CALCAREOUS MANURES -PRACTICE. 95 



to the other, and was not mowed at all the last year, being thin and low, 

 and almost eaten out by wire-grass, {Cynodon dactylon.) 



1826. In corn— and It was remarkable that the difference shown the last 

 year was reversed, the muscle-shell marling now having much the best 

 crop. 



In these and other applications to neutral soils, I ascribe the earliest 

 effects entirely to gypsum, as well as the peculiar benefit shown to clover, 

 throughout. The later effects, and especially on grain, are due to the cal- 

 careous earth in the manure. 



CHAPTER VIII. 



DIGRESSION to THE THEORY OF THE ACTION OP GYPSUM AS MANURE. SUPPOSED 

 CAUSE OF ITS WANT OF POWER AND VALUE ON ACID SOILS. 



Proposition 5 — continued. 



Another opinion was formed from the effects of gypseous marl, as stated 

 in the foregoing chapter, which may lead to profits much more important 

 than any to be derived from the limited use of this, or any similar mineral 

 compound — viz. : tliat gypsum may he profitably used after calcareous ma- 

 nures, on soils on wiiich it ivas totally inefficient before. I do not present 

 this as a fact fully established, or, even if established, of universal application ; 

 for the results of some of my own experiments are directly in opposition. 

 But, however it may be opposed by some facts, the greater weight of evi- 

 dence, furnished by my experiments and observations, decidedly supports 

 this opinion. If correct, its importance to our low country is inferior only 

 to the value of calcareous manures alone — which value may be almost 

 doubled, if the land is thereby fitted to receive the wonderful benefits oi' 

 gypsum and clover. 



It is well known that gypsum has failed entirely as a manure On nearly 

 all the land on which it has been tried in our tide- water district; and we 

 may learn from various publications, that as little general success has been 

 met with along the Atlantic coast, as far north as Long Island. To account 

 for this general failure of a manure so efficacious elsewhere, some one of- 

 fered a reason, which was received without examination, and which is still 

 considered by many as sufficient, viz. : that the influence of salt va^wrs de- 

 stroyed the power of gypsum on and near the sea-coast. But the same 

 general worthlessness of that manure extends one hundred miles higher 

 than the salt water of the rivers — and the lands where it is profitably used 

 are much more exposed to sea air. Such are the rich neutral soils of 

 Curie's Neck, Shirley, Berkley, Brandon, and Sandy Point, on James river, 

 on all which gypsum on clover has been extensively and profitably used. 

 On acid soils, I have never heard of enough benefit being obtained from 

 gypsum to induce the cultivator to extend its use further than making a 

 few small experiments. When any effect has been produced on an acid 

 soil, (so far as instructed by my own experience, or the information of 

 others,) it has been caused by applying to small spaces comparatively large 

 quantities ; and even then, the effects were neither eonsidej-cilile, durable, 

 nor profitable. Such have been the results of many small experiments 

 made on my own acid soils — and very rarely was the least perceptible 

 effect produced. Yet on some of the same soils, after marling, the most 

 evident benefits have been obtained from gypsum on clover. The soils on 

 which the 1st and 10th experiments were made, (at some distance from thes>^ 



