Smart Farming Solutions

Do you have problems growing turf due to compacted soil? Does water puddle on your lawn after a rain shower? Do you have drainage issues due to a hard pan?

If the answer is yes, then you may need to aerate your soil.

Before discussing methods of aeration, it is important to understand soil properties.

Oxygen in the soil must be plentiful to allow root respiration. A well aerated soil will hold approximately 20% oxygen- slightly less than our atmosphere. Likewise, the soil must be moist to provide mass flow of nutrients to root zones. Excessive moisture will replace oxygen and waterlog the roots, killing the plant. Not enough moisture will result in wilting and plant starvation.

Compacted soils (due to the particle composition) retain too much water after a rain event and do not allow oxygen to penetrate between particles.

Soil consists of three general particle sizes- sand, silt and clay. Particles smaller than 0.002 mm (clay) have several interesting characteristics. A spoonful of clay has the surface area of a football field. Like colloids they hold negative charges. In addition, they are dotted with micro-pores, giving them tremendous water holding capacity. The mutual attraction between water molecules and charged particles makes the clay exhibit increasing stickiness or plasticity as particle size decrease. This means that clay particles can be greatly compacted, leaving no room for air. In addition roots have great difficulty growing between tightly bound particles.

There are four ways to aerate a compacted soil.

1) Mechanically- By spiking the soil or turf. Lawn maintenance companies offer this service by driving a spiked roller on top of the turf. However this method has limitations. Spikes compress the soil they perforate, so unless the spikes have a small diameter, the soil gets more compacted in the spiked zones. This is particularly true with heavy clay soils. In other words, spiking loamy or sandy soils may be very beneficial, where as spiking clay soils may be counter productive.

2) Applying dolomite or gypsum- Calcium and magnesium in theses rocks have positive charges. When mixed in the soil they will bind to the negative surface of the clay particle thereby forming microscopic clumps called floccules. These clumps have more space between them then tightly compressed clay particles, (think of the space between a stack of basket balls and a stack of golf balls); as a result air is able to penetrate and roots have more space to develop. However, to be effective, the dolomite or gypsum must be incorporated in the soil. Meaning the soil must be tilled or disked to break it up, then the dolomite or gypsum spread and mixed in the soil. Usually 500 lbs to 1,000 lbs per acre is needed to be effective. This is an expensive option but may make sense on a new construction.

3) Liquid Flocculants- There are certain molecules such as Ammonium Laureth Sulfate (found in shampoos), which also carry positive charges and flocculate the soil just as effectively as dolomite and gypsum but without the need to disk the soil. They are normally sprayed on the yard with a hose-end sprayer. Note that liquid flocculants are not surfactants (soaps) which break water tension. Dish washing soap will break water tension, allowing water to penetrate in the soil, but it will not clump the clay particles together to allow air to penetrate. Nevertheless brands of liquid flocculants will also contain a certain amount of surfactant, which helps drive the active ingredient deep into the soil.



4) Microorganism such as bacteria and fungi also play an important role in aeration, by occupying space between clay particles. Many gardeners and lawn care enthusiasts apply beneficial bacteria on their soil. Some of these bacteria rapidly break down grass clipping into organic matter which penetrates in the soil providing space between clay particles and nutrients for the turf. Worms and ants also provide aeration.

Labels: aerating your lawn, hard pan, soil aeration