By Blake Thaxton
Pearl Millet in bloom.
Fall crops are the focus of many small farmers in Florida this time of year, but it would be prudent to take a peak forward and start planning for the spring season. Many small farmers that sell directly to consumers at venues like farmers markets and farm stands feel the demand from consumers for “Local,” “Pesticide Free,” or “Organic” produce. Although most have chosen not to become certified organic, they do try to abide by the regulations and keep their produce “synthetic pesticide free.” When growing in this manner many farmers choose to take advantage of cover crops to reduce pests and build the health of the soil, as wells to boost the fertility of the subsequent cash crops. Below are a few tips for managing cover crops to boost the yields of the cash crops that follow.
Sample Soils for Existing Fertility Levels – send a soil sample to the UF/IFAS Extension soil testing lab or another soil lab for analysis. The analysis will show the current fertility of your soils and recommend amounts of fertilizer that may need to be added to make a good yield. If you have difficulty understanding the report, call your local County Extension Agent for assistance.
Calculate fertility from cover crops – many small growers who produce using “organic” methods utilize cover crops to build their soil in between cash crops. Fertilization credits from the cover crop need to be taken into account while looking at fertility for the cash crop. To establish how much nitrogen is provided by a cover crop, the biomass and percent of nitrogen in the plants must be determined just before termination. The SARE (Sustainable Agriculture Research and Education) handbook, Managing Cover Crops Profitably, (chapter entitled Building Soil Fertility and Tilth with Cover Crops) explains in detail how to properly calculate the nutrient benefit of cover crops. To determine the biomass, this equation can be used after sampling a small section of the crop:
The Nitrogen percentage of the cover crop is most accurately determined in a lab, but estimates can be used when time is a factor. Estimates seen below:
- Annual legumes – 3.5 to 4 percent prior to flowering and 3 to 3.5 at flowering.
- Perennial legumes – 1 percent less than annual legumes
- Grasses – 2 to 3 percent prior to flowering and 1.5 to 2.5 after flowering
Also consider how much will be available to the crop this year and in subsequent years due to the minerailzation rate of the cover crop. In our southern climate you can divide the amount of nitrogen that will be provided by 2 to get a conservative estimate of what will be available to the crop that follows.