Florida’s sandy, nutrient-poor soils present a persistent challenge for row crop producers. After a summer corn harvest, fields often sit bare through winter. In Florida’s subtropical climate, that empty period comes at a cost. Nutrients leach away, topsoil erodes, soil carbon decreases, and the land loses ground it may struggle to regain. UF/IFAS researchers in the Department of Soil, Water, and Ecosystem Sciences (SWES) have been studying whether winter crops in Florida’s sandy soils could make a difference in protecting them.
Two studies offer some revealing answers, both for the land and for producers’ bottom lines. The project took place at the UF/IFAS Plant Science Research and Education Unit in Citra, Florida. The soil there is more than 95% sand.
“That makes it one of the more challenging environments to manage for nutrient availability and soil health,” Julia Barra Netto-Ferreira, a SWES doctoral alumna, said. “Nutrients move quickly and organic matter is hard to build and easy to lose.”
Netto-Ferreira and her colleagues compared several winter crop options against a bare winter fallow. The treatments included:
- a herbicide-maintained fallow, a management adopted by many Florida growers
- cereal rye, a typical grass grown as a cover crop by many Florida growers
- crimson clover, a typical legume grown as a cover crop by many Florida growers
- a rye-clover mixture
- wheat, a less typical grass cover crop
- a commercial chickpea variety, a new legume crop in Florida
The researchers chose chickpea as a dual-purpose crop. Producers could harvest it for grain while the plant protects the soil. Additionally, its residues return to the soil as a cover crop at the end of the season. A companion study narrowed the focus to chickpea, rye, and fallow. That study also used crop simulation modeling to extend the findings beyond the two-year field trial into 10-year projections.
What Winter Crops did for Florida’s Sandy Soils
The field results were encouraging. Compared to a bare winter fallow, chickpea and clover measurably improved soil health. Those produced 90% higher potential nitrogen mineralization. That means the soil was better prepared to release nitrogen in a plant-available form when the following corn crop needed it. Enzyme activity tied to nitrogen cycling was 80% higher, and carbon-cycling activity was almost two times greater than fallow soil. The key appears to be residue quality, and legume residues have a lower carbon-to-nitrogen ratio that can be an indicator of that.
“The lower C:N ratio of legumes allows them to decompose more quickly and release nutrients faster,” Netto-Ferreira said, “stimulating more microbial activity.”
The grasses (rye and wheat) and the mixture produced substantial biomass. However, that did not lead to the same short-term boost in most soil health indicators.
Despite measurable improvements in soil health and nutrient availability following legume crops, corn yield was similar across all treatments, including fallow.
“While soil health and fertility are essential for agroecosystems, crop productivity is influenced by a complex interplay of site-specific factors,” Gabriel Maltais-Landry, SWES associate professor and Netto-Ferreira’s main dissertation advisor, said. “Soil health status and nutrient availability are just some of the variables that play a part.”
In this case, the research team fully fertilized and irrigated the corn according to standard Florida recommendations, as most growers would likely do on a real operation. Though doing so may have masked any additional benefit the winter crops could have provided.
Modeling Chickpea’s and Rye’s Impact
Because two years of field data can only tell part of the story, a crop simulation model (DSSAT) projected what might happen over a 10-year rotation. The modeling work offered a more optimistic view of winter crops’ long-term value, just not for yield.
The simulation showed fields with chickpea or rye could hold over 15% more soil organic carbon than fallow fields. In Florida’s sandy soils, where carbon does not accumulate easily, even marginal improvement matters.
“When optimal management is applied to corn, yield improvements may not be the primary benefit of including winter crops in rotation, even in the long term,” Netto-Ferreira said.
“Instead, slowing down the loss of soil organic carbon, and potentially stabilizing it at a higher concentration, could lead to benefits in terms of greater nutrient retention and improved soil conditions,” Chris H. Wilson, Netto-Ferreira’s dissertation co-advisor, added.
Studying the potential role of chickpea as a dual-purpose winter crop in Florida showed promising results. In the first year of the experiment, chickpea produced a harvestable grain yield. It also showed soil health benefits comparable to clover. Germination and disease challenges in year two limited the harvest, which indicates that agronomic management of this crop still needs refinement. However, the modeling work suggested that once agronomic management of chickpea is adjusted, the crop can be a viable addition to Florida corn rotations and their soil health management.
The two studies offer a consistent message for agriculture and the environment. Planting something during the winter fallow period is better than leaving ground bare. Winter crops broadly appear to slow down the long-term loss of soil organic carbon.
Both studies were funded by the Southern Sustainable Agriculture Research and Education (SARE) program (grants LS21-354, GS22-262) and a University of Florida Graduate School Funding Award. The soil health study was published in Soil Use and Management (https://doi.org/10.1111%2Fsum.70262), and the modeling study was published in Agronomy Journal (https://doi.org/10.1002%2Fagj2.70524).
Featured image above from Julia Barra Netto-Ferreira.
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