It is more important today to make sure that when you water, the water can soak into your soil and not run off.
The soil in the urban areas of the Antelope Valley has very poor soil structure. In tract homes around the valley, there may have been good soil prior to building. In the process of building homes, the soil is graded, packed, watered and packed some more. This reduces the pore space in the soil from the normal 50% to less than 10%, making the soil denser. If the soil cannot easily soak up water it is less likely to expand with water and shrink when the soil dries. This shrink-swell capability of soil can cause your house to crack.
Reducing the pore space lowers the shrink-swell rate. This is great from your home and very bad for your garden and landscape. This year, with the increased rainfall, the raindrops act like little hammers packing your soil, and walking on wet ground also can pack the soil surface.
Many sources suggest adding gypsum or gypsite to your soil to improve water movement into your soil. But gypsum will not break up soil compaction. A rototiller or a lot of labor with a shovel is the only way to break-up compaction. Gypsum and gypsite are used to improve the soil structure, which can improve water absorption. However, they can only improve soil structure and water absorption if your soil is high in sodium.
Soil structure is the arrangement of sand, silt, and clay into a small group. This smallest group is called a ped. Several peds may arrange into a larger structure called an aggregate. Several aggregates may combine into a larger structure called a clod. Most of you are familiar with clods, because you have probably thrown one or two in your lifetime. The key to forming these structures is organic matter. Organic matter is often called the glue of the soil, because it ‘’glues’’ the sand silt and clay together into the different structures.
As important as the structure of the particles (sand, silt and clay) is for the soil, the spaces between the particles are more important. When your soil has, poor structure the spaces or pores are very small. As structure improves the total pore space stays the same, however the size of the pores increase. The larger the pore space the easier water and fertilizer can be absorbed by your soil.
Since organic matter is the glue of the soil, it is a very important component. If your soil lacks organic matter, it cannot form peds. The clay particles move towards the soil surface, followed by silt with sand on the bottom. With clay on the surface it forms a barrier that is hard for water to penetrate. Because of the clay surface many people feel they have a clay soil, but in fact just have poor structure.
If you have a lot of organic matter in your soil and still seem to have poor structure it could be caused by high sodium levels in your soil. There are areas in the Antelope Valley that have high sodium levels, most are in low areas (old ponds/lakebeds) of the valley. Some may be causing their own sodium problems by dumping their spa water on their garden or landscape. Most spa chemicals are
high in sodium.
Just like laundry detergent the sodium in the soil breaks down the organic matter, not allowing the organic matter to form structure. If your soil is high in sodium you need to add gypsum or gypsite. These products help replace the sodium in your soil, allowing the soil to form structure.
The other problem is that the soils of the Antelope Valley are very low in organic matter. No or low organic matter means no soil structure, again gypsum or gypsite will not help this soil. Adding compacted soil together with no organic matter and you have very poor structure. Adding gypsum or gypsite again will do very little to improve these soils. Gypsum and gypsite will help improve a sodic soil, however for most soils in the Antelope Valley a good dose of organic matter rototilled into your soil is the answer to improve your soil structure.