Abstract:

This experiment investigated water and soil conservation functions of hybrid sorghum grass. Changes in soil scourability resistance were measured at different growth stages through the growing season， in order to clarify the role of the root system in promoting soil stability. A stand of the hybrid sorghum grass Chuannong Liangcao No.1 （CL1） was used in this experiment and soil samples were collected at three positions 0-15 cm， 15-30 cm and 30-45 cm distant from individual plant bases in both the horizontal （H） and vertical （V） directions. The seasonal changes in sediment content of runoff at different crop growth stages were studied using an undisturbed soil scouring method and a soil anti scour index calculated in each case. In conjunction with these measurements a WinRHIZO2000 root analysis system was used to obtain root length， root surface area， root volume and average root diameter data in order to explore the effect of roots on soil scourability resistance at various stages during the growth period of CL1. It was found that： 1） The runoff sediment content and soil anti-scourability index of CL1 have different horizontal and vertical directional trends. In the horizontal direction the runoff sediment content was H_0-15 （0.10 g·L^-1）<H_15-30 （0.14 g·L^-1）<H_30-45 （0.17 g·L^-1）， while in the vertical direction values were V_15-30 （0.08 g·L^-1）<V_0-15 （0.10 g·L^-1）<V_30-45 （0.14 g·L^-1）. The soil anti-scourability index was negatively correlated with the runoff sediment content in the horizontal direction， but there was no significant correlation in the vertical direction. Specifically， values were： V_15-30 （152.09 min·g^-1）>V_30-45 （118.74 min·g^-1）>V_0-15 （95.65 min·g^-1）. 2） As the growing season progressed， the relationship between the runoff sediment content of CL1 was as follows： heading and maturity stage （0.05 g·L^-1）<prophase of jointing stage （0.11 g·L^-1）<seedling stage （0.14 g·L^-1）<late jointing stage （0.17 g·L^-1） and heading， and the relationship between its soil anti-scourability index was as follows： maturity stage （233.30 min·g^-1）>prophase of jointing stage （56.64 min·g^-1）>late jointing stage （51.30 min·g^-1）>seedling stage （44.33 min·g^-1）. 3） During the growth period of CL1， the enhanced soil anti-scourability value ranged from 1.10-364.52 min·g^-1， with the enhancement rate being between 2.29%-462.27%. The increase in root parameters ranged from 2.87%-326.87%， and was positively correlated with the enhancement of soil scourability resistance. In summary， during the growth period of CL1， the soil scourability resistance was significantly improved in both horizontal and vertical directions， and it was closely related to the root radiation growth at various growth stages. The implementation of daily management and protection measures during the planting stage could be adjusted for further enhancement of water and soil conservation.

Key words: soil erosion, scourability resistance index, runoff sediment concentration, root characteristics, hybrid sorghum grass