Phosphorus and nitrogen in the soil interface between two plant residues differing in C/nutrient ratio: A short-term laboratory incubation study

Abstract

In studies on the effects of mixing residues with different properties on decomposition rate and nutrient release, the extent of contact between the different residues is not known. In this study, we used an experimental design where crop residues were spatially separated by a layer of soil. Microcosms were set up using young faba bean residue (low carbon (C)/nutrient ratio, L) and mature barley straw (high C/nutrient ratio, H). The microcosms comprised of two caps of PVC tubes, each filled with moist soil. Between the two caps, there were three layers each separated from the others by fine nylon mesh with the middle layer being the moist interface soil. Microcosms had similar (H/H or L/L) or different (L/H) residue types, or only residue type (H/S or L/S) while the other cap had no residue. In treatments with only one residue, measured parameters, except microbial biomass P (MBP), were higher in L/S than H/S. In treatments with two residues, all parameters were lowest in H/H. In L/H compared to L/L after 14 days, available P and microbial biomass N (MBN) were lower, available N was similar and MBP was higher. After 28 days, available P and N were lower in L/H than L/L, but MBP and MBN did not differ. In L/H, measured resin P, MBP and MBN were higher than expected whereas available N was lower. The experimental design used in this study allows assessing the effect of residues on properties of the soil between them.