Effects of brewer’s spent grain biochar on the growth and quality of leaf lettuce (Lactuca sativa L. var. crispa.)

Abstract

The need for organic soil amendments is increasing in the Republic of Korea against the backdrop of increased soil acidification and nutrient losses. The pyrolysis of biomass produces biochar which not only increases soil productivity but also provides environmental benefits through carbon sequestration. The portion of the brewer’s spent grain (BSG) recycled is by far less than the amount generated, but pyrolysis can help to reverse this trend by turning BSG waste into a valuable soil amendment. The current study, therefore, evaluated the effects of brewer’s spent grain biochar (BBXXX) produced at three different temperatures of 300 °C, 500 °C and 700 °C on the yield and quality characteristics of the leaf lettuce as well as the effects on soil chemical properties through a pot experiment. Each of the BBXXX and BSG were added to the soil at two rates of 2% and 5% by weight. The pH and carbon content of the BBxxx increased with increasing pyrolysis temperatures and the trend was replicated in the soil upon biochar application i.e. the soil pH and carbon content increased alongside temperatures at which biochar was pyrolyzed. On the other hand, however, the soil electrical conductivity (EC) diminished with the increasing pyrolysis temperatures of the biochar applied. With regards to crop growth, the BB500 5% amendment produced the highest marketable yield of the leaf lettuce and while the lettuce grown on the control produced leaf lettuce with the lowest content of nitrate nitrogen, BB500 5% amendment generally produced the highest quality lettuce. The results indicate that BB500 performed agronomically better than the rest of the amendments and is thus recommended as an effective BSG recycling measure.