Del Voight - Agronomy Extension Agent
Many areas of Pennsylvania are experiencing a severe drought due to the lack of rain since late May. Corn growth has stopped in many areas and in the worst areas corn fields are beginning to dry up. Other grain and forage crops are drought stressed as well. Although we can do little to change the weather, we can make some management decisions now to help minimize losses and salvage as much from a bad situation as possible. Some key questions that silage and grain producers should consider are listed below.
What should be done now? There are several things that should be initiated immediately. The condition and yield potential of the crop should be assessed. Dairy and livestock producers may want to collect a forage sample to assess moisture, forage quality and nitrate levels. Grain farmers may want to begin identify ways to market their crop as silage. All producers should be check with their crop insurance or FSA representative before harvesting the crop.
What is the yield potential of the field? This will be variable depending on the severity of the drought. For corn fields that are losing leaves and not unrolling at night, the yield potential will be likely low- from 0-50 bushel/acre or so. For fields that have a good stand and are exhibiting leaf rolling only during the day, there may still be good yield potential if the drought is broken soon. Even many of these fields have lost a significant amount of their top end yield potential, perhaps 50 bushels per acre or more, if conditions would be perfect until the end of the season.
When should you decide to salvage the crop and harvest for silage? When leaves cease to unroll at night and the tops start to brown out, the plants are probably not going to recover. As browning of the crop continues, the forage quality will decline as the plants are using stored carbohydrates in the leaves and stalk to sustain itself. Producers should probably consider harvesting it for silage. Delaying harvest will reduce yield and quality and reduce the potential for planting a second crop. The moisture content may be higher than desired, so a dry feedstuff like chopped ear corn or hay may need to be to adjust the silage moisture and energy for good fermentation. If the forage is extremely wet (greater than 75-80%), then harvest should likely be delayed. No definitive guidelines are available, but I would suggest that if half the leaves are dead or dying it would be a good candidate for evaluating for silage harvest.
What is the yield potential of this type of crop? A rough estimate of wet (70% moisture) silage yield is about 1 ton per foot of height of corn without ears or poorly pollinated ears. This estimate may be high on very short (1-3 foot tall) crops.
What kind of silage will this crop produce? This crop will likely be higher in protein than normal silage and lower in energy. A ballpark estimate of silage quality might be an NEL of 0.60- 0.64 and a crude protein of 9-12 percent. Some preharvest forage testing may be appropriate to assess the quality, the level of nitrates, and the potential use of the forage. If it were to rain, fields that have some recovery potential could produce some good quality silage. in these drought stressed crops that recover the ear to stover ratio will be good and the fiber digestibility is usually high.
Are nitrates a concern in this kind of crop? Yes. The potential is greatest for high nitrate levels in young plants, especially in the stalks and especially in heavily manured fields. The potential is generally greatest for 3-4 days following a drought ending rain, but can be a problem anytime. High nitrates can contribute to animal feed problems and deadly silo gas. Producers should be especially cautious when filling silos with these suspect crops. Nitrates can be reduced by leaving a 12 inch stubble in the field- this would reduce yields, however, and may not be advisable unless a forage test confirms the presence of nitrates. Because the nitrate potential can be reduced through ensiling, grazing and green chopping drought stressed corn are less desirable harvesting alternatives.
Is it worth harvesting these crops? On some fields it may be a tossup. The variable costs such as fuel, labor and repairs, associated with chopping a light corn crop are in the $15 to $25/acre range, so if producers can harvest at least one ton of silage per acre valued at perhaps $20/ton they will break even. To achieve this yield may require corn about two feet tall.
What should grain producers be assessing? Grain producers in the worst areas may need to be identifying silage markets for their crop. This will help to alleviate potential feed shortages and provide a market for drought damaged corn crops that will produce little grain. They could also be considering plans for establishing other fall forage crops- there may be a significant market for these crops this fall.
What crops are a potential for replanting following corn? This will depend on the herbicide program used for corn. Generally, sorghum-sudan grass may be the most viable option if planting can be achieved by early August. Small grains or soybeans are also alternatives in some situations, but the dry weather may make atrazine carryover high which will damage the more sensitive crops like oats and soybeans. Check herbicide labels for replanting restrictions. If corn fields are unsatisfactory for planting fall forage crops, producers may want to consider no-tilling into small grain stubble fields- although these soils may be hard until it rains again. Call the Extension Office for copies of raising alternative crops which will detail seeding rates and how to properly establish the different crops.
Department of Agronomy
Penn State University
Nutritive Value of Drought Soybeans as a Forage Crop
R. S. Adams, Emeritus, Professor of Dairy Science
Penn State University
Drought stricken soybean plants can be used as a forage crop. Allow plants to
mature as much as possible before harvesting. Some pod or bean development
enhances feeding value of plants harvested either as hay or silage. Soybean
forages are high in calcium (about 1.3% on a DM basis). For this reason it
should be avoided as the major forage for dry cows.
