In 2013 a farmer in central PA moved to a new farm with some very challenged year old alfalfa stands. He pulled soil samples, and broadcast a soil amendment blend that included compost, rock phophate, gypsum, K-Mag, various trace minerals and some other rock powders on all the alfalfa acres.
On one section he applied a foliar application seven days after the first cutting was removed. A second section received a foliar application after both the first cutting and after the second cutting. A third section received no foliars at all. I visited the farm a few days before they cut the third cutting, you can see the plant differences in the photo.
In the third cutting, the control with no foliar yielded .75 tons per acre, the single foliar produced 1.25 tons, and the double foliar produced 1.5 tons per acre.
The section with two foliars had the largest stems, and stems were completely filled. The no foliar control had the smallest stems, and they were hollow.
This third cutting was dried as dry hay, and not crimped. Which section would you guess dried down the fastest?
I would have guessed the control with the smallest and hollow stems. And I would have been wrong. The largest stem, full stem dried down the fastest, and the stem was dry before the leaves. How does that work?
These plants were so healthy, the leaves continued to respire after the plant had been cut, and sucked all the moisture out of the stem. I have since learned this (obviously) won’t work when the stem is crimped. The thin hollow stemmed alfalfa would have benefited from crimping, but not the healthier full stemmed section.
Which of these sections contributed the most to regenerating soil health? We know the crop with the most biomass above ground has an equivalently larger biomass below ground, and contributes more root exudates to the soil profile.
Also, the section with a much larger biomass absorbed a lot more nutrients from the soil. The quantity of calcium and magnesium and phosphorus moved to the barn would have been much higher in the section with double the biomass. Yet, all the sections received the identical soil amendment broadcast. In the section with the foliar applications, photosynthesis was increased, which resulted in more root exudates, which resulted in more aggressive microbial activity, which released more minerals from the soil reserves and applied amendments, and produced a more nutritious crop.
This example is a perfect illustration of why I believe foliar applications of nutrients are one key practice to accelerate the system. Photosynthesis is the only way we can bring new energy into the system, and properly designed foliar sprays can turbocharge the process within a crop.
Not only did these foliar sprays increase yields, they also regenerated soil health, improved soil biology, and increased profitability.
We can increase the performance of our photosynthetic engine with well designed foliar applications. So why wouldn’t we?
When foliar applications don’t produce these types of responses, it is either because there are other non-nutritional limiting factors that are limiting the photosynthetic engine; not enough carbon dioxide, water, or sunlight; or, the foliar spray was not designed correctly.
What was in these foliars sprays? There is no benefit in knowing the exact combination, because what your crops needs is likely to be quite different from what this crop needed. In principle, we need to make sure we address all the nutrients that are needed for the photosynthesis process. This doesn’t mean you need to add each of these nutrients. It just means you need to make sure your crop has enough of each of them. If they already have enough, why would you add more?