Field Crop News

Website Address: http://fcn.agronomy.psu.edu/

September 3, 2008    Vol. 08:26

IN THIS ISSUE:

• Weather Outlook
• Recalibrate Seeder before Planting Hulless Orchardgrass
• Late Season Cornstalk Nitrate Test and Dry Weather
• Seeding Pastures Ahead of a Hurricane
• Moisture Saving Tips
• PA Soybean Sentinel Plot Report
• Dry Weather May Lead to Stalk Lodging in Corn
• Save the Date: Keystone Crops and Soils Conference

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

After one of the driest Augusts in many years (perhaps since 1972), the remains of Hanna will likely change that theme for September, particularly in the eastern half of the state. A couple more very warm, dry days — though increasingly humid, are expected. A cool front approaching from the Great Lakes may reach the Lake Erie shoreline before retreating later Thursday ahead of Hanna. This soon to be hurricane again will reach the north Florida coast as a strong hurricane (Cat 2) on Friday and then head northward along the Piedmont plateau. Heavy rain and gusty winds (along with rather sticky air) are expected on Saturday. The western third of the state may miss most of the rain. The eastern third could measure between 2 and 4 inches of rain with lesser amounts in the central section. A push of somewhat cooler and much drier air is most likely on Sunday. More cool air will arrive by the middle of next week, preceded by a broken band of showers (centered on Tuesday). At this time, it seems that neither Ike nor Josephine will have any direct impact on our weather for the next week or so.

Odds still favor a warmer than average October followed by a chilly November and this may translate into a later than usual frost in the southern half of the state plus an early and vigorous start to the lake effect snow season.

Recalibrate Seeder before Planting Hulless Orchardgrass — Marvin Hall, PSU Forage Specialist

In the past five years there has been an increase in the number of companies marketing hulless orchardgrass. However, no seeding rate charts on seeders, that I am aware of, have been adjusted to achieve a recommended orchardgrass seeding rate with hulless orchardgrass. Consequently, it is important to calibrate your seeder prior to planting hulless orchardgrass.

Hulless orchardgrass has the palea and lemma (hull) removed from the orchardgrass caryopsis. Removal of the hulls allows the seed to flow through the seed metering device easier. Removing the hulls probably has limited affect on the number of seeds/lb (approximately 440,000) but it does significantly reduce the volume per lb of seed. A 50 lb bag of hulless orchardgrass is smaller than a 50 lb bag of hulled orchardgrass seeds. Since most seed metering mechanisms are based on volume, the seeding rate for hulless orchardgrass will be greater than at the same setting for hulled orchardgrass. Unless the seeder is calibrated for the hulless orchardgrass farmers will be overseeding and consequently my need to buy more bags of seed to plant the desired acreage.

Coating the hulless orchardgrass seed with various products, as several companies are now doing, enlarges the seed so that there are fewer seeds/lb. A 50 lb bag of hulless and coated orchardgrass may contain less than 25 lbs of seed. Recommended seeding rates for coated seeds are difficult to establish because the thickness of the coating (volume/lb) varies with coating material.

Late Season Cornstalk Nitrate Test and Dry Weather — Douglas Beegle, PSU Soil Fertility and Nutrient Management Specialist

The Late Season Corn Stalk Nitrate Test is a reliable end of season indicator of crop N status. It provides a good assessment of whether the crop had the right amount of N or too much N or whether it ran out of gas. This information combined with records of N management can be very useful for making future management decisions.

A common question this year is how will the dry weather that we have had the last several weeks affect this test? In general, dry weather will result in higher stalk nitrate levels. This is why there is concern with high nitrates in drought stressed silage and why chopping higher is sometimes recommended to avoid including the high nitrates in the lower stalk in the silage. Actually even in dry conditions, the late season stalknitrate test is accurate. If the stalk nitrate test is low, then the crop definitely did not have enough N, and if the there are high nitrates in the stalk, then N was not limiting production, moisture was the limiting factor. The problem is that these results only provide useful management information for a dry year when moisture is the limiting factor. It does not give you good feedback on whether your N management would have been optimum in an adequate moisture year.

Another important weather related sampling issue with the stalk test is do not sample immediately following a dramatic change in the weather. If we start getting more rain, give the plant several days or a week to adjust to the change and stabilize before sampling.

One other related question is whether samples can be taken after silage harvest. Research in Connecticut has found that samples could be taken up to 24 hours following silage harvest. For this to work, the corn must be chopped at least 14 inches high so that you can still get the correct sample ie. 8-inch long sections of corn stalk starting 6 inches above the ground. Don’t delay any longer and, in general, be careful if there is any stalk deterioration.

