ISSUE 7 June 14, 2001
WEATHER REASONS TO CROP RESPONSES
Corn and soybean response to wet weather will depend on duration of any flooding, crop developmental stage as well as air and soil temperatures.
How long can crops stay submerged? Small soybeans, if not completely submerged, can survive several days to a week if air temperatures are below 90F; however, scout for seed and seedling diseases such as Phytophthora and Pythium in saturated fields. Corn just isn't as flexible as soybeans when it comes to flooding. Prior to the sixth-leaf stage, corn can survive underwater only up to four days. At soil temperatures reach above 77F, they may not survive 24 hours. Cooler temperatures will prolong survival. Studies at Iowa State in the 1960s found that flooded, six-inch corn underwater for 72, 48 and 24 hours reduced yields by 32, 22 and 18 percent when nitrogen rates available were low. At high soil nitrogen rates, yield reductions were only 14-19 percent. Continued soil saturation can also result in crazy top and common smut in corn. Corn root development can also be reduced with a possible increase in root, crown and stalk rots. To evaluate plant condition, check the growing point. Splitting a corn plant that has been dug up (remember the growing point is below ground until the fifth-leaf stage) to check for a white or cream colored growing point will insure the plant is alive. Darkening or softening of the growing point indicates plant death. Also, new leaf growth should occur within 3-5 days after water drains from a field.
Ponded soils that have been saturated for 2-3 days lose nitrate-nitrogen by denitrification (to the atmosphere) or by leaching. Watch the color of the corn 3-5 days after soils are no longer ponded on the surface. If corn is very yellow but the growing point is intact and healthy and heat units have allowed photosynthesis to continue at a healthy rate, you may need to consider side-dressing corn (up to the V8 stage to limit excess root pruning and limit nitrogen losses) or spray or dribble nitrogen solutions on the soil surface with drop nozzles (at later stages) rather than broadcasting as burning the foliage will further stress or set back corn. Urea can be broadcast but will allow granules to lodge in the corn whorl and produce cosmetic brown spots and some losses of nitrogen from volatilization will occur. Limit compaction as much as possible. Corn can benefit with adequate nitrogen through silking but nitrogen losses increase due to limitations to incorporate fertilizer. If just spots are wet in a field and only these areas show continued short, yellow corn, try simply cultivating rather than adding more fertilizer, once soil is dry enough, to help corn in these areas.
EFFECTS OF WIND AND HAIL ON CORN AND SOYBEANS
Recent high winds, some with small hail, may have affected crops. Corn at the fifth-leaf stage has the growth point at or slightly below the soil surface. Corn at this stage or earlier should recover from any wind or hail damage. At the sixth-leaf stage, the growing point on corn is above the soil surface and the plant has initiated rapid stem elongation. Fields at growth stages beyond this sixth-leaf stage should be carefully scouted and monitored to insure that corn will recover. Lodging of corn plants may only be a temporary condition, unless high winds or hail snapped off the main stem completely. With complete loss of the main stem and if no tillers are present and viable, consider the corn growth stage to determine if the growing point was protected and regrowth can occur. With good growing conditions, three to five days should show if the corn will recover. With soybeans, plants cut off below the cotyledons will not recover. While some damaged plants may have trouble recovering, regrowth can occur on soybeans from either one of the axillary buds located at the point where the cotyledons are attached to the main stem or from any of the branch axils. Bruising of either crop may also have occurred. Bruised stems weaken the plants and may cause them to break at a later time. However, yield is not affected by bruising as long as plants do not break.
CROPS AND FARMERS FEEL THE NEED FOR SPEED
Many may be wondering at this point if there is anything one can do to speed the maturity of the corn and soybean crop. Right now the maturity of the crops is dependent on weather conditions. Additional fertilization generally will not hasten maturity, unless there is a deficiency. Step back from the field, allow 3-5 days of good sunshine and heat units and corn and soybeans should respond. Allow these days to see if corn and soybean greening evens out across fields. Several factors can cause uneven crop appearance. Cool temperatures, cloudy weather, loss or lack of nitrogen, compaction, lack of aeration, residue breakdown leading into nitrogen tie-up, allelopathy and higher pHs or salinity as well as flooding in the immediate residue area can all contribute to uneven color and stands in crops. These conditions really test your mettle and your crop maturity management strategy. The old standby saying to plant 50 percent of each crop in the region's normal maturity range, 25 percent in an earlier variety and 25 percent in just over the medium maturity range, will probably test true this year. Also remember that with weather kept cool by frequent showers, rain-fast herbicides are taken up more effectively. The herbicide may take longer to react on weeds, but once absorbed the weeds will react and likewise, crops may take longer to metabolize herbicides that are not contact chemicals.
Crop Production Specialist
FOXTAIL MILLETS FOR HAY
Foxtail millets are grown primarily for shortseason emergency hay crops. Several landraces have been developed over time and are grown in North Dakota.
Planting of foxtail millets can be delayed until mid-June into July. When used for emergency hay production, late planting is usually encountered.
Plant into moist soil about 1 inch deep. Shallower seeding may be desirable on heavy textured soils with good moisture. Germination is fairly rapid but early seedling vigor is lacking.
Foxtail millets have low seedling vigor and in general are poor competitors with weeds. A seeding rate of 15 to 30 pounds per acre is recommended. The higher rates are recommended in eastern North Dakota with the higher rainfall potential. In western North Dakota, 15 pounds is adequate on weed free fields.
Hay Millets Include The Following:
Common Foxtail millet is fine-stemmed and leafy. Seedhead is cylindrical and compact and tapers toward the tip. The lower portion is less compact than the mid- and tip portions. Seedhead varies from 5/8 to 3/4 inch in diameter and 4 to 6 inches in length with pale yellow bristles. It is one of the earliest foxtail millets, maturing in about 70 days and producing a hay crop in about 50 days.
