N E W J E R S E Y Greensand as a Soil Amendment By J.R. Heckman and J.C.F. Tedrow

The benefits in plant growth sometimes observed following greensand application are likely not due to nutritional benefits, but from changes in soil physical proper- ties. reensand is composed largely of often exists as -sized pellets, as shown , a unique that in the photo below. Glauconite does not G occurs as a natural geologic deposit behave like typical sand, since it is a mica- that stretches as a belt across like complex composed mostly of musco- from Monmouth County to Salem County. vite- and illite-like , contain- Greensand also occurs in parts of Dela- ing many micro-pores. Also, unlike a true ware, Maryland, and Virginia. Although sand, the micro-pores in greensand contrib- there are several theories of origin, green- ute to soil water-holding capacity. In this sand is generally thought to have formed way, it differs from true , which are in shallow marine seas near the interface composed of minerals such as and of water and land. feldspars. Greensands typically have a high Since the late 1800s, millions of tons cation exchange capacity (ranging from 20 of greensand have been spread over soils to 30 cmol/kg). Addition of greensand to in New Jersey and other parts of the U.S. sandy soils enhances the ability of the soil For this reason, greensand may occur to store exchangeable nutrients such as today in many soils where it was not origi- calcium (Ca), magnesium (Mg), nally present. The presence of greensand (K), and micronutrients. These desirable may still be benefiting crops by improving physical and chemical properties may ex- the soil’s ability to hold water and store plain how greensand can be useful as a soil nutrients. In the early part of the 20th cen- amendment. tury, there were about 80 open pit mines Pure glauconite generally contains up in New Jersey where greensand was mined. to 8% K2O and small amounts of phospho- There are only rus (P), Ca, and trace elements. However, a few of these since greensand contains other non- mines operat- ing today. The photo at left shows a view of a modern mine. The olive green-colored glauconite mineral in greensand is unusual. Un- like most types Modern greensand mining of clay, which operation in Gloucester County, are very fine, Glauconite pellets from the Hornerstown formation New Jersey. glauconite (photo by R. Holzer).

16 Better Crops/Vol. 88 (2004, No. 2) beneficial constituents as well as glauco- Table 1. Yukon Gold potato tuber yield and nite, the K content of commercial prod- specific gravity in response to green- ucts generally falls well below this value sand application in the seed furrow (from 0.1 to 7% K2O). prior to planting in 2003. The issue of K availability from green- th Greensand rate, Tuber yield, Tuber specific sand has been studied since the 19 lb/A cwt/A gravity century, when positive crop responses were 0 91 1.063 occasionally observed following applica- 125 105 1.061 tion. Almost all investigators have con- 250 107 1.063 cluded that greensand has very little value 500 105 1.063 as a nutrient source. Greensand is some- Significance* times recommended as a natural K source (check vs. others) 0.04 NS for organic agriculture. Recent research *The check was significantly different than the suggests that greensand benefits may be a treatments @ p=0.04. result of changes in soil physical proper- ties and not improved plant nutrition. K2O, respectively. Tissue analysis revealed A field trial near New Brunswick, New no differences in nutrient concentrations Jersey, evaluated the response of potatoes in the potato leaves. Thus, the positive to various rates of greensand applied in the yield response was not likely related to an row at time of planting with the seed pieces influence of greensand on plant nutrition, (see photo)photo). The study was conducted on but improved soil properties. a Sassafras sandy loam soil that had rela- Conclusion tively low organic matter content and poor In general, greensand should be con- physical condition as a result of many years of continuous cropping to vegetables. sidered more valuable as a soil conditioner than as a . Micro-pore spaces Thus, this field site afforded the opportu- within glauconite can enable greensand- nity for greensand to express soil-condi- tioning attributes. Potato tuber yields were amended soils to have improved water- holding capacity and increased ability to on average 16% higher where the green- store and retain nutrients. These changes sand treatments were applied (Table 11). The crop was uniformly fertilized with 108, may or may not result in a positive plant response, depending on the specific soil. 7, and 134 lb/A of nitrogen (N), P O , and 2 5 Although organic matter additions may also improve soil water holding capacity and nutrient retention, the changes result- ing from adding greensand to soil are permanent. BC

Dr. Heckman is Extension Soil Fertility Specialist with Rutgers University; e-mail: [email protected]. Dr. Tedrow is Profes- sor Emeritus, Department of Ecology, Evolution, and natural Resources, Rutgers University. Additional information regarding greensand is available from: J.C.F. Tedrow, 2002. Greensand and Greensand Soils of New Jersey: A Review. Rutgers Cooperative Extension, Bulletin E279. Greensand applied in the seed furrow before planting Website: >www.rce.rutgers.edu/pubs/pdfs/e279<. potatoes.

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