C.O.R.N. Newsletter: 2014-28
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BEST MANAGEMENT PRACTICES TO KEEP PHOSPHORUS ON THE FIELD
Looking at current Ohio field research and the literature available on the topic of minimizing losses of phosphorus at the edge of the field the following recommendations are a starting point to maximizing productivity while minimizing environmental impacts on water quality.
Phosphorous Rate, Application and Timing
Avoid overloading soils. Soil test and follow tri-state fertilizer recommendations. Where soil test levels are above 40 ppm Bray P1 or 58 ppm Mehlich III-ICP, do not apply additional phosphorus in the corn-soybean rotation. These soil test levels require no additional fertilizer, according to the Tri-State Fertilizer recommendations. Fertilizing soils testing above these levels increases risk of P in runoff and tile drainage.
Avoid winter application. Eliminate surface application of manure or fertilizer to frozen or snow-covered fields. Frozen ground is ground that is frozen to the degree that tillage is not possible. Surface applied manure or fertilizer is subject to runoff events that may occur before the ground thaws and allows nutrients to bind to soil.
Avoid surface application of fertilizer/manure. Surface applications of phosphorus are subject to higher loss if runoff producing rainfall events happen close to application. Placement of nutrient below the surface of the soil reduces loss. If tillage is planned in the crop rotation, P applications should be applied prior to the tillage and till before a rain event. Full width tillage has the potential to increased soil erosion and total phosphorus losses. New placement tools or strategies need to be implemented that place P below the surface with minimal soil disturbance. Until these tools become available, use banded application or the minimal amount of tillage to mix nutrient in the soil.
Farm and Field Features
Minimize erosion. Appropriate conservation practices should be implemented to minimize erosion. Maintain 30% cover as crop residue/cover crop. Filter strips, grassed waterways and water diversion structures are appropriate tools.
Slow the movement of water. Surface water flows from fields directed to tile via standpipes should be converted to blind inlets. As risk loss potential increases for a field consideration should be given for edge of field treatments which control water movement or treat water as it is leaving the site. Drainage water management control structures, in ditch treatments such as two stage ditches and other stream practices can reduce loading.
Know your field’s risk. Soil test P, field proximity to water and soil hydrologic class impacts edge of field losses of phosphorus. The NRCS Ohio P Risk index provides a risk of loss index and should be used as part of the development of a Nutrient Management Plan to assess the individual field risk.
Strive to build soil quality. Soil condition is a mitigating factor. Increasing the water infiltration by reducing compaction and improving soil structure increase water retention, nutrient cycling, crop rooting capacity and crop yield.
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SELECT A LIME SOURCE BASED ON ENP
A soil analysis will tell whether a field needs lime to raise the soil pH. The lime rate per acre will be determined from the buffer pH or lime test index of the soil analysis. Lime recommendations are generally given as tons per acre.
Any lime source may be used to correct soil acidity; however, lime sources will vary in price and quality of material. The Ohio Department of Agriculture evaluates all liming sources sold commercially in Ohio. Part of the evaluation process requires an analysis of the lime material to determine its effectiveness to neutralize soil acidity in a timely manner, which will be reported as the Effective Neutralizing Power (ENP). A retailer selling lime in Ohio is required to have the ENP value as part of the lime analysis and have the lime analysis available for the buyer. The value will be expressed as pounds per ton. The ENP value incorporates all quality components of lime: purity (calcium and magnesium content), particle size, and water content. The ENP allows producers to compare different liming sources regardless of differences in purity, fineness of grind or water content between sources.
To determine the amount of lime needed with the ENP value use the following equation:
Tons of lime material = (Lime rate from soil test) * (2000/ENP)
The actual cost of a lime source may also be used with ENP by the following equation:
Cost ($/acre) = (Lime rate from soil test/ (ENP/2000)) * ($/ton)
Economics and the ability to evenly apply the material should be the primary factors in selecting a lime source. Calcium content and magnesium content of a lime source should not matter unless the soil analysis shows a need for one of these nutrients. If the soil test magnesium levels are less than 50 ppm (100 lbs) then dolomitic lime should be use since it will cost considerably less than other magnesium sources. Hi cal (calcitic) lime should be used if the percentage of base saturation of calcium from the soil analysis is equal to or lower than the percentage of base saturation of magnesium. If the soil test does not show a special need for magnesium or calcium then select the least expensive lime source for your area whether it be dolomitic or hi-cal.
Since ENP incorporates grind size in its formula, pelletized lime may be compared to regular lime sources. Pelletized lime is a regular lime source that has been ground to a finer particle size and held together by a binder to form a pellet. A pelletized lime will also have an ENP value from the lime analysis sheet. The lime rate for pelletized lime will use the same formula as regular lime to determine the tons of material by using the ENP value.
