Efficacy of roots and shoots of napier and lemon grasses to control runoff and sediment outflow under simulated rainfall and overland flow conditions
Loading...
Date
2021-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
In this study, extensive laboratory experiments were conducted under controlled environment of a laboratory with simulated rainfall and overland flow conditions using a soil filled hydraulic tilting flume as test plot. As per mandate of this study, the effects of root and shoot characteristics of Napier grass and Lemon grass on runoff and sediment outflow at different growth stages with four simulated rainfall intensities of 4.0 cm/h, 6.5 cm/h, 8.3 cm/h and 9.4 cm/h and four overland flow rates of 6.6 l/s/m, 9.0 l/s/m, 10.7 l/s/m and 12.4 l/s/m to observe runoff and sediment outflow at three land slopes of 1%, 2%, and 3% were observed. After each experiment, different morphological characteristics such as Leaf Area Index (LAI), Shoot Length (SL), Number of Leaves (NL), Number of Tillers (NT), Shoot Biomass (SB), Root Density (RD), Root Length (RL), Root Biomass (RB), and Total Biomass (TB) of grasses were measured at Stage-I (90DAP), Stage-II (120DAP) and Stage-III (150DAP) for both crops. Runoff samples were collected for whole plant plot and root plot for various combinations of input variables and in total 936 runoff samples were collected and analyzed to determine sediment concentration and sediment outflow rate. The analysis of findings revealed that Napier grass and Lemon grass were very effective to reduce runoff and sediment outflow and their efficacy increased with the extended growth stage. The reduction in runoff and sediment outflow at stage-I, i.e. 90 DAP, was approximately 56% and 85% for Napier grass, and 52% and 82% respectively for Lemon grass. At stage-II, i.e., 120 DAP, the reduction in runoff and sediment outflow was approximately 68% and 90% for Napier grass, and 59% and 87% respectively for Lemon grass while at stage-III, i.e., 150 DAP, it was observed as 74% and 96% for Napier grass, and 69% and 94% respectively for Lemon grass as compared to bare plot under simulated rainfall conditions.The sediment outflow rate reduction from roots was 9%, 17% and 33% more than the shoots at 90 DAP, 120 DAP and 150 DAP respectively under over land flow conditions. Napier grass with its higher values of above-ground biomass parameters (shoots) and below ground bio mass parameters (roots) as compared to Lemon grass was found to be more effective to reduce runoff and sediment outflow. It was also observed that the contribution of shoots in runoff rate reduction was higher than the roots and maximum reduction was observed at low rainfall intensity. Similarly, root part of the plant has more contribution in sediment outflow rate reduction as compared to shoot part of the plant. The relative contribution of the roots of Napier grass in sediment outflow reduction varied from 61% to 78%, and contribution of shoots was found to be 22-39%. On the other hand, for Lemon grass, the relative contribution of roots in sediment outflow reduction varied from 59% to 78%, and contribution of shoots varied in the range of 22% to 41% under selected rainfall intensities, land slopes and growth stages as compared to whole plant. Mathematical models were established and for runoff and sediment outflow in terms of root and
shoot parameters. Developed models were found to be very satisfactory based on the values of various performance indicators.