Strip Tillage and Compost Influence Carrot Quality, Yield, and Net Returns

Abstract

Management practices that build soil organic matter—including reduced tillage, cover cropping, and compost applications—may be useful for protecting vulnerable crops from extreme weather events, reducing energy costs, and suppressing pests in carrot (Daucus carota subsp. sativa) production systems. The primary objective of this research was to assess the effects of strip tillage, compost, and carrot cultivar on carrot quality, yield, and profitability. An important secondary objective was to evaluate the impact of tillage and compost on establishment of important weeds in carrot systems—including two species that have developed resistance to linuron: Powell amaranth (Amaranthus powellii) and common purslane (Portulaca oleracea). Field experiments were conducted in 2009 and 2010 comparing conventional tillage (CT) to strip tillage (ST) under two rates of mature compost addition (0 or 3 dry t·ha−1) for three processing carrot varieties (‘Canada’, ‘Finley’, and ‘Recoleta’). In the ST system, a pre-established barley cover crop was left to grow as a windbreak between crop rows until carrots were established. Partial budget analysis was used to estimate net returns associated with all treatments. Compared with CT, the ST system resulted in 1) either equivalent or greater (2010, Finley cultivar) total carrot yields and net returns; and 2) either equivalent or lower summer annual weed densities. Addition of compost resulted in equivalent (2010) or higher (2009) carrot yields and gross returns but did not affect net returns as a result of the increased costs associated with compost application. Compost reduced the density of common purslane in 2009 but resulted in a threefold increase in the density of Powell amaranth in 2010. Our results demonstrate that both ST and compost applications are potentially valuable tools for improving the profitability of carrot production systems. Future research examining the mechanistic basis for compost and tillage effects on carrots and weeds as well as the long-term effects of these practices on profitability of rotational crops would be helpful for optimizing their use in vegetable production systems.