Using compost with gypsum improves clay soils

Gypsum, otherwise known as calcium sulfate, can be used to amend clay-based soil and also to improve soils with high concentrations of sodium.

Amending clay-based soils with gypsum leads to healthier and more productive plant growth. Gypsum also improves soil structure and infiltration rates when there are high concentrations of sodium.

Aguinaga’s General Purpose Soil Amendment 1 (GPS 1) is one of Aguinaga’s special blends. It consists of general purpose mulch, recycled green matter, turf plus, and gypsum. The blending of these products has brought forth an excellent balanced planting soil amendment that has a multiplicity of uses throughout the garden area, regardless of soil texture. Sandy soil will begin to retain moisture and clay soil will have improved drainage and aeration.

The addition of turf plus improves the nutrient levels in the product and adds organic nitrogen for long term, slow-release microbial activity. The improved levels of soil bacteria greatly enhance root development and stimulate plant growth. GPS 1 particle size is 0 to 1/2 inch. It is nitrolized and stabilized and fully composted.

All of Aguinaga's products are STA Certified.

pH and Compost

What is pH?
pH Factor means potential Hydrogen and measures soil’s acidity or alkalinity. The scale runs from 0 to 14 where 7 represents a neutral soil. Numbers below 7 indicate the degree of acidity, and numbers above 7 indicate the degree of alkalinity. The pH scale is logarithmic and each jump is a ten fold increase. A soil with a pH of 4 is 10 times for acidic than one with a pH of 5 and 100 times more acidic than one with a pH of 6.

Composting and the pH Factor
The microorganisms in compost operate best under neutral to acidic conditions with the pH in the range of 5 to 8. In the beginning stages of decomposition, organic acids are formed. Conditions that are acidic are best for the growth fungi and breakdown of lignin and cellulose. As composting goes on, the organic acids become neutralized. “Mature” compost generally has a pH between 6 and 8.

If there is not enough oxygen (anaerobic), the acid accumulation can lower the pH to 4.5 and limit microbial activity – thus slowing down the composting process. Aeration is needed to return the compost pH to an acceptable range.

Compost and Plants
Most garden plants do best in a slightly acidic to neutral soil – around pH 6.5 to 7. Compost can modify and stabilize pH. When compost is added to the soil, it acts as a chemical buffer and increases the plants tolerance to pH. Adding compost to a slightly alkaline soil will make it more neutral.

pH, STA Certification, and Aguinaga
Each month, Aguinaga sends a sample of compost to the US Composting Council where the pH and other properties are tested. By passing these lab tests every month, the US Composting Council awards us with the Seal of Testing Assurance (STA Certified.)