Producing soybeans
The humidity of the air is a surprisingly important factor in deciding when to harvest soybeans fields.
Relative humidity of the air significantly affects soybean plants, primarily through its influence on seed moisture content and the associated risk of so-called shatter loss. The moisture content of the plant fluctuates quit a bit with air humidity, temperature and wind. It can increase with overnight dew or rain and decrease during dry, hot and/or windy conditions.
Shatter
Soybean shatter loss during harvest refers to the premature opening of pods, leading to seed loss. It is a significant yield risk during harvest, with losses escalating sharply as seed moisture drops below 11%. Multiple wetting and drying cycles further exacerbate this loss. Shatter loss can also be introduced due to insects, such as grasshoppers and bean leaf beetles.
Lower yields can mean you’re harvesting a crop that is no longer economical feasible. Shatter losses add up quickly: Dropping only four seeds per square foot will cost you one bushel for every acre. Beyond yield loss, shatter can also introduce problems for the next growing season as dropped seeds become volunteer weeds.
In practice this means a farmer needs to know the bean moisture content and avoid harvesting when beans are too dry, which can happen in the late morning and afternoon when relative humidity of the air is lowest.
To complicate this, if the beans are to be stored on or near the farm, they should not be too wet! So, not too dry for harvest, not too wet for storage. Who said farming is easy?
The academics have figured out that optimal moisture content for harvesting soybeans is 13% and thus that’s when you get the best yield (and price) for the crop. In one study, Ohio State University Extension researchers documented up to 8% loss when soybeans moisture content drops from 13% to 9%.
Night-life is coming
The last two days the moisture content has been dropping to 12%. Given that for growing soybeans commercially, harvest is the most costly operation of production, a change is called for.
An ‘annoying’ consequence of precision agricultural machinery is that this combine tests the humidity pretty much in real time and estimates the shatter loss. It’s prominently displayed on the screens in the cab. Claiming ignorance is not going to work!
A study by Arkansas University System shows the effect of the experience of the operators of the harvest machinery. A new operator may see a loss of 2.6 Bushels per Acre. An average operator can reduce that to 1.6 Bu/A, while an expert can harvest the same crop with losses in the 0.9 Bu/A range. Observing and responding to observations is key. Frequent and adequate fine-tuning of for instance combine forward speed, reel speed, reel height, fan speed and thresher adjustment, can increase income by several hundred dollars per day.
All this to say that harvesting is now on an evening and early night duty schedule. Harvesting with the bright LED lights is doable, but it is noticeable more taxing on the brain and body.