CFS Growing Insights 6.05.2019

Weather Update

Weather improved this last week to get some field work done, as planting for the year is beginning to wrap up. The heat finally started to pick up this week, but it still puts 2019 20-25% behind on GDU’s.

The first week of June has ushered in above average GDU accumulation, as the average for first part of June is about 15 GDU’s per day, and we’ve had 20-25 GDU’s per day the last 3 days! However, 4” soil temperatures have only been hovering around 60o.

There is a lot of corn in the V1-V2 leaf stage, and the traditional herbicide and side dressing time around V5 will be here fast. Based on heat, it will take approximately 3-5 days to advance a leaf stage, so V5 corn may only be a 10-14 days away!

 

Agronomic Considerations for the Week:

With some of the planting challenges that we have seen, some of the impact will show up as corn beings moving through growth stages. Here’s a few things to look for:

1) Sidewall compaction (picture above) has restricted root growth across acres that were planted “a little less than ideal.” The image below shows roots growing horizontally down the seed trench. Corn seedlings transition from nutritional dependence on kernel reserves to nutritional dependence on the nodal roots around the V3 leaf stage. If root growth is restricted, we could potentially see some yellow, discolored corn as it makes the transition. It may be tempting to try to fix the color with an application of nitrogen or sulfur, but make sure you diagnose the problem first, as it might be a root growth/compaction issue that can’t be fixed with extra nitrogen!

2) Seed Trenches: If it rapidly dries out in the first few inches of soil, we could potentially see seed trench sidewalls open back up (like the image below) and observe Rootless Corn Syndrome or Floppy Corn syndrome. Rootless corn occurs in plants with poorly developed root systems (often due to compaction) and is usually observed at V3-V8 stages. Symptoms include corn laying on the ground or about to lodge. Before the problem is evident, corn plants may appear vigorous and healthy but can fall over due to limited or no support later. Adequate rainfall will be the main recovery mode of action to promote nodal root development.

3) Cool wet soil conditions from repeated rainfall events across southern MN can create the potential for the development of some seedling diseases in corn. Scout seedling emergence and stand establishment in the next few weeks to diagnose any problems. Rotted seed prior to germination, discolored seedlings after germination prior to emergence, post-emergence seedling damping off or discoloration of the mesocotyl/crown area could signal early season disease’s that may warrant V5 fungicide applications. The image “Root System of Stunted V2 Plant” From Purdue University gives an idea of things to look for.

Yield Potential

As the corn market has improved over the last few weeks, a later planting season has growers questioning what the value is of managing a crop that’s already off to a late start. The University of Minnesota offers insight on yield potential from their research:

  • Planting between April 20 and May 10 or 15 = corn yield is within 2% of the maximum yield potential
  • Planting occurred by May 15 to 20 = corn yield within 5% of the maximum
  • Planting occurred by May 20 to 25 = corn yield within 8% of the maximum
To go along with the University of MN data, we can use WinField United’s R7 Field Forecasting Tool to run scenarios on yield potential, tassel date, and potential black layer date. The table below outlines some of the FFT results using a field near Mankato and running different planting dates and the corresponding yield potential in bu./acre the model is signaling. (Graph Below)
 
As planting dates got later into May, the estimated tassel date and black layer (maturity) date didn’t change much. This occurred because we didn’t accumulate many GDU’s between May 1st and May 15tth, so most of the GDU’s had to be gained in the remaining part of the season. 

Purdue University tells us that as planting is delayed, corn maturities come closer together and requires 6.8 less GDU’s to reach black layer as planting is delayed beyond May 1. So, if you’re planting at the end of May, you can subtract 200 GDU’s off the required GDU to maturity total.

The main takeaway is that we only lose some yield potential from a later planting date. Several other factors, such as rainfall during the season, GDU accumulation, the weather during and after pollination, crop nutrition and in-season management have an even bigger impact on yield potential. Yield loss from choosing to reduce the management of a crop that was planted later can be much more dramatic than a late-May planting date!