Soil and vegetation responses to sewage sludge on a degraded semiarid broom snakeweed/blue grama plant community

Abstract

Three rates of dried sewage sludge (22.5, 45.0, and 90.0 Mg (megagrams) ha-1), were applied to a degraded semiarid grassland site on the Upper Rio Puerto Watershed in west-central New Mexico. Various soil and plant parameters were determined over 4 growing seasons. Most soil macronutrients, such as nitrogen (N), phosphorus (P), and potassium (K), and micronutrients, such as copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), increased linearly with increasing sludge amendment rates. Heavy metals (cadium (Cd) and lead (Pb)) did not change as a result of sludge amendment in the first 3 growing seasons. However, concentrations of soil Cu, Mn, and Cd were just above maximum acceptable standards in the heaviest sludge treatment after 4 growing seasons. Plant density, specks richness, and diversity all decreased with increasing sludge rates. However, total plant foliar cover and herbaceous yields increased significantly with the application of sludge. Blue grama (Bouteloua gracilis (H.B.K.) Lag.) cover and yields, in particular, increased 2 to 3 fold over the control as a result of sludge amendment, whereas broom snakeweed (Gutierrezia sarothrae (Pursh) Britt. + Rusby) density decreased over 4 growing seasons. The most favorable soil and vegetation results were from the 22.5 and the 45 Mg ha-1 sludge application rate.