Lime recommendations from soil testing laboratories assume a soil incorporation depth of eight inches. Rates should be adjusted for incorporation depths less than eight inches. For no-till fields or lime left on the surface, assume 4 inch incorporation. Adjust your lime rate by the following equation:
Lime rates for < 8 inches incorporation = (Soil test lime rate/8) * lime incorporation depth
More detailed information on lime may found in the OSU Fact Sheet: Soil Acidity and Liming for Agronomic Production (http://ohioline.osu.edu/agf-fact/0505.html)
Recommendations and the lime discussion in this article are for Ohio. Lime regulations often vary from state to state and may be different than Ohio.
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CORN SILAGE HARVEST TIMING
Corn development has accelerated with the recent warm temperatures. Silage harvest has begun in some parts of Ohio with earlier planting dates. Proper harvest timing is critical because it ensures the proper dry matter content required for high quality preservation, which in turn results in good animal performance and lower feed costs.
Harvesting corn too wet (low dry matter content) results in souring, seepage, and storage losses of the silage with reduced animal intake. Harvesting too dry (high dry matter content) promotes mold development because the silage cannot be adequately packed to exclude oxygen. Harvesting too dry also results in lower energy concentrations and reduced protein digestibility.
Corn silage that is too dry is almost always worse than corn silage that is slightly too wet. So if you are uncertain about the dry matter content, it is usually better to err on chopping a little early rather than a little late. Follow the guidelines below to be more confident in your assessment.
Harvest Moisture Guidelines
Corn preserved between 30 and 38% dry matter (62 to 70% moisture) generally provides excellent silage fermentation and animal performance. The optimal dry matter content varies with type of storage structure (Table 1).Table 1. Optimal dry matter contents for different storage structures.
Type of Structure
Optimal % dry matter
Horizontal bunkers
30 to 35
Bags
30 to 38
Upright, top unloading
33 to 38
Upright, bottom unloading
35 to 40*
The higher DM concentration for bottom unloading silos is a compromise between
forage quality and unloader requirementsKernel stage not a reliable guide for timing silage harvest
Dry matter content of whole plant corn varies with maturity. Research has shown that the position of the kernel milk-line is NOT a reliable indicator for determining harvest timing. Geographic location, planting date, hybrid selection, and weather conditions affect the relationship between kernel milk-line position and whole plant dry matter content. In a Wisconsin study, 82% of the hybrids tested exhibited a poor relationship between kernel milk-line stage and whole-plant % dry matter. In Ohio we have seen considerable variation in plant dry matter content within a given kernel milk-line stage.
Appearance of the kernels should only be used as a guide of when to begin sampling for dry matter content, see section below When to Begin Field Sampling.
Determining Silage Moisture
The only reliable method of determining the optimal time to harvest corn silage is to sample and directly measure the % dry matter of whole plants.This information combined with average whole plant dry-down rates can be used to roughly predict the proper time to chop corn silage.
How to Sample Fields
Collect about 5 representative plants from the entire field, from areas with representative plant population and not from edge rows. Collect separate samples from areas that may have different dry down rates, such as swales, knolls. The moisture concentrations of plants can vary within a field (plants will be wetter in low lying area and drier on knolls) and this should be considered when collecting your sample plants.
As soon as the plants are collected, chop them uniformly (using a cleaver, machete, chipper shredder, or silage chopper) and mix thoroughly to obtain a sample with representative grain to stover ratios for dry matter determination. Put representative sample in a plastic bag and keep it cool (refrigerate if possible). Some farmers prefer sampling only 2 or 3 plants without any additional sub-sampling to reduce the chances of a non-representative grain to stover ratio that can affect the results. In this case, choosing representative plants is even more critical.
Determine the dry matter content by drying the plant material using a Koster oven tester, microwave, convection oven, a vortex dryer, or taking to a lab. For more details on these and other methods, see the following links:
http://www.extension.org/pages/Dry_Matter_Determination
http://ohioline.osu.edu/agf-fact/0004.html
http://abe.psu.edu/vortex-dryer
Make sure the sample does not dry down and keep it cool until the dry matter determination is performed. The accuracy of the dry matter value is largely affected by the care taken in sampling, drying, and weighing the samples. Whole kernels and cob pieces can be difficult to dry completely without burning the leaf tissue.
From our work, on-farm measurement of dry matter is probably only accurate to +/- 2 units. So if you measure a DM of 30% it could easily be 28-32%. Keep this in mind as you plan harvest timing.
When to Begin Field Sampling
We know that kernel milk stage is NOT reliable for determining the actual harvest date, but its appearance is a useful indicator of when to begin sampling fields to measure plant dry matter content.
Corn in Ohio should be first sampled to measure dry matter at full dent stage (100% milk, no kernel milk-line) for conventional tower or bunker silos. Full dent stage happens about 40 days after silking in Ohio. For sealed (oxygen-limited) tower silos begin sampling when the milk-line is one-fourth down the kernel (75% milk remaining). It is important to begin sampling early as a precaution against variation in dry down. (Photo: The milk-line of on these ears is about one-fourth to one-third down the kernel. This stage might be about right for oxygen limited silos but could be too late for conventional tower or bunker silos.)
