Healthy soil has high percentages of soil organic matter, which improves water-holding capacity, nutrient cycling and retention, and provides nutrients for microbes, along with other benefits. Unfortunately, Sarah Strauss noted, most citrus soils in Florida typically have 1 to 2 percent soil organic matter, “which is basically non-existent.”
Strauss and other scientists are researching two ways of improving soil organic matter in groves – cover crops and compost. Strauss, a University of Florida Institute of Food and Agricultural Sciences soil microbiologist, discussed the issue at this year’s virtual Citrus Expo.
Strauss reported some “really encouraging results” after just one year of cover crop research. The compost research has just begun, so there are no reportable results yet.
With cover crops, researchers are already seeing increases in soil organic matter and soil microbes. “This is very promising,” Strauss said. Additionally, weed density is being reduced by up to 84 percent. Cover crops can also provide nitrogen, reduce soil erosion and increase soil moisture, she said. “Influence of cover crops on citrus will likely require several years,” she added.
Cover crops in citrus will require multiple plantings annually so they are growing year-round, Strauss said, adding that most species don’t grow year-round.
Nitrogen-fixing crops include cowpeas, vetches, crimson clover, sunn hemp and perennial peanut. Other cover crops provide nematode management or weed suppression. Strauss said she and her fellow researchers are using a mix of different crops to give “better overall coverage of different strategies.” The research will include studies of fruit yield and quality, economic benefits, and root growth and density.
Turning to compost, Strauss said it is something most growers are familiar with and are either using or have used. Compost is usually available and easy to apply, and can provide a great nutrient source for soil microbes and potentially for trees, the researcher said.
But, she added, compost is expensive; and application, timing and determining how much to apply “can be a little bit tricky.” There is also much variability in compost quality and type, and compost can be a source of weed seeds.
Strauss is also involved in a small trial combining compost and cover crops. Researchers are applying compost to the grove, then planting cover crops. No statistics are available yet on that research.
See Strauss’ full Citrus Expo presentation here. The presentation, and the continuing education units (CEUs) available to those who watch it, will remain online through the end of 2020.
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