Foliar Spraying for Improved Plant Health

| 1/5/2016 9:22:00 AM

Tags: fertilizer, soil nutrients, plant health, soil health, Joshua Burman Thayer, California,

Many of us deal with less than ideal soil. Whether too much clay, too much sand or a history of contamination, dealing with poor soil can hinder potential harvests. As organic gardening practitioners, we are in the business of ongoing soil building. By amending the soil with organic matter and by green mulching on site, we can see marked improvement to soil tilth over seasons of cultivation.

Please see my past article on soil building here. While building soil is a constant practice for long-lasting organic farming success, this article focuses on this season’s growth by enhancing plant nutrient uptake, not by the rhizosphere, but rather by the plant’s leaf directly. If getting an added boost in your production by applying weekly foliar spray piques your interest, read on.

Plant Stomata Regulate Growth Rates

In his book Plant Life in the World’s Mediterranean Climates, author Peter Dallman describes the way that plants have adapted to surviving drought. “Leaves lose water mainly through small surface pores that are lined by specialized guard cells, regulating the size of the opening to a chamber underneath.”[1] These stomata “function as hydraulic valves, adjusting pore size according to; light intensity, temperature and humidity.”[2]

It seems these seldom discussed valves on the undersides of leaves are key ways that plants adjust to the ever-changing weather. Much like our pupils dilating with changing light conditions, so too do plants adjust in how they exchange gasses.

In the case of arid-adapted species, such as the 6,000+ plants native to California, these plants have become masters of closing these stomata to slow metabolism and to retain as much moisture as possible. This allows them to temporarily open the stomata in winter storms to maximize growth, then to hunker down and conserve for the long drought.

In other wetter areas of the globe, such as the tropics, a plant can grow much faster and exchange much more carbon dioxide/oxygen by keeping these stomata wide open to maximize gas exchange. How does this apply to the crops we grow? Keep reading.

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