Alfalfa is harvested more frequently in summer and less frequently in the spring and fall, when growth slows due to cooler weather. In California, many growers schedule 28-day harvesting schedules after the first cutting. However, considerable evidence indicates this might not be ideal. Numerous factors can affect both pest problems and the yield, quality and profitability of alfalfa, including harvest timing, cutting height, windrow management, wheel compaction by harvesting equipment, and border harvesting.
Usually, the choice of harvest time represents a compromise between the customer’s demand for quality and the grower’s desire to maintain high yields and a vigorous stand of alfalfa. The highest quality of alfalfa is low in fiber and high in digestible protein and total digestible nutrients (TDN). The best time to harvest alfalfa to maximize quality is during the very young vegetative stages to early bud stage. However, cutting at these very early growth stages produces low yields and can greatly weaken alfalfa stands, since the plant does not have sufficient time to replenish carbohydrate and protein root reserves. Harvesting after the plant has replenished root carbohydrate reserves increases yields and significantly improves health and competitive ability of the alfalfa stand. The benefits of long cutting schedules are often carried over from season to season.
Although clear economic incentives exist for growers to produce early-harvested, high quality forages, repeated early-stage cutting schedules can be devastating to alfalfa persistence, growth and yield, and lead to severe weed infestations. Several 'long' cutting intervals over the year will allow sufficient replenishment of root reserves, maintain high yields, and provide for the continued health of the stand. We recommend that growers consider a ‘staggered’ approach to cutting schedules. This involves alternating ‘short’ (26 day) with ‘long’ (35 day) intervals over the season. Some harvests could be cut early for quality, and a subsequent harvest would be cut late for high yields and stand health. Precise cutting schedules are difficult to recommend because the growth rate of alfalfa depends on location and time of year.
Early harvest may be a good strategy to avoid further damage when an alfalfa crop has a high (late) infestation of alfalfa weevil in the spring, or Lepidoptera (moths and butterflies) damage in the summer. Early harvest may also allow you to avoid spraying insecticides. However, after harvest, growers should monitor fields carefully to detect early damage to young shoots, which can be devastating to the following regrowth.
Ideally, the last harvest of the season should be early enough to allow plants enough time to build up reserves before the first frost, although this is not critical in more Southern regions where frosts are later or non-existent. Sufficient canopy coverage is important to suppress winter weeds. However, dense winter canopies can lead to high Sclerotinia infestations, and clipping (even late fall clipping) is an important management tool when conditions are right for Sclerotinia.