Abstract:

Sandy soils have low clay content, low organic matter content, and high macro-porosity, which can easily lead to soil water leakage and water wastage. Straw resources are abundant in China. Biochar produced by crop straw can be used as an excellent soil conditioner to improve soil water holding capacity. To investigate the effect of biochar prepared by maize straw on soil porosity and water holding capacity, 8 biochar application treatments were set up at 0%, 1%, 2%, 3%, 4%, 6%, 8%, and 10% based on the mass fraction (dry mass) of the biochar and tested soil. The treatments were denoted as CK, 1BC, 2BC, 3BC, 4BC, 6BC, 8BC, and 10BC, respectively. The water characteristic curve was measured by the centrifuge method, and soil water holding capacity and porosity were calculated to investigate the effects of different amounts of biochar on soil particle density and available moisture. The results showed that the soil particle density decreased with the increase of the biochar amount. In the 10BC treatment, the soil particle density decreased to 2.53 g∙cm^-3 and was 5.6% lower than that of the CK treatment. In the 2BC treatment, the soil aeration pores ≥50 μm decreased, and the pores <20 μm and 20-50 μm increased, compared to that in the CK treatment. There were no significant differences in pore distribution between the CK and other treatments. Soil field capacity, wilting water content, and available water content increased with the increase of the biochar amount. Compared to the CK treatment, the soil field capacities increased by 14%, 26%, 39%, 59%, 83%, and 103% in the 2BC, 3BC, 4BC, 6BC, 8BC, and 10BC treatments, respectively. The effective soil water contents increased by 17%, 67%, 100%, 133%, and 150% in the 2BC, 4BC, 6BC, 8BC, and 10BC treatments, respectively, compared to the CK treatment. Therefore, biochar of maize straw can increase the water-holding capacity of sandy soil, improve the water-holding pore distribution of sandy soil, and reduce macropore distribution of sandy soil. In addition, the application amount of biochar should be more than 2% to gain significant results. The economic investment and return of the large-scale application of biochar also need to be considered. The application of biochar of maize straw can be regarded as a good measure to improve sandy soil.

Key words: biochar, sandy soil, soil pores, effective water, centrifuge method

摘要：

砂土中土壤黏粒含量少,有机质含量低,大孔隙度较多,土壤水分容易渗漏,易造成水资源浪费。中国秸秆资源丰富,利用作物秸秆生产的生物炭作为土壤改良剂,可以改善土壤的持水特性。为探究玉米秸秆制备的生物炭施入砂土中对土壤孔隙和持水性的影响,将玉米秸秆生物炭和供试土壤分别按照0、1%、2%、3%、4%、6%、8%和10%的质量比（以干质量计）均匀混合,设置了8个生物炭施用量处理,分别记为CK、1BC、2BC、3BC、4BC、6BC、8BC和10BC,每个处理3次重复。利用比重法测定土粒密度,离心机法测定水分特征曲线,并计算土壤持水性和孔隙度。结果表明,土粒密度随着生物炭用量的增加而降低,在10BC处理中土粒密度降到2.53 g∙cm^-3,相比CK降低了5.6%;在2BC处理中,≥50 μm的土壤通气孔隙减少,<20 μm和20—50 μm的孔隙显著增加;其他处理的孔隙分布与CK处理之间无显著差异;土壤田间持水量、萎蔫含水量和有效含水量随生物炭用量增加而增加,2BC、3BC、4BC、6BC、8BC和10BC分别使土壤田间持水量增加了14%、26%、39%、59%、83%和103%;与CK相比,2BC、4BC、6BC、8BC和10BC使土壤有效含水量分别增加了17%、67%、100%、133%和150%。因此,秸秆生物炭可以提高砂土持水能力,提高砂土持水孔隙分布,减少大孔隙分布,且当生物炭施用量≥2%才有显著效果;同时也要考虑大量施用生物炭的经济投入和回报。施用秸秆生物炭是改良砂土持水性的一种良好的措施。

关键词: 生物炭, 砂土, 孔隙分布, 有效水, 离心机法