This study was undertaken to investigate the impact of compost on urban soils’ ability to retain water. Data from past studies led to the development of the hypothesis that compost will increase soil’s water-holding capacity up to a certain point, but, if too much compost is present, the soil will become hydrophobic. To test this hypothesis, four treatments were chosen in the form of compost layers of increasing thicknesses (0-inch compost layer, 1-inch compost layer, 2-inch compost layer, 3-inch compost layer), and three repetitions of each treatment were randomly assigned to twelve planting plots of equal size. Kale seeds were planted evenly in each plot and were tended as needed and watered consistently for the duration of two thirty-day trials. Soil moisture, temperature, and conductivity were measured with a soil probe twice weekly throughout the trials. The data showed an inverse relationship between compost and soil moisture: Soil moisture decreased as compost thickness increased. The same trend was seen between conductivity and compost. Temperature was not impacted by compost. This data led to a rejection of the hypothesis that compost increases soil’s water-holding capacity up to a certain limit. These unexpected results could be attributed to the shallow soil measurements achieved by the probe. In future research, a different method should be used to measure soil moisture in order to determine the characteristics of the soil below the compost layer. This study revealed implications for plants of different rooting lengths and provided insight for future designs of urban soil research projects.
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Drew, Anna Louise, "Compost Amendments on Urban Soils vs. Water Retention" (2020). Honors Theses. 255.