Cotton Stalk Management and Cover Crop Use on CLRDV Incidence and Soil Properties

Abstract

Cotton leafroll dwarf virus (CLRDV) was reported in cotton (Gossypium hirsutum L.) in Alabama in 2017. CLRDV can now be found as far west as Texas, and as north as Virginia. Due to such wide distribution and potential yield loss, CLRDV has been explored across various disciplines. However, there have been few investigations involving agronomic management. This study recorded CLRDV presence in cotton following various cotton stalk destruction methods with and without a cover crop, as well as the effect on soil properties in 2021-2022. Stalk destruction methods were (1) Destroy, which included two diskings, followed by chisel plowing and a repeat disking for final leveling, (2) mowing (Mow), and (3) mowing followed by pulling (Mow/Pull) with a stalk puller. A mixture of cereal rye (Secale cereale L.) and crimson clover (Trifolium incarnatum L.) was used for the cover crop treatment. Two cotton varieties were included, DP 2055 B3XF and PHY 400 W3FE. Trial locations were in the Alabama Agricultural Experiment Station System at the E. V. Smith Research Center (EVS), Shorter, AL; Wiregrass Research and Extension Center (WREC), Headland, AL; and Gulf Coast Research and Extension Center (GCREC), Fairhope, AL. Data collection included soil moisture and soil strength values, cover crop biomass, various cotton growth measurements, pre-bloom aphid presence, CLRDV infection, and cotton lint yield. Soil moisture results show that all values are relatively consistent across stalk management treatments. At all locations in both years, soil moisture values in the 0-6 in depth tended to be higher in cover crop treatments at all locations as expected. Some discrepancies were seen between the two sampling depths but overall no dramatic differences were observed. Area under the curve for cone index (AUCC.I.) was used to represent soil strength across all depths and row positions. In 5 of 6 site years, Destroy treatments resulted in the lowest cone index values. In 2022, elevated soil strength values at WREC were seen across all stalk destruction methods, regardless of cover crop. While there were differences among treatments, cotton stands were adequate at all locations. Greater cover crop biomass was obtained across all locations in 2022 (7720 lb/A) as compared to 2021 (5878 lb/A). In regards to locations, cover crop biomass was least at EVS (4102 lb/A) as compared to GCREC (8074 lb/A) and WREC (8216 lb/A). Overall, presence or absence of a cover crop failed to consistently reduce CLRDV incidence or affect yield or fiber quality. Stalk management treatment had no effect on yield in 5 of 6 site years. Fiber quality results showed minimal differences among treatments. CLRDV was confirmed at all locations in both years through PCR testing. August sample results from GCREC in 2021 indicated extremely low virus incidence, and thus, re-sampling for CLRDV and PCR testing was initiated after harvest at all locations in November. From the August to November sampling dates, incidence of CLRDV increased 2 to almost 12-fold, with an average of 309% increase over the 6 site locations. Even though significant main effects and few interactions were observed within the recorded data, results suggest that imposed treatments lacked a consistent effect on CLRDV incidence, cotton yield, or fiber quality. However, it was especially noteworthy that CLRDV sampling dates (August and November), revealed dramatic differences in detectable virus incidence, and the high level of virus present in November indicated prevalence of the virus across the region. More research is needed in order to determine ways to mitigate CLRDV incidence in cotton.