Managing Forages in Dry Years

Livestock producers are always aware of the need to put up enough forage. This can be very challenging in extremely dry years. Dry weather creates even more immediate problems in pasture situations during the "summer slump". In dry years, strategies such as rotational grazing and the use of corn silage, can help to ensure adequate feed inventories.

"A dry year will scare you, but a wet year will starve you" is an old saying quoted by some dairy farmers. Excessively wet years often result in poor forage quality and problems getting milk out of cows. In a dry year, second and third cut yields will be reduced, but quality is usually good - no rain damage, high leaf/stem ratio and reduced fibre. First cut yields are largely a function of temperature, whereas second and third cut yields are more a function of moisture. Two-thirds of total yield is typically from the first cut. Severely drought stressed alfalfa can sometimes produce alkaloid-like compounds that may reduce palatability and intake.

Alfalfa is deep rooted and has considerable drought tolerance, particularly during shorter periods of dry weather. Birdsfoot trefoil also has reasonably good drought tolerance. Red clover has poor drought tolerance and stands can be reduced during extended hot, dry conditions. Timothy, the most commonly grown grass, has poor regrowth potential and drought tolerance. Reed canarygrass has better drought tolerance and regrowth, but requires earlier first cut harvest management.

By the time you know you're in a serious drought situation, it is often too late to do much about it as far as seeding different crop species. Corn silage is the most commonly used annual for emergency situations. Corn silage is usually cheaper, readily available, and is easily harvested, stored and fed. Spring seeded cereals need to be cut by the first week of July for the boot/early head stage. Warm season annual grasses like Forage Sorghum and Pearl Millet can be handled using conventional haying equipment to put up haylage. Be aware of prussic acid risks with sorghums and sudangrass.

Moderate stress from dry weather can cause alfalfa plants to reduce stem numbers and stem elongation. Carbohydrates produced are stored in the root system, and are available as energy for regrowth after cutting and when moisture returns. If there is adequate alfalfa growth to economically justify cutting, and a 30 to 35 day harvest interval can be maintained, go ahead and cut. Cutting alfalfa after rains return will stimulate regrowth, particularly at the flower stage, by encouraging growth of new crown buds.

On the other hand, cutting red clover during drought conditions can cause stand reductions. Birdsfoot trefoil also maintains lower levels of root carbohydrates during the summer, so cutting at a more mature stage with a longer stubble, will improve regrowth potential.

The significance of Potato Leafhopper (PLH) damage in alfalfa is greatly underestimated. PLH damage is often blamed on the hot, dry weather that accompanies it. PLH feeding affects the transportation of fluids and nutrients in the plant and significantly worsens the effects of dry weather. New seedings are very susceptible. Once the symptoms of "hopperburn" are noticed, the damage is already done. PLH can be managed by scouting and spraying at threshold levels, and by the use of PLH resistant varieties.

Early spring seedings are usually the most successful. Late spring seedings can be severely affected by dry weather. Summer seedings often fail when seeds germinate and then starve for moisture during extended dry weather. Delayed germination can result in inadequate growth before a killing frost in the fall to ensure winter survival. Lack of moisture is a risk, so if soil conditions are extremely dry with no rain in the forecast, consider abandoning your plans for summer seeding.

Cutting alfalfa during the 6 week Critical Fall Harvest Period (refer to Publication 811, Agronomy Guide) is not recommended, but sometimes done because of low forage inventories. This results in the plants using root reserves for regrowth and increases the risk of winterkill. The highest risk time to cut is 3 weeks after the start of the Critical Fall Harvest Period, so avoid this time if possible. Leaving more stubble to hold snow, and adequate soil K fertility will also help.

Tremendous variation can occur in drought stressed corn fields. Some fields will have short plant height with more normal ears. Yields will be reduced, but forage quality may be close to normal. Other fields will be more normal in height but have very small ears or no ears. Growers attempting to salvage drought damaged corn fields by harvesting them as forage should be aware of some of the harvesting and nutrition implications. Ensiling at the correct whole plant moisture is critical, but often more difficult to determine.

Be aware of the potential for nitrate poisoning. Nitrates accumulate in corn plants and grasses when there is a large amount of soil nitrates, and a lack of moisture that interferes with normal plant growth. Nitrate accumulation is often greatest following a rain that ends a dry period. The increased nitrate potential also increases the risk of silo gas.