Month: March 2012

Frost to Alfalfa

Frost/freeze on alfalfa(as in Dervin Druist, as in ISU Extension

by Steve Barnhart, extension forage agronomist, Department of Agronomy

Pinning down precise air and tissue temperatures in a standing alfalfa crop, and then predicting the impact on growth (or death) is not an exact science. The air temperature reported on the weather report or on your local thermometer may not be what the alfalfa crop is experiencing. Topography of the site (cold air “flows” into low-lying areas), wind, and the moderating influence of the warmer soil mass greatly influence the microclimates in the standing alfalfa canopy and from site to site in the field. My descriptions here should be considered subjective, with an appropriate amount of acceptable variability that reflects real-world conditions.

Light frost (27° to 31° F)

Once alfalfa plants have broken spring dormancy, their tolerance of low temperatures is greatly reduced. Leaves on new alfalfa shoots will often be killed at tissue temperature of about 27° to 28° F (or colder). Buds and growing points are somewhat better insulated at 27° to 28° F and will often continue to grow normally. The only evidence of a light frost will be the loss of several sets of trifoliate leaves down the stem that correlates with the chronological time of the frost. Most plants in the field of a low-lying area will exhibit the same general leaf loss pattern. At these light frosts, the top few inches of alfalfa stems may curl–similar in appearance to 2,4-D herbicide epinasty. Alfalfa plants outgrow this.
Management implications: Morphological plant development should not be affected by a light frost, and there is no need to change harvest management plans.

Moderate frost–26°-27° F

Temperatures that freeze the upper few inches of the stem tips cause serious damage to that stem’s terminal growing point, as well as the supporting stem tip and associated leaves. The entire stem is not dead. At each leaf position lower on the stem is a dormant bud that can develop into a stem branch. Buds from the crown can also begin to develop new stems with the loss of the terminal buds. The frozen stem tips will dry out, and weather, losing nutritive value. The lower stem and any lower (or shorter) stems may still have their terminal growing points in tact and will continue to grow normally.
Management implications: For the next few weeks following the moderate frost, the morphology of the plant will be mixed. The unaffected stems will continue to develop normally and progress through stem maturation, budding, and flower formation as they normally would. The plants that may have only received temperatures in the light frost range (described above), will also progress through the reproductive stages normally. The lower stem tissue on stems that have lost the terminal growing points will continue to mature (increase in fiber, decrease in feed quality). The new side branches and frost-induced crown shoots will remain vegetative (and higher in feed quality) for a longer period than the associated older stems. Making harvest decisions then must be made on the basis of the feeding quality goals for the crop. Harvest for dairy quality forage should be based on the maturity of the most mature stems. In some cases this may mean the remaining old, maturing stems of frosted shoots that now have new vegetative branches are exhibiting maturity several weeks younger than their stem bases. For high nutritive forage quality, cutting decisions should best be made based on scissors clippings and testing–visual indicators will be giving mixed messages. If using PEAQ (predictive equations of alfalfa quality), try to find areas of the field that were not frosted as you best guide for the quality changes going on in the field as a whole. Using stem maturity and height of new, post-frost stems in the PEAQ assessment will overestimate the quality of the standing forage as a whole. You may see some yield sacrifice from the frost loss.
Physiologically, the moderately frosted plants still have had nearly constant full leaf area and will not have been greatly stressed enough to delay harvest because of frost stress. An exception may be for fields that are recovering from winter injury and have been recovering slowly. These fields would benefit from a week or so delay in harvest, or harvest when the plants reach early- to mid-bloom. Some producers are asking if they should cut alfalfa a week or two earlier than normal, simply because the stem tips have been frozen. This strategy would not only net a yield reduction for the cutting (because of early harvest), but may increase physiological early cutting stress in the plants.

