Compost Tea Effects on Production and Extraction of Nitrogen in Ryegrass Cultivated on Soil Amended With Commercial Compost

Abstract

A ryegrass fertilization pot experiment was carried out with volcanic soil of central Chile during the 2009-10 season using two commercial composts (Vitafert and Biostabilized Swine Manure) and conventional fertilization with total nitrogen doses of 135 mg kg⁻¹. We successively applied compost tea prepared with Vitafert compost and set up eight treatments: control without fertilization (C), control with compost tea in each irrigation (C1), control with compost tea every second irrigation (C2), conventional fertilization (CF), biostabilized swine manure without compost tea (B1), biostabilized swine manure with compost tea in each irrigation (B2), Vitafert without compost tea (V1), and Vitafert with compost tea in each irrigation (V2). The crop was established in Dec. 2009 and maintained until May 2010; four cuttings were carried out at 5 cm aboveground on plants averaging a 20-cm height. Dry matter (DM) production and N concentration was determined in each cutting. Relative DM production, total and for each cutting, N extraction, as well as apparent efficiency of N recovery (AENR) in the fertilized treatments were determined. Results indicated that the highest total DM production was obtained with CF, B1, and B2; and it was mainly concentrated in the first cutting. Adding compost tea to the soil without fertilization did not affect DM production when compared to the control, but it had a positive effect on the treatments with commercial composts. The highest extraction of total accumulated N was obtained with CF and B2. The highest AENR in the fertilized treatments was achieved in CF (69%), B1 (54%), and B2 (68%). Results indicate that there is a positive effect of compost tea when relatively soluble carbon sources, such as nutrient amendments, are used before. In turn, using compost tea in unamended soil had no effect on the evaluated parameters.