Tuesday, August 8, 2017

Now is the Time to Begin Evaluating Corn Fields for Harvest

For most corn fields in Wisconsin, pollination and the "lag" phase of kernel development is wrapping up and we are in a "linear" phase of development where kernels are accumulating 4-6 bu/A per day. The grain filling period of corn lasts approximately 60 days (Figure 1). The "lag" phase starts with the kernel ovule fertilized by pollen and for the next 7-10 d cell division occurs in the endosperm. The "linear" phase is most important for yield and lasts about 40 days. For a 200 bu/A yield level, starch accumulates in the kernel endosperm at the rate of 5 bu/A per day during this phase. The grain filling period ends with a 7-10 d "maturation" phase when the kernel moves from 50% kernel milk to the black layer stage. During grain filling most management options are no longer available unless irrigation is available when water and N can be applied during the first half of grain filling.

Figure 1. Typical corn kernel development in Wisconsin.

Early August is the time to get a sense of what to expect and plan for in the coming harvest. Lots of things can still happen and we still have a long way to go before harvest, but now is the time to schedule custom harvest operations, plan the harvest queue, and make sure that adequate drying and storage capabilities are available. Also, marketing adjustments might need to be considered.

First determine the success of pollination.  There are two techniques commonly used to assess the success or failure of pollination. One involves simply waiting until the developing ovules (kernels) appear as watery blisters (the "blister" stage of kernel development). This usually occurs about 10 days after fertilization of the ovules.

Another more earlier means can be used to determine pollination success. Each potential kernel on the ear has a silk attached to it. Once a pollen grain "lands" on an individual silk, it quickly germinates and produces a pollen tube that grows the length of the silk to fertilize the ovule in 12 to 28 hours. Within 1 to 3 days after a silk is pollinated and fertilization of the ovule is successful, the silk will detach from the developing kernel. Unfertilized ovules will still have attached silks. Silks turn brown and dry up after the fertilization process occurs. By carefully unwrapping the husk leaves from an ear and then gently shaking the ear, the silks from the fertilized ovules will readily drop off. Keep in mind that silks can remain receptive to pollen up to 10 days after emergence. The proportion of silks dropping off the ear indicates the proportion of fertilized ovules (future kernels) on an ear. Sampling several ears at random throughout a field will provide an indication of the progress of pollination.

If harvesting corn for silage, use the following guidelines to time silage harvest:
  1. Note hybrid maturity and planting date of fields intended for silage.
  2. Note tasseling (silking) date. Kernels will be at 50% kernel milk (R5.5) about 42 to 47 days after silking.
  3. After milkline moves, use kernel milk triggers to time corn silage harvest.Use a drydown rate of 0.5% per day to predict date when field will be ready for the storage structure. See http://fyi.uwex.edu/silagedrydown/ 
  4. Do final check prior to chopping. Adjust cutter height if forage needs are adequate. Raising cutter bar 1 foot, lowers silage moisture 2 to 4 points.
If harvesting corn for grain, estimate yield using the component method:

  1. Count the number of harvestable ears in a length of row equivalent to 1/1000th acre.
  2. On every fifth ear, count the number of kernel rows per ear and determine the average. Try to use a system such as the 5th, 9th, and 13th ears from one end of the row.
  3. On each of these ears count the number of kernels per row and determine the average. (Do not count kernels on either the butt or tip of the ear that are less than half the size of normal size kernels.)
  4. Yield (bushels per acre) equals (ear number) x (average row number) x (average kernel number) divided by 89.605* = bushels per acre
  5. *or multiply by 0.01116
  6. Repeat the procedure for at least four additional sites across the field.
Other methods for calculating corn grain yield can be found at http://corn.agronomy.wisc.edu/AA/A033.aspx.

Friday, May 5, 2017

How Quickly Can Farmers Plant Corn in Wisconsin?

Today, corn planters will begin to roll again in many areas of Wisconsin. We have some good weather coming up and quite a few acres will be planted. I was curious about how quickly can Wisconsin farmers plant corn?

We are just finishing Week #17 in the USDA-NASS reporting system. I pulled 31 years of data to analyze and use to answer the question. We typically have about 50% of our corn acres planted by May 15 (see Figure 1). One of the earliest planting seasons was 2010. In the last 30 years 2016, 2010, 2006, 2005, 2000, and 1999 were earlier than normal planting seasons, while 2014, 2013, and 1996 were later than normal planting seasons.

Figure 1. Wisconsin corn planting progress from 1987 to 2017. The bold blue line is the 30-year normal. Other lines are years that were earlier- or later-than normal using + one standard deviation. Click figure to enlarge.

There have been four times when over 1.5 million acres of corn were planted in a week in Wisconsin. The record week jump in planting progress occurred  during Week #18 of 2000 when 1.54 million acres (44% of 3.50 million acres) were planted. During 2015, 1.52 million acres (37% of 4.10 million acres) were planted during Week #18. During 2007, 1.54 million acres (38% of 4.05 million acres) were planted during Week #19. During 1999, 1.51 million acres (42% of 3.60 million acres) were planted during Week #18.

In the U.S., Iowa planted the most acres in a week during 2011 when 8.60 million acres (61% of 14.10 million acres) were planted during Week #18. Minnesota during Week #17 of 2000 and Ohio during Week #18 of 2003 planted the greatest proportion of acres at 65% (MN= 4.68 of 7.20 million acres and OH= 2.14 of 3.30 million acres).

Safety First and Pay Attention to Detail

Please remember SAFETY FIRST! during the planting season. Patience is key. Make sure fields are fit, equipment is maintained and that you are well rested. Remember to pay attention to detail. The planting process sets up your whole season. The "sins of the past WILL come back to haunt you" if you are sloppy or careless during this important time.

Wednesday, May 3, 2017

Corn Planting Date Concerns for 2017

The recent cool, wet weather has some farmers concerned about corn planting. We are currently in the optimum range for the corn planting date response. Soon we will be on the downhill side of this response where grain yield decreases AND grain moisture increases. However, there can be quite a bit of variability associated with this response.

Figure 1 shows the corn planting date response at Arlington during the 2010s. During this time, the average planting date that produces maximum corn grain yield is May 4 (the range has been May 1-7). Farmers can still be within 95% of the maximum yield between April 18 and May 20. The narrowest planting date "window" where you could still achieve 95% of the maximum yield was during 2014 between April 25 and May 19 (24 days). The widest window was during 2011 between April 11 and May 21 (40 days).

Figure 1. Grain yield response to planting date for full-season corn hybrids at Arlington from 2010 to 2016.

We planted our first planting date at Arlington on April 17. We planted the hybrid grain and silage trials at Montfort on April 24, Janesville on April 25 and Hancock on April 28. Some university agronomists have written about the potential for imbibitional chilling (see IA and NE) during this growing season. At Janesville and Hancock corn was planted just prior to and during the recent cool, wet weather conditions. We will see how well these trials emerge. They will also be a good test for measuring seed quality differences among hybrids and companies.