Hard frost–25°-26°F or colder

Cold air that kills alfalfa tissue, deep within the canopy, does lead to important considerations.
Stems present at the time of frost will not produce any additional yield, and plants will attempt to regrow from crown buds.
Management implications: If you are to salvage the nutritive value of the severely frozen alfalfa, you need to begin the harvest and curing process soon–before the frozen plant tissue begins to weather, and lose nutritive quality. Physiologically, this is an early harvest and may lead to slower-than-normal regrowth from early cutting stress. This will also set the harvest schedule a week or two earlier for the remainder of the harvests of the year. If you do nothing, new crown shoots (essentially the 2nd growth) will grow up through the frost-killed stems and be at late bud/early flower, ready for harvest 4 to 5 weeks later. The presence of the dead, old stems will add to the dry matter yield of the combined 1st and 2nd crop but will also contribute significant, less desirable fiber.
Frost damage to alfalfa
An alfalfa plant showing symptoms of frost damage.

This article originally appeared on pages 67-68 of the IC-494 (8) — May 2, 2005 issue.

National Yield Champ Grows 429-Bushel Corn Efficiently

Some of you might be interested in how the Hulas grew their tremendous corn yield last season. Here are their inputs.
John Pocock of the National Corn Growers details the inputs. from
Mar. 9, 2012

Inputs used

The Hulas start with a popup fertilizer (3-18-18) in the furrow with the seed at planting, using a 30-in.-row Kinze 3600 12-row planter. The planter is equipped with Dawn Curvetine closing wheels “that help fluff up the soil in the seedbed” and Keeton Seed Firmers. In addition to the popup fertilizer, they also apply starter fertilizer (66 lbs. N/acre, 33 lbs. phosphate/acre, plus sulfur, zinc and Boron) 3 in. to the side and 2 in. below the seed.

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Nitrogen was applied twice to corn at the V5 and V9 growth stage with a high-clearance sprayer. On their contest field, which had been in rotation with wheat and double-crop soybeans, they also applied a late N application just prior to tasseling when the corn was 14 ft. tall.
“We couldn’t get in the field with our sprayer, so we just walked down the corn rows with 2.5-gal. jugs and applied it over the roots,” Hula says. “Next year, we plan to use drip-tape irrigation instead to apply N late in the season.”
Growth stimulant products are also part of the input mix on the Hula’s contest acres. Last year, they used Stoller’s Bio-Forge ST (seed treatment) growth promoter, Biovante’s Pentilex seed treatment (a phosphate-based growth stimulator product), and Biovante’s BioGold product.
“BioGold is a highly concentrated liquid soil amendment that contains free-living soil microbes,” he says. “It helps the soil to capture and release N. Both Pentilex and BioGold are promising products, and I have a high degree of confidence in them. For Bio-Forge, I still want to evaluate it more before we put it on all our acreage.”
For the contest field, he planted a 120-day Pioneer P2088HR hybrid, with Herculex 1 Insect Protection. The seed came with a Poncho 1250 insecticide treatment (for billbug and grub control), and he also used Syngenta’s Dynasty seed treatment fungicide with it.
Hula planted the field in mid-April, dropping between 45,000 and 46,000 seeds/acre. While sidedressing, he scouts for weed and insect control needs. The field’s herbicide program consisted of Roundup and metribuzin (Sencor) for a late-winter burndown, Trizmet as a pre-emergence herbicide and Halex GT as a postemergence product.
On his contest acres, he sprayed foliar fungicides three times (at V4, V7 and brown silk), rather than just twice. “We had an environment for diseases to be present, so we decided to be proactive, and it paid off. We used Headline at V4 and V7 and Headline AMP at brown silk. We also tank-mixed insecticides with the fungicide application to control various corn worms, stink bugs and Japanese beetles.”
Hula harvested his contest field close to the population that he’d planted it, “right at 44,000 plants/acre,” he says. “The goal now for the future is to at least duplicate or exceed another 400-bu./acre corn yield and to do that profitably.”

Improving Diesel Fuel Efficiency for Spring Field Operations

Del Voight – Penn State Extension 
Here is an interesting article detailing some methods to reduce fuel consumption. Thanks to Iowa State for this timely article. 

