Sapindus mukorossi is a native tree in southern China that has multiple useful functions, including high landscaping, ecological, esthetic, and economic values. More importantly, its fruits are being rapidly developed as raw materials for bioenergy and saponin production in southern China. To provide a standardized phenological description of the species, this study firstly used the BBCH (Biologische Bundesanstalt, Bundessortenamt und CHemische Industrie) scale. In total, eight principal stages—i.e., bud, leaf and shoot development, inflorescence emergence, flowering, fruit development, fruit maturity, senescence and beginning of dormancy—and 58 secondary stages were described. It ranges from vegetative bud dormancy to the onset of the next beginning of the dormancy, using a two-digit numerical coding system. In addition to the descriptions, we provide photographic images of some major developmental stages to standardize morphological characteristics and the phenological observation of S. mukorossi. This study will be an asset for biological researches and cultivation management in Sapindus, and will provide valuable information for other fruit trees.

Inappropriate fertilization management practices have led to low timber production in intensive plantation systems in China. Thus, optimized conventional or advanced fertilization management practices are needed. We aimed to quantify whether optimized furrow fertilization (FF) is comparable to advanced drip fertigation (DF) and to make recommendations regarding fertilization management strategies for poplar plantations. A completely randomized block design experiment with two fertilization methods (DF and FF) and four N application amounts (F₀: 0, F₁: 68, F₂: 113, and F₃: 158 kg N·ha⁻¹·yr⁻¹) was carried out on a Populus × euramericana cv. ‘Guariento’ plantation. Fine root biomass density (FRBD), fine root length density (FRLD), specific root length (SRL), soil total nitrogen (STN), soil inorganic nitrogen (SIN), soil ammonium (NH₄⁺-N) and nitrate nitrogen (NO₃⁻-N) were measured. The productivity increment was calculated based on tree surveys. The results showed that FRBD and FRLD decreased with the soil depth, and more than 86% was distributed within the 40 cm soil depth. FRBD, FRLD, productivity increment and soil N increased with an increasing amount of N application. DF treatments achieved 117%, 94% and 10% higher FRBD, FRLD and productivity increments, respectively, than did FF treatments. The averages of STN, SIN, NH₄⁺-N and NO₃⁻-N under FF were higher than those under DF, leading to higher concentrations of residual NO₃⁻-N in deep soil. Beneficial management practices for fine root growth were evaluated in the following order: water coupled with N > only N ≥ only water > control. FRBD was positively correlated with the productivity increment. Therefore, fine root extension to increase soil resource absorption yields greater productivity under DF treatments. Drip fertilization is recommended as a better fertilization method to greatly promote the growth of fine roots, as well as productivity and residual lower soil N for poplar plantations.