7a WHAT ARE physical soil properties PROPERTIES WHAT IS IT? WHY IS IT IMPORTANT? these Texture The size of soil particles, Soil texture affects soil behavior, in particular its soil properties sand, silt and clay, retention capacity for nutrients and water. affect soil function. determines the let’s take a look at what texture of a soil. they are and why they are important. let’s start with physical soil properties Structure The clumping of the soil The soil structure affects aeration, water movement, textural components of sand, conduction of heat, plant root growth and resistance silt and clay forms aggregates to erosion. Water has the strongest effect on soil and the further association structure due to its solution and precipitation of of those aggregates into minerals and its effect on plant growth. larger units forms soil structures called peds. Porosity Pore space is that part of The air space is needed to supply oxygen to plant the bulk volume that is roots and soil organisms. Pore space also allows not occupied by either the movement and storage of water and dissolved mineral or organic matter nutrients. but is open space occupied by either air or water. Ideally, the total pore space should be about half of the soil volume. Water Infiltration is the downward Infiltration indicates the soil’s ability to allow water infiltration entry of water into the soil. movement into and through the soil profile. Soil temporarily stores water, making it available for root uptake, plant growth and habitat for soil organisms. many of PHYSICAL these properties can be easily measured using simple tools check Color Soil color is caused by the minerals present and by Soil color does not affect the behavior and use of soil; the organic matter content. Soil can exhibit a wide however, it can indicate the composition of the out the soil testing range of color; grey, black, white, reds, browns, soil and give clues to the conditions that the soil is methods manual! yellows and under the right conditions green. Soil subjected to. color is described by using general terms such as “dark brown” but can also be described more technically using Munsell soil color charts. Soil Soil moisture, also known Soil moisture or soil water is important as it serves moisture as water content, is the as a carrier of plant nutrients, to regulate soil quantity of water temperature, to assist microbial activity and many contained in soil. more crucial activities that are essential for plant growth. Soil Testing MANUAL Methods Compaction Refers to the increase in Soil compaction impairs soil functions and impedes Soil Testing Methods Soil Testing soil bulk density/decrease roots penetration and water and gas exchange. Soil Doctors Global Programme in soil porosity. A farmer-to-farmer MANUAL training programme Did you know that soil CA7164EN/1/12.19 © FAO, 2019 © FAO, Thanks to the financial support of compaction can reduce crop yields by as much as 60%? .