By Mark Hanna and Dana Petersen, Department of Agricultural and Biosystems Engineering

Spring is here and, not surprisingly, diesel prices are trending upward. Taking time to implement a few simple management techniques can reduce farm fuel consumption and keep machinery running smoothly.
Even with an established tillage strategy, it may be time to review profitability potential. Once you till beyond the first 3 to 4 inches of soil in a given tillage operation, the amount of fuel used increases directly with tillage depth. Even on some colder, wetter glacial till soils on Iowa State University research farms in north central and central Iowa, corn yields have been as good or better from chisel plowing at a 6 to 8 inch depth as compared to subsoiling or ripping at depths of 12 inches or more. Three-to-five year averages from tillage plot comparisons at ISU research farms around the state generally have shown no yield differences  across systems (e.g., no-till, chisel, subsoil/rip) when soybeans were grown (PM 2089D, Limiting field operations).
Regardless of tillage management, some spring tractor operations will be required. Several techniques can help to save 5 to 15 percent or more of fuel. Consistently changing engine air and fuel filters on a timely basis, as suggested in the tractor operation manual, saves 3 to 4 percent of fuel (PM 2089L, Tractor maintenance to conserve energy). Cooling system maintenance is also important to ensure that the optimal combustion occurs.
Tractor operations required for row crops often don’t demand peak power from the tractor. When pulling lighter drawbar loads such as small tillage equipment or a planter that many be mismatched to the tractor’s power, improve fuel  efficiency by shifting the transmission to a higher gear and reducing the engine throttle setting (PM-2089M, Shift up and throttle back to save tractor fuel). Tractor tests indicate average fuel savings of 10 percent can be obtained when operating at three-fourths tractor load and approximately 20 percent savings at one-half load. Some newer, higher horsepower tractors offer the option to do this automatically through use of electronic load sensors and a continuously variable transmission.
Tractor drive wheels must slip a bit to develop optimal fuel efficiency on soil surfaces. Optimal slip varies with conditions, but for heavier drawbar loads slip should be in a range of about 8 to 13 percent on firm (untilled) soil and slightly greater, about 10 to 15 percent slip on tilled soil throughout most of Iowa. Slip is difficult to see with the naked eye at these levels, but measurement is often available from the dashboard on newer/higher horsepower tractors. If slip is outside these ranges, consult the operation manual (or PM 2089G, Ballasting tractors for fuel efficiency) for further information on proper ballasting.
Tire inflation also affects wheel slip and fuel economy. Know the correct inflation pressure for the weight the tire is carrying, use a good tire inflation gauge capable of reading lower pressures – less than 30 pound per square inch (psi) – in 2 psi increments and check pressure periodically.
Most diesel tractors are relatively fuel efficient even at partial loads when the operator follows these tips, and shifting to a higher gear and reducing the throttle setting is particularly important for partial loads. Before purchasing a new or used tractor, it’s still a good idea to consider size requirements, including engine power, hydraulic system capacity and braking ability. Information from OECD (Nebraska) tractor tests can be used to help compare projected fuel use by tractors under consideration (PM 2089O, Fuel efficiency factors for tractor selection). 
More information on these and other farm energy management topics from ISU Farm Energy can be found at http://farmenergy.exnet.iastate.edu/ .

Mark Hanna is an extension agricultural engineer in agricultural and biosystems engineering with responsibilities in field machinery. Hanna can be reached at hmhanna@iastate.edu or (515) 294-0468. Dana Petersen is  an extension program coordinator for ISU Farm Energy. She can be reached at petersen@iastate.edu  or 515-294-5233.

Organic Insecticides What works? What does not?

Del Voight as in Vegetable Gazette Via
Scott Guiser, Horticulture Educator

In late January I was fortunate enough to hear Dr. Galen Dively of the University of Maryland give an overview of organic insecticides at the Mid-Atlantic Fruit and Vegetable Grower’s Conference. Did you miss it? I’ll try to provide a recap.

I have a copy of the Conference Proceedings (write-ups of the presentations) as a reference which will help me recall key points. If you missed the Mid-Atlantic Conference, mark your calendar for Jan 29-31, 2013… it’s a fantastic educational (and social!) event.

