Decomposition of seawater-irrigated halophytes : implications for potential carbon storage

Abstract

Seawater-irrigated halophytes are a non-traditional crop that may serve to offset anthropogenic carbon dioxide emissions through long-term carbon storage. To assess the feasibility of storing carbon as cultivated halophyte residues in coastal desert soils, the decay rate, microbial activity and microbial decomposer abundance of post-harvest residues were investigated for three potential halophyte crops. Decay rates were determined by measuring weight loss from residues in litterbags in both the field and laboratory. The effect of incorporating residues into the soil was examined by locating litterbags both on and below the soil surface. Microbial decomposition activity was measured as the CO2 efflux from residue amended soil columns in the greenhouse. The abundance of bacteria, fungi, and nematodes was assessed in decomposing residues using litterbags in the field. The three halophytes decomposed at rates similar to those of conventional, non-saline residues (0.20–0.30% d-1) whether placed on the surface or buried at 30 cm. Residue type affected microbial activity in soil columns during the first 21 days, but decomposition was similar for the three halophytes thereafter. Residue type affected the abundance of nematodes, but not of bacterial and fungal decomposers. Because the rate of halophyte residue decay and the number of microbial decomposers associated with the residues are similar to those of fresh water systems, there appears to be no advantage in storing carbon as plant residue in this saline agricultural system.