled alfalfa.
Seeding rates, depth, and timing
Table 3. Planting guidelines for alternative forage crops
| Crop | Seeding Rate | Planting Depth | Seeding Date |
| Red clover | With grass: 9 kg/ha (8 lbs/acre) New stand: 11 kg/ha (10 lbs/acre) | Clay or Loam: 6-12 mm (0.25-0.5 in.) Sandy soil: 12-18 mm (0.5-0.75 in.) | April-May August |
| Italian (annual) ryegrass | Patching: 16-33 kg/ha (15-30 lbs/acre) New stand: 39-45 kg/ha (35-40 lbs/acre) | 0.5-1.5 cm (0.25-0.5 in.) | April-May August |
| Spring cereals | 100 kg/ha (90 lbs/acre) | 2.5 cm (1 in.) | Oats: April-August Barley: April-June |
| Cereal/pea mixtures | Cereals same as above Peas: 50-75 kg/ha (45-70 lbs/acre) | 2.5 cm (1 in.) | April-June August |
| Sorghum-sudangrass | 22-44 kg/ha (20-40 lbs/acre) | 2-4 cm (0.75-1.5 in.) | June 1-15 |
| Millet | 9-20 kg/ha (8-18 lbs/acre) | 0.5-1 cm (0.25-0.5 in.) | June 1-15 |
The seeding dates in Table 3 suggest timings that result in the best yield during a “normal” year. It is more important to wait until soil conditions are good for planting than following the calendar. Just like with other crops, when establishing forages it is important to get good seed-to-soil contact, uniform depth, and to plant into moisture. Keep in mind that warm-season grasses will not germinate until soil temperatures are at least 12°C.
Fertility for alternative forage crops
A winterkilled alfalfa stand provides a nitrogen credit to the following crop. This should be factored into the fertility plan to reduce the risk of nitrate toxicity from excess nutrients. To factor in nitrogen credits, subtract the appropriate credit from the crop nitrogen requirement. Some of the credits for alternative forage crops in Table 4 have not been validated by research, rather they are estimates based on similar crops with known responses to nitrogen from a previous legume crop.
Table 4. Nitrogen fertility guidelines for alternative forage crops following winterkilled alfalfa
| N credit from alfalfa | Crop N Requirements | ||||
| Crop | 2018 alfalfa seeding | 33-50% established alfalfa | >50% established alfalfa | Starter Fertility | In-Crop Application |
| Red Clover | N/A | N/A | N/A | N/A | N/A |
| Italian (annual) ryegrass | 78 kg/ha (70 lbs/acre) | 55 kg/ha (50 lbs/acre) | 110 kg/ha (100 lbs/acre) | 55 kg/ha (50 lbs/acre) | 55 kg/ha (50 lbs/acre) after each cut |
| Spring Cereals | 45 kg/ha (40 lbs/acre) | 55 kg/ha (50 lbs/acre) | 110 kg/ha (100 lbs/acre) | 45-55 kg/ha (40-50 lbs/acre) | N/A |
| Cereal/Pea Mixture | 45 kg/ha (40 lbs/acre) | 55 kg/ha (50 lbs/acre) | 110 kg/ha (100 lbs/acre) | 20-30 kg/ha (18-27 lbs/acre) | N/A |
| Sorghum-sudangrass | 78 kg/ha (70 lbs/acre) | 55 kg/ha (50 lbs/acre) | 110 kg/ha (100 lbs/acre) | For 1-cut: 100 kg/ha (90 lbs/acre) For 2-cut: 50 kg/h (45 lbs/acre) | For 2-cut: 50 kg/ha (45 lbs/acre) after 1st cut |
| Millet | 78 kg/ha (70 lbs/acre) | 55 kg/ha (50 lbs/acre) | 110 kg/ha (100 lbs/acre) | For 1-cut: 100 kg/ha (90 lbs/acre) For 2-cut: 50 kg/h (45 lbs/acre) | For 2-cut: 50 kg/ha (45 lbs/acre) after 1st cut |
Phosphorus and potash fertility guidelines are based on a current soil test. These can be found in OMAFRA Publication 811: Agronomy Guide for Field Crops (http://www.omafra.gov.on.ca/english/crops/pub811/p811toc.html). The recommendations for cereals and cereal/pea mixtures can be found on pages 131 and 132. For all other forages see pages 88 and 89.
There are lots of forage options to replace winterkilled alfalfa. Producers should move quickly to assess their fields, make a plan, and order any seed they need. Good planting conditions could arrive at any moment. Alternative forage crops can provide good yield and quality if they are given a strong start.
References
J. Bagg, 2006. Red Clover Haylage. Ontario Ministry of Agriculture, Food, and Rural Affairs. http://www.omafra.gov.on.ca/english/crops/facts/info_redclover_haylage.htm
J. Bagg, 2014. Italian ryegrass forage options. Field Crop News. https://fieldcropnews.com/2014/06/italian-ryegrass/
J. Johnston and M. Bowman, 1998. Annual ryegrass for stored feed and pasture. Ontario Ministry of Agriculture, Food and Rural Affairs. http://www.omafra.gov.on.ca/english/crops/facts/98-039.htm
B. Lang, 2001. Millets: Forage Management. Iowa State University Extension. https://www.extension.iastate.edu/sites/www.extension.iastate.edu/files/iowa/MilletFS55.pdf Publication 811: Agronomy Guide for Field Crops. Ontario Ministry of Agriculture, Food and Rural Affairs. http://www.omafra.gov.on.ca/english/crops/pub811/p811toc.html