There are in excess of 50 elements in plants and to the best of our knowledge eighteen of them are considered essential for a plant to grow and reproduce. Three of these elements are obtained from the atmosphere: Hydrogen, Carbon, and Oxygen. The rest of the elements come from mineral sources in the soil. These minerals must be in plant-available form to be intercepted by the plant’s roots. The mineral component of these elements also needs to be in the soil in sufficient quantities and in the proper balance for the biological conversion that a plant can utilize. Over time a tree can receive most its nutritional needs from a healthy, minerally and biologically balanced soil. While working towards this goal, prescribed, specific bioavailable soil and foliar fertilizer applications will be necessary to keep the tree functioning properly. These recommendations are based on soil testing and monitoring the tree through tissue testing or sap analysis.
An additional benefit of trees receiving their nutritional needs from healthy, minerally and biologically balanced soil is we no longer over use synthetic nitrogen. Lessening our use of synthetic nitrogen will play a large part in enhancing brix levels, decreasing water consumption, and reducing pest and disease pressure.
One of the fundamental theories learned from Albrecht type soil consultants is that not all soil testing is created equal. Simplistic N-P-K and pH tests are fine for determining fertility needs, but worthless when it comes to rebuilding soils. Based on this premise, we began a regimen of soil testing. These tests are not analyzing soluble nutrients, but rather testing 17 soil minerals including total base saturations and cation exchange capacities. These concepts are based on the work of Dr. William Albrecht written in The Albrecht Papers. Each year based on those soil test results, we apply minerals like Calcium in the form of HiCal Lime or Gypsum, Magnesium, Potassium and trace minerals like Boron, Manganese, and Zinc to build levels in the soil. The goal we are striving towards is to balance the soil because balanced soils are more conducive to supporting biological systems.
In addition to mineral balancing, we implemented additional practices reinforced by the 1930 journal of Florida Citrus Hall of Fame inductee, E.F DeBusk, Extension Specialist in Citriculture, University of Florida, The Need of Organic Matter in Fertilizing Citrus Trees.
>>Click here to read the full article: The Need of Organic Matter in Fertilizing Citrus Trees<<
This journal article detailed how over 100 years ago healthy citrus was grown employing cover cropping, composting and green manures. We took this to heart and implemented a program focused on cover crops, organic matter and soil biology as the primary methods of fertilizing our trees. One common theme heard over and over again in various seminars we attended, focused on the majority of a crop’s nitrogen needs being supplied from the atmosphere. The air over every acre of land is over 70% nitrogen gas. It is the soil and foliar microbes that grab that gas and change it into a form in the soil or on the leaf that the plant can utilize. What has transpired from the mineral balancing, soil biology approach is that the trees at the research farm are maintaining desired Nitrogen levels with minimal Nitrogen being applied to the soil.
Beggarweed cover crop in an early 1900's citrus grove.
These additional practices have proven themselves true in the research farm. The Total Nitrogen and Phosphorus levels in the trees are typically at optimum levels. This has been documented by regular leaf testing results. The majority of the trees’ Nitrogen needs are coming from the atmosphere, through Nitrogen fixing biology in the soil and on the leaf. Phosphorous needs are being supplied by formerly unavailable forms of Phosphorous (that were “locked up”) now being released by the fungal networks in the soil.
Hume, H. Harold. “Cover Crops.” Citrus Fruits and Their Culture, Orange Judd Company, 1911, pp. 290–291.