An introduction to agriculture . beans Compare the flowers of a number of legumes and note theirsimilarity. 70 LEGUMINOUS CKOPS 71 63. Legumes as Nitrogen Gatherers.— We havealready mentioned the fact that clover and other legumeshave a special way ofgetting available ni-trogen from the soil,which non-legumin-ous plants do nothave. Since nitro-gen is in the air, wemight expect that allplants could get thisnitrogen through their leaves, but noplants are able to dothis. All le2;iiminousplants usually haveon their roots, littleswellings called nod-ules or tubercles con-tain bacter
An introduction to agriculture . beans Compare the flowers of a number of legumes and note theirsimilarity. 70 LEGUMINOUS CKOPS 71 63. Legumes as Nitrogen Gatherers.— We havealready mentioned the fact that clover and other legumeshave a special way ofgetting available ni-trogen from the soil,which non-legumin-ous plants do nothave. Since nitro-gen is in the air, wemight expect that allplants could get thisnitrogen through their leaves, but noplants are able to dothis. All le2;iiminousplants usually haveon their roots, littleswellings called nod-ules or tubercles con-tain bacteria which have the power not only of takingthe gas, nitrogen, from the soil, but also of making itinto a nitrate, by uniting it with other elements. Thisnitrate serves as a raw food material for the plants onwhich the bacteria live. Carefully dig up a clover, pea or bean plant, and gentlyshake the soil from the roots and notice the tubercles. Itwill not do to pull up the plants, as the tubercles will thenbe left in the RED CLOVER ROOTS Showing Tubercles 72 AN IKTKODUCTION TO AGEICULTUKE Amounts of Nitrogen in Legumes.— One ton of redclover hay contains approximately -iO lbs. of nitrogen;one ton of alfalfa hay, 47 lbs., and one ton of soy beanhay, 48 lbs. It has been estimated that the roots andstubble of red clover and of alfalfa plants contain aboutone-third as much nitrogen as is found in the partsof the plant harvested. When the roots of legumesdecay, the nitrogen they contain readily becomes avail-able for the crops which follow. This is one of thereasons why planting of legumes has such a beneficialeffect upon the crops which follow them in thefields. Inoculation.— Sometimes the bacteria which makethe tubercles on the roots of alfalfa, soy beans and alllegumes, are not found in the soil where these crops areplanted. Then, unless there is enough available nitro-gen in the soil to supply the relatively large amountthese plants require, they will not grow well.
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