THE INFLUENCE OF ROLLED EROSION CONTROL-SYSTEMS ON SOIL-MOISTURE CONTENT AND BIOMASS PRODUCTION - PART II - A GREENHOUSE EXPERIMENT

A controlled greenhouse experiment conducted under high shortwave radi ation flux explored the relationship between seven rolled erosion cont rol systems (RECS) and a bare control treatment on soil moisture conte nt (SMC), ryegrass yield, and ryegrass nutrient assimilation. All RECS conserved more moisture in the soil profile than the bare treatment. But, differences between RECS occurred. Geojute was the poorest perfor mer, with mean SMC values commonly 18-30 per cent lower than the other RECS studied; and under drought-induced conditions SMC values were up 22-45 per cent lower than the other systems. Ryegrass yields varied w ith surface cover, with statistical testing indicating that the bare G eojute(R) and P300(R) treatments were not significantly different. How ever, the remaining RECS (Futerra(R), BioD-Mat(TM) 70(R) C125(R), SC15 0BN(R) and Curlexo(R) I) had significantly higher ryegrass yields, wit h Curler I(R) being 25 per cent higher than its nearest competitor, SC 150BN(R). Ryegrass nutrient concentrations of nitrogen and sulfur were generally similar between rolled erosion control treatments, and no m easured macronutrient was considered to be deficient. This information coupled with correlation analysis indicated that the soil thermal reg ime was the most important limiting factor on biomass production. Addi tionally, of all variables examined by stepwise regression (microclima te and cardinal properties of RECS) only surface albedo (shortwave ref lectivity) was significantly related with ryegrass yield. Closer atten tion needs to be given to the three-dimensionality of rolled erosion c ontrol fibers, and their radiative properties if designers are interes ted in maximizing biomass production from slopes covered by RECS in su btropical/tropical and semiarid environments. (C) 1998 John Wiley & So ns, Ltd.