The effects of nutrients on plant growth have been widely studied. In agricultural research, some studies have showed significant root growth in high-nutrient-supplied soil, however, some other studies, reported better lateral root growth in low-nutrient-supplied conditions. However, the effects of NPK (nitrogen, phosphorous, potassium) water-soluble fertilisers on plant roots and shoot growth in bioengineered soil slopes and their influence on soil suction and water-retention ability are still unclear. This paper quantifies the growth of a tree in NPK nutrient-supplied soil and its effects on tree-induced soil suction and water-retention ability during evapotranspiration. Three replicates of Schefflera heptaphylla (Ivy tree) were grown for 6 months in nutrient-poor and nutrient-supplied compacted soils typical of bioengineered slopes and embankments. Plant characteristics, induced suction and volumetric water content (VWC) were monitored throughout the growth period. After 6 months of growth, leaf area index (LAI) and peak root area index (RAI) increased by 350 and 133%, respectively, in nutrient-supplied soil compared with the nutrient-poor soil. This is because nitrogen stimulated chlorophyll synthesis enabling plants to produce larger leaves. Additionally, nitrogen mediated phosphorous to be utilised by roots in soil to induce growth of fine roots and thus increase the root surface area and root volume in soil pores. After 3 days of drying, the vegetated nutrient-supplied soil induced 15–50 kPa higher suction than the vegetated nutrient-poor soil due to the higher RAI, LAI and root volume of the plants grown in nutrient-supplied soil, which enable plants to absorb and transpire more water. In contrast, the water-retention ability reduced in the nutrient-rich vegetated soil because more clustered fine roots in soil pores decreased the pore diameter and increased suction.