ISSUE 5 May 31, 2001
FROST ON SMALL GRAINS
The recent cool temperatures have undoubtedly been a blessing considering all the late planted small grains. However, in North Western North Dakota there has been valid concern about the effect of frost on the early emerged small grain crop.
Frost damage to small grains is highly dependant on the stage of the crop, the temperature and duration of the low temperature, and environmental conditions that existed before the frost occurred.
Small grains are among the most frost tolerant of crops. When temperatures fall below 50E F for several days before a frost, the crop goes through a hardening process and develops more tolerance. Drought stress can also cause hardening. Up to Jointing small grains can easily withstand temperatures of 25E F. A healthy wheat or barley plant can sustain substantial loss of foliage prior to jointing with out significant impact on yield. After jointing the growing point moves above the soil surface and is more susceptible to frost damage.
Small grains are most susceptible to frost from the late boot through flowering. Frost injury occurs during boot through flowering when temperatures fall below 28E F. This is the stage when reproductive tissue development is occurring. Anthers, the pollen producing structures are easily damaged preventing or severely reducing pollen production. Barley is more susceptible to frost injury during the boot stage because it flowers while still in the boot.
Air and soil temperature information can be obtained from the North Dakota Agriculture Weather Network at
Michael D. Peel
Extension Small Grains Agronomist
WICKED WEATHER MOVES CHOPS TO TOPS
In areas hit with consistent rain, one option is to hop to chops-corn silage or forage soybeans. If a farmer has the ability to utilize the forage on farm or can sell the crop to another user, examining this option may provide a way to gain ground cover during the season and still make hay.
As the spring wanes, use of a corn hybrid that is also selected for normal grain maturity rating will allow a good pick for silage, green-chop or grazing. Silage hybrids are usually five days later in maturity than hybrids grown for grain, but lateness of the season dictates that silage choice be more carefully picked so harvest is insured. The best quality silage is cut when the grain is in the late dough stage. Moisture at harvest will be critical. Besides hybrid choice, proper storage is important. If silage is stored in bunkers, limit exposure to oxygen, rain and high temperatures by first harvesting at the correct moisture: 68-72 percent if not processed; high moisture corn at 26-28 percent; and high-moisture ear corn at 36-38 percent. Fill bunkers quickly (within nine days) and pack throughout the filling process. To force air out, top packing with heavy tractors or wheeled (not tracked) bulldozers can pack at a rate of 800 to 1,000 hour-pounds per ton. Pack in thin layers (six inches or less) for denser silage. Corn silage should be more than 17 pounds of dry matter per cubic foot while haylage should be just over 15 pounds of dry matter per cubic foot. After filling a bunker, cover with plastic and weigh down with rubber tires. Use about 20-25 tires per 100 square feet. Covering can return as much as $5 per ton. The feed out phase can corrupt silage quality by allowing air infiltration. Remove only enough for each day's feeding, without pulling extra silage to the floor and utilize each bunker completely before moving to other supplies.
Soybeans may also be grown for annual hay or as a pasture crop. Ensiled or fed green, the soybean is one of the few annual legumes suitable for hay production, although usually fed with other kinds of hay. In a study out of Wisconsin, use of soybeans as high-quality forage was examined (Agron. J. 86:59-62 1994). The nutritive value was a function of the composition of the individual plant components (leaf, stem, pod). Harvest maturity had the greatest effect on dry matter partitioning. Neutral-detergent fiber (NDF), acid-detergent fiber (ADF), and acid-detergent lignin (ADL) concentrations increased as plants matured, especially from R1 To R7 while crude protein (CP) decreased for leaf and stem components. The pod component showed an opposite trend with CP increasing between stages R5 and R7. Row spacing, planting rate and cultivar had little effect. From the animal utilization aspect, it was beneficial to decrease the proportion of dry matter present in the stem, as the older, coarser, more mature stems were less readily consumed, as shown in three other studies. Higher plant populations did not greatly influence dry matter partitioning and nutritive value, but did produce thinner stems that were more palatable. In Canada studies on soybean forage, narrow rows and higher populations were slightly preferred. Dry matter yields increased for later maturing varieties. Soybean forage harvested between R6 and R7 (when leaves begin to turn yellow, but before they fall off the plant) was comparable to alfalfa hay harvested at an early bloom stage of development for CP, ADF and NDF. Since soybean seeds have higher oil content, the ether extract (EE) content is higher than that of alfalfa forage. The nutritional impact appears desirable, but EE concentrations of rations should be limited to 5 percent, thus soybean forage harvested at the R7 stage should be limited to no more than 50 percent of the total dry matter in the ration (EE content in lactating cows can increase milk production, but it also decreases intake and reduces fiber digestion). Soybean ensilage mixed with corn silage shows little difference in value to straight corn silage. Mix at 2_3 parts corn and 1 part soybean to make well-balanced silage that keeps well and is readily eaten by cattle.
