CMEG Crop Management Extension Group

Field Crop News

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

July 1, 2008    Vol. 08:17

IN THIS ISSUE:

Weather Outlook — Paul Knight, Pennsylvania State Climatologist

A rapid warming trend is expected on Wednesday with excellent drying conditions under considerable sunshine (15 hours of daylight). A cold front will slowly cross the state during the second half of Thursday with the northwest third of the state likely to receive between a quarter and half inch of rain while much of the remainder of Pennsylvania will get less than a tenth of an inch. The period from Friday through Monday will bring an opportunity for showers each day in parts of the state, with Saturday and Monday most likely to have widespread afternoon thundershowers. Temperatures will start slightly below normal and return to above normal with a notable increase in humidity by Monday afternoon. A short—lived period of sultry weather is expected on Tuesday and part of Wednesday ending with scattered strong thunderstorms later Wednesday. Drier weather will return later Thursday and continue into the following weekend. Odds favor another spell of hot weather between July 12–16. There is a risk of a heavy rain in eastern parts of the state during the second half of the month. The longer range outlook favors much above normal temperatures in late August and the first half of September.

Check out the predicted Growing Degree Days (base 55) for Pennsylvania for the next two weeks at: http://climate.met.psu.edu/data/regional_gdd.php

Mid—season Corn Growth Considerations — Dr. Greg Roth, PSU Grain Production Specialist

Corn is growing rapidly throughout the state as it progresses through the late vegetative stages and begins to tassel. The rapid growth is accompanied by rapid nutrient uptake and differences in growth can be related to nutrient availability or other stress factors. This is a great time to evaluate corn and provide feedback on management issues that could be developing.

One common observation during this period is the marginal leaf necrosis associated with potassium deficiency. This is an example of the distinctive symptoms in a field I observed today. This can be caused by low soil potassium levels or other factors that restrict root growth, such as corn rootworm damage or soil compaction. High yields of corn silage or hay crops can remove high levels of potassium and manure applications may not be sufficient to replace the amount removed. Field areas where manure is not applied, on slopes or next to houses, will often be the first to show symptoms. Often fields are quite variable in soil K levels and striving for more uniformity can help to manage this situation more economically.

Rootworm affected areas can be diagnosed by examining injury to the root system and observing the feeding larva, which are present now. Often the worst affected areas are on drier sections of the field where a combination of drought stress and insect feeding cause root recovery to be limited.

Soil compaction derived symptoms are often associated with traffic patterns in the field and worse on end rows and driveways in the field. Often the root systems will show signs of distortion.

Observing fields for tassel development can also be a diagnostic tool to look for differences in crop growth and development. Frequently areas that have experienced stress will be shorter and tassel later. This can be a simple tool to identify stressed areas in fields that may need attention in the future. Take time now to watch the corn crop and interpret the symptoms and growth patterns you observe to help with management decisions next year.

That Great Vigor After Tillage — Dr. Sjoerd Duiker, PSU Soil Management Specialist

Someone once said “you need to go on at least a month—long vacation after planting your no—till corn”. That seems again to be the case this year. We hear reports of great looking corn after conventional tillage compared to somewhat pale—looking and small corn in no—till fields. It is important to understand soil processes to start to understand this phenomenon, and to avoid being alarmed. The soil temperature will be lower under a mulch cover that acts as an insulating blanket. The mulch also causes the soil to stay moist, and it takes a lot more heat to warm up a moist soil than a dry soil. So early corn growth is expected to be a bit slower in no—till than conventional tilled soil. The tillage also speeds up decomposition of organic matter, and this organic matter typically contains about 4% nitrogen. That extra nitrogen can give the corn a rapid early growth spurt leading to dark—green corn. All these things will give better early growth in conventional tillage, but will hurt the crop during the summer season, when the crop suffers from drought and the early spurt of nitrogen release is gone. The end result under Pennsylvania conditions is equal or better corn yields in no—tillage. In addition, we reap the benefits of lower fuel use, erosion control, great infiltration, build—up of organic matter etc. There are ways of alleviating the slow early growth in no—tillage (1) Use continuous no—tillage — the soil surface becomes darker, has better tilth, and contains a large pool of organic matter that releases more nitrogen leading to better early growth of corn as well as improved planter performance. (2) Use diverse crop rotations — planting corn after a legume can typically results in better early growth. (3) Use row cleaners to speed up soil warming. (4) Use starter fertilizer. (5) Use proper planting depth.

