CORESTA Congress, Online, 2020, Agronomy/Phytopathology Groups, AP 20

Winter cover crop management in the production of organic flue-cured tobacco

North Carolina State University, Department of Crop & Soil Sciences, Raleigh, NC, U.S.A.

The production of organic flue-cured tobacco requires costly nitrogen (N) management strategies, intensive tillage and bedding, and repeated cultivation for bed maintenance and weed control. This study was conducted to determine if cover cropping could mitigate the significant economic investment of N fertilization in organic tobacco. In 2018 and 2019, the effects of three winter cover crops: hairy vetch (Vicia villosa Roth); Austrian winter pea (Pisum sativum var. arvense L.); and crimson clover (Trifolium incarnatum L.), were compared to typical N management without a cover crop, and investigated for their potential to supplement N to a flue-cured tobacco crop in North Carolina. Tobacco yields were significantly greater under cover crop treatments in both years. In 2018, all cover crops improved yields by an average of 30 %, and hairy vetch increased yields at one location by 38 % (3,242 kg ha-1) compared to no cover (2,357 kg ha-1) in 2019. Crop value was significantly greater in legume cover crop treatments at one location in 2019 by $2,985 ha-1, and did not differ from the control in 2018. In 2019, in-season soil samples showed cover-crop N was removed from the system at topping, a critical marker of a necessary N-free period for the maturation of the leaves. Only hairy vetch at the Kinston location showed elevated nitrogen at topping compared to the control, however this did not have a negative effect on quality, yield, or value. Cover crops are not traditionally used in tobacco production due to concerns with unpredictability of nitrogen supply and extended N mineralization compromising the quality of the cured tobacco leaf. Our research did not support these concerns, and found evidence supporting the potential use of cover crop N as a cost-effective management strategy in the production of flue-cured tobacco.