The Final 700: Irrigation Strategy for the Remainder of the Year

August 9, 2018

The Final 700: Irrigation Strategy from Central Valley Ag on Vimeo.

As I look around the majority of our area, it is safe to say that Growing Degree Day accumulation continues to move along very well. In fact, for most of us, we are in the later stages of our Corn development, being the dent stage. Regardless of whether you are planting a 113-day maturity or a 108-day maturity, North or South, planted May 1st or May 12th, most of us will be looking at about a 700 GDD need to finish out or crop. One of the things that we fight every year about this time, however, regardless of corn or beans is a desire to be done managing for the season. While this year hasn’t been as challenging as most from an irrigation standpoint, there are still those of you out there that have expressed to me the thoughts that this crop is almost wrapped up. So for the remainder of today, I want to debunk that thought process and make sure we all understand the water needs this crop needs to finish out for maximum yield.

First of all, for those of you that are not irrigators, take heart, this is not just a discussions about irrigation, but also a discussion on yield forecasting. Today we can go take ear and kernel counts to project yield, but we don’t know the magical number of kernels per bushel to plug into the calculation. Today, I start at 90,000, but as the season and moisture situation unfolds, I have a good idea if that number is going to creep to 80,000 or even down to the 7X,000 range. Projecting an accurate yield helps us understand the logistics we will face at harvest.

For me, the final 700 GDD’s is defined as dent to black layer in corn. For that 112-day maturity corn, that is a process that should envelop around three to four weeks and five inches of water. What does that five inches of water get us? In straightforward terms, kernel depth and test weight. Today, we have about 2/3 of our dry matter accumulated. The next three inches of water get us to 90% dry matter. The reason that every year I harp so hard on making sure our corn is not shorted at the end of the season is that the last two inches of water give us about 8-10% of our dry matter. That is a difference in 56-pound corn vs. 60-pound corn. The last inch of water gives us around 4% of our dry matter accumulation. That inch of water is the difference between 230 yield and 240 yield. That ten-bushel difference costs you about $10 per acre but yields us $30 or more.

On soybeans, the story is different but is also more of the same. I know I am beginning to sound like a broken record here, but there is a long way to go on these soybeans. Today, most of our soybeans are between the end of pod elongation and beginning seed fill. That means we all have at least 6.5” of moisture that we need to get to finish our soybeans in the next roughly six weeks, or a bit more than one inch per week. And again, at the risk of sounding like a broken record, once the beans begin to turn yellow, we still need two inches of water. However, the reason I harp on these facts, again and again, year after year is that for those of you that are irrigators, is that the irrigation system you have is the most profitable piece of equipment you have within your operation in the next eight weeks. With ROI’s of 2X or 3X, or even more, knowing your situation is extremely critical.

So the take home for today is that regardless of our situation, scouting for maturity development and moisture conditions is far from over. Remember that last year we sat around at the half dent stage for weeks, and used a lot of water during that time, but we were also rewarded with test weight for those efforts. I seriously doubt the same situation will play out this year, but the lesson remains. For those of you that are part of our AquaSystems platform, continue to monitor your probes daily, and be mindful of what the ACS team is adding in the notes section for you. For those of you that have a scout or a do your own, continue to pull cores, but don’t be afraid to ask your FSA or Regional ACS Manager what they are seeing in your area. The essence of our challenge is like so many other things in life, it is the final push when you are tired and out of energy and want to be done, that solidifies your result and your success at the end of a race.
by Keith Byerly
Posted: 8/9/2018 1:29:28 PM by Kelli Reznicek | with 0 comments