Rain Damage to Hay — Paul H. Craig, Dauphin County Cooperative Extension

Men and women who harvest forage crops need to follow the weather predictions closely. Across the state the weather pattern has recently shifted to the “chance of showers” weather pattern. For most hay producers this weather pattern presents the greatest challenge to making top dollar forages. The question is: do we mow and risk rain damage to the hay or do we wait for better weather and let the crop lose value to maturity. One producer commented that his attitude is that “showers are not rain”, meaning that he aggressively mows hay taking the risk that those pesky but often welcomed showers will pass him by.

Rain causes decreases in hay value by leaching of the soluble plant nutrients in the leaves; leaf loss from shattering caused by additional tedding or raking; bleaching or browning of the color which affects price; and molds, bacteria and yeasts that consume the soluble carbohydrates while the forage is laying in the windrow. The period when the rain reaches the forage, how hard a rain it is and how long it lasts differ in the effect on forage quality and quantity.

Producers managing around “chance of showers” weather need to take into account these different affects of rainfall on hay. Forage rained on shortly after mowing has less negative effects than hay that is almost fit and then rained on again. Obviously a short duration rain causes less leaching than a long duration rain event but research has also shown that given the same amount of rainfall the shorter, more intense rain event would leach more soluble compounds from the leaves than a longer, more gentle rain.

The end product of rained—on hay will be loss in desirable plant carbohydrates and the remaining forage dry matter comprised of less digestible cell walls, hemi—cellulose and lignin resulting in higher acid and neutral detergent fiber with limited nutrient value and reduced value at the hay auction. How risky you manage hay harvest depends on many factors and how well you trust your local forecaster.

Value of Legume Cover Crops — Dr. Sjoerd Duiker, PSU Soil Management Specialist

Leguminous cover crops are receiving more attention these days with the rising price of nitrogen fertilizer. The value of hairy vetch became obvious to me in a 20 acre trial in Centre County where we compare different tillage systems, such as moldboard plowing, chisel/disking and continuous no—till.

We planted hairy vetch at the end of August after oat harvest. Volunteer oats came up with the vetch and winterkilled. By May 12th, when the vetch was terminated, there was 2 tons/A of vetch dry matter which typically has 4% nitrogen content. The N—content of the above—ground biomass was therefore approximately 160 lbs N/A. We planted corn towards the end of May, 2006, and only put on 200 lbs/A of 12–25–10 (no other fertilizer was used). Yields were 150 bu/A in long—term no—till, 138 bu/A in chisel/disk, and 119 bu/A in moldboard treatments.

Following this experience, we started trials to determine the nitrogen fertilizer value of fall—established red clover, crimson clover, and hairy vetch. The cover crops were established close to Sept. 1st, and terminated about May 10th in trials in Centre and Lancaster Counties. The seeding rate used was 20 lbs/A for hairy vetch, 15 lbs/A for crimson clover, and 10 lbs/A for red clover. The average nitrogen content of hairy vetch was 4.4%, of crimson 3.1%, and red clover 4.1%. Yields from last year revealed that the nitrogen value of red clover established in August/September is very small due to the limited growth it puts on, but of the other cover crops it is quite significant. Without nitrogen fertilizer application, corn yields were 83–90 bu/A in the check, 103–107 bu/A after red clover, 123–140 bu/A after hairy vetch, and 128–141 bu/A after crimson clover.

We observed a yield benefit to hairy vetch that went beyond its nitrogen value, especially in our Landisville trial. The yield was 130–137 bu/A after fallow, crimson, or red clover, but it was 168 bu/A after hairy vetch in that location. The yield boost due to hairy vetch in our Centre County location was 9 bu/A at the highest nitrogen fertilizer rate (150 lbs/A). The studies will continue. A few lessons we are learning in our legume cover crop work is the great importance of timely establishment (Mid August in northern PA and at higher altitudes, September 1 in Central, September 15 in southern PA), the use of viable rhizobium inoculants, proper establishment, and termination early—mid May for crimson, or mid—May for hairy vetch (no earlier).