A final issue regarding end of season N assessment and drought is the practice of visually assessing the crop N status by the number of green leaves below the ear. Generally if you have at 4 green leaves at and below the ear at silage harvest time, the crop had adequate N. This assessment is based on the assumption that the yellow or brown leaves at the bottom of the plant are due to N deficiency. However, very dry conditions will also cause the lower leaves to senesce. Be careful not to confuse this with N deficiency. Nitrogen deficiency is characterized by a distinct “V” shaped pattern starting at the tip of the leaf and going back the mid-rib. Drought senescence does not follow a distinct pattern but most commonly starts at the tip and goes back the leaf often more on the edge of the leaf. Because of the drought caused senescence, a reliable visual N assessment may not be possible this year.

The late season stalk nitrate test is available through the Penn State Agricultural Analytical Services Laboratory (AASL). Information about the test including sample submission forms and detailed sampling instructions are available on the AASL Web site. A video on taking samples for the late season stalk nitrate test is available on the Crop Management Extension Group (CMEG) Web site.

Seeding Pastures Ahead of a Hurricane — Paul Craig, Dauphin County Educator

When pasture producers consider overseeding of a pasture the most common time period is in late winter and referred to as a “frost seeding”. Frost seeding is thought to provide adequate soil freezing and thawing actions to allow the grass/clover seeds to become somewhat covered by soil to allow for seed to soil contact to enable seed germination. Unfortunately most frost seedings are not very successful for many different reasons. One major reason that limits new seedlings from developing in the spring time is from competition from existing plants in the pastures and from summer annual weeds that germinate and develop at the same time as the new overseeded crops. The most successful pasture producers who incorporate overseeding in their pastures to thicken them up will continuously apply seeds multiple times a season and frequently for three years or more in a row.

Another opportunity for overseeding some of the rough looking pastures across PA at this time is quickly approaching. That opportunity is named Hanna and weather forecasters are predicting that this latest hurricane will be approaching PA this weekend.

If we consider reseeding in a natural environment then there is a role for hurricanes in the natural cycle. At this time all grass species, cool and warm season grasses will have completed their reproductive stages and the mature seeds are held in the seed heads or dropped to the soil surface waiting for ideal conditions for germination. Along comes a hurricane with heavy rains and extended rainfall periods to knock these seeds out of the seed heads and then mix the seeds into the surface area of the soils. Afterwards the soil has been recharged of moisture allowing the new seedlings to develop. Typically in a pasture there is sufficient crop residue on the surface to limit seed loss due to runoff.

Overseeding prior to a hurricane can provide an excellent opportunity to thicken up thin pasture stands. The weakened existing plants will not provide too much competition to the seedlings and only the fall germinating weeds will be present. If existing pastures have a lot of annual weeds such as crabgrass or foxtails or pigweeds and lambsquarters a treatment with Gramoxone ahead of over seeding and the hurricane will provide excellent weed control and not injure the existing pasture grasses.

Pasture producers must still address other issues related to grass stand management to ensure optimum production levels. These issues include overgrazing, fertility and lime additions, weed control, pasture rotations to provide a rest period for grasses to recover before the next grazing cycle.

No one asks for a hurricane or the severe damage that one can bring but sometimes even an unwelcomed event can provide opportunities if planning is considered. Overseeding can be accomplished with a no till drill or even a well maintained conventional drill or simply by broadcasting seed over the pasture. When broadcasting seed be certain to increase suggested seeding rates by 30% or more. Because of the less than ideal success of any overseeding, a second overseeding before the next hurricane would be beneficial if the opportunity presents itself.

Moisture Saving Tips — Sjoerd Duiker, PSU Soil Management Specialist

The lack of precipitation this past month is pushing the crops to their limit. While it is too late to do anything to save moisture at this point in time, it makes us contemplate what we could do different next year to reduce the likelihood of moisture stress. It is helpful to consider the different components of the water balance when thinking about water-saving strategies. The water balance is: P + I = ET + R + D ± ΔS, where P = precipitation, I = irrigation, ET = evapotranspiration, R = runoff, D = deep percolation. We won’t discuss ways to increase precipitation, irrigation, or reduce deep percolation. Reducing transpiration is not a viable option, because it reduces crop production. So our discussion will focus on reducing evaporation from the soil surface, reduce runoff losses, and increase soil water storage.

1. Maintain residue cover

   Residue cover is a most effective means of moisture conservation. Residue protects the soil surface against raindrop impact which helps to increase infiltration. It also acts as a protective barrier reducing evaporation of water from the soil surface. The best way to maintain residue cover is to no-till into crop residue of last year’s crop or of a cover crop.

