By Jon Frank
Foliar feeding plants is a powerful tool that can be used in many ways to:
- Increase Yields
- Supply Deficient Trace Minerals
- Push Plants toward Vegetative Growth
- Push Plants toward Reproductive Growth
- Increase Quality and Flavor
- Improve Plant Health
Yet, for all its amazing usefulness, it is only 1/3 of a comprehensive program. For best results use nutritional foliar sprays on top of a proper foundation.
A few years ago I was listening to a teacher explain how life can be looked at as many different sets of 3. In family structure it is father, mother, and child. In theology it is the concept of the Trinity. In education you have mentors, peers, and students. In crafts you have masters, journeymen, and apprentices. Almost everywhere you will find sets of 3.
This got me thinking about plants and agriculture. Where is the "trinity" in growing crops? Last year I had an "aha" moment when I realized everything I teach can fit into 3 different categories.
- Feed the Soil
- Feed the Plant
- Feed the Leaf
Since the aticles in this blog are all about feeding the leaf it is important to reference each of the other aspects starting with the soil.
Feed the Soil
Productive soils are always in motion. As plants grow and yield their harvest, minerals are taken away. When the rain falls it pushes calcium into the subsoil. If biostimulants and microbial inoculants are added they increase the digestion of insoluble nutrients and facilitate greater withdrawals of minerals from the soil.
In order to keep intensive gardening and agriculture productive, there must be a regular analysis of the soil followed by a return of nutrients. The copper that was taken up by the plants needs to be replenished. The preexisting deficiencies also need to be corrected.
The soil test you select allows you to see the profile of the soil; 1) which nutrients are excessive and should not be added, 2) which nutrients are just about right and only need a small addition for the next crop, 3) Those nutrients that are critically low and need to be applied in larger quantities.
Here are the basic rules I suggest when feeding the soil.
- Soil Test Yearly Followed by a Broadcast of Minerals
- Optimize Toward Ideal
- Apply What is Deficient
- Omit What is Excessive
- Address all 4 Classes of Nutrients: Major Minerals, Secondary Minerals, Trace Minerals, and Rare Earth Elements
For farmers this has to be done economically. That means triage is needed to get the biggest bang for the buck. Start with the major minerals and work your way toward the rare earth elements as far as your budget allows.
We all know that the microbial and living aspect of the soil is one of the keys to success with farming and gardening. It is the level of available nutrients and ratios between nutrients that creates the environment for soil biology. In other words if you want your soil teeming with microbes don't just supply copious amounts of microbial inoculants. Yes keep using the inoculants but focus on building the right levels and ratios of available minerals in the soil. This will allow biology to thrive.
As an example; an excess of potassium and phosphorous coupled with a deficiency of calcium is a poor environment for soil biology and plant roots. This is a sure path to low quality food. Most grain fields do not have this problem because economics won't allow such a buildup of Phosphorous (P) and Potassium (K).
Feed the Plant
The next factor that lays the foundation for success with foliars is to feed the plant. This is quite different that feeding the soil. Building up the right levels and ratios in soil is a long-term process. It may take 3-5 years of aggressive mineralization to bring your soil around. Holding it in this pattern is an annual, ongoing process.
Feeding the plant references the need for adequate electrical conductivity in the soil. Soluble nutrients in the soil carry an electrical charge. These available nutrients can come as a result of microbial activity or by applied fertilizers such as liquid fish or calcium nitrate. Either way the nutrients function as electrolytes in soil. As the plants pick up these nutrients the supply of electrolytes in the soil is reduced and the electrical conductivity in soil is lowered. The heavier plants feed, the lower the conductivity drops.
Monitoring electrical conductivity is done with a simple direct probe meter. If you raise plants, this this is by far your most important tool. Put it in the budget and get one.
By maintaining an adequate conductivity in the soil foliar sprays work well. If conductivity is too low, foliar sprays give a poor ROI--essentially they don't work. For row crops I suggest keeping soil conductivity in the 400-800 micro Siemens per centimeter (or .4-.8 milli Siemens per centimeter) range. If your soil is in the low 300's or less don't foliar spray. Instead first get your conductivity up and then spray.
One last thing. As the soil is optimized toward ideal the microbial system will work more efficiently causing a better supply of soluble nutrients to be deposited in the soil. This will reduce the inputs needed to maintain soil conductivity.
In the next article we will take a closer look at foliar feeding and why it has such a huge impact on plants.
