102 VERMONT AGRICULTURAL REPORT. 



than a pound of loaf sugar in a single lump. Why? Simply 

 because there is a larger surface area for the fluid to attack 

 when the sugar is granulated than when it is in either of the 

 other two forms. If some force broke the lump and loaf 

 sugar into fine particles they would dissolve more quickly. 

 Similarly, if through plowing, harrowing, spading, cultiva- 

 tion in general, the soil particles, already minute, are still 

 further subdivided and made smaller, their total surface area 

 is increased and the opportunity is bettered for the battery 

 of solvents present in every soil to attack and to dissolve the 

 plant food. 



The natural plant food of a soil, if it could all be made 

 available as. needed, would last indefinitely ; but it is mainly 

 insoluble. Had it been the plan of creation to make it all 

 available at once it would have been leached out long ago. 

 Continuous cropping without restitution of the plant food 

 removed, however, depletes the stock of soluble ingredients. 

 This condition may be remedied by the direct addition of 

 available plant food, by tillage, or both. It is quite possible 

 by thorough tillage to greatly increase crop production, in 

 part because of the fining of the soil and the greater chance 

 for solution. 



Nature's soil solvents are water, the root and humus 

 acids, nitric acid and nitrates, etc. They act in conjunction 

 and their work may be hindered or favored according as op- 

 portunity is afforded them by tillage. 



2. Tillage and soil breathing. A good agricultural soil 

 breathes, inhaling and expiring air as does an animal. The 

 rush of air is sometimes observed in wells in open soils to be 

 strong enough to blow a flame. This soil breathing is caused 

 more particularly by alterations in air pressure, barometric 

 changes and by changes in temperature between day and 

 night. It presents new air to the same soil particle and pro- 

 motes its disintegration. 



3. Tillage aids bacterial growth. The effect of the air 

 on the growth of the lower organisms is most important. All 

 soils contain bacteria, minute plants of microscopic size. Cer- 

 tain species are beneficial, others detrimental, and yet others, 

 so far as are known, are without effect. As a broad and gen- 

 eral rule, those which are harmful thrive best where the air is 

 lacking. Hence in proportion as tillage opens up a soil and 

 increases its breathing, within limits, its aerobic or air-loving 

 bacterial life is favored and its anaerobic or air-shunning 

 bacterial life is hindered. 



Among the bacteria which are indispensible to plant 

 growth, whose activities are in some measure affected by the 

 amount of air which is available, may be mentioned those 



