Permanent grassland hay-derived biochar increases plant N, P and K uptake on an acidic soil

Abstract

The importance of permanent grasslands in the feed production has decreased in Estonia in the last decades, because of the low feeding value of the biomass. Therefore, there is a need for new solutions for utilization of this biomass. One way of giving value to this resource would be its application in the production of biochar (BC) and its subsequent use for increasing the carbon (C) and nutrient concentration of previously low-fertility soils. This study examined (i) the properties of biochar produced from permanent grassland hay at three (300°C, 550°C and 850°C) pyrolysis temperatures and (ii) the impact of biochar on the uptake of N, P, K, Ca and Mg and the biomass yield of perennial ryegrass (Lolium perenne L.) on a strongly acidic (pH 4.2) soil. It was found that the permanent grassland hay dominated by reed canary grass (Phalaris arundinacea L.) is a suitable raw material for biochar production. This biochar is a potassium (K) rich fast-acting liming agent, which also contains a remarkable amount of N. The addition of this biochar into acidic soil reduces soil acidity and significantly increases plant uptake of N, P and K, which has a short term positive impact on biomass yield. The increase of pyrolysis temperature changes biochar properties like neutralization capacity, acidity (pH), nutrient concentration and the release of nutrients from biochar, but these changes do not have a significant impact on the effect the biochar has on plant nutrition and yield. The only exception was phosphorus (P) uptake, which was the highest when the biochar was produced at 550°C temperature.