| | Many producers are looking at the high feed prices and considering fall and winter options this year. A few growers are just now taking late first cuts, some are taking second cuts while others have already turned animals onto haylands to try to recover from this summer's dry conditions.
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"There are always unintended consequences to unusual events, and this past summer was anything but usual," says Bjorn Berg, forage specialist with Alberta Agriculture and Rural Development. "When hardening in and storing winter reserves, remember that alfalfa needs about 40 days of uninterrupted growth before a killing frost to store a good reserve of carbohydrates along with a cap of protein for the winter."
Normally, a producer should let the alfalfa grow during this period. If it's an irrigated field, reduce the water that is applied. Heavy fall watering increases the water in the plant tissues resulting in frost damage to those tissues and frost heaving during the subsequent winter. Lastly, if it must be cut, ensure the field has stubble high enough to catch and retain an insulating snow layer.
The process of getting the field ready for winter is called 'hardening.' Winter is basically a drought with cold temperatures. Hardening forces plants to reduce the water content of their tissues to prevent freezing damage, and store sufficient reserves for the winter so that it can regrow the following spring.
Producers can manipulate the field conditions to harden the plants and enhance survival over the winter.
"Haylands are usually a mix of grasses and legumes. They need some special consideration because the various plants do not harden the same way," says Berg. "During a drought, have you ever wondered why the alfalfa is so green while the grass is brown and short? It's because the plants have two different responses to dry conditions."
Many common grass plants respond to low moisture by shrinking their root systems and the plant gradually goes dormant so it can survive the dry conditions with the least energy expenditure. Eventually each of the grass plants will have a small bunch of roots near the soil surface close to the plant crown, and a small number of brown, senescent leaves on the surface. If the grass stays drought-stricken, the roots stay in the top three inches of the soil and get sod-bound and unproductive.
Alfalfa has an opposite response. As it hardens during drought, alfalfa extends its root system, building reserves and searching for whatever water may still be available deeper in the soil. Before it goes completely dormant, the alfalfa plant will have a few, very green leaves and a thin, deep tap-root.
During a drought, another factor comes into play when producers haven't got sufficient pasture or hay to adequately sustain their herd. There is a strong temptation to overharvest hayland during its fall hardening period.
"The feed produced from these fields is usually very high-quality stuff, although the volumes may not be great," says Berg. "With some older or poorer feed to mix in, this might make the difference between getting through the winter or selling stock. And there might be another advantage - if the stand is older or due for a renovation, the late harvest can be considered a treatment that will weaken the stand preparing it for renovating next spring."
The risks of late season harvest must also be considered. During a drought, the majority of growth in the field will be alfalfa. Harvesting this plant during the early part of its hardening-in period may significantly affect its ability to withstand the winter or initiate growth next spring.
Under normal conditions, well-managed stands between two- and four-years of age will lose about 15 per cent of the resident plants each year. This is a natural thinning process that occurs in all alfalfa stands. Heavy use in the critical hardening-in period on a drought-stricken stand could result in attrition as high as 50 per cent.
During the last two decades in Alberta, a mid-winter warming with no snow cover followed by a severe temperature drop has been a common occurrence. Fields become iced, roots freeze, crowns are starved of oxygen, and fungus invades the damaged tissues in the early spring. Many well-managed alfalfa stands have been decimated while those in poor condition didn't stand a chance. It only makes sense to manage these valuable haylands properly during the fall to ensure they come back in the spring.
Berg has a few suggestions, "If you must harvest your hayland alfalfa late this year, cut high to leave some stubble, or leave strips uncut to catch snow. For winter-hardy alfalfa cultivars, a killing frost is -10° C for two hours or -6° C all night. Cut as close to a killing frost as possible or several days after so the leaves can dry a bit. And remember, dry down is more difficult in cooler weather. If you are using the field for late-season pasture, again, don't overharvest, try strip grazing and leave some stubble. Watch for early signs of bloat, generally one hour after the start of grazing in the morning or evening, and be prepared to move animals to a grassy field for 24 to 48 hours after the killing frost."
For more information, visit the following websites:
Contact:
Bjorn Berg
403-381-5835
Ag-Info Centre
310-FARM (3276) |
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