Cover Crop Termination Times for Building Soil Carbon in South Florida Soils.

The agriculturally important limestone-plowed soils of South Florida are inherently low in nutrients and organic carbon. Growing and incorporating cover crops during fallow periods is an effective method of building soil organic matter, improving soil structure, and preventing erosion- all of which are crucial to improving the productivity of these agricultural systems. Climate variability is expected to increase in time, making it critical to identify best cover crop practices under current conditions. The purpose of this study is to identify the appropriate termination and incorporation times of three warm-season cover crops for maximum benefit. Sunn hemp (Crotalaria juncea L. cv. ‘Tropic Sun’), cowpea (Vigna unguiculata L. cv. ‘Iron Clay’), and sorghum sudangrass (Sorghum bicolor x S. bicolor var. sudanense) were grown within a randomized split plot design in a food forest on the main campus of Florida International University. Leaf samples were taken and tested for total carbon and nitrogen (CN) every two weeks. Two non-destructive handheld sensors, the Greenseeker (Normalized Difference Vegetation Index) and SPAD (soil/plant analysis development) were used to measure chlorophyll throughout the growing period. Bi-variate correlation analyses were used to compare CN laboratory results and sensor data to determine whether handheld sensor technologies can replace laboratory analyses to determine incorporation times of greatest benefits to farmers. ANOVA was used to determine differences in CN between treatments.