Strip-Tillage, Compost, and Planting Density Effects On Carrot Quality and Yield

Biotic and abiotic stresses during carrot stand establishment can greatly reduce carrot quality and yield.  Practices which increase soil organic matter including reduced-tillage, cover cropping, and compost addition may improve crop resilience to these stresses.  In Michigan, innovative carrot growers are experimenting with use of pre-established barley or wheat cover crops combined with strip-tillage to provide wind-protection for vulnerable carrot seedlings while building soil health.  The central objectives of this research were to evaluate the interactive effects of tillage (strip vs conventional) and compost (none vs 2.8 T/A) on weed suppression, soil N dynamics, soil enzymes considered short-term indicators of beneficial changes in soil organic matter, and carrot quality and yield.  A secondary objective, carried out on-farm, was to evaluate the impact of planting density on yield and culls of three processing carrot varieties.  Key findings from 2009 field trials included: 1) strip-tillage had no effect on N-dynamics, soil enzyme activity or carrot quality and yield relative to conventional tillage; 2) compost applications resulted in higher yields and lower percentages of forked carrots in a field heavily infested with root-knot and lesion nematodes; and 3) higher planting densities improved yields and reduced the percentage of culls from 17% to 2% in a grower field with substantial stand losses due to heavy early rains.  Our results suggest that strip-tillage, seeding rate, and compost application are all useful tools for reducing the risk of yield losses due to biotic and abiotic stresses in carrot production systems.