Predicting the Harvest Date
Once whole-plant % dry matter is determined, use an average dry down rate of 0.5% unit per day to estimate days until the optimal harvest moisture is reached. For example, if a given field measures 30% dry matter at the first sampling date, and the target dry matter is 35% for harvest, then the field must gain an additional 5% units of dry matter, thus requiring an estimated 10 days (5% units divided by 0.5 unit change per day).
This procedure provides only a rough estimate for the harvest date. Many factors affect dry down rate, such as hybrid, planting date, general health of the crop, landscape position, soil type, and weather conditions. Early planted fields and hot and dry conditions can accelerate dry down rates to 0.8 to 1.0 % unit per day. Fields should be monitored closely and more frequently under those conditions. As mentioned above, corn silage that is slightly too dry is usually worse than corn silage that is slightly too wet. So harvesting a little early is usually better than waiting too long.
More Management Guidelines
For additional details on management of corn silage, see the article by Bill Weiss in the Buckeye Dairy News (August 2010), available online athttp://dairy.osu.edu/bdnews/Volume%2012%20issue%203%20files/Volume%2012%20Issue%203.html#Harvesting.
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COVER CROPS PLANTED AFTER CORN SILAGE
Farmers who harvest corn silage will often drill cereal rye at 2-2.5 bushel per acre 1 inch deep (no more than 2 inches deep) , apply manure, and then harvest 3-5 wet tons (1.5 to 2.5 tons dry matter) of spring forage before planting corn or soybeans. Manure or extra nitrogen (50-75 pounds actual N) is critical for good forage growth in the fall and spring and to prevent the corn from turning yellow (N deficiency) next spring. Cereal rye will absorb 3-3.5%N and 0.2% of its total biomass as N and P respectively.
Oats drilled immediately after corn silage at 2 bushel per acre is another option if forage is desired this fall possibly resulting in 1-3 tons (.5-1.5 tons dry matter) with adequate moisture by Mid-December. Oats harvested in Early December should be wet baled to preserve forage quality. If the farmer does not want forage, 0.5 to 1 bu/A oats, cereal rye or barley makes a great cover crop going to soybeans. Other options include a mixture of crimson clover (8 pounds) and radish (2 pounds) which can either be broadcast or drilled (0.25-0.5 inches deep) or winter peas (20 pounds seeded 1 inch deep) and radish (1-2 pounds seeded 0.25-0 .5 inches deep) in alternating rows.
In general, farmers should avoid planting grass cover crops before corn due to a high carbon to nitrogen ratio unless they are willing to apply a large amount of N fertilizer or have manure to help decompose the cover crop biomass. Farmers need to remember that soil microbes feed first and organic residues generally need more nitrogen to decompose, so next year’s corn crop is either second or third in line for soil nitrogen. To avoid yellow corn or N deficiency in the spring, apply 50 to 75 pounds of actual nitrogen in your starter. Soil microbial populations double with every 10˚ F increase in soil temperature, so coming out of a cold winter with cold soil temperatures, the soil microbes are not recycling as many soil nutrients until the soil warms up.
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SEPTEMBER TRAINING FOR NEW AGRICULTURAL FERTILIZER APPLICATOR CERTIFICATION PROGRAM
The first of 3 late summer sessions for those who would like to attend the training for the new Agricultural Fertilizer Applicator Certification Program are scheduled for September 12, 25 and 26. Attending one of these training events will meet the requirements for “Agricultural Fertilizer Applicator Certification Program” as established in legislation Senate Bill 150 that is administered by the Ohio Department of Agriculture.
Preregistration is required by going to http://go.osu.edu/fertilizer .
Fulton County
September 12th, 8:30 a.m. – 11:30 a.m.
Founders Hall at Sauder Farm and Craft Village
22611 State Route 2
Archbold, OH 43502
Hancock County
September 25th, 8:30 a.m. – 11:30 a.m.
The Lighthouse Banquet Facility
10055 W. U.S. Rt. 224
Findlay, OH 45840
Paulding County
September 26th, 8:30.a.m – 11:30 a.m.
OSU Extension Office
503 Fairgrounds Drive
Paulding, OH 45879
More detailed information will be posted at https://agcrops.osu.edu/calendar
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PAT CREDITS OFFERED AT AG EQUIPMENT FIELD DAY
Extension will offer both private and commercial Pesticide Applicator Training credits at a field day sponsored by Independent Ag Equipment, 4341 Sandhill Road, Bellevue, OH 44811. The field day will be held Thursday, September 4, 2014 with PAT sessions beginning at 10:45 a.m. Although this is a company field day, pesticide training is open to the public. Field Specialist Dr. Steve Prochaska and Huron County Extension Educator Mike Gastier will offer one hour of core training and one half hour in category 2A and 2C ( Category 1 private). Certified Crop Advisor continuing education credits will also be offered. No reservations are required. If more information is needed please call the Huron County Extension office at 419-668-8219.
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
Contributors
Disclaimer
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
CFAES provides research and related educational programs to clientele on a nondiscriminatory basis. For more information, visit cfaesdiversity.osu.edu. For an accessible format of this publication, visit cfaes.osu.edu/accessibility.