| Abstract: | Aims : The aim of this study was to explore interactive effects between quality (types) and quantity (application rates) of biochar as well as of arbuscular mycorrhiza (AM) symbiosis on the growth of potato plants. Methods : A low P sandy loam soil was amended with 0%, 1.5%, or 2.5% (w/w) of either of 4 types of biochar, which were produced from wheat straw pellets (WSP) or miscanthus straw pellets (MSP) pyrolyzed at temperatures of either 550°C or 700°C. Potato plants grown in pots containing the soils or soil biochar mixture were inoculated with or without AM fungus (AMF), Rhizophagus irregularis. The experiment was carried out under fully irrigated semi‐field conditions and plants were harvested 101 days after planting. Results : Application of high temperature biochar decreased growth, biomass and tuber yield of potato plants, while the low temperature biochar had a similar effect on yield as plants grown without biochar amendment. Total biomass of potato plants were decreased with the increasing rate of biochar. Arbuscular mycorrhizal fungus inoculation stimulated the growth of potato plants in all organs, increased tuber biomass significantly in 1.5% MSP700 amended plants, and to a lesser degree for WSP700, MSP550, and WSP550. In addition, plant biomass gain was linearly related to N, P, and K uptake, the ratio of P to N in the leaf of plants indicated that all treatments were mainly P‐limited. A multiple linear regression using P uptake and biochar rate as independent variables explained 91% of the variation in total biomass. The single effect of AMF inoculation, type and rate of biochar affected plant N, P and K uptake similarly. While AMF inoculation significantly increased P uptake in potato plants grown in soil with WSP700 or MSP700 despite of the rate of biochar. In general, application of biochar significantly increased AMF root colonization of potato plants. Conclusions : The application of MSP550 at 1.5% combined with AMF stimulated growth of potato the most. Furthermore, the results indicated that the interactive effect of AMF inoculation, biochar type and application rate on potato growth to a large extent could be explained by effects on plant nutrient uptake. |
