Fertilisation Effects on Edaphic Properties in Different Soil Types in Relation to <i>Castanopsis sieboldii</i> Sapling Growth

Abstract Background Urban soils often have low-nutrient levels, reduced biota, and frequently depauperate humus. Castanopsis sieboldii trees planted in cities may grow poorly in some areas. This study investigated the effects of soil chemical and biological properties on C. sieboldii growth. Methods Individual and compound impacts of N (nitrogen), P (phosphorus), K (potassium), and Ca (calcium) on saplings grown in humic topsoil, humic subsoil, and river sand were investigated. Results Addition of N alone and combined with P, K, and Ca affected C. sieboldii growth in humic topsoil and subsoil. Applications of N alone, in river sand with low levels of available nutrients, had no impact. However, combined nutrients such as N with P, K, and Ca increased shoot and root dry weights, number of leaves, and soil and plant analyser development (SPAD). Additionally, NPCa and NPK resulted in higher values than individual N for dry weights of shoots and roots as well as for shoot dry weights in river sand. NPKCa application resulted in increased diameter at the base of the first branch in humic topsoil over N alone. NPK produced more leaves in humic subsoil than just N. Moreover, C. sieboldii produced the greatest growth in humic topsoil, followed by humic subsoil, and finally unfertilised river sand. Conclusions Nitrogen application with additional P, K, and Ca was beneficial to growth under test conditions. Castanopsis sieboldi growth was enhanced under field conditions with humic topsoil and combined nutrients. Low available P, K, and Ca may be limiting factors restricting performance impacts of N when added alone to low-nutrient soils.