An in vitro perfusion method to estimate rates of plant residue breakdown and associated nutrient release

Abstract

Procedures are required to screen leaf litter and crop residues to estimate breakdown rates and to examine the effects of chemical treatment or soil biota on decomposition rates. A simple, cheap and effective apparatus has been developed, utilizing a hospital drip bag and administration set, and the results from this apparatus compared with those from a more elaborate glass apparatus. The C release rate and total C release from barrel medic (Medicago truncatula) hay were found to be the same from both systems over 42 days. The UNE (University of New England) in vitro perfusion apparatus is cheap enough to make and simple enough to operate for sufficient sets to be run to allow statistically valid comparisons between residues or residue treatments. The C and nutrient release from wheat straw, chickpea trash, barrel medic hay and two tree legumes, Flemingia macrophylla and Albizia chinensis, were studied over 84 days. Carbon release was highest from chickpea and medic. Carbon release from Albizia was lower than from medic despite it having a lower C:N ratio. Nutrient release rate differed between nutrients and between the residues.