If ensiling, it is important to ensile before plant moisture drops below
60-65%. If possible, mix soybeans with other forages, preferably during
ensiling, to enhance their palatability. If plants are high in moisture and
lack pod or bean development, add 100-200 lb of ground grain per ton when
direct-cutting rather than wilting to 60-65% moisture.
Stems are not very palatable, and if animals have the opportunity, they will
sort them out. Chopping hay and feeding it in a total mixed ration (TMR) will
help prevent sorting, and stretch forage supplies.
If soybean forage contains substantial amounts of developed beans, reduce the
amounts of other fats and oils in the ration, or the ration may be too
laxative. Also, it may be difficult to dry down pods for hay if beans are too
well developed. Soybeans can be pastured. If cows are removed before all
stems are eaten, there may be regrowth.
The table below gives some estimates of the nutrient content of soybean forage
on a dry matter basis:
Expected Nutrient Content of Soybean Forage
Stage of Maturity CP % ADF %Nel Ca % P % Mg %
avg silage, hay 17.7 35 .54 1.25 .49 .34
avg hay 16.5 35 .55 1.20 .47 .32
mid bloom 17.8 35 .57 1.25 .49 .34
seed developing 17.5 35 .59 1.20 .47 .32
seed dough stage 16.8 35 .61 1.15 .45 .30
The dry matter content for average silage is 28%, while that for hay is 88%.
Test soybean forage or mixed forages containing soybeans to enable proper
You need to consider some of the herbicide restrictions. If you look on page
118 in the 1995-1996 Agronomy Guide, you will fine Table 6-17. Feeding
restrictions on soybean forage and grain. Unfortunately with few exceptions,
most soybean herbicides do not allow feeding the soybean plant as forage. The
exceptions are Basagran, Lexone, or Sencor, and Lasso/MicroTech. I suspect
that the reason that most of the newer herbicides don’t allow this use is
because the ingredients simply never received a forage tolerance. Soybeans are
not typically harvested as forage and it costs the manufacturer a great deal
of money to conduct tolerance/residue studies. Think about how few product we
have labeled on alfalfa. Although this explanation may not help, its what on
the product use label.
Insects of Importance during a drought
Adult Corn Rootworm Emergence - Adults of the corn rootworm are beginning to emerge in central Pennsylvania. Emergence begin about 10 days ago in the southwest, southeast, and south central areas of the state. Expect emergence to begin in the more northern and highland areas around the first of August. Adult
numbers appear to be very high this year. Because of the drought conditions, there is a chance that some fields may benefit from sprays to control adults and prevent silk clipping which leads to poor pollination. Counts from corn rootworm scouting can be used to determine whether adult control in the current year is advisable or whether larval control during the next cropping year is warranted. If beetle numbers exceed the
economic threshold, a corn grower may decide to rotate to a crop other than corn next year, apply an insecticide at-planting time or control adult populations to prevent egg laying in the field. Depending on whether adult control is aimed at preventing silk clipping or to eliminate adults before eggs are laid in the field, different economic
thresholds are used. Five beetles per plant is enough to warrant control to avoid economic levels of silk clipping, which can interfere with pollination of the ear. If an adult control program is desired to prevent economic populations for next, the economic thresholds are the same as for a at-planting time application: 1.0 beetle per
plant in first year corn fields and 1.5 beetles per plant in field that have been in corn for two or more years. Adult control should be implemented when the economic threshold is exceeded. For prevention of silk clipping, an insecticide should be applied just prior to silk emergence or when an economic infestation is noted. Note: Once at least 50% of the plants have brown silks, an indication that pollination is complete, treatment is no longer justified. Sevin, Lorsban, dimethoate, Asana, Warrior, malathion, Lannate,
Penncap-M, Ambush, and Pounce are registered for adult corn rootworm control. With the exception of Sevin and malathion, the insecticides should provide at least 7 to 10 days of silk protection. If beetle numbers begin to increase to economic levels before 50% brown silk, a second application may be necessary. It is important not to
get over anxious and apply insecticides to whorl stage corn when number get high. Too early an application will kill beetles in the field at that time, but may not provide protection once corn begins to shed pollen. At that time new beetles will be attracted in the field that may cause economic silk clipping.
Potato leafhopper - Numbers of this pest continue to be extremely high across the state. The third and fourth cutting will very vulnerable to severe stunting and injury by the pest. New seedings are particularly vulnerable to feeding by this pest. In some areas of the state, reports of dimethoate (Cygon) and chloropyrifos (Lorsban) not
holding up are coming in. Maryland is reporting similar problems. It is not clear why these failures are occurring.
Two-spotted Spider Mites - The dry, hot conditions in recent weeks are perfect for population explosions of mites in soybeans. Soybean fields should be watched closely over the next few weeks for the development of the pest. Several fields in the Landisville, Pa area are already showing evidence of injury. The recent rains will help
reduce numbers, but if the hot temperature return mite numbers will rapidly increase. Applications of dimethoate will reduce mite populations if injury is noted to the soybeans.
