为研究氮肥污染对桂林红黏土物理力学性质的影响,使用氨水(NH₃·H₂O)溶液对具有代表性的桂林雁山红黏土进行浸泡,考虑氨水质量分数(0,4.5%,9.0%,13.5%,18.0%)和养护时间(1,7,14 d)双因子因素,通过室内试验,分析氨水污染对桂林雁山红黏土物理力学性质的影响规律。试验结果表明:随着氨水质量分数及养护时间的增加,桂林雁山红黏土的质量、含水率、相对密度和液塑限均增大,压缩模量减小,土体压缩性增强;碱-土作用是引起红黏土物理力学性质发生变化的主要原因,其相互作用导致红黏土颗粒间的胶结物被溶解后又重新生成絮状物,使其原本稳定的结构状态发生改变。

In the aim of exploring the effect of nitrogen fertilizer pollution on the physical and mechanical properties of red clay, the change regularity of typical red clay from Yanshan mountain, Guilin was analyzed. The red clay specimens were immersed in ammonia (NH₃·H₂O) solution with ammonia concentration (0, 4.5%,9.5%, 13.5%, 18%) and curing time (1 d, 7 d, 14 d) as controlling factors. Results show that the mass, moisture content, specific gravity, liquid limit and plastic limit all increased with the increase of ammonia concentration and curing time; but compression modulus decreased, while compressibility of soil is enhanced. The alkali-soil interaction is the fundamental cause of the weakening in physical and mechanical performance of alkali-contaminated red clay in Guilin area. Such interaction results in the dissolution of the binder between red clay particles and the formation of flocculants, hence changing the original stable state of the structure.

近年来，生物炭作为土壤改良剂在降低盐碱土壤盐分、养分流失和改善土壤性质方面具有良好表现。为更好发挥生物炭在盐碱土壤改良方面的应用潜力，选用骨炭（AB）和竹炭（PB）为改良材料，以浙江省台州市重度滨海盐碱土为研究对象，设置4种不同施用量（0、2%、5%、8%，w/w），通过室内土培实验，研究并分析骨炭和竹炭这两种生物炭在不同施用量下对滨海盐碱土壤的理化性质和养分含量的影响效果及可能规律，以筛选最佳处理，为生物炭应用于滨海盐碱土壤改良提供基础科学依据。结果表明，两种生物炭对盐碱土均具有一定的改良效果，（1）随骨炭施用量增加，盐碱土的土壤有机质（SOM）、总氮（TN）、总磷（TP）、碱解氮（AN）和有效磷（AP）含量呈现上升的趋势，添加2%—8%的骨炭，较对照（CK）相比分别提高了43.9%－125%、61.1%－238%、632%－1973%、49.3%－155%和42.9%－89.2%；（2）随竹炭施用量增加，土壤理化性质得到明显改善，添加8%的竹炭时，土壤含水量、孔隙度和阳离子交换量（CEC）较对照（CK）提高了8.37%、1.59%和179%，土壤容重和含盐量降低了6.03%和22.7%，土壤SOM含量显著提升了535%。综上，两种生物炭均能起到改善盐碱土壤结构和提高土壤持水能力、降低土壤盐碱程度并抑制土壤养分流失的作用，其中，骨炭适用于提高盐碱土壤的孔隙结构和养分含量，而竹炭有更强的提升盐碱土壤的理化性质的能力。考虑到经济成本和施用效果，5%施用量的骨炭是进行滨海盐碱土养分含量及有效性的改良的理想选择，5%施用量的竹炭是改良盐碱土壤理化性质的理想选择。

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。

生物炭是生物质在缺氧或低氧环境中经热裂解后产生的富炭固体产物，近年来作为土壤改良剂、肥料缓释载体及碳封存剂等备受关注。本研究采用盆栽试验方法，在喀斯特山地石灰土中施用4种不同比例（生物炭/土壤质量比：1%、2.5%、5%和10%）的3种生物炭（稻壳炭RHB、棉花秸秆炭CSB和木炭WCB），研究了生物炭对喀斯特山地石灰土pH值、毛管持水量、有机质和有效养分含量以及刺槐（Robinia pseudoacacia L.）出苗期（45 d）生长性状和根系参数的影响。结果表明：生物炭处理可促进刺槐苗期根系发育和生长。与对照（CK）相比，RHB_2.5处理刺槐幼苗总根长、总表面积、0～0.6、0.6～1.2、1.2～1.8 mm直径范围内的根长分别显著增加了198%、125%、287%、209%、146%；RHB₅和WCB_2.5处理刺槐幼苗根系活力分别显著提高了36%和32%；CSB₁₀处理刺槐幼苗株高、地径、地上生物量、总生物量分别显著增加了30%、6%、147%、118%；CSB₅处理刺槐幼苗根冠比显著降低了57%。同时，生物炭处理有利于改善石灰土水分与养分供应状况，且随着施用量增加，改良效果不断加强。与CK相比，RHB₁₀、CSB₁₀和WCB₁₀能分别使土壤有机质含量增加25%、195%和68%；碱解氮含量增加49%、105%和45%；有效磷含量增加114%、766%和115%；速效钾含量增加170%、27%和89%；RHB₁和WCB₁₀分别使土壤pH值提高1.22%和1.48%。因此，施用生物炭可改善喀斯特山地石灰土土壤质量，促进刺槐苗期根系发育和生长，对改良喀斯特石灰土和恢复植被具有重要意义。

Biochar is a carbonrich solid material produced by heating biomass in an oxygenlimited environment, which has been widely concerned as a soil conditioner, fertilizer release carrier and carbon (C) storage agent in recent years. In this study, a pot experiment was conducted to investigate the effects of three kinds of biochar (rice husk biochar, RHB; cotton straw biochar, CSB; woodchip biochar, WCB) amended with 1%, 2.5%, 5%, 10% (dry mass basis) on pH, capillary capacity, organic matter and available nutrient concentrations of limestone soil, and the growth traits, root characteristics of Robinia pseudoacacia L. seedlings (45 days old) at a karst site. The results showed that biochar application improved root characteristics and promoted the growth of <em>R. pseudoacacia</em>. Compared with CK, RHB_2.5 significantly accelerated total root length, total root surface area and the root length of 0-0.6, 0.6-1.2, 1.2-1.8 mm in diameter of <em>R. pseudoacacia</em> by 198%, 125%, 287%, 209% and 146%, respectively. RHB₅ and WCB_2.5 significantly increased the root activity by 36% and 32%, respectively. CSB₁₀ increased seedling height, basal diameter, aboveground biomass, and total biomass by Symbol`@@30%, 6%, 147% and 118%, respectively. Root/shoot ratio was decreased significantly by 57% after CSB₅ application. Moreover, biochar application remarkably improved soil water and nutrient availability, and the effects increased with the increase of application rate. Compared with the CK, RHB₁₀, CSB₁₀ and WCB₁₀ increased soil organic matter by 25%, 195% and 68%, available N by 49%, 105% and 45%, available P by 114%, 766% and 115%, and available K by 170%, 27% and 89%, respectively. RHB₁ and WCB_10 increased soil pH by 1.22% and 1.48%, respectively. Therefore, biochar application can improve quality of limestone soil in karst area, and promote root development and growth of <em>R. pseudoacacia</em> seedlings, which is of importance to the improvement of limestone soil and revegetation in karst area.