Some field observations from the research team working in our Lancaster County plots, sampling and collecting data on almost all the King’s corn hybrids we sell, including several experimental hybrids that have not yet been released commercially.
Corn can perform quite differently each year, depending on the weather conditions, the relative maturity, and the planting date. 2013 has been a year of abundant warmth and moisture (often with too much at once), which translated to rapid growth spurts and different pest and disease problems that were related to conditions that could almost be described as tropical. During this year’s silage cuts at our Lancaster County research plots, we’ve made a few observations that truly set this year apart.
Think About Your Indicators
We usually think of milk line as a quick, fairly accurate read on whole plant moisture. (When viewing a cross section of a broken cob, a line across each kernel will be visible which divides the dry part of the kernel from the section that is still in milk stage. The kernel dries from the outside in, proceeding from soft dough stage to early dent stage to ½ milk to ¾ milk) so this line moves from the top of the kernel down. 50% milk line is generally considered the point at which the corn is roughly at 65% moisture and ready to chop for silage. Unfortunately, this may not be true if the plant got overloaded with signals like excessive heat or moisture.
Overabundant heat or moisture (or a combination) can push the physiological growth of the plant and results in quicker growth. It hits the reproductive stage early so it can produce seed while it is still alive. This may mean that kernels start to dry down and mature before the plant as a whole matures beyond the vegetative growth stage. For corn, that looks like a brown, dry plant.
Here we run into more possible confusion. Abundant moisture in the Northeast this summer caused lots of Northern Corn Leaf Blight, which starts as small brown lesions on the leaves that expand and eventually turn the leaves brown – leading to the illusion that the plant is dry and mature. The blight also reduces the plant’s overall resistance to other pest and disease problems, like stalk rot and corn borer. The spores spread easily when leaf moisture is present for periods of 6-18 hours and temperatures are between 66 and 80 degrees F.
The result of these weather patterns, then, was mostly brown leaves on some hybrids, belying a true moisture (which comes primarily from the stalk of the plant) that was too high for proper ensilage. That high moisture became apparent only when the plants were chopped for silage samples and felt quite damp to the touch. A rough test of ideal moisture is to squeeze a handful of the chopped-up plant, tightly for about 90 seconds in your hand, release your grip and observe the ball of chopped silage. If the ball falls apart slowly with no free juice and feels like a slightly damp sponge to the touch, then you should be within the 60 to 70% moisture range. If the ball falls apart very quickly and feels dry to the touch, it is probably below 60% moisture. If the ball holds it shape with just a little free juice it may be 70 to 75% moisture. If the ball holds its shape and there is considerable juice, then it is over 75% moisture.
Corn silage harvest should be targeted when the entire plant or (whole plant moisture) is between 60 and 70% moisture, at which point it will give you the best dry matter yield and appropriate moisture for digestible silage. This range of moisture is also the range that is best suited for fermentation to take place when the corn is ensiled.
So this year, the hybrids that stand out in the plots are those with the least susceptibility to the blight and show good standability. High numbers of broken plants are a problem, especially plants broken below the ear, for obvious reasons. Broken or lodged plants may just be an indicator of too-thin or weak stalks, but more likely the plants fell victim to corn borer damage.
Milk line and leaf color were therefore less than reliable indicators this year. We sampled many plants whose ears were at 80-90% milk line, while the plant itself was at an ideal silage moisture (60-65%).
One way to tell if corn is ready for chopping is to weigh a chopped sample, then microwave it until the dry weight does not decrease any more. , Then take the final dry weight and subtract it from the initial wet weight, which will give you the weight of the moisture in the sample, figure out the percent moisture from the ratio of (Wet weight – Dry Weight)/ (Wet Weight) x 100
Divide the moisture weight by the wet weight which will give you a decimal and multiply by 100 to figure the percent moisture.
The main thing is – be aware just how much abnormal weather can throw off corn maturity signs. We saw a big range in milk lines that weren’t necessarily a good reflection of plant readiness. Whole plant moisture is a much better indicator to determine if the corn is ready for silage.
Short-season versus long-season
We have two sets of plots at this location – early-planted (early May) and late-planted (June 1). We saw something interesting in the early plots. A wide swath of shorter-day to longer-day hybrids seemed to mature almost all at once (or at least in quick succession), making timely chopping a challenge. This group of hybrids experienced a perfect storm of high temperatures, long daylight hours and high moisture that likely converged around critical development stages (tasseling and silking). Hybrids that ranged from 82-day to 118-day maturity all pushed at a rapid pace with fewer distinctions than normal in their timing to maturity.
