CMEG Crop Management Extension Group

Field Crop News

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

August 30, 2006    Vol. 06:18

IN THIS ISSUE:

Weather Outlook — Paul Knight

Expect a very moist time ahead. Some rain may linger along the southern border counties of the state on Wednesday and Thursday, most sections will see little more than drizzle and a bit cooler conditions. The remnants of Ernesto will travel move steadily northward causing rain to spread from south to north across the region on Friday. The rain should diminish on Saturday and may end in most sections during the afternoon. The exact track of the storm will determine who will receive the highest rainfall, regardless many sections should get between 1 and 3 inches of additional rain. Odds favor the eastern half feeling the brunt of the storm due to enhanced onshore flow. Highest amounts should be between 6 and 10 inches, perhaps near the same areas that were inundated in late June. Sunday is expected to bring a dry interlude, but unsettled conditions will return on Monday to southern sections with a few thunderstorms. Another period of rain associated with a slow—moving disturbance is possible at mid—week.

Nitrate Potential in Corn Silage — Greg Roth, Grain Crop Management

Crop conditions have turned from dry to wet in many areas and our corn silage harvest in continuing. This has raised some concerns about the potential for nitrates in corn silage. Nitrates are a possibility under these conditions and are often hard to predict when then will show up. Frequently, nitrates are most severe on drought stunted, heavily manured fields for 3—4 days following a drought ending rain event. We will likely have some fields that fall in that category.

Overall, we feel that the nitrate risk may not be as great this year in most of the state as in some previous years for several reasons. First, this year’s crop had good early season growth and was not as stunted as some of our previous crops. Secondly, with the price of N this year, many farms are tending to be more conservative on N fertilizer rates. Third, the heavy rain in June many areas has caused some N losses and has actually created some N deficiency in corn fields this year. So overall, this year the risk should be reduced, but should not be ignored.

Editor’s Note: Univ. of Wisconsin researchers indicate fresh chopped corn with less than 4400 ppm of N03 on a dry matter basis would be considered safe for livestock. http://www.uwex.edu/ces/forage/pubs/nitrate.htm

Too Late for Forage Seedings? — Paul H. Craig, Dauphin County

Forage producers across the state are questioning whether they have missed the opportunity for a late summer seeding of their forage crops due to the drought conditions in August. As a result of extremely dry soil conditions and recalling last summer’s seeding failures many forage producers kept their seeds in the bag throughout August. Now with the recent rainfall and the approaching hurricane the question is asked if it is too late for a late summer seeding.

Agronomists and seedsmen and women note that under optimum seeding conditions a forage crop should have at least 6 to 8 weeks of development prior to fall⁄winter dormancy. In many areas of Pennsylvania there is still an opportunity to get some forage stands established. However there will soon be a time when it is too late to sow. Then fall management practices should change to make preparations such as weed control, fertility corrections and residue management for planting next spring.

Any time a new seeding is made there are associated risks. The greatest risk of a really late summer seeding is that seedlings will not be able to develop sufficient root systems to protect the seedling against heaving injury. Producers have a few strategies in their arsenal that could be incorporated to minimize this risk.

The first strategy would be to get the seeds into the ground as soon as possible. Estimating fall dormancy in the south central region a seeding by September 10 would have a high chance of having 6 weeks to develop. This might not be the same situation in northern PA where it probably is too late already. Soils and fields that tend to be wet should be avoided for seeding this late in the season. The risk of heaving is far greater on wetter soils.

The use of oats as a nurse crop can help to minimize root heaving. One bushel of oats seeded with forage crops at this time can help to minimize heaving losses. Avoid seeding too high of a rate which can result in smothering of the forage crop.

Unfortunately soil moisture will also benefit the development of winter-annual weeds such as chickweed, dead nettle and henbit. These weeds will compete with the forage seedings for nutrients and can quickly choke out the stand. Pay attention to crop and weed development and apply necessary controls in a timely manner. Refer to the Penn State Agronomy Guide for alternatives.

Unlike small grains, seeding rates will not need to be increased at this time. At typical seeding rates there are plenty of seeds available for a successful stand if the seedlings will be able to survive. Increasing seeding rates will not significantly increase survival.

An important practice to consider is soil fertility management. Corn growers recognize the benefit of using a corn starter fertilizer high in phosphorous to provide nutrients to developing corn seedlings in cold soil conditions. The same situation would apply to fall soil conditions. Ensuring soil fertility levels are high, in the surface zone, is critical to all seedings but especially true in late establishments. Topdressing, at establishment, with 20 units of N, 50 to 100 pounds of P and 50 units of K will assist new seedings to develop strong root systems. Of course, soil pH levels need to be in the optimum range for optimum development. Additional nutrients next spring will greatly benefit these younger stands.

