Abstract: In order to investigate the fractal characteristics of soil particles and the changes of soil nutrients in alfalfa (Medicago sativa L.) field under different water and fertilizer treatments,the alfalfa field with four irrigation gradients (W₁,W₂,W₃,W₄) and five fertilization gradients (F₁,F₂,F₃,F₄,F₅) was used as the research object for four consecutive years. Soil particle composition and nutrient indexes under different water and fertilizer treatments were measured,and fractal dimension was calculated by using fractal theory. The results showed that the amount of irrigation and fertilizer application had significant effects on the fractal characteristics and nutrient content of soil particles,and the interaction between water and fertilizer was significant. In the 0~60 cm soil layer,the content of clay,silt,and fractal dimension increased first and then decreased with the increase of irrigation amount,while the content of sand decreased first and then increased. The content of clay,silt,and fractal dimension decreased first and then increased with the increase of fertilizer application rate,while the changes of sand content was reversed. Different irrigation and fertilizer amounts had different effects on soil nutrient content. When the amount of irrigation was 6 000 m³·hm^-2 and the amount of fertilizer was 585 kg·hm^-2,the soil structure was relatively stable. The fractal dimension of soil particles was positively correlated with the content of clay,silt,and alkali-hydrolytic nitrogen,but negatively correlated with the content of sand.

Key words: Water and fertilizer coupling, Soil particle composition, Fractal dimension, Soil nutrient

摘要： 为了探究不同水肥处理下苜蓿（Medicago sativa L.）地土壤颗粒分形特征和养分变化规律，以连续4年进行4个灌水梯度（W₁，W₂，W₃，W₄）和5个施肥梯度（F₁，F₂，F₃，F₄，F₅）的苜蓿地为研究对象，测定不同水肥处理下土壤颗粒组成和养分指标，运用分形理论计算分形维数，结果表明：灌水和施肥量对土壤分形特征和养分含量均影响显著，且水肥交互作用显著。在0~60 cm土层，黏、粉粒含量和分形维数随灌水量的增加呈先增后减的趋势，砂粒含量呈先减后增的趋势；黏、粉粒含量和分形维数随施肥量的增加呈先减后增的趋势，砂粒含量反之；不同灌水和施肥量对土壤养分含量影响不同。当灌溉量为6 000 m³·hm^-2，施肥量为585 kg·hm^-2时，土壤结构较为稳定。土壤颗粒分形维数与黏粒、粉粒和碱解氮含量呈显著正相关，而与砂粒含量呈显著负相关。

关键词: 水肥耦合, 土壤颗粒组成, 分形维数, 土壤养分