There were still differences, though, and these were even more apparent in the later-planted plots. The hybrids that were most disease resistant tended to be the later-day hybrids. This is not true every year (it depends largely on WHEN the weather stress coincides with the plant’s development), nor of every hybrid, but is often the case because the plant remains in a vegetative state This means that it is actively growing and has not yet sent all its resources into producing ears. A plant in the vegetative stage is much more resistant to disease and pest pressure, but again, this varies by hybrid.
A side note: what does this mean for the dairy farmer? He has an advantage over the grain-to-market farmer. Harvesting the corn sooner in its development greatly narrows the disease window, since the plant is not left in the ground long after its vigorous vegetative state wanes. Add to this the fact that some corn infections and pests thrive more on the grain than the vegetation. So what does this in turn mean? Traited hybrids with pest resistance may be more applicable to corn grown for grain than for silage. By the time many of the usual threats would become a major problem, the silage crop is about ready to come off.
Pure observation showed us that later-day hybrids also tend to be higher yielders, simply because they have more time to continue photosynthesis and growth, and put on more biomass. We like to recommend planting a spread of different maturity ranges, though, since disease or drought pressure may hit as later-day corn is maturing, while early-day corn matures pre-stress, or vice versa. This is a classic and simple way to spread risk in your corn crop.
Once again, a favorite corn hybrid, outshined many others in the plots. A 102-day hybrid, it’s a strong yielder with excellent disease resistance and adaptability to the wetter conditions of the Northeast. Sometimes the best way to tell that is with exposure to a year like 2013.
A note on comparing hybrids
When you have different hybrids in the same field and want to make comparisons on performance, make sure you are comparing apples to apples. The most telling comparisons are often in the hybrids of the same maturity class planted at the same time (for example, 90-95 day relative maturity), since the same weather conditions hit the different hybrids at roughly the same physiological stage.
When comparing tech to non-tech corn, it’s almost essential to compare the conventional and traited versions of the same hybrid, so you have eliminated differences in the rest of the genetics. These base genetics, or differences in conditions or management, may be responsible for differences in adapting to the environmental conditions, rather than the tech traits themselves.
It’s not all about eye appeal
Appearance is often a good clue to corn’s health, but it can be misleading. A tall plant is quite appealing, but height does not necessarily mean significantly higher yield, since most of the plant’s weight is at the ear and below – tall, thin tops actually don’t contribute much.
A deep green plant is also eye-catching, but some hybrids’ genetics simply make them paler and this means little in terms of nutritional value or plant health. On the other hand, leaf yellowing or purpling is usually a sign of nutrient deficiency, and leaf curling of course means moisture deficiency.
A word on population
Population directly contributes to yield, but so do your conditions. It’s quite likely that the population you plant at will not be the population you get. This is particularly critical to account for when we are managing and sampling from research plots.
If your planter is not properly maintained or calibrated, you are probably planting a much higher or lower population than you think. If you are no-till planting into heavy residue, chances are you will end up with a lower population than you planned and will have to compensate by planting a higher rate. Other conditions that you may not have thought of also throw it off. For example, our research plots are no-till planted into Hagerstown Silt Loam that tends toward heavy clay. The coulters cut into it fine, but because we had high levels of rainfall the soil, was moist and the clay held the moisture,, the press wheels had problems closing it back up – so the planting slit was starkly evident in the row over three months later. An open slit gives birds, insects and other fauna easy access to the seeds you just planted, and reduces the soil contact the seed needs for proper germination.
In our no-till research setting, we cut three replicated samples of 17.4 inches (1000th of an acre for easy math) per hybrid. Even within these relatively small plots, there was lots of variation in the stand. We planted at a population of 27,700, but it was not unusual to get anywhere from 18,000 to 30,000 from any given sampling, and this range could easily occur within a 60 foot by 10 foot plot. When sampling to test yield, then, this variation in stand means that a given sample in the plot might not be representative of the whole field, and the sample has to be adjusted for the population at that particular spot. Replicated samples were taken to get a representative average per foot row of corn.
Starch vs. stalk
Nutritionists are usually looking for the percentage of starch in corn silage. Often we hear that corn silage is 50 percent starch/50 percent forage, but weighing the cobs in our samples revealed quite a range here as well, with differences between each hybrid. Our samples were often closer to 30-40 percent (ear weight % of total weight) which was contributed primarily from the grain. This is something to consider as you build your ration, as well as the important consideration that king’s corn hybrids produce more floury starch than most other brands, and thus can often ferment and be ready to feed in less than half the time of most hybrids on the market.