SOIL EXHAUSTION AND ROTATION OF CROPS. Igf 



16 bushels to 36 bushels, aud kept it steadily at that point for 

 nineteen years ; so that the difference between 16 and 36 bushels, 

 that is, 20 bushels, was the crop which was produced from that 

 field by the use of fourteen tons of stable manure in one case, and 

 four hundred pounds of salts of ammonia in another. It was the 

 stable manure and ammonia salts in those quantities which im- 

 proved the "condition" of the land by the equivalent of 20 

 bushels of wheat. 



We understand, then, that there is a natural quality in the soil 

 which we cannot easily bring below a certain limit ; and there is a 

 "condition," an artificial, temporary or adventitious fertility, 

 which we can easily increase aud easily exhaust. 



There are many circumstances which necessitate or justify a 

 Rotation of Crops. I will not attempt to enumerate' them all. 

 Differences of soil and climate, the quantity of fertilizers accessi- 

 ble, the demand in the markets, ease of transportation, politicians, 

 when they make fluctuating tariffs, weeds which come to infest 

 the fields, insects even, may make it advisable to alternate our 

 crops. It may not be uninstructive to go back in history and 

 give a sketch of the gradual development of the practice of Rota- 

 tion. 



The earliest husbandry was simply pasturage. When the 

 people of temperate climates found they could not support them- 

 selves by killing wild animals and gatheriug fruits, the natural 

 produce of the country, they began to tame animals and keep 

 herds of cattle, sheep, etc.; and you know that on the vast plains 

 of Asia and South America, this sort of pastoral husbandly is still 

 the only one known. As population became more dense, and land 

 more valuable, people crowded each other, and there was not room 

 •enough to roam about at will and settle upon pasture wherever it 

 could be found, unless, for a change, the people fell to fighting, 

 and partially killed each other off, thus leaving land enough for 

 the survivors. When civilization began, it became necessary to 

 cultivate forage crops, or, at least, to take some care of the natu- 

 ral meadows. The next step was to assist these natural resources 

 by growing some grain, and people began to break up a little land, 

 and cultivate wheat and the various grain crops ; afterwards, at- 

 tention was given to root crops. It ma}' not be possible now to 

 show how these steps of progress have taken place in any given 

 locality ; but this is a general history of the development of 

 husbandry all over the world, wherever it has attained any perfec- 



