凹凸棒土添加对土壤蒸发及裂缝特征的影响

水分是限制干旱与半干旱地区植被恢复和农业发展的最重要因素之一,减少土壤水分无效蒸发损失可提高水分利用效率。凹凸棒土(ATP)作为一种黏土矿物,其亲水性和吸附性对限制土壤蒸发具有重要作用。本研究选取黄土高原干旱与半干旱区3种不同质地的典型土壤(黑垆土、黄绵土、风沙土),设置5种ATP添加量(0%、1%、2%、3%、4%),使用微型蒸发器在自然条件下进行土壤蒸发试验,探究ATP添加对不同土壤蒸发过程和蒸发面裂缝特征的影响。结果表明: 当ATP添加量<3%时,在同一种土壤下累积蒸发量与蒸发损失率随ATP添加量的增加而减小;ATP添加量为3%时,黑垆土、风沙土的累积蒸发量和蒸发损失率均减小,黄绵土的累积蒸发量和蒸发损失率增加;ATP添加量为4%时,黑垆土的累积蒸发量减小、蒸发损失率增加,风沙土的累积蒸发量增加、蒸发损失率减小,黄绵土的累积蒸发量和蒸发损失率均减小。不同土壤平均累积蒸发量表现为:黑垆土>黄绵土>风沙土。在同一种土壤的整个蒸发过程中,施加ATP处理的土壤含水量始终高于对照。累积蒸发量与时间平方根关系的模拟结果表明,蒸发结束时ATP处理下土壤样品可以释放的水量高于对照。添加ATP后黑垆土和黄绵土的裂缝面密度显著增加,风沙土裂缝面密度随ATP添加量的增加而增加,3种土壤的裂缝面密度在ATP添加量为4%时均达到最大值。ATP添加量为3%时可以在最大程度上减少土壤水分无效蒸发。

Effects of attapulgite addition on soil evaporation and crack characteristics

Water is one of the most important factors limiting vegetation recovery and agricultural development in arid and semi-arid areas. The reduction of ineffective soil evaporation can improve soil water use efficiency. As a kind of clay mineral, attapulgite (ATP) plays a critical role in limiting soil evaporation due to its hydrophilicity and adsorption. In this study, three typical soils with different textures (dark loessial soil, cultivated loess soil, and sandy soil) were selected from the arid and semi-arid area of the Loess Plateau, and five ATP additions (0%, 1%, 2%, 3% and 4%) were set for conducting soil evaporation experiments under natural conditions using micro-evaporators to investigate the effects of ATP addition on different soil evaporation processes and the characteristics of evaporation surface cracks. The results showed that the cumulative evaporation and evaporation loss ratio of the same soil decreased with the increases of ATP addition when the ATP addition was <3%. When ATP was added at 3%, the cumulative evaporation and evaporation loss ratio of dark loessial soil and sandy soil decreased, while those of cultivated loess soil increased. When ATP was added at 4%, the cumulative evaporation decreased and the evaporation loss ratio increased for dark loessial soil, the cumulative evaporation increased and the evaporation loss ratio decreased for sandy soil, and the cumulative evaporation and evaporation loss ratio decreased for cultivated loess soil. The average cumulative evaporation of different soils followed an order of dark loessial soil > cultivated loess soil > sandy soil. Soil water content of ATP treatment was consistently higher than that of control throughout the whole evaporation process in the same soil. Simulations of cumulative evaporation versus the square root of time indicated that the amount of water released from the ATP-treated soil samples at the end of evaporation was higher than that of the control. After the addition of ATP, the crack area density of dark loessial soil and cultivated loess soil increased significantly, and the crack area density of sandy soil increased with the increase of ATP addition. The crack area density of all three soils reached the maximum at 4% of ATP addition. In summary, ATP addition of 3% could minimize the ineffective evaporation of soil water.