plant density measurement protocol using quadrat Count the number of plants using a quadrat. A quadrat is a frame of a know area. Set the quadrat on the soil and count the number of plants inside it. Repeat this observation as often as mentioned in your sampling protocol. Total number of plants= [(total number of plants counted inside the quadrat during all the observations)/ (quadrat area)/(number of observation)]x field size. plant population measurement protocol using quadrat plant density measurement protocol