AGRICULTURAL CHEMISTRY AND GEOLOGY. 173 



It is well known that peas often refuse to cook soft, even after hours of boiling. The 

 reason of this is not at all understood. It has been asserted that manuring the crop with 

 plaster gives the peas this quality ; but the contrary is also asserted. This is a point to bo 

 studied. 



Influence of the soil on the action of plaster. The character of the soil must necessarily 

 greatly affect the operation of this fertilizer. A soil already rich in sulphate of lirne of course 

 cannot be greatly benefited by addition of more. A poor, light, or exhausted soil, deficient 

 in mineral plant-food, as phosphoric acid, potash, &c., cannot be expected to become fertile 

 by treatment with plaster ; for this substance cannot supply those matters which are want- 

 ing, and without which no plant can flourish. Cold, wet, heavy, and impenetrable soils are 

 usually almost unaffected by plaster; sometimes, its use has been apparently disadvantageous 

 on them. Porous soils, either sandy or loamy, which readily dry after rains, and which are 

 well dunged, experience the most benefit from plastering. Excess of moisture and poverty of 

 the soil are the chief hinderances to the action of gypsum. On lime and chalk soils it is no less 

 effectual than on others. In general, it may be stated that unless the other conditions of good 

 culture be observed and provided for, the farmer who uses gypsum will "lose his money and 

 his trouble." It is undoubtedly a fact, that the circumstances which insure the best effect 

 from gypsum are nearly identical with those which are otherwise most favorable to vegetable 

 growth. 



Effect of climate and weather. Countries, like South England, the greater part of France, 

 Bohemia, &c., where, on account of the vicinity of the* sea, or the existence of forest and hill 

 ranges, the climate is uniform ; and where, during the growing season, the rain-falls are fre- 

 quent, but moderate ; where, in other words, it is neither too wet nor too dry, there gypsum 

 stands in greatest favor. It is doubtless the fact that the frequent wetting of the soil assists 

 the action of plaster by bringing it into solution ; yet the weather probably exerts more influ- 

 ence on the plant itself directly than on the action of the plaster with which it is manured. 

 Climate modifies the conditions of vegetable growth to a wonderful degree. In the more 

 northern part of our temperate zone, a stiff clay soil is very intractable and unproductive ; 

 while in Egypt, where it never rains, a similar soil yields the most profitable returns. We 

 should, therefore, expect to hear from a Canadian farmer that plaster has little good effect on 

 clay soils ; while in the warmer South, they might be benefited most of all. 



Quantity and time of application. In England and Germany, it has been found that 250 to 

 400 pounds per acre is the best quantity to apply. The advantage of larger applications is 

 usually very inconsiderable. Gypsum is usually applied in the spring, and in case of clover, 

 &c., when the vegetation is 3 to 4 inches high. In the United States, it is applied to corn and 

 potatoes in the hill at planting, but more frequently when they have attained the above- 

 mentioned height. 



Many farmers are of opinion that plaster acts best when it remains adhering to the leaves 

 for some time. Accordingly, it is highly recommended to sow plaster just before or after a 

 gentle rain, or when the dew is on the plants. Warm, moist weather insures the full action 

 of plaster. If the weather be cold at the time of sowing, its effect is stated to be very insig- 

 nificant. This is, however, doubtful. In Germany, the first of May is generally considered 

 the best season for plastering ; and experiments made in Saxony, especially to ascertain the 

 most favorable time, have confirmed the opinion. Not a few, however, deem it indifferent 

 whether the plaster adhere to the plant or fall directly upon the soil. 



Dombasle employed the following method : He plastered his meadows at the time of seed- 

 ing, and repeated the dose in the following spring. Clover treated in this way grew very 

 luxuriantly; sometimes even to the detriment of the grain with which it was sown. It is re- 

 ported that clover thus plastered is less injured by frosts, and is ready to cut a week or two 

 earlier than when gypsum is not applied. 



Duration of effect. According to Girardin, " experience has established that plastering (of 

 clover?) should not be repeated oftener than once in five or six years, if any action is to be 

 expected from it." Other writers agree in admitting that its benefit continues nearly or quite 

 as long. Its effect has often been observed to be greater the second than the first year after 

 application, and is often unabated the third season. The duration of its action is doubtless 



