Compost effect on water retention and native plant establishment on a construction embankment

ABSTRACT:

Compost amendment of soil provides benefits that are well documented for agricultural soils, but not for disturbed soils in urban environments. The objective of this study was to determine if yard-waste compost increased soil moisture and native plant establishment along a construction embankment (cut slope with mean of six percent) in Altoona, Iowa. Compost was surface applied or incorporated at the beginning of the study period at a rate of 143.1 Mg dry matter ha⁻¹ (63.8 t ac⁻¹) and compared to a control that received no compost. Plant community composition shifted during the three-year study period from annual grass- (primarily foxtail, Setaria sp.) and forb-dominated communities to perennial communities. After three years, species composition was similar, although species density was greater in compost treatments compared to the control at the upper slope (10.9 vs. 6.3 species m⁻²). Shoot biomass was greater in compost treatments compared to the control (395 vs. 154 g m⁻²; 0.86 vs. 0.32 lb 10.76 ft⁻²). Following significant rainfall (greater than 2 cm or 0.79 in), water storage (0 to 15 cm; 0 to 6 in depth) was greatest when compost was incorporated (5.7 cm; 2.2 in), but surface application also resulted in greater moisture (5.4 cm; 2.1 in) than the control (5.0 cm; 2 in). While treatment effects on soil moisture (p less than 0.05) occurred following rain, slope-position effects only occurred under dry conditions. Surface applying or incorporating yard-waste compost to construction embankments can increase water retention after rainfall and increase plant growth.