166 QUANTITIES OF MARL REQUIRED. 



become the best land, at least for wheat and for grass.* The moro 

 acid the growth of any soil is, or would be, if suffered to remain, 

 the more increase of crop may be expected from ma^l; which is 

 directly the reverse of the effects of putrescent manures. The in- 

 crease of the first crop on my worn acid land, I have never known 

 under fifty per cent., and more often it is as much as one hundred; 

 and the improvement continues to increase, under mild tillage, to 

 three or four times the original product of the land. (See Exp. 

 11, page 185, and Exp. 4 and 6.) In this, and other general state- 

 ments of effects, I suppose the land to bear not more than two 

 grain crops in four years, and not to be subjected to grazing during 

 the other two ; and that a sufficient cover of marl has been laid on 

 for use, and not enough to cause disease. It is true, that it is 

 difficult, if not impossible, to fix that proper medium, varying as it 

 may on every change of soil, of cropping, and of the kind of marl. 

 But whatever error may be made in the proportion of marl applied, 

 let it be on the side of light dressing (except where putrescent 

 manures are also laid on, or designed to be laid on before the next 

 course of crops begins) ; and if less increase of crop is gained to 

 the acre, the cost and labour of marling will be lessened in a still 

 greater proportion. If, when tillage has served to mix the marl 

 well with the soil, sorrel should still show to any extent, it will 

 sufficiently indicate that not enough marl had been applied, and 

 that it may be added to, safely and profitably. If the nature of the 

 soil, its condition and treatment, and the strength of the marl, all 

 were known, it would be easy to direct the amount of a suitable 

 dressing ; but without knowing these circumstances, it will be 

 safest to give not more than 200 or 250 bushels of marl, of say 40 

 per cent, to the acre of worn acid soils. Twice or thrice as much 

 might be given, safely and profitably, to newly cleared wood-land, 

 or well manured land. Or, I would advise that the first dressing 

 should not exceed the quantity which would furnish one per cent, 

 of carbonate of lime to the soil, for its ploughed depth. If only 

 3 inches deep, 218 bushels of marl, of 40 per cent., would furnish 

 1 per cent, to the soil. Besides avoiding danger, it is more profita- 

 ble to marl lightly at first on weak lands. If a farmer can carry 

 out only ten thousand bushels of marl in a year, he will derive 

 more product, and confer a greater amount of improvement, by 

 spreading it over forty acres of the lancl intended for his next 

 crop, than on twenty ; though the increase to the acre would pro- 

 bably be greatest in the latter case. By the lighter dressing, the 

 land of the whole farm will be marled, and be storing up vegetable 

 matter for its progressive improvement, in half the time that it 

 could be marled at double the rate. 



* Confirmation. "On clay lands more lime is necessary than on light 

 and sandy soils." Johnston's Lectures, p. 382. 



