Without taking into account its value in terms of phosphorus, potassium and other mineral contents, nitrogen from seed meal costs at least eight times as much per pound as nitrogen from urea.

Newspapers, even with colored inks, can be safely used in compost piles.  Though some colored inks do contain heavy metals, these are not used on newsprint.

However, before beginning to incorporate newsprint into your composting, reconsider the analyses of various types of compost broken out as a table in the previous chapter.  The main reason many municipal composting programs make a low-grade product with such a high C/N is the large proportion of paper used.  If your compost is intended for use as mulch around perennial beds or to be screened and broadcast atop lawns, then having a nitrogen-poor product is of little consequence.  But if your compost is headed for the vegetable garden or will be used to grow the largest possible prized flowers then perhaps newsprint could be recycled in another way.

Cardboard, especially corrugated material, is superior to newsprint for compost making because its biodegradable glues contain significant amounts of nitrogen.  Worms love to consume cardboard mulch.  Like other forms of paper, cardboard should be shredded, ground or chopped as finely as possible, and thoroughly mixed with other materials when composted._

__Pet wastes_ may contain disease organisms that infect humans.  Though municipal composting systems can safely eliminate such diseases, home composting of dog and cat manure may be risky if the compost is intended for food gardening.

Phosphate rock. If your garden soil is deficient in phosphorus, adding rock phosphate to the compost pile may accelerate its availability in the garden, far more effectively than adding phosphate to soil.  If the vegetation in your vicinity comes from soils similarly deficient in phosphorus, adding phosphate rock will support a healthier decomposition ecology and improve the quality of your compost.  Five to ten pounds of rock phosphate added to a cubic yard of uncomposted organic matter is about the right amount.

Rice hulls: See Buckwheat hulls.

Rock dust. All plant nutrients except nitrogen originally come from decomposing rock.  Not all rocks contain equal concentrations and assortments of the elements plants use for nutrients.  Consequently, not all soils lustily grow healthy plants.  One very natural way to improve the over all fertility of soil is to spread and till in finely ground rock flour make from highly mineralized rocks.

This method is not a new idea.  Limestone and dolomite—­soft, easily powdered rocks—­have been used for centuries to add calcium and magnesium.  For over a century, rock phosphate and kainite—­a soft, readily soluble naturally occurring rock rich in potassium, magnesium and sulfur—­have been ground and used as fertilizer.  Other natural rock sources like Jersey greensand have long been used in the eastern United States on some unusual potassium-deficient soils.