Using organic soil conditioners and amendments is a time proven way to not only increase the soil's fertility but to also improve the structure of the soil. One such soil additive is greensand, a naturally occurring conglomerate of minerals and necessary plant nutrients that is mined from what were once ancient seabeds. Greensand is sold commerically in both bagged quantities and in bulk amounts. Its uses as a soil additive have been known since the 18th century and it is considered one of the best organic sources of the prime plant nutrient potassium.
Sandy sediments containing large amounts of the mineral glauconite are the source of greensand and give it a greenish to blue green color. Greensand is known to contain iron, silica, potassium, magnesium, and as much as 30 other trace minerals making it a good organic fertilizer for all gardening regions. In commercial fertilizers, potassium is the third listed chemical ingredient referred to by the three numbers used in fertilizer descriptions such as 8-8-8. Potassium or potash which is its more common name, plays an important role in the formation of flowers, being necessary for large and numerous blooms. Iron and magnesium are both needed by plants to keep their leaves green and healthy and for healthy root growth.
It is not just the chemicals contained in greensand that make it such a good organic soil additive. The physical makeup of greensand gives it the ability to help loosen heavy, clay filled soils so both water and oxygen can move through them more freely. Greensand has a natural affinity for moisture so it will help sandy soils to hold on the available moisture. By loosening the soil structure it allows plant roots to grow more freely and probe deeper and wider for the available plant nutrients and water. Because of the moisture retaining characteristic of greensand, it is a long acting organic fertilizer that does not need to be reapplied frequently and it will not leach quickly from the soil to become a water pollutant. In terms of gardening supplies, greensand is a main stay for all types of gardening.
It is easy to apply greensand using a regular broadcast type fertilizer or in small gardens it can simply be spread by hand. The rate for applying greensand is generally accepted to be 50 to 100 lbs. tilled into every 1000 square ft. of garden area. A 1000 sq. ft. area is an area that measures 10 ft. by 100 ft. or any two side dimensions that multiply together to make 1000. The nutrients in greensand are available to the plants right away, it does not need to breakdown or decompose like some other organic fertilizers. Greensand can be applied right at the time of planting or later in the gardening season. It can be worked into the soil to place it closer to plant roots and to guard against it being washed away in heavy rains.
It is always best to have your soil tested before adding any mineral rich amendments to it. Greensand will not in itself have much of an effect on soil pH and soil pH is very important when it comes to plant health. Many plants will only thrive in soils having a pH withing a certain range such as azaleas and camellias that have to have acidic soils with pH's below 7. Having soil with too acidic a pH can mean that certain minerals will be locked up making them unavailable to plants even if they are in the soil. Having the soil tested will tell you if the pH needs to be adjusted and by how much. Greensand is not normally a source of nitrogen so it does not promote the quick greening of plants. It will also not burn plant roots or harm the normal soil organisms like commercial fertilizers are known to do.
Buy a bag of greensand and use it on part of your garden this year to see the difference it will make. Next season you will be using on every plant you grow.