School of Ecosystem and Forest Sciences, Faculty of Science, The University of Melbourne, 500 Yarra Boulevard, Richmond 3121, Victoria, Australia.
School of Ecosystem and Forest Sciences, Faculty of Science, The University of Melbourne, 500 Yarra Boulevard, Richmond 3121, Victoria, Australia.
Sci Total Environ. 2020 Feb 25;705:135856. doi: 10.1016/j.scitotenv.2019.135856. Epub 2019 Dec 2.
Soil water limitations often restrict plant growth in unirrigated agricultural, forestry and urban systems. Biochar amendment to soils can increase water retention, but not all of this additional water is necessarily available to plants. Differences in the effectiveness of biochar in ameliorating soil water limitations may be a result of differences in feedstock cell structure. Previous research has shown that feedstock cell structure influences the pore structure of biochar and consequently the volume available for water storage. The availability of this water for plant uptake will be determined by biochar pore diameters, given its role in determining capillary forces which plants must overcome to access pore water. Therefore, we hypothesized that differences in hardwood feedstock cell structure would result in differences in the plant available water holding capacity of biochar. Before pyrolysis, we measured the wood morphology of 18 Eucalyptus species on three replicates of equal age on a gradient of wood density (572-960 kg m). Wood samples were then pyrolysed (550 °C) and the resulting biochars were sieved and their particle size distribution was standardised before their physical properties, including water holding capacity, plant available water and bulk density were measured. Our results show that biochar made from lower density eucalypt wood had up to 35% greater water holding capacity and up to 45% greater plant available water than biochar made from higher density eucalypt wood. Further, feedstock wood density related well to fibre cell wall thickness and fibre lumen diameter. Therefore, wood density could be used as a proxy for wood cell structure, which can in turn be used to predict plant available water in biochar. The simple measure of feedstock wood density can inform feedstock choices for producing biochars with greater plant available water, optimal for the use as soil amendment in water limited environments.
土壤水分限制常常限制了无灌溉农业、林业和城市系统中植物的生长。向土壤中添加生物炭可以增加水分保持力，但并非所有这些额外的水分都一定可供植物利用。生物炭在缓解土壤水分限制方面的有效性差异可能是由于原料细胞结构的差异造成的。先前的研究表明，原料细胞结构会影响生物炭的孔结构，进而影响可用于储水的体积。由于其在确定植物必须克服以获取孔水的毛细力方面的作用，因此这种水的可用性将取决于生物炭的孔径。因此，我们假设硬木原料细胞结构的差异将导致生物炭的植物可用水分保持能力的差异。在热解之前，我们在三个相同年龄的桉树物种的复制品上测量了 18 种桉树的木材形态，其木材密度梯度为 572-960kg/m³。然后对木材样本进行热解（550°C），并将所得生物炭过筛，使其粒径分布标准化，然后测量其物理性质，包括持水能力、植物可用水和体积密度。我们的结果表明，由低密度桉树木材制成的生物炭的持水能力比由高密度桉树木材制成的生物炭高 35%，植物可用水高 45%。此外，原料木材密度与纤维细胞壁厚度和纤维腔直径密切相关。因此，木材密度可以用作木材细胞结构的替代物，而木材细胞结构又可以用来预测生物炭中的植物可用水。简单地测量原料木材密度可以为生产具有更大植物可用水的生物炭的原料选择提供信息，这对于在缺水环境中作为土壤改良剂使用非常重要。