Timeliness is critical to successful cropping practices. Unfortunately Mother Nature does not always cooperate with our plans. There is still a small opportunity for summer seedings but the window is quickly closing. The sooner seeds are placed in the ground, at ¼ to 3/8 inch, the better. Pay attention to soil fertility levels and get extra nutrients on the fields immediately so small roots can get to them. Adding oats can also aid in minimizing the risk of root heaving which is the main factor affecting survival of late seedings.

Late Season Stalk Nitrate Testing Early Sampling Questions — Douglas Beegle, Soil Fertility Specialist

Several questions have come up recently regarding time of sampling with the stalk nitrate test. The biggest question relates to how early can we sample. The recommendation is to sample between ¼ milk line and up to 3 weeks after black layer by taking 8—inch long sections of corn stalk starting 6 inches above the ground. However, due to the dry weather and farmers chopping earlier because of silage moisture concerns, people are wanting to sample before ¼ milk line. Almost all of the research with the stalk nitrate test was done sampling at black layer and beyond. However, Dick Fox here at Penn State and Tom Morris at the University of Connecticut did look at sampling at normal silage harvest time, around ¼ milk line. This research indicated that sampling at this stage worked fine. Unfortunately, there does not seem to be any data for going earlier. I talked to Greg Binford at University of Delaware, who did most of the original research on the stalk nitrate test at Iowa State, and he suggested that the critical levels would likely be a little higher at earlier sampling. Thus, if you take samples earlier than ¼ milk line I would still use the recommended optimum range of 700 to 2000 ppm NO3—N but realize that if your results are at the low end of the optimum range you may have been N deficient and if your results are slightly above 2000 ppm, this may not indicate a significant excess. If your results are not near these break points in the interpretations, no adjustments are necessary.

One other related question is whether samples can be taken after silage harvest. Tom Morris also looked at this and 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.

More details on the Late Season Stalk Nitrate Test can be found on the Penn State Agricultural Analytical Services Lab web site at: http://www.aasl.psu.edu/Corn_stalk_nitrate.html

Hard As A Rock — Soft As A Sponge Sjoerd Duiker — Soil Management Specialist

After a long dry spell, we are now blessed with abundant rainfall in many parts of Pennsylvania. Until this week, soil was hard as a rock in many fields, but now they have turned into soft sponges that are highly susceptible to compaction. As farmers continue or start their corn silage harvest and start spreading manure, there is the potential to cause significant soil compaction. The key to soil compaction avoidance is to stay out of the field when it is too wet. If the soil is drier than the ’plastic limit’ the threat of compaction decreases dramatically. A rough guide to determining the plastic limit is to take some soil and try to make a ball out of it. If that is possible, the soil is too wet for either traffic or tillage. Don’t fool yourself by taking soil from the surface only.

Surface compaction is caused by high contact pressures. Road tires inflated to 100 psi and iron wheels cause very high contact pressures. Surface compaction can cause high yield losses the year immediately following the act, especially in no—till. Even surface tillage does not completely alleviate surface compaction. In a series of international compaction trials in northern Europe and America researchers observed on average 15% yield loss due to the combined effect of subsoil and surface compaction the first year after compaction. In some cases (especially clay soils) yield losses amounted to 50% in the first year. The soil was moldboard plowed, but this did not alleviate surface compaction completely. In no—till, of course, yield losses due to surface compaction can be a lot more dramatic. Surface compaction is alleviated eventually due to natural and human means, but typically causes yield depression for a 4-5 year period. Research from Kentucky has shown that in long—term no—till soils will recuperate from most surface compaction without tillage within one whole year. Using flotation tires or tracks helps reduce surface compaction by increasing the foot print of farm equipment.

Subsoil compaction depends on axle load, not on contact pressure. If you traffic soil that is wet with axle loads of 10 tons or higher, you’re likely causing subsoil compaction below 20 inches. Research has shown that this compaction is there to stay. Freeze—thaw and wetting—drying cycles will not remove this compaction, nor will biological forces such as earthworms, roots, or microbial activity. Subsoilers usually don’t go this deep, nor can they completely alleviate this subsoil compaction (and at considerable cost!). Research in experiments in seven European and North American countries showed a 5% yield decrease due to subsoil compaction that lasted longer than 10 years. Although you don't traffic 100% of the field with high axle loads in one year, you will probably get there in three years, so a 5% yield decrease due to subsoil compaction is not unrealistic. Flotation tires or tracks will not reduce subsoil compaction, although they help to reduce surface compaction and sinkage. The key to subsoil compaction avoidance is to reduce axle load. This can be done by reducing the load or increasing the number of axles.

