A study on root system development ability of alfalfa cultivars with different fall dormancy rates in the Guizhou area

The abilities of different fall-dormancy alfalfa cultivars to develop root systems were studied in the Guizhou area to analyze their adaptabilities.Root neck diameter initially decreased but then increased as the fall dormancy rate increased.Root neck diameter of UC-1887(FD10) was the largest(1.439 cm).Taproot length initially increased,then decreased with Pierce(FD8) having the longest taproots(59.75 cm).The number of secondary roots gradually,decreased:Vernal(FD2) had the most(19.33),and Pierce(FD8) the fewest(12.25).Taproot diameter,taproot volume,taproot biomass,lateral root volume,lateral root biomass,root system volume,and root system biomass tended to increase as the fall dormancy rate increased.First year underground root systems grew mainly in the 0-20 cm depth zone.The proportions of root system volume were 77.82%-92.35% and root system biomass rates were 75.14%-90.96%.Based on the integrated performance and cluster analysis of alfalfa with different fall dormancy rates,the fall dormancy rates of alfalfa with the greatest root system development ability ranged from 7 to 10.