. Productive agriculture . ans-forming vegetable matter into available plant foods. Theprocesses due to bacterial organisms are accompanied by chemicalchanges. Air is essential to these processes. Improving Soils by Plowing under Green Manure Plants. —?Green manure crops are grown and plowed under to enrichthe soil. Any cropplowed under addsorganic matter to thesoil, and causes moreplant foods to be setfree. Green manurecrops are of twoclasses: 1. Cover crops suchas rye and wheatsown in the autumnand left on the soilthrough the winter to protect the land, and plowed under in thespring. 2. The
. Productive agriculture . ans-forming vegetable matter into available plant foods. Theprocesses due to bacterial organisms are accompanied by chemicalchanges. Air is essential to these processes. Improving Soils by Plowing under Green Manure Plants. —?Green manure crops are grown and plowed under to enrichthe soil. Any cropplowed under addsorganic matter to thesoil, and causes moreplant foods to be setfree. Green manurecrops are of twoclasses: 1. Cover crops suchas rye and wheatsown in the autumnand left on the soilthrough the winter to protect the land, and plowed under in thespring. 2. The legume crops, which are grown in summer and plowedunder in the autumn. Even if the legume hay is removed, the soil will be somewhatimproved. However, the main value of a green manure cropcomes from the organic matter that is added to the soil. Summary. — Low yields are due often to soil that are in poor physical condition seldom produce goodcrops, because they do not liberate plant foods fast Fig. - Turning under a green manure crop improvestlie soil pliysically and chemically. 3o6 PRODUCTIVE AGRICULTURE The physical condition of soil is improved by tillage, by additipnof organic matter, by growing legumes, and by proper rotationof crops. Good physical condition of soils is favorable to chemi-cal processes which make plant foods available. An acid soil ismade neutral or sweet by the addition of lime, but lime shouldnot be depended upon alome as an improver of soils. Organicmatter should be added also. In attempting improvements ofthe soil, both the physical character and chemical nature of thesoil should be kept in mind. LABORATORY EXERCISES 1. Essay on Low Yields. — Write a two hundred word essay, giving thecauses of the low 3delds of some particular field in your neighborhood. 2. To Test Soils for Acidity. — Have pupils bring several samples of from garden and fields are preferred. Test each soil for acidity asdirected in a preced
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu, booksubjectagriculture
