Effects of Straw and Biochar Amendments on Grassland Productivity and Root Morphology

Abstract

The objective of this research was to determine the effect of straw and biochar amendment on the root system morphology and aboveground biomass of a red clover/grass mixture (Lolium. perenne L., Phleum pratense L., Festuca pratensis Huds., F. arundinacea Schreb., L. multiflorum L., L. westerwoldicum Breakw., Trifolium pratense L.). A grassland experiment was conducted from 2014 to 2018. Straw was collected from miscanthus (Miscanthus × giganteus), winter wheat (Triticum aestivum L.), and biochar was produced from the biomass of those species. The following treatments were applied: wheat straw at a rate of 5 t ha−1 (WS), miscanthus straw at a rate of 5 t ha−1 (MS), wheat biochar at a rate of 5 t ha−1 (WBH), wheat biochar at a rate of 2.25 t ha−1 (WBL), miscanthus biochar at a rate of 5 t ha−1 (MBH), and miscanthus biochar at a rate of 2.25 t ha−1 (MBL). A treatment with mineral fertilizer but without organic amendments (MCTR) was used, and a control treatment (CTR) without mineral fertilizer and without any amendments was also tested. The botanical composition and the aboveground yields were determined. The roots were sampled in 2018, and the root morphology parameters were determined using an image analysis system. The applied soil amendments resulted in increased root lengths, surface areas, volumes, and mean root diameters. There were no differences between the treatments with different feedstock types (miscanthus vs. wheat), materials (straw vs. biochar), or amendment rates (5 vs. 2.25 t ha−1). The resulting root system characteristics were reflected in the aboveground biomass productivity. The soil amendments, i.e., the straw and biochar, significantly increased the productivity in comparison to that of the control treatment. However, these differences were noticed only during the first and second cuts. Recommended practice in grassland management is to improve soil with straw. The conversion of straw into biochar does not provide a better effect on grassland productivity.