Why are soil colloids important in soils? Why are soil colloids important in soils? Soil colloids is a measure of the maximum water available for plants use after the water has drained from large pore spaces. As one of the shapes of an individual ped, soil colloids control rooting of plants. Soil colloids are an indication of soil moisture. The higher number of colloids, the greater the soil moisture is. Soil colloids have a neutralizing effect, increasing the overall alkalinity of soil and making them prime for certain agricultural crops. Without colloids, leaching will dissolve important chemicals from the soil, making them unavailable to plant.