Agronomic values of greenwaste biochar as a soil amendment

TLDR

The study examined how biochar derived from greenwaste affects radish yield and soil quality in an Alfisol. A pot experiment applied biochar at 10, 50, and 100 t ha⁻¹, with or without 100 kg N ha⁻¹, to a hard‑setting Alfisol. Biochar alone did not raise yield, but when combined with nitrogen, higher biochar rates increased radish dry matter by 95–266 % and improved soil pH, organic carbon, cations, tensile strength, and field capacity, though a slight yield drop occurred at 10 t ha⁻¹.

Abstract

A pot trial was carried out to investigate the effect of biochar produced from greenwaste by pyrolysis on the yield of radish (Raphanus sativus var. Long Scarlet) and the soil quality of an Alfisol. Three rates of biochar (10, 50 and 100 t/ha) with and without additional nitrogen application (100 kg N/ha) were investigated. The soil used in the pot trial was a hardsetting Alfisol (Chromosol) (0–0.1 m) with a long history of cropping. In the absence of N fertiliser, application of biochar to the soil did not increase radish yield even at the highest rate of 100 t/ha. However, a significant biochar × nitrogen fertiliser interaction was observed, in that higher yield increases were observed with increasing rates of biochar application in the presence of N fertiliser, highlighting the role of biochar in improving N fertiliser use efficiency of the plant. For example, additional increase in DM of radish in the presence of N fertiliser varied from 95% in the nil biochar control to 266% in the 100 t/ha biochar-amended soils. A slight but significant reduction in dry matter production of radish was observed when biochar was applied at 10 t/ha but the cause is unclear and requires further investigation. Significant changes in soil quality including increases in pH, organic carbon, and exchangeable cations as well as reduction in tensile strength were observed at higher rates of biochar application (>50 t/ha). Particularly interesting are the improvements in soil physical properties of this hardsetting soil in terms of reduction in tensile strength and increases in field capacity.