Integrated Agronomics
August 13, 2014
Volume 2, No 19
Mark S. Johnson, Extension Field Agronomist, markjohn@iastate.edu,
http://www.extension.iastate.edu/ag/newsletters-integrated-agronomics
http://www.extension.iastate.edu/ag/field-agronomists
Crop Update – Corn – The cool weather during pollination, the rain shortly after and cool nights since
have all been great.
The one concern is the cool days. Ideal would be nice warm sunny days – with highs in the mid to high
80s and then cool nights, much like we have been having. With less warmth in the days, we will delay
maturity and so crops may not mature until after the best drying weather is past. If that happens, we
will have wet crops and they will be slow to dry.
Soybean – There have been multiple reports of finding soybean aphids, but to date, only a few that
have reached economic threshold. Continue to scout until beans reach R5.5.
Going by NASS’ estimates, we are ahead of the 5 year average in terms of the corn crop reaching dough
stage. Keep in mind, this is a compilation of reporter’s estimates.
We are still behind on GDDs
GDD
Apr
11-30
Carroll
Ames
Toledo
Perry
Newton
Indianola
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140
130
128
147
158
168
May
Norm 1-31
Norm
140
144
126
137
147
156
373
385
352
372
395
396
358
354
334
378
384
386
June
1-30
592
571
554
592
613
604
Norm
562
578
548
568
639
587
July
1-31
554
543
520
562
626
596
Norm
Aug 112
Norm
686
696
672
694
721
715
219
218
208
226
239
228
238
242
234
240
254
250
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April 11-Aug 12
2014 Norm Variance
Carroll
Ames
Toledo
Perry
Newton
Indianola
1863
1816
1744
1905
2020
1982
1999
2045
1932
2011
2156
2104
136
229
188
106
136
122
As we know, we have not been as dry the last 5 weeks as we were during that time the last two years.
Precipitation
Carroll
Ames
Toledo
Perry
Newton
Indianola
April
May
June
July
Aug 112
Combined
3.33
5.08
6.87
3.60
6.39
5.54
3.86
5.40
2.24
3.65
4.67
6.95
7.78
8.04
9.34
10.97
6.39
5.56
5.85
4.68
7.54
2.93
4.71
2.66
3.24
1.67
0.62
3.24
1.15
1.96
24.06
24.87
26.61
24.39
23.31
22.67
Cover Crops – It won’t be long before aerial seeding of cover crops can take place. For seeding into standing
corn, seed just as the corn reaches physiological maturity. If you can see the black layer (BL), go for it. Even
when the milk line is just about to the bottom but you don’t see a black layer yet, you can proceed. For
seeding into standing soybean, seed when the leaves start to yellow.
If you are waiting to drill or have your retailer air seed, do so as soon after the combine as possible regardless
of 2014 crop being soybean or corn. This can continue right up to the end of October, but the sooner the
better.
Now is the time to be looking at possible herbicide/cover crop interactions. Here are a couple of resources:
http://practicalfarmers.org/farmer-knowledge/research-reports/2014/herbicide-carryover-injury-cover-crops/
http://extension.psu.edu/plants/crops/soil-management/cover-crops/herbicide-persistence/herbicide-carryover-table
If you are still trying to decide which cover crops to use, here is a good resource: http://www.mccc.msu.edu/
Click on cover crop selector tools.
Dates – Series of grazing meetings across Iowa the week of August 22. Extension Beef Specialists will be
working with grazing consultant Jim Gerrish, local producers, & other resource people to deliver 5 workshops
and 8 pasture - http://www.iowabeefcenter.org/news/GerrishSeriesReminder2014.html
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