Galen prefaced his remarks about specific products with these observations:

·         In organic systems, insecticides are used as a tool of last resort… after all non-chemical approaches have been employed. They are not intended as the basis for insect management in these systems. This often puts the products at a disadvantage because they frequently work best on immature stages of pest’s life cycle.

·         Many pest control products are listed at OMRI (Organic Materials Research Institute) and are approved under the USDA National Organic Program but double check with you certifying agency before proceeding.

·         Organic insecticides have several problems or limitations compared to conventional insecticides, including:

o   Short residual activity

o   Most have limited contact activity, requiring ingestion to be effective

o   Less effective on mature insects, requiring precise timing to hit immature insects

o   None have systemic activity

o   Short shelf life

o   Lacking in reliable efficacy (do they work?) data

o   Expensive

Interesting…an article in the February 2012 issue of Vegetable Growers New echoed Galen’s points about the limitations of these products.  Still, growers found them useful. So, despite these limitations, organic growers have several good tools for insect management. Here is an overview:

ü  Azadirachtin products, such as Neemix and Aza-Direct are extracts of oils found in the Neem tree. These products are insect growth regulators and prevent insect molting (slow) and also serve as feeding deterrents and repellents. Fair to good control of beetles (Cuke, Colorado potato, Mexican bean, and flea) is reported. Note however, that with cuke beetles, even minimal feeding can transmit the bacterial wilt organism to cucumber and cantaloupe. 

ü  Pyrethrum is the naturally derived insecticide found in daisy flowers and commonly marketed as Pyganic. Quick knockdown but very short residual activity are key traits. Fair to good control of aphids, whiteflies, thrips as well as knockdown of cuke, Colorado potato and flea beetles were noted.

ü  A new product called Azera is a combination of a pyrethrum (like Pyganic) and azadirachtin (like Azadirect/Neemix). Control of Japanese beetle, aphids, imported cabbage worm, leafhoppers and cucumber beetles was improved over use of azadirachtin alone in recent studies. It even provided good squash bug control if timed to target nymphs, just after egg hatch. The limitations of one ingredient are partially covered by the other.

ü  Bt products are well known for their ability to control lepidopteron (caterpillar) larvae such as imported cabbage moths in cole crops. Good spray coverage and repeat applications are important. Some Bt strains control non-lepidopterons. Not all Bts are alike and some are not labeled for organic production.

ü  Spinosad, sold as Entrust to the organic market, provides very good control of caterpillars and thrips.  Fair to good control of flea beetles and Mexican bean beetle was noted.  Some growers note control of Colorado potato beetle. 

ü  Soaps and oils – provide good knockdown of soft bodied insects such as aphids and mites. Repeat applications and excellent plant coverage are important. Oils provide more residual activity than soaps but still this effect is short lived. Both soaps and oils have potential for phytotoxcity.

ü  Plant Extracts such as d-limonene (citrus) and rosemary extras disrupt insect neuroreceptors and act as anti-feedants. Fair to good control of aphids and spider mites reported.

ü  Mineral dusts kaolin clay sold as Surround, repel and/or irritate insects and disrupt feeding and egg laying. Maryland research showed that Surround applied alone or in combination with sulfur, Azera or Trilogy provided 55-86 % stink bug control. Residue from Surround may not be acceptable for some fresh market crops.

In conclusion, Galen provided the following suggestions for improving the efficacy of organic insecticides:

ü  Use 50 -100 gallons of spray solution to ensure good plant coverage.

ü  Arrange nozzles (such as drop nozzles) to improve plant coverage.

ü  Monitor pH of spray water and buffer as needed.

ü  Calibrate sprayers.

ü  Apply controls when pests are in the early stages of development.

ü  Consider adjutants to increase coverage and efficacy. 

           

More than 130 participants were attracted to Galen’s excellent presentation. As he noted, efficacy data on organic insecticides is sparse. His work and presentation were very much appreciated.