What is the ideal structure for soils?
Ideally, soils should be made up of round, irregular shaped aggregates between 5mm and 10mm in diameter. This structure allows for the maximum number of large pores to transport water and air through the soil, and will not restrict root growth. When there are many aggregates less than 5mm diameter (eg. in a fine seedbed), the soil tends to seal off or crust in heavy rain and also slow water movement down through the profile. Soils with fewer large aggregates limit the number of larger conducting pores and restrict the growth of crop roots. When these large aggregates also set hard or are very dense (eg. like the blocks that can arise after cultivating a compacted zone), a large proportion of the soil is not available for the crop to extract water and nutrients.
