Influence of soil water content on growth and panicle production of fall panicum (Panicum dichotomiflorum)

Abstract

Fall panicum is a problematic weed in cropping systems including rice in southern Florida. There is limited information on growth and reproductive ability of fall panicum in water-stressed environments. The objective of this study was to determine the effect of 12.5, 25, 50, 75, and 100% pot soil water content (SWC) levels on fall panicum growth and panicle branch production under greenhouse conditions. Fall panicum height, number of leaves and tillers decreased over time as SWC decreased. Fall panicum height decreased by 65 and 50% at 12.5 and 25% SWC, respectively relative to height achieved at 100% SWC. Plants at 50 to 100% SWC were able to achieve 50% tiller production within 31 to 43 days compared with 28 days at 25% SWC. The 50% tiller production was not reached at 12.5% SWC during the duration of the study. Fall panicum shoot and root biomass, total leaf area, and number of panicle branches plant-1 at 56 days after SWC treatment initiation decreased as SWC decreased. Fall panicum biomass decreased 83 to 85 and 66 to 68% at 12.5 and 25% SWC, respectively relative to 100% SWC. Leaf area declined 79 and 65% at 12.5 and 25% SWC levels, respectively compared to the 100% SWC. Fall panicum was able to produce panicles at all SWC levels although the number of panicle branches were significantly lower as SWC decreased. Plants at 12.5 and 25% SWC produced 82 and 59% less panicle branches, respectively compared with plants at 100% SWC. This study shows that SWC influences the growth and reproductive capacity of fall panicum. Although fall panicum did not reach its full growth potential at low SWC levels, it was able to survive and develop panicles showing its ability to adopt and reproduce under dry conditions.