The Roots of the Wheat Plant. 187 



tend to the recommendation of them as top-dressings for wheat, 

 and to be used in the spring or very early summer. Such 

 manures as are rich in ammonia, and of such a consistency or in 

 such a condition as to be capable of giving off this gas equally 

 and abundantly, are those most to be commended ; and if my 

 notions be correct, the circumstances which would tend to this, 

 namely, warm days after occasional spring showers acting on a 

 field in which the soil has been loosened by hoeing, are just those 

 under which the wheat-plant would grow vigorously and well. 



It should be mentioned that the crust which forms in some 

 soils in winter should be loosened in spring, to facilitate this very 

 action, as well as to destroy weeds, which latter should never be 

 allowed in a wheat-field, as being a set of plants whose mode of 

 respiration is different from the wheat ; from which cause, and 

 being nearer the soil, they rob the crop of some of its most valu- 

 able food, and so blighted straw and starved grain is nearly 

 always the result of dirty farming. 



It would make this Essay too long to advert to all the special 

 manures which have been adopted for top-dressing of wheat ; I 

 shall therefore only remark upon a few that are most commonly 

 used, of which the following is a short list : — 



1. Decomposed or prepared night-soil. 



2. Farm-yard dung. 



3. Guano. 



4. Nitrate of soda. 



5. Soot. 



6. Common salt. 



If farm-yard manure or night-soil be applied as a top-dressing, 

 it should be in a high state of decomposition, when it often acts 

 very advantageously ; but the difficulties attendant upon its ap- 

 plication are so manifest as in a great degree to discourage their 

 use. As respects night-soil, could it be rendered in a form in 

 which it could be readily and equally distributed, its richness in 

 nitrogenous matters and great abundance ought to ensure its 

 very general adoption ; but all plans to effect this have hitherto 

 resulted in rendering it as dear, if not for its results dearer, 

 than guano or special chemical substances. 



Guano has been found in most hands to be a serviceable top- 

 dressing for the wheat-crop : it is applied in various quantities, 

 according to the previous cropping and the state and condition of 

 the land ; but much disappointment has been experienced in its 

 use from its want of genuineness, or, if good, the state of the 

 weather has much to do with its success. 



Nitrate of soda is often mixed with guano in various propor- 

 tions. I have seen 1 cwt. to 2 cwt. of guano to the acre produce 

 very decided effects upon light soil. In this mixture it is likely 