2. Improve soil structure

   Soil structure is the arrangement of soil particles in small aggregates, called aggregation. If soil aggregates are stable, they don’t slake quickly, and the soil maintains good porosity. That helps to avoid soil sealing and crusting and improves water infiltration. Soil structure can be improved by eliminating or reducing tillage, increasing soil organic matter content, and maximizing soil occupancy with fibrous roots that hold soil particles together.

3. Increase organic matter content

   Organic matter acts as a sponge and helps to increase the amount of water the soil can hold on to and release for plant growth. Organic matter can be increased by soil management practices such as no-tillage, cover cropping, adding compost or packed manure, and growing high-residue crops.

4. Optimal management of cover crops

   Two principles are important: living cover crops consume water, whereas dead cover crops preserve water because of the mulch cover they provide. Thus cover crops should be killed approximately 2 weeks prior to main crop establishment, but should produce maximum residue with high C:N ratio to provide a thick, long-lasting mulch. Early fall establishment of cover crops assures higher biomass early in the spring. Increasing seeding rates of cover crops is another strategy to increase biomass production.

5. Optimal weed control

   Weeds compete with crops for water so they need to be absent to reduce water competition.

6. Avoid summer crop establishment after first cutting of hay

   This is the scenario where moisture stress shows up most evidently because the hay crop depleted soil moisture, while no mulch is present to preserve soil moisture in the summer. It is therefore recommended to fall-kill a hay crop.

7. Avoid soil compaction

   In our research on well-drained soils we have shown the worst compaction effects in dry years because of two reasons: (1) Crop establishment was endangered in the hard soil surface, an (2) root growth was inhibited. With a reduced root system, crops cannot as great a soil volume for water, resulting in greater moisture stress. Soil compaction should therefore be reduced as much as possible.

8. Spread corn planting window or plant corn with different tasseling dates

   Corn is most sensitive to drought at the time of pollination. If tasseling dates are spread out on the farm, drought risk is reduced.

9. Increase summer crop diversity.

   Some crops like sudangrass and sorghum-sudangrass are known for their drought resistance. Some forages like teff can do well in the heat of summer. Crop diversity spreads the risk of moisture stress.

10. Planting a mix of winter and summer crops.

    Although monthly precipitation is approximately uniform in Pennsylvania, evapotranspiration is much smaller in the winter and early spring. Winter crops therefore commonly suffer less from moisture deficit.

PA Soybean Sentinel Plot Report — Justin Dillon, PSU Research Support Assistant

Editor’s Note: The soybean samples are supplied to Justin from the counties mentioned below. The pests listed are not necessarily those found throughout the county or region of the state, as the samples are from one location. The information is supplied for producers’ awareness of pests that are present in soybeans.

August 23, 2008: The soybeans are in the mid-to late reproductive stages (R3-R6). The diseases include Septoria Brown Spot, Frog-eye Leaf Spot, Downy Mildew, Bacterial Leaf Blight, Cercospora Leaf Blight, and 1 possible Soybean Mosaic Virus infection. I haven’t had it tested, but the symptoms (light green and dark green areas, and leathery crinkled/puckered appearance) indicate the infection. The infection was only on 1 leaf.

Mercer Co. — Septoria Brown Spot, Cercospora Leaf Blight, Frog-eye Leaf Spot, Downy Mildew, Bacterial Leaf blight, and Poss. SMV infection.

Lehigh Co. — Septoria Brown Spot, Frog-eye Leaf Spot, Downy Mildew, Bacterial Leaf blight, and Aphid damage.

Armstrong Co. — Septoria Brown Spot, Frog-eye Leaf Spot, Downy Mildew, and Bacterial Leaf blight.

Landisville — Septoria Brown Spot, Frog-eye Leaf Spot, Bacterial Leaf Blight, Aphid damage, Spider mite damage and carcasses, Leafminer damage.

Bedford Co. — Septoria Brown Spot, Downy Mildew, and Leafminers.

Franklin Co. — Septoria Brown Spot, Frog-eye leaf spot, Downy mildew, Bacterial leaf spot, Aphid damage, Old Spider mites.

Lycoming Co. — Septoria Brown Spot, Downy Mildew, Bacterial Leaf Blight, Frog-eye leaf spot, Aphid damage, spider mite carcasses, Mexican bean beetle, Japanese beetles, and green clover worm damage.

Dry Weather May Lead to Stalk Lodging in Corn — Candace Pollock, Ohio State University

Despite recent rain from the remnants of Fay, parts of Ohio remain abnormally dry, and the drought-like conditions may cause stalk rot and lodging problems in corn.