Grasshoppers - So far there has not been many report of grasshopper injury to field crops. However, the dry, hot conditions are ideal for the development of localized outbreaks. If the dry, hot conditions continue, keep your eyes open for the development of high populations and crop injury. Sevin 4-Oil, Furadan 4F, dimethoate, Asana, malathion, and Penncap-M are registered for grasshopper control. See the Agronomy Guide for rate information.
Japanese Beetle - This pest is now attacking corn and soybean fields in the state. As corn fields begin to silk, keep an eye out for significant silk clipping. If an average of two to three beetle per ear are seen feeding on silks before pollination, then an insecticide application may be warranted. Several formulations of carbaryl (Sevin),
methoxychlor, and Penncap-M are registered to control this pest. Carbaryl and Penncap-M are also registered for corn rootworm beetle control. See the Agronomy Guide for rate information.
MANAGING ALFALFA DURING AND FOLLOWING A DROUGHT
Alfalfa in some areas of Pennsylvania is experiencing water stress and the question of alfalfa management during this time is being raised. But before we discuss the management of water-stressed alfalfa, lets look at how alfalfa responds to drought conditions. Alfalfa is commonly referred to as a drought tolerant plant. During the onset of drought conditions, alfalfa will stop using carbohydrates for stem and leaf production and store those carbohydrates in the roots. This provides high levels of root carbohydrates for long term survival if drought conditions persist and the leaves become photosynthetically inactive. However, alfalfa's ability to survive a drought does not mean that alfalfa will not show drought related symptoms. Water-stressed alfalfa will experience decreased stem elongation and in some cases mature more rapidly. Leaf production is less effected by water stress than stem elongation. This results in higher forage quality of water-stressed plants than their unstressed counterparts.
To Harvest or Not to Harvest?
The primary criterion influencing the decision to harvest drought-stressed alfalfa should be based on the cost of harvesting and the value of the forage. The alfalfa plants may look weak and severely stressed during a drought; however, harvesting at the stage of plant development when you would normally harvest is recommended as long as adequate alfalfa is present to justify the cost of harvesting. The plant, even though it may be very short, will already have stored more than enough root carbohydrates to insure survival if the drought persists or insure regrowth is sufficient rains remove the drought conditions.
EMERGENCY FORAGES IN DRY YEARS
Because of the drought conditions and the resulting less than anticipated forage
growth, I'm sure you have been asked what alternatives farmers have for forage production once the drought breaks. Here are some suggestions and sources for more detailed information.
FARMERS WHO GRAZE:
These farmers may not have been able to produce sufficient hay/silage to get
through the winter. For them, an option is to plant some forage crops in August
(hopefully it will be raining again by then) that can provide grazing this fall and allow hay/silage to be made from their traditional pasture land. Following are some
• Forage Brassica (e.g. Rape or turnip):
• Small Grains (e.g. wheat, barley, rye, or triticale) For additional information on growth characteristics, establishment, fertility, and grazing management of these crops refer to Agronomy Facts 33, "USE OF BRASSICA CROPS TO EXTEND THE GRAZING SEASON" and Agronomy Facts 41, "STRATEGIES FOR EXTENDING THE GRAZING SEASON".
FARMERS WHO DON'T GRAZE:
Most of the crops that could be planted at this late time and produce some forage are better suited for harvesting as silage rather than hay. These crops are listed below along with sources for more detailed information.
• Summer-Annual Grasses (e.g. Sorghum, Sudangrass, Sorghum-sudan hybrids, and Millet). After July 15 these crops are really only an option for Pennsylvania's more southern and warmer counties. For most of the State these crops will not mature before cool fall weather and frost stop their growth. In a situation where the drought damaged corn has been harvested in July then these crops may be the only option because of herbicides used on the corn and the greater potential for carryover due to the dry conditions. For more information refer to Agronomy Facts 23, "SUMMER-ANNUAL GRASSES FOR SUPPLEMENTAL OR EMERGENCY FORAGE"
• Small Grains (Oats and Rye, use taller varieties). Small grains should be planted as soon as possible and harvested for silage in the milk to soft dough stage. Generally, the milk stage is less desirable than the early dough stage because it is less palatable and studies indicate that animal performance may be reduced. Moisture levels between 60 - 70% are best for ensiling small grain silage. Small grain silage below 60% moisture is difficult to pack and excessive heating and nutrient loss may occur. In addition, making sure that the theoretical length of cut is less than 3/8 inch is important with small grains because some stems are hollow and filled with air. Minimizing the length of the chopped material will help minimize silage heating and maintain forage quality. In a Penn State study conducted at the Landisville (Lancaster Co.) Research Center small grains yielded more than sorghum-sudan grass when both were seeded on August 5.
Yield and TDN of four crops seeded on August 5
Corn (harvest on 10/5) - 1.5 ton/a and 61.2% TDN
Sorghum-sudan hybrid (harvest on 10/5) - 1.6 ton/a and 61.2% TDN
Oat (harvest at soft dough) - 2.1 ton/a and 75.8% TDN
Rye (harvest at soft dough) - 2.1 ton/acre and 68.4% TDN
Dr. Marvin Hall
Penn State Forage Specialist