A Look at Citrus History through Fresh Old Eyes

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I have reviewed 100 plus years of resources, citrus culture textbooks, periodicals, and bulletins from university professors and extension agents. My goal has been trying to get an understanding of what growers did right and where we can improve. Our ancestors used some cultural practices that worked like mulching and cover cropping, but they did not have the science and technology to understand specifically why it worked. One example I found came from a document published in 1930 where the opening paragraph reads:

“From the beginning of citrus fruit cultivation in Florida it has been a general practice to supply organic matter to the soils of citrus groves by growing cover crops and applying various green manure crops and animal manure” Excerpt from the opening paragraph of The Need of Organic Matter in Fertilizing Citrus Trees. - by E.F. DeBusk a Florida Citrus Hall of Fame inductee, Extension Specialist in Citriculture, University of Florida.

>>Click here to read the full article: The Need of Organic Matter in Fertilizing Citrus Trees<<

Below is a excerpt from “Citrus Fruits And Their Culture” by H. Harold Hume, Professor of Horticulture and Botany as well as Dean of Agriculture at the University of Florida. 

Despite the concepts detailed in the above articles working for citrus growers, the industry started the widespread commercial application of synthetic NPK fertilizer around the turn of the century reducing the “need” for cover cropping and composting. This transition along with more clean cultivation, started the influx of increasing pest and disease pressure. It also started the necessity for foliar insecticides and fungicides. These not only controlled the pathogenic organisms, they also killed much of the naturally occurring beneficial biology on the trees and throughout the groves. This biology was the foliar and soil microbes that were helping to protect the trees in the 1800s.  

The early years of excessive plowing and discing, along with the over use of the Acme harrow and later the mechanical tree hoe where growers attempted to keep their grove floors completely clean were actually practices that had detrimental effects on the soil. I was guilty of all of these in the 1970s.

 
The belief was that these cultural practices pulled up moisture from below and provided an insulation layer to reduce evaporation. Growers also believed the weeds and grasses were robbing nutrients from their trees. I too was schooled in this process in my “Citrus Grove Machinery” class by Dr. Rupert Prevatt and Professor Thomas B. Mack at Florida Southern College (FSC). In the long term, these cultural practices were having the opposite effect.   

In defense of my college instructors, they also shared with us the importance of cover crops in our citrus groves. In fact, a chemical company came to the FSC Citrus department and gave a presentation on herbicide application and calibration techniques. When we returned to the classroom, Dr. Prevatt announced, “Ladies and gentlemen, this is the way citrus culture is progressing. But for those of you that go into the citrus industry as production managers, tell your grove owners that if they want to see a golf course, they need to go play golf. You need to be growing cover crops in your groves.”  

Just as in the 1800’s, the root systems of diverse cover crops are aerating and flocculating the soil today. They are secreting exudates containing carbohydrates and organic acids that are summoning and feeding a wide variety of bacteria, protozoa, and fungi which in turn are creating micro and macro aggregates to give the soil more porosity. This process is promoting water infiltration, water holding capacity, and gas exchange (oxygen in and carbon dioxide out). This phenomenon is evident at the research farm.