The 2007 growing season is experiencing a swing in conditions, which include a frost in the late spring and excessively dry conditions in late spring and summer which have drastically affected forage crops. Rainfall patterns have varied greatly in Michigan this summer; however, most areas in the state are far below normal rainfall. This has adversely affected both alfalfa and grasses used for haylage, hay, and pastures. Alfalfa growth is slow and plants are under stress. Alfalfa under these conditions, is unlikely to re-grow much after harvest, at least until the rains return. Even though alfalfa is a unique crop in its ability to go dormant during extended dry periods, it requires an inch or several inches of rain to recover depending on its state of dormancy and the current soil conditions. To maximize the yield from the current stand, alfalfa should be managed to ensure survival. The cutting management, fertilization and insect control methods should be examined.
When alfalfa is subjected to drought conditions, the feed quality often increases. This is because the plant responds by decreasing the stem number and their elongation, inadvertently increasing the leaf to stem ratio. This results in an increase in forage quality (higher crude protein and digestibility, especially a reduction in Acid Detergent Fiber [ADF]). Additionally, photosynthetic activity continues during the early phase of drought, allowing nutrients to accumulate while growth slows. It should be noted, that although quality is increasing, dry conditions also reduce nodule formation and nitrogen fixation, therefore extended dry conditions will eventually reduce plant metabolism.
Harvest your alfalfa only if there is sufficient yield to justify harvesting costs. It is also important to maintain enough leaf material for the stressed plant to continue photosynthesis and root growth. Some experts recommend using a threshold of 10 inches in height and mid to full-flower to trigger harvesting. Full bloom is when virtually every stem has one or more flowers open. At this point, yield has reached its maximum, and quality will begin to decrease, even if rain occurs. Harvesting at this stage will also allow the plant to build root reserves and fully recover from dry weather and cutting stresses; providing the best yield scenario for the subsequent harvest. If areas of the field vary in development, base the decision to harvest on the slowest developing plants in the field.
Cutting height should be as short as possible to maximize yield and quality. However, one should also raise the cutting height if plants have been cut early and frequently in previous seasons. This will also avoid contaminating the hay with dirt and foreign material.
If the alfalfa is less than 10 inches tall, cutting it will reduce stand longevity. Therefore, it is recommended to leave the stand and harvest it at the next harvesting interval, or until sufficient precipitation occurs. At that point you may either,
1. Harvest the old growth for a low quality feed, exposing the newly initiated crown buds to sun, allowing them to produce a high quality subsequent harvest, or;
2. Delay cutting the old growth until the new stems have reached their optimum stage and harvest both the old and new growth for a medium quality feed.
Both options will not affect the over wintering ability of the stand as long as the final harvest is 6 weeks before a killing frost (-28 degrees Fahrenheit). See Fall Management of Alfalfa Article
If the
stand was seeded this spring it may be harvested this fall without detrimental
effects to the plant. However, similar to established stands, only harvest
if enough biomass exists to justify harvesting costs and if the stand is at
least 10 inches in height, and no later than six weeks prior to a killing
frost. Cutting height should be as short as possible to maximize yield and
quality, but high enough to avoid contaminating the hay with dirt and foreign
material. It is also important to maintain enough leaf material for the
stressed plant to continue photosynthesis and root growth.
Similar
to alfalfa, grass yields are reduced under dry conditions; therefore only
harvest your grass if there is sufficient yield to justify harvesting costs.
Unlike alfalfa, dry conditions reduce feed quality as fiber levels increase and
protein and energy levels decrease. To maximize yield and quality, grass
stands should be harvested at heading; at this stage little gains in yield are
obtained but quality decreases rapidly. Grass stands less than 10 inches
tall may be left unharvested without harming plant health. However, excess
growth should be removed prior to winter to reduce the risk of stand loss to
snow mould, especially for those grasses known not to stand up well from snow
fall (ex, orchard grass). If moisture levels improve, adding approximately
30 to 40 lbs of inorganic nitrogen fertilizer (not manure) is a good tool to
stimulate fall growth, and potentially provide some additional feeding.
Moisture-stress pastures should also be mowed to control weeds and small brush.
It is important to ensure that all fertility levels both alfalfa and grasses are optimum in order for it to regain lost yield when moisture levels return to normal. Since dry weather lowered the yield of alfalfa, most producers will not need to apply as much topdress fertilizer on the alfalfa crop. If a soil test has not been taken in the past two years, it would be a good idea to sample for fertility levels and make necessary adjustments in fertilizer application.
Insect Control
Potato leafhopper (Empoasca fabae) (PLH) populations in times of drought are adversely affected; however, this does not diminish the need for control. The PLH is an insect that reduces movement of essential nutrients within the plant by plugging the phloem when it pierces the vascular tissue with a hollow tube on its snout. This blockage results in even greater stunting in times of drought. The PLH also survives on at least 300 host plant species and is very mobile. When cuttings are delayed by drought producers should select an insecticide that has greater residual activity. One example of an insecticide with above- average residual activity is Baythroid XL (cyfluthrin) which may reduce PLH for as many as 14 days.
Since forage quality is significantly affected by extended dry conditions, be sure to test all your feed before feeding and adjust rations accordingly.