Ingredients
Greensand is a marine sedimentary deposit formed 70-80 million years ago during the Cretaceous Period, when shallow seas covered what is now the New Jersey coastal plain. The green color comes from glauconite — an iron-potassium silicate mineral that formed on the ocean floor as marine organisms died and their shells interacted with iron-rich sediments under reducing conditions.
Greensand (also called glauconite or New Jersey greensand marl) is mined from Cretaceous-era deposits primarily in New Jersey, with smaller deposits in Delaware, Virginia, and Texas. The material is a soft, sandy mineral that crumbles easily in the hand and contains 0-0-3 NPK with 6-7% potassium (K₂O), 15-20% iron oxide, 3-5% magnesium, and over 30 trace minerals including manganese, silica, cobalt, and molybdenum.
Organic growers use greensand for three reasons: slow-release potassium that feeds plants over 2-3 years without risk of salt burn, iron supplementation that prevents chlorosis (yellowing) in alkaline soils, and clay-like soil conditioning properties that improve both water retention in sandy soils and drainage in heavy clay.
Greensand’s potassium delivery is exceptionally slow — the glauconite crystal structure releases K₂O only as soil acids and microbial activity gradually dissolve the mineral surface. This means greensand provides virtually no immediately available potassium (unlike potassium sulfate or langbeinite), but sustains low-level potassium availability for 2-3 growing seasons from a single application.
The iron content (15-20% as iron oxide) is significant for organic growers in the Rogue Valley, where calcareous soils can bind iron and cause chlorosis in blueberries, azaleas, and other iron-sensitive crops. Greensand’s iron is released through the same slow dissolution process as its potassium — not fast enough for acute deficiency correction, but effective as a long-term iron maintenance source.
Daley Organics uses three potassium sources in the 25-ingredient fertilizer blend, each with a different release speed. Kelp meal provides the fastest potassium (available within days as water-soluble K). K-Mag (langbeinite) provides medium-speed potassium (available within 2-6 weeks as the sulfate dissolves). Greensand provides the slowest potassium (available over 2-3 years as glauconite gradually weathers).
This three-tier potassium strategy ensures plants have access to potassium from the first day of planting through the second and third growing seasons — no single source could provide this breadth of coverage.
Greensand is a component of the mineral fraction in our 25-ingredient fertilizer, present in Daley’s Mix ($140/yd), Premium Soil Mix ($130/yd), Grow Blend 5-4-2, and Bloom Blend 2-7-7. Beyond its nutrient value, greensand’s plate-like mineral structure (similar to montmorillonite clay) increases the cation exchange capacity of the overall mix, helping retain nutrients from other amendments that would otherwise leach.
At our Grants Pass soil yard, we source horticultural-grade greensand screened to a fine sand consistency for even distribution during blending.
For general soil improvement, broadcast 5-10 lbs per 100 square feet and incorporate into the top 6-8 inches. For heavy clay conditioning, apply 15-20 lbs per 100 square feet annually for 2-3 years — the glauconite particles physically open clay structure while adding potassium and iron. For established fruit trees, apply 5-10 lbs per tree at the drip line annually.
Greensand is one of the safest soil amendments to use — it cannot burn plants, has no odor, doesn’t attract animals, and provides sustained benefits over multiple growing seasons from a single application.
Common Questions
Greensand contains 6-7% potassium (K₂O), 15-20% iron oxide, 3-5% magnesium, and over 30 trace minerals including manganese, silica, cobalt, and molybdenum. Its NPK analysis is 0-0-3, with all potassium released slowly over 2-3 years.
Greensand releases potassium very slowly — over 2-3 growing seasons — as soil acids gradually dissolve the glauconite crystal structure. It provides virtually no immediately available potassium, which is why Daley Organics pairs it with faster sources like kelp meal and K-Mag.
Greensand is mined from 70-80 million-year-old Cretaceous-era marine sediment deposits, primarily in New Jersey. It formed on the ancient ocean floor when marine organisms' shells interacted with iron-rich sediments under reducing conditions, creating the green glauconite mineral.
No. Greensand cannot burn plants at any application rate. Its nutrients are locked in a crystal structure that releases only through slow geological weathering. It's one of the safest organic amendments available — no odor, no animal attraction, and sustained benefits over multiple seasons.
Used In Our Blends
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