Some Considerations for Winter Harvest

Late planting, a cool season and fall weather have conspired to push corn harvest into winter months in some geographies. The University of Wisconsin has studied these phenomena in the past ~25 years and I’ll try to summarize their findings so our customers have an idea of what to expect. The biggest question is dry down and Table 1 below is the best graphic representation of what you can expect as we move from fall to winter harvest. The table does not correspond well with our typical ideas that temperature, dry air and wind are necessary to dry corn. From plot work earlier in my career I have first-hand experience that once the crop goes through one or more hard freezes in December and January, it will get very near storage moisture with no real “drying days” taking place. In conversations with growers I used the term “freeze drying” for lack of better terminology.

Other considerations have to be field losses. UW has a stark contrast of data in Table 2, showing two successive seasons, probably the best and worst case scenarios, having corn in the field through the winter. Losses can occur from ear drop, lodging, ear rot or molds and wildlife feeding. In the case of the 2000 crop year, there was very heavy snowfall in the winter leading to lodging, ear drop and problems with harvestability. Note the yield increases from March to April in the 2000 crop year after the snow melted. The winter following the 2001 crop year had atypically light snowfall and the yield “hit” was minimal.

At this moment the Midwest is in a wet weather pattern, which would suggest a higher than average snowfall winter. Though I don’t want to be the bearer of negative news, you should however use a realistic field loss number such as the “Mean” of the 2000 and 2001 seasons. As you can see in the table above, storage in the field is not free.

Corn Yields: Can They Go Higher?

In the past 40 years, the national average for corn yield has increased by nearly 80 bu. per acre. Roughly half of that increase is due to changes in cultural practices by creating a controlled environment through companies like this involves better weed control, precision planters, increased plant populations, and taking the less productive fields out of production. The other half of this increase is due to genetic improvements through breeding and biotechnology. Can we expect a similar trend to continue? Have we reached a yield ceiling in corn? Based on information shared with me, genetic improvement for grain yields will continue and some exciting yield potentials are ahead of us. These improvements will result from the development of new biotech traits and the use of a breeding tool known as “Marker Assisted Breeding”.

Marker Assisted Breeding is a concept employed by corn breeders to help them develop new improved hybrids. Before this tool was available, breeders constructed breeding populations and developed thousands of new inbred parents from those populations in their nurseries. They then made “test crosses” with these new inbred parents by crossing them with other, unrelated inbred parents. This process creates thousands of new hybrids that the breeder evaluates. This process is repeated year after year. Typically, only a couple of these hybrids are good enough to be commercial hybrids but it takes years of testing to identify which ones. This whole process is a combination of art, science, and a bit of luck. Marker Assisted Breeding is a science-based tool that has all but replaced the art portion of this process and has greatly reduced the luck component. It is based on a concept known as indirect selection. The idea of indirect selection is to select for a trait that is easy to identify and select for, yet it is highly correlated to giving you the results you want. As an example of indirect selection, if you select for plants that can produce more kernels per plant, you indirectly select for plants that have more yield per acre. There are many components of grain yield in corn but it typically comes down to some combination of more grain weight per plant and /or more plants per acre. The corn plant has roughly 35-40,000 genes. It is estimated that about 250 of these genes directly influence grain yield. About 20 clusters of these genes work together to have the most impact. These are genes that breeders would like to easily manipulate and select-for (indirectly) during the process of developing new hybrids.

Let’s back up. Genes have one function in living organisms. They are a set of instructions to produce proteins. We cannot select for specific genes by looking at them under a microscope. We can, however, select for their presence or absence by doing an analysis for the proteins they produce. Since several yield genes are working together in clusters, it is almost impossible to do a protein analysis for those genes per se but if there was a gene next to that gene cluster that was easily traced due to the specific protein it produces, that gene would be an excellent marker. Another thing to remember is that genes are passed from generation to generation in groups so that genes that are close to each other travel together to the next generation. The closer that gene is to the cluster of yield genes, the more effective it is as a genetic maker for grain yield. Selecting for plants that are identified to have a marker or set of markers that the breeder knows are next to clusters of genes that he is looking for, gives that breeder a high probability of successfully selecting the most desirable plants.

To make all this work, extensive studies are done to identify the makers that are near the gene clusters of interest. To complicate things, different genetic families may have different clusters that influence yield. Therefore, different makers are necessary. The end result, however, is that breeders have a very effective tool to use in their selection process. It makes them more effective and efficient in selecting material that goes into their breeding pools, as well as selecting potential new inbred parents during the inbreeding stages.

I believe that genetic gain for grain yield in corn will continue not at the rate we have seen in the past, but will be even greater. This will mean new hybrids will continue to come out at a fast rate. Hybrid life spans of 3 – 4 years will be common because they will be replaced by newer hybrids that are 5 – 10 bu./acre better. I also believe future hybrids will be even more stable across environments. This will be due to additional biotech traits as well as identifying markers that are linked to genes that have a major effect on stability and plant efficiency. Yes, corn yields will continue to rise. It will be exciting to see just how much.

April 2012 Earfull Newsletter
Written by Dr. Rick Batty

Watch Those Soil K Levels for Maximizing Yields

K Levels

As the 2011 growing season closes out, it is time to think carefully about how to maximize yields in 2012. Of course there are numerous factors which will impact grain yields this next year, but I thought I would address one important factor that we can control. It can have a major impact on plant health, standability, and grain yield. Let’s talk about the nutrient potassium.

A standard benchmark for a 180 bu/acre corn yield is that it will uptake 240 lbs. of potassium per acre. To supply this level of K to the plants the soil test must show 165 ppm of the nutrient. As yield expectations increase above this level, typically plant populations and units of nitrogen are also increased. Given these trends and expectations, the standard benchmark levels of K may not be enough. Studies have shown that increasing K levels in the soil test to 200 – 250 ppm enhanced grain yield and standability as nitrogen units and plant populations were increased. One study showed that 40 and 100 additional ppm of K over and above the 165 ppm level increased corn grain yields by 40 and 70 bu/acre, respectively. Nitrogen application was held at 160 lbs. of N/acre; an excellent return on investment.

A corn crop that does not have access to adequate amounts of K may have poor root development, low protein content in the grain, susceptibility to water loss and wilting, susceptibility to diseases, and weak stalk strength. Therefore, any environmental stress that the crop encounters in its growing season will be exaggerated if the plant has not had optimum availability of K. One of the largest stresses that a plant may encounter is high grain yield. In some high yield environments, this yield stress can lead to stalk lodging from the plant cannibalizing itself. If adequate K levels are available to the developing plants, the plant will have a better chance of having healthier, stronger stalks at harvest. And the grower will have a much happier combine season.

Compaction in wet soils can limit the uptake of potassium. So, whether the K is available but is not
in optimum quantities or it is not available due to other factors like compaction, the result is the same. Optimum performance will be compromised and it begins very early in the plant’s growth stages. More than 50% of the total K that is required by the plant is taken up in the first 50 days of plant growth. In the critical weeks just prior to pollination, the corn plant removes over 15 lbs. of potash from the soil per day. It is no wonder why we see such positive responses from keeping optimum levels of K available to our valuable crop.

In closing, I recommend fertilizing for a great crop and avoid compaction. Keep all the nutrients and micronutrients in proper balance with your expectations and cultural practices. Conduct some studies of your own to see if increasing K levels beyond the soil test recommendation gives you a positive return. Don’t let inadequate K levels be a limiting factor to achieving maximum yields and plant health.