This section is from the book "Vegetable Gardening", by Ralph L. Watts. Also available from Amazon: Vegetable Gardening.
Many growers of vegetables would never buy manure were it not for the necessity of maintaining the supply of soil humus. That is, it would be cheaper for thousands of gardeners to purchase commercial fertilizers for the needed plant foods than to buy bulky manure, pay freight and then haul several miles perhaps, not to mention the cost of spreading and of composting. But a liberal supply of soil humus is absolutely essential to success in growing all classes of vegetables. It increases the water-retaining capacity of soils; secures improved soil aeration; aids important chemical changes; increases soil temperature; helps to create favorable conditions for the work of friendly bacteria ; improves the texture of soils; makes it possible to begin work earlier in the spring and reduces the labor of tillage. Stable manures are superior to green manures as humus-making materials because they decompose more rapidly and are, therefore,' of greater value to the crops under cultivation.
 
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