Pierce Paul, an Ohio State University plant pathologist with the Ohio Agricultural Research and Development Center, said that dry conditions experienced during grain fill often increase the potential for stalk rot and lodging problems, which can have a significant impact on harvest losses. “Since the dry spell occurred during grain fill, the damage, unfortunately, has already been done,” said Paul, who also holds an Ohio State University Extension appointment. “Any rain in corn production is useful, but it may be a little too late for some of the corn in the state.”

Stalk rot and lodging may occur when stalks are weakened as a result of drought or any other stress that negatively affects the photosynthetic efficiency of the plant. Under drought stress conditions, leaves roll up to reduce water loss and as such intercept less light for photosynthesis. The corn plant responds by "cannibalizing" the leaves, stalks and roots in favor of ear development. While the process ensures a supply of carbohydrates for the ear, the removal of carbohydrates results in premature death of the stalk and root tissues, predisposing the plant to fungal infections and, consequently, stalk rot and lodging.

“The presence of stalk rots in corn may not always result in stalk lodging, especially if the affected crop is harvested promptly. Many hybrids have excellent rind strength, which contributes to plant standability even when the internal plant tissue has rotted or started to rot,” said Peter Thomison, an OSU Extension agronomist. “However, strong rinds will not prevent lodging if harvest is delayed and the crop is subjected to weathering.”

Thomison said that growers can assess the potential for stalk lodging by squeezing the stalk between the thumb and finger. “A common symptom of stalk rot is the deterioration of the inner stalk tissues so that one or more of the inner nodes can be easily compressed when squeezed,” said Thomison.

The “push” test is another way to predict lodging. “Push the stalks at the ear level, six to eight inches from the vertical. If the stalk breaks between the ear and the lowest node, stalk rot is usually present,” said Thomison. “To minimize stalk rot damage, harvest promptly after physiological maturity (about 30 percent grain moisture). Harvest delays will increase the risk of stalk lodging and grain yield losses, and slow the harvest operation.”

Drought-stressed corn also faces the potential for mycotoxin development and nitrate problems. Mycotoxins, especially aflatoxins, are produced by Aspergillus flavus, an ear mold fungus, and drought-stressed corn is most susceptible to infection. Mycotoxins can cause animal and human health problems. “As the corn dries down and we get closer to harvest, producers should start checking for ear molds by stripping back the husks and examining the ears of 80–100 plants sampled from across the entire field,” said Paul. “Since not all ear molds are associated with mycotoxin contamination, it is important to properly identify ear molds before harvest in order to determine if mycotoxin will be a concern and to make adequate marketing and storage decisions.”

Dry conditions can also lead to the development of toxic levels of nitrates in corn harvested for silage, which can be harmful to livestock. Nitrates are major constituents of fertilizers, and when processed properly by the plant, are converted to harmless proteins. During times of dry weather, plants are unable to convert nitrates into proteins and the nitrates accumulate in the stalks and stems. Research has shown that the lower one-third of a corn stalk can have a nitrate concentration of as much as 5,000 parts per million. By comparison, the leaves accumulate less than 20 parts per million in nitrates.

Thomison said that the best recommendation growers can follow to minimize nitrate toxicity is to delay harvest, especially if drought-stressed corn is suddenly subjected to rainfall. “You don’t want to harvest right after a rainfall,” said Thomison. “If growers can wait, say two or three weeks after rainfall before harvesting to allow that nitrogen to be metabolized into amino acids and proteins, then that’s the safest for the animal.”

For information on testing and feeding corn with varying nitrate-nitrogen levels, check out the following publication: Nitrates in Dairy Rations.

Save the Date: Keystone Crops and Soils Conference — Paul Craig, Dauphin County Educator

The 2008 Keystone Crops and Soils Conference will be held on Tuesday October 21 and Wednesday October 22, 2008 at the Holiday Inn in Grantville, PA. The conference will begin at 8:30 on both days. Topics include: Forage Harvesting; Ethanol and Its Implications for Agronomists; Managing N with High Grain and Input Prices; Sweet Corn Insect Management; Wheat Production; Establishing Switchgrass; Precision Ag Technologies; plus many more. Certified Crop Advisor and Nutrient Management Credits will be provided. Watch for additional information in the near future.

Contributors: Extension Educators: Susan Alexander (Jefferson), Paul Craig (Dauphin), Andrew Frankenfield (Montgomery), Kevin Fry (Armstrong), John Rowehl (York), H. Grant Troop (Lebanon), Del Voight (Lebanon); Department of Crop & Soil Sciences: Douglas Beegle, Sjoerd Duiker, Marvin Hall, Ron Hoover, Dwight Lingenfelter; Department of Entomology: John Tooker

Editor: Dwane Miller, Schuylkill County

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