On both silages, make sure no mold growth occurs, including white mold on soybean plants in the field prior to cutting. Also, check herbicides planned to be used to narrow down selections to those that have no restrictions on timed application intervals prior to feed harvest (such as Assure, Fusilade, Pinnacle, Poast, Pursuit or Sencor as well as others).
DECISION TO REPLANT CAN BE DIFFICULT
Unexpected stand losses from flooding, late spring frosts, hail, insect or disease damage, herbicide or fertilizer injury or other causes can put corn and soybean producers in the position of evaluating the crop for possible replanting. Growers should assess the need to replant carefully and not make a quick or uninformed decision.
Especially with low crop prices making it important to hold production costs down, careful consideration of the replant decision is essential.
Growers faced with a thin stand should first scout the field thoroughly to determine the plant population and compare the actual stand to the desired population. Requirements of a crop insurance plan may be a consideration when considering replanting. Another major point is to compare the original planting date to the likely replanting date.
Besides considering crop losses from a planting made at a later date, add in the cost of the replant seed and other replanting and pest control costs. This information along with yield loss or gain from a later planting can be used to determine if replanting is worth the time, money and effort.
Estimating plant population involves counting the number of viable plants in a length of row that equals 1/1000 of an acre in several spots across the field? in six to eight spots across every 20 acres is a good sample. Average these counts and multiply by 1000 to get the plant population.
Length of row needed to equal 1/1000 acre varies with planting width. In 22-inch rows the length will be 23.8 feet; in 30-inch rows it is 17.4 feet.
Actual stand counts will give a good estimate of plant population. Guessing at the population remaining in the field is more difficult, but the National Crop Insurance Service corn loss instruction book shows that a 75 percent stand will result in a 10 percent yield loss, a 50 percent stand in 26 percent loss, and a 25 percent stand in a 43 percent yield loss. Yield losses may increase with uneven distribution or large gaps or skips in the stand.
Actual stand counts are important in soybeans, as guessing at the remaining population is even more difficult. Length of row to equal 1/1000 of an acre goes from 87 feet in 6-inch rows, to 52.3 feet in 10-inch rows, and 17.4 feet in 30-inch rows. Yield loss in soybeans may increase if seedlings are unevenly distributed.
After determining the plant population, the next step is to compare that population to the target population of the original planting and determine the cost of the loss field by field. Growers need to consider the yield loss incurred from replanting at a later date. Yield losses from adapted corn hybrids in North Dakota and northwestern Minnesota are negligible until after May 15, when later planting will result in a shorter than normal growing season. In this northern area yield losses accumulate rapidly, from 7 percent or more through May 20, 13 percent or more to May 25, and 24 percent or more to June 1.
With soybeans, yield losses of adapted varieties in the Red River Valley are usually negligible until May 20. Depending on weather, possible yield loss can be around 13 percent from May 26 until June 9, when late planting losses can be around 24 percent. Soybeans planted as late as mid June can have a 43 percent or more yield loss compared to more timely plantings.
Replant considerations vary across farms and locations. Growers need to carefully weigh potential yields from a replanted crop against current plant stands, and base decisions on current crop pricing and prevented planting options.
Extension Crop Production Specialist