Lebanon Crop Management Video


01 June 2016

Procedure for Using Corn Leaf Chlorophyll Meter Readings to Predict the Need for Sidedress Nitrogen Fertiliz

1. The chlorophyll meter test procedure is applicable only for what we classify as “High Organic N Input” fields (Table 1).
Table 1

High Organic
Moderate Organic
Low Organic
Manure since previous crop

First year after forage legume (alfalfa, alfalfa/grass, clover)

Last manure in spring or fall before previous crop
Second year after alfalfa
First year after soybeans
All other fields:
No manure for at least two last crops
At least one crop since soybeans
At least two crops since alfalfa

2. Choose “High Organic N Input” fields that did not receive any blanket preplant or at-plant fertilizer N or N with the herbicide.  No more than 15 lbs N/ac in the starter fertilizer is OK.

3. Take chlorophyll meter readings at each field to be tested as close to the six-leaf stage as possible.  It is better to do readings a few days later than the six-leaf stage rather than doing readings before the field is at the six-leaf stage.  (See Appendix A).  Always take readings of the fifth leaf of each plant.  Since the meter will hold and calculate an average for up to 30 readings, you should probably try to take close to 30 readings in a field.  You may want to do more than one average per field if the field is very large or seems to have distinctly different areas of N fertility. Specific techniques for using the meter and taking leaf readings are explained in Appendix B.

4. Use the Table 2 to determine whether a field needs sidedress N or requires a second meter reading ~4 to 7 days later. 

Table 2

High Organic  @ LS 6

Average meter reading

< 42.0
42.0 to 45.9
= or > 46.0
N Recommendation
Sidedress 80 lb N/ac

Test again
or Sidedress 50 lb N/ac
No sidedress N needed

5. Do meter readings ~4 to 7 days later on those fields that require a second meter reading.   Plants should now be at the seven to eight-leaf stage.  Depending on weather conditions, fields usually advance one leaf stage in about three to six days.  Use the same procedures as for the first reading.  Make sure you are reading leaf five.  Use Table 3 to predict whether a field needs to be sidedressed.

6.  If the first reading is taken at LS 7-8 skip Table 2 and go directly to Table 3 for interpretations and recommendations.

Table 3

High Organic @ LS 7-8

Average meter reading
< 43.0
= or > 43.0
N Recommendation
Sidedress 50 lb N/ac
No sidedress N needed

Late Planting Soybean Considerations

Del Voight - Penn State Extension
As we near the June 15 deadline for crop insurance growers need to make small adjustments to soybean planting. The biggest might be leaning toward planting in not so ideal soil conditions.

Soil Considerations
With tilled soil planting into wetter conditions may lead to compaction and more damaging soil crusting. These fields if planted will need to be checked to determine if the surface has become compacted enough to inhibit the seedling to pop through to sunlight.  In the past I have run a cultipacker over top of crusted soybeans with no ill affect accept for an immediate jump in the emerged plants. This season my soybeans wered tilled and I noted crusting but fortunately additional rains came and aloud the beans to push through.
In no till fields, that  are still wet however crusting does not present a major damage. Perhaps considering a shallow seeding.  I recall the floods of 1993 in Iowa we were forced to blow soybeans onto bare ground and they pretty much all emerged showing the flexibility in the soybean plant. The goal should be to place the soybean seed in the ground slightly taking care to remove any residue to limit hairpinning of residue within the row thereby not allowing the swelling bean access to soil moisture.

There has been talk about moving to a shorter maturity. Past experience in this area would say stay the course. Our double crop beans planted with full maturity over the last several years have matured with no ill problems in the fall. This simple table best illustrates the impact of planting date.

Approximate yield response 
of soybean to changes in planting date.
Date                                                 Full yield potential (percent)
May 10                                                      100
May 20                                                        98
May 30                                                        95
June 10                                                         88
June 20                                                         76
June 30*                                                        70
July 10*                                                         60
Developed from Ohio, Indiana, Minnesota, and Pennsylvania data.
*Relevant only in areas where double cropping is possible.

Row Width and population
This is where we can improve the position of the soybeans in later plantings. First off narrow rows to below 15 inch is a good idea.  Our work at Landisville has shown the detrimental affect of wide rows planted late so narrow the rows is certainly any easy change to increase yields perhaps by 5% or more.
Population increases with later planting is also another easy adjustment that has sound science behind its utility. We have shown increases in stand from 150 to 200,000ppa in double crop scenarios so I would advise treating this later plant time as a double crop situation and increase populations accordingly as June progresses through July.

Seed Treatment and Inoculation
Inoculation is still recommended regardless of planting date. Remember inoculation is not seed treatment!  Soybeans should emerge rapidly at this point with soil temperatures and moisture ideal so the natural reaction would be to eliminate them. I would lean toward continuing to use them where a field with a history of bean leaf beetle and or soybean aphids tend to crop up.  The insecticide portion might prove useful.  The fungicidal part of seed treatment is necessary however if a field has a history of phytophtora I would include it prevent infection and possibly a higher level. Further with soil at or above field capacity water molds tend to thrive so I would include this in the treatment as well.  This one is difficult however I tend to believe that the fungicidal aspect in a wet planting season prove their worth al be it not obvious until  a replant becomes apparent.