Siberian millet has medium-sized stems and possesses some drought tolerance. The seedhead is cylindrical, 5/8 to 3/4 inch in diameter, 4 to 6 inches long, and has purple bristles. It matures in about 75 to 80 days and produces a hay crop in 55 to 60 days. Manta, a South Dakota release, is an early Siberian millet.
Hungarian millet is characterized by a small, compact, slightly lobed seedhead which is 1/2 to 5/8 inch in diameter and 4 to 6 inches long. Bristles vary in color from clear to pale yellow through purple and black. Stems are medium in size. It is reported to do better under more favorable moisture conditions. Maturity is about 70 days and a hay crop can be ready in about 55 days.
German millet has thicker stems and broader leaves. The seedhead is distinctly lobed, measuring 1 to 1 ½ inches in diameter and 6 to 9 inches long. Bristles are greenish to purple. It is a longer season foxtail, which takes about 90 or more days to mature and 65 to 70 days to produce a hay crop. Because of its increased stem size, it takes better management than the other foxtail millets to produce good quality hay.
Harvest millets for hay in the late boot to early bloom growth stage. Any delay after full head emergence will reduce quality. Bristles become hard as maturity approaches and may cause sore mouth, lump jaw and eye infections when fed to livestock. Hay protein content is highest when the ratio of leaves to stems is high. Curing foxtail millet requires attention as light stands tend to sun dry rapidly after cutting, while heavy stands, especially of the German type, cure at a slower rate. If expected yield levels are greater than 1 ½ tons per acre, crimping will help the curing process. Potential yield of foxtail millet hay is influenced by moisture relationships. Research trial yields from North Dakota Experiment Stations ranged from 1.5 to 3.4 tons/acre.
HAIL DAMAGE IN OILSEED & ROW CROPS
Hail damage to crops occurs somewhere in the state every year. Reports have already been made last week and this week of hail in some areas of the state. When hail damage occurs on corn, soybean, dry bean and sunflower early in the growing season, replanting is possible; but deciding whether to replant is usually difficult. Total stand reduction, leaf loss, stem injury, weed control, and calendar date are factors to consider when making this decision. At this time (Mid-June) its too late to consider a replant.
Corn: The growing point remains below ground 2-3 weeks after the plant emerges (5-leaf). If the growing point is not damaged, corn will recover and perform better than replanted corn. Split the stalk down the center and inspect the growing point. If normal, it will appear white in color and firm in texture. Injured growing points will appear brown or discolored 2-3days following the hail. Complete loss of leaves early to corn when small usually does not greatly affect grain or silage yields. Corn in the silking and tasseling stage when damaged by hail can result in severe yield losses.
Soybean and Dry Bean: The growing points of beans are located in the top of the plant and in leaf axis. Growing points of beans are easily damaged by hail soon after emergence. Regrowth will not occur if hail stones cut the stem off below the cotyledonary node. If the tip of the plant is damaged, regrowth can occur from one or more axillary buds. Bean stems may be bruised or broken. The damage may not be severe enough to kill the plant. However, the plant may lodge later as the callus tissue is weak and cannot support the pod weight. Reduction in soybean stands to four plants per linear foot of row in 30 inch row spacings can still produce fair yields. For dry beans one can get down to two plants per foot of row and still get fair yields.
Sunflower: Sunflower may be more tolerant than beans, but the degree of hail tolerance depends on the intensity of the hailstorm and the stage of growth. Sunflower is least tolerant during the seedling and budding stages, and most tolerant after flowering. Hail damage may be direct or indirect. Direct damage results from stand reduction, loss of recoverable heads because of severely bruised or broken stems, and head shatter at later stages. Indirect damage results from defoliation and disease infestation to injured plant tissue.
Research conducted on simulated hail losses in sunflower indicated that a one-to-one relationship does not exist between stand reduction and yield loss. A 50% stand reduction resulted in only a 28% yield reduction. Defoliation of sunflower by hail was reported to be most damaging during the bud stage. Defoliation of 80% at the bud stage resulted in yield reduction of 53%. Whereas 80% defoliation at the 50% mature stage resulted in only a 12% yield loss.
Canola: Plantings in seedling stages can have stands reduced by 50% and still produce acceptable yields. An average stand of 11-12 plants/ft2 can be reduced to 4/ft2 before yield losses exceed 10 percent. Prior to bolting and flower development, canola can withstand hail without much economic loss. Canola with leaves that are torn and shredded suffer only partial loss, while leaves bruised on the main vein or torn and broken will be lost. Leaf area destroyed will result in seed yield loss. Seed yield losses in canola is approximately 25 percent of leaf area lost. If leaf defoliation is 50 percent, then yield loss would be approximately 12.5 percent.
Canola plants injured in late bolting or early flowering stages seldom die. The well developed root systems and ability to rebranch and develop secondary flower clusters help the plants recover. When buds or flowers are destroyed, the canola recovers rapidly by development of flowers which normally would have aborted. New branches also develop from growth buds lower down on the plant. Seed yield loss will depend on both percent leaves and branches lost. For example, if canola has 60 percent lost branches 7 days into flowering, seed yield loss is estimated at 18 percent, whereas 21 days into flowering, yield loss would be an estimated 60 percent. If hail strikes late, such as during pod filling or ripening, plant recovery is not possible. The time needed to develop new growth, flowers and mature is limited before a killing frost. Canola seed yield loss if injury occurs at the ripening stage depends directly on the loss of branches, individual pods and seed knocked out of pods. Severe hail losses have occurred in canola swaths.
Duane R. Berglund