The best way to simultaneously overcome all of these liabilities is first to permit the bales to thoroughly spoil and become moldy through and through before composting them.  When I have a ton or two of spoiled hay bales around, I spread them out on the ground in a single layer and leave them in the rain for an entire winter.  Doing this sprouts most of the grass seed within the bales, thoroughly moistens the hay, and initiates decomposition.  Next summer I pick up this material, remove the baling twine, and mix it into compost piles with plenty of more nitrogenous stuff.

One last word about grass and how it works when green manuring.  If a thick stand of grasses is tilled in during spring before seed formation begins, its high nitrogen content encourages rapid decomposition.  Material containing 2 percent nitrogen and lacking a lot of tough fiber can be totally rotted and out of the way in two weeks, leaving the soil ready to plant.  This variation on green manuring works like a charm.

However, if unsettled weather conditions prevent tillage until seed formation has begun, the grasses will contain much less nitrogen and will have developed a higher content of resistant lignins.  If the soil does not become dry and large reserves of nitrogen are already waiting in the soil to balance the high C/N of mature grass, it may take only a month to decompose But there will be so much decomposition going on for the first few weeks that even seed germination is inhibited.  Having to wait an unexpected month or six weeks after wet weather prevented forming an early seed bed may delay sowing for so long that the season is missed for the entire year.  Obstacles like this must be kept in mind when considering using green manuring as a soil-building technique.  Cutting the grass close to the soil line and composting the vegetation off the field eliminates this problem.

Hoof and horn meal. Did you know that animals construct their hooves and horns from compressed hair?  The meal is similar in nutrient composition to blood meal, leather dust, feather meal, or meat meal (tankage).  It is a powerful source of nitrogen with significant amounts of phosphorus.  Like other slaughterhouse byproducts its high cost may make it impractical to use to adjust the C/N of compost piles.  Seed meals or chicken manure (chickens are mainly fed seeds) have somewhat lower nitrogen contents than animal byproducts but their price per pound of actual nutrition is more reasonable.  If hoof and horn meal is not dispersed through a pile it may draw flies and putrefy.  I would prefer to use expensive slaughterhouse concentrates to blend into organic fertilizer mixes.

Juicer pulp: See Apple pomace.

Kelp meals from several countries are available in feed and grain stores and better garden centers, usually in 25 kg (55-pound) sacks ranging in cost from $20 to $50.  Considering this spendy price, I consider using kelp meal more justifiable in complete organic fertilizer mixes as a source of trace minerals than as a composting supplement.