216 MISCELLANEOUS FARM SUBJECTS 



Summer Fallow and Summer, Fall, and Winter Plowing. 

 These are all efficient measures in the extermination of injurious in- 

 sects, the first being especially valuable in this direction, because it 

 not only tends to exterminate all insect life in the fields thus treated, 

 but prevents their becoming infested during the period of fallow. 

 Next to this, in point of efficiency, might be placed midsummer plow- 

 ing without further cultivation until fall plowing. (Y. B. 1905.) 



An increase in the number of bacteria in the soil means an in- 

 creased available supply of plant food, hence the aim of a philosoph- 

 ical system in crop rotation is to include in that system such crops as 

 favor the development of bacteria and the elaboration of plant food 

 in the soil. Such crops are hoed crops, as potatoes, or forage crops, 

 as clover. (Del. Col. B. 40.) 



Crops in their growth, it is now believed, have an important toxic 

 (poisonous) reaction upon the soil in which they grow that is, they 

 give off from their roots during growth matter of a toxic or poison- 

 ous nature. Aeration, oxidation, and the chemical recombinations 

 incident to the decay of organic matter are important aids in break- 

 ing up and removing these poisonous excretory compounds. Differ- 

 ent classes of crops excrete somewhat different kinds of toxic matter. 

 The crops in the rotation should therefore be so arranged as to pre- 

 vent the toxic effects due to the continuous growing of the same 

 crop. (Y. B. 1908.) 



Rotation for Tobacco Farms. Crop rotation can also be made 

 to serve a most useful purpose in many cases by preventing or min- 

 imizing the danger from insect enemies, especially those which spend 

 a portion of their life cycle in the soil. Take, for example, the two 

 greatest pests of newly set tobacco, and of many other crops for that 

 matter cutworms and the so-called wireworm, or stalkworm. Their 

 presence depends almost entirely upon the character of the vegeta- 

 tion growing upon the land during the previous season; that is, 

 whether it was attractive or not to the adult forms of these insects 

 during the period when they deposited their eggs. To apply this 

 principle, it is necessary to see that the soil is not occupied at the 

 egg-laying season by vegetation which is attractive to the adult in- 

 sect or, better still, to see that it is occupied by a form which is alto- 

 gether repulsive. It is generally known by tobacco growers in many 

 sections that after heavy growths of weeds, particularly the iron- 

 weed or stickweed, the soil is very likely to be seriously infested with 

 the dreaded wireworm; indeed, it is frequently infested to such an 

 extent as to render it almost impossible to secure a stand of tobacco 

 until the pests leave or pupate, when it is too late to secure anything 

 like a normal crop. A field intended for tobacco, or corn, or any 

 other crop which these pests attack should not be allowed to grow up 

 in ironweed during the previous year. A field which has grown 

 cowpeas the previous season, provided they have been kept clean of 

 weeds, will be free from both cutworms and the wireworm. This 

 fact, if taken advantage of, is of inestimable value to tobacco grow- 

 ers, because the presence of wireworms or cutworms in the soil is a 

 most serious drawback to any effort toward the increased use of 