A new direction that is being adopted by some is to use precision traffic. In these systems, traffic is limited to permanent ’tram’ lanes. Soil between the tram lanes is never trafficked, and is no longer impacted by compaction. The system has great potential but has not been widely adopted because of the need to engineer all heavy pieces of field equipment to identical tire spacings. Another concern with precision traffic is the lost yield from the tram lanes.

Whether severe compaction is caused or not can be identified with the penetrometer or soil compaction tester. Guidelines for its use are given in the Penn State fact sheet “Diagnosing soil compaction using a penetrometer” (http://cropsoil.psu.edu/extension/facts/agfacts63.cfm). Another resource to evaluate whether a soil suffers from compaction is the Pennsylvania Soil Quality Assessment Card (http://pubs.cas.psu.edu/FreePubs/pdfs/uc170.pdf). Finally, once crops are actively growing in the field, root systems can be visually inspected and compared with non—compacted areas of the field. If severe compaction has been caused, some tillage may be necessary to alleviate it. It is recommended to use tillage tools that fracture but not invert the soil and leave crop residue cover intact.

Act 38 Winter Manure Application Requirements — Jerry Martin, Senior Extension Associate, Nutrient Management Education Program

Pennsylvania’s Nutrient Management Law (referred to as Act 6) was originally passed in the spring of 1993 and became effective on October 1, 1997 when the State Conservation Commission's (SCC) regulations detailing the requirements under Act 6 went into effect in Pennsylvania. In 2005, Act 6 was revised and is now referred to as Act 38. In addition, the SCC has revised the nutrient management regulations which will become effective on October 1, 2006.

There are several significant changes to Pennsylvania’s Nutrient Management Program. A summary of these changes, along with a comprehensive source of information on the program, can be found on the program’s website (http://panutrientmgmt.cas.psu.edu/). The direct link to “Revisions to PA Nutrient Management Regulations“ is http://panutrientmgmt.cas.psu.edu/pdf/lr_act38_Reg_Sum.pdf.

One of the key areas of change relates to manure application setbacks and winter manure application requirements.

The revision of Act 6 to Act 38 incorporated year-round manure application setbacks. The Act 38 requirements are:

Year—round 100 foot setback from streams, lakes, ponds and open sinkholes.
Unless there is at least a 35 foot permanent vegetated buffer next to the stream, etc., in which case manure may not be applied within 35 feet of the stream, lake, pond or sinkhole.
" Year—round 100 foot setback from active drinking water sources (wells, springs)

In addition, the revisions to the nutrient management regulations include specific requirements related to the winter application of manure.

First of all, a definition of winter is outlined. It is winter if one or more of the following conditions exist: between the calendar dates of December 15 — February 28, or when the ground is frozen to a 4—inch depth, or when the ground is snow—covered.

Secondly, fields that will receive winter applied manure must have a minimum of 25% ground cover.

Thirdly, there additional application setbacks required for winter applied manure. These additional setbacks are:

100 feet from prior delineated wetlands adjacent to exceptional value streams.
" 100 feet from intakes to ag drainage systems.

In summary, an Act 38 nutrient management plan for agricultural operations planning to apply manure during the winter must include a “Winter Manure Spreading Procedures” section which will list the fields or crop management units where winter application is either planned or restricted, the manure application procedures to be used including application, applicable setbacks, the ground cover and conditions of the field during application, and the type of manure planned to be applied.

Contributors: State Specialists: Dr. Sjoerd Duiker, Dr. Greg Roth, Dr. Doug Beegle, Jerry Martin, Senior Extension Associate Extension Educators: Del Voight (Lebanon), Paul Craig (Dauphin), Dave Messersmith (Wayne), Kevin Fry (Armstrong), Jeffery Graybill (Lancaster)

Editor: Don Fretts, Senior Extension Educator, Fayette County

Real time pest and heat unit activity: http://psu.zedxinc.com/cgi-bin/site.cgi?location=2&user=psu#

Calendar of Events: http://www.events.psu.edu/cgi-bin/cal/webevent.cgi?cmd=opencal&cal=cal209&

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