Soil tillage at both the garden and field scale should take place only within the soil moisture range of 50–75% of field capacity (see Appendix 1, Estimating Soil Moisture by Feel, and Unit 1.5). Whether using a spade and fork, or tractor-drawn tillage tools, tillage executed at soil moisture levels higher than 75% of field capacity can increase soil compaction, degrade soil structure, increase surface crusting, and increase erosion potential.
Soil tillage undertaken when soil moisture is below 50% of field capacity may pulverize soil aggregates, resulting in poor soil structure and increasing the risk of soil erosion due to wind. 2. Soil texture classification (see also Unit 2.1,
Soil Physical Properties) a) Sandy soil: Sandy soils with relatively large particle size and large pore spaces are often naturally well drained, aerated, and friable. These features, combined with the relatively inert nature of the sand particles, lead to soil conditions in which organic matter oxidizes rapidly and unstable soil aggregates form.
Though less susceptible to compaction when tilled outside of the ideal moisture range, tillage systems in sandy soils must generally be conservative in order to retain soil aggregates and maintain desirable soil physical properties. b)
Clay soil: Soils with a high percentage of clay (>40%) have many micropore spaces and often exhibit poor drainage and gas exchange characteristics. Heavy clay soils often require an extended period (5–7 or more years) of frequent, deep tillage in order to incorporate adequate amounts of mineral soil amendments and organic matter to create the desirable soil physical conditions. Clay soils must be worked at optimal soil moistures (50–75% field capacity) to avoid creating clods—larg