Texas greensand (Glauconite) is an iron potassium, silicate that is green in color due to the minerals it contains. Greensand is a marine deposit that contains traces of many if not all of the elements which are in seawater. It has been used successfully for enriching soils for over 100 years. Approximate analysis is 0-2-5. This is a natural source of phosphorous, potash, and trace minerals. Texas greensand is different than the glauconite from the New Jersey area.
The natural Texas product contains about 19 percent iron and about 2 percent magnesium. Its pH is 8.3, but don’t let that fool you. Use it on all plants for an effective green-up. Research proved green sand to be better than most iron products in helping plants overcome chlorosis in high pH soils, slightly better than granite sand. The iron supplement that we recommend the least is Ironite because tests have shown that it has high levels of lead and arsenic. The company agrees with the existence of the heavy metals but argues that the risk is slight since the product is in the galena form and not quickly available. As a soil conditioner Texas greensand can be used at 10-50 pounds per 1000 square feet on lawns or tilled into the soil. It is also an excellent amendment for golf greens and tees. In potting soils it can be used at a rate of 5-20 pounds per cubic yard.
In a research project demonstration an eroded field that was low in organic matter with a pH of 8.3 was tested 66 test plots of peas, peppers and okra grown in each plot. All were fertilized equally with organic fertilizer and then each plot got an additional product. Many of them were iron products. Texas Greensand plot at 150 pounds per 1,000 square feet outperformed all other iron test products in the plants green color and growth. It even beat the iron sulfate plot. The only plots that did as good or even better were the compost plots.