A Few Things to Consider When Field—testing Products on the Farm — Ron Hoover, PSU On—farm Research Coordinator

Where grain prices will end up is the talk of all involved with crop production. The high prices being offered farmers have many considering the use of yield-increasing products that can help “squeeze those last few bushels” out of an acre. Seemingly, every business that markets pesticides and/or fertilizers has an assortment of products to help achieve that goal. Which products are worth using? Perhaps some on—farm testing would be worth your while.

In the mid—March Field Crop News, I outlined some ideas to take into consideration when planning and conducting on—farm tests. Those details can be found on our Field Crop News website at: FCN Vol. 08:03, March 11, 2008.

If you are going to the effort to do an evaluation, please be sure to replicate the treatments. Don’t settle for a simple side—by—side comparison. Previous field history, differences in soil type and other factors can give one side of the field a yield advantage over the other side, an advantage that may be unknown to the farmer. Including at least 3 or 4 replicates in one wide field or in several nearby fields with similar cropping histories and randomly assigning treatments to those areas enables the farmer to make multiple comparisons. A new product on beans or corn that results in increased yields on most or all replicates gives one greater confidence that the effect is “real”. Without these multiple comparisons (replications), one does not know if the increased yield is due to the product being tested or that it’s the result of some random effect or of some variability in the soils that exists in all our fields. The need for multiple replications cannot be overemphasized. Your local extension agent or I can provide assistance in planning your test and analyzing your data.

I thought it worthwhile to provide some additional details and to reemphasize a few points made in the March article, especially those issues that relate to evaluations of products in soybean. Ground—spraying soybeans that are drilled or planted with splitter units typically result in some soybeans being driven down. Even if the application is made during the early part of the season and some recovery of driven—down plants occurs or adjacent plants compensate, the grain yield from the 10 feet in which the spray tracks are located will often be less than that harvested from either side. Plan ahead: recognize that by avoiding both spray tracks of a sprayer pass during harvest will result in “clean” data are more easily interpreted (because you avoided introducing interactions between wheel traffic damage and products being tested). If, because of spray boom length, combine platform width, and field width considerations you simply MUST harvest from one or both wheel tracks in a strip plot, be sure that you harvest plot areas that contain the same one or 2 wheel tracks in ALL plots in the study. While this is less desirable than totally avoiding wheel tracks, it helps to minimize the variability that will be introduced when some, but not all plots, contain the wheel tracks.

Ron Hoover can be reached at (814) 865–6672 or rjh7@psu.edu

Penn State Agronomic Diagnostic Clinic Reminder — Dwight Lingenfelter, PSU CMEG

All interested people are invited and encouraged to attend the Penn State Agronomic Field Diagnostic Clinics held on July 22 and 23, 2008 from 9am – 4:30pm at the Penn State Agronomy Research Farm near Rock Springs, PA. Each day offers the same agenda.

The clinic sessions can be viewed at Clinic Presentations for more information about each topic. The fee is $60/person until July 16th and $80 after that. To register, please visit: PSU Agronomic Diagnostic Clinic Registration and use the “on—line” registration system or complete the hard—copy form and fax or mail it. Phone—in and email registrations are discouraged. Credit card payments can be accepted. (Note: we are using a new registration system this year, so please make sure to complete the necessary procedure.)

If you have questions about the Clinic please contact Dwight Lingenfelter at 814–865–2242.

Contributors: Dept. Crop & Soil Science: Marvin Hall, Ron Hoover, Sjoerd Duiker, Dwight Lingenfelter, and Greg Roth. Extension Agents: Andrew Frankenfield (Montgomery), Paul Craig (Dauphin), Kevin Fry (Armstrong), Mena Hautau (Berks), Joel Hunter (Crawford), Jonathon Rotz (Cumberland), Jeff Graybill (Lancaster), and Mark Madden (Sullivan).

Editor: Mark Madden

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