Weights For Plant Pots . The weight of the soil can compress and compact the soil, thus affecting drainage and root growth. You can add either lightweight or heavy pot fillers into the bottom of your pot. Light Weight Terracotta Pots & Poly Planters Tuscan Imports from www.tuscanimports.com This chart will help you translate container sizes for standard clay pots and black nursery pots and give you an approximation of how much soil each will require (again these are dry soil measures): $20.00 coupon applied at checkout save $20.00 with coupon. The dry volume of this pot is 1.5 gallons or 5.678 liters.