Organic cropping systems are required under the
National Organic Program regulations to include cover crops.  Cover crops offer ecological services that
include pest suppression.  Sunn hemp (Crotalaria juncea) is currently the most
widely used cover crop in organic strawberry in Florida and provides off-season
suppression of weeds and sting nematodes (Belonolaimus
longicaudatus).  We propose that
organic strawberry cropping systems in the southeastern US can be more
resilient with greater cover crop diversity. 
To this end, we compared sunn hemp at a seeding rate of 44.8 kg/ha with
hairy indigo (Indigofera hirsuta), jointvetch
(Aeschynomene americana), and
short-flower rattlebox (Crotalaria
breviflora), each with a seeding rate of 22.4 kg/ha, for their utility in
suppressing weeds and sting nematodes during the off-season.  The study was conducted in two locations in
Florida: on-farm in Plant City and on-station in Citra with planting dates of
July 18 and July 30, 2013, respectively. 
The experimental design was a randomized complete block with the four
cover crop treatments and a weedy control treatment replicated four times.  Nine weeks after planting (WAP) just prior to
termination sunn hemp was the tallest cover crop by at least 49 cm at Plant
City and 53 cm at Citra and had the largest amount of dry shoot biomass at both
locations (9584 kg/ha and 6811 kg/ha, respectively). At Plant City, hairy
indigo and jointvetch produced an intermediate amount of biomass, whereas at
Citra the biomass of the three alternative species was not significantly
different.  At 3 WAP the sunn hemp canopies
were most effective at suppressing photosynthetically active radiation (PAR) penetration.  However, by 6 WAP only short-flower rattlebox
had more than 12% PAR penetrating its canopy at Plant City and at Citra only
sunn hemp and hairy indigo had slightly less than 25 % PAR penetration.  At Plant City, broadleaf weed biomass was suppressed
with hairy indigo and jointvetch as effectively as with sunn hemp.  However, at Citra, all the cover crops were equally
effective at suppressing broadleaf weed biomass.  Grass and sedge biomass at Plant City and
sedge biomass at Citra were not significantly lower with the cover crops than
with the weedy control.  However, grass
biomass was effectively suppressed to an equivalent extent by the four cover
crops in Citra.  Neither location
appeared to harbor sting nematodes as none was observed in soil sampled before
planting and after termination of the cover crops.