220 FUNDAMENTALS OF FRUIT PRODUCTION 



ing influence on the trees, though they themselves may not be able to 

 use any of it. The good results frequently obtained from the use of 

 acid phosphate and credited to the influence of the phosphorus may be 

 due in part to the sulphur carried by that fertilizer. 



This question of the influence of different fertilizer treatments on the 

 nature of the plant population in undisturbed soil has been studied very 

 carefully at the Rothamstead Experimental Station in England. Differ- 

 ences are to be expected with varying soil conditions and without doubt 

 the response in an orchard would be different from that in an open meadow 

 such as that in which the Rothamstead investigations were conducted. 

 Nevertheless the following statement from the summary of this work 

 is very suggestive: 



"In the produce grown continuously without manure the average number of 

 species found has been 49. Of these, 17 are grasses, four belong to the order 

 Leguminosfe, and 28 to other orders. The percentage, by weight, of the grasses 

 has averaged about 68, that of the Leguminosae about nine, and that of species 

 of other orders about 23. 



"In the produce of the plot already referred to as the most heavily manured, 

 and yielding the heaviest crops, the average number of species found has been 

 only 19, of which 12 to 13 are grasses, one only (or none) leguminous, and five to 

 six only represent other orders; whilst the average proportions by weight have 

 been — of grasses about 95 per cent., of Leguminosse less than 0.01 per cent., and 

 of species representing other orders less than 5 per cent. 



"On the other hand, a plot receiving annually manures such as are of little 

 avail for gramineous crops grown separately in rotation, but which favor beans 

 or clover so grown, has given, on the average, 43 species. Of these, 17 in number 

 are grasses, four Leguminosse, and 22 belong to other orders, but by weight, the 

 percentage of grasses has averaged only 65-70, that of the Leguminosae nearly 

 20, and that of species belonging to other orders less than 15. . . . 



"It is found that there is a considerable difference in the percentage of dry 

 substance in the produce, and very considerable difference in the percentage of 

 mineral matter (ash) in that dry substance. There is still greater difference in 

 the percentage of nitrogen in the dry matter, and, again, a greater difference still 

 in the percentage of individual constituents of the ash. When, indeed, it is 

 remembered that a plot may have from 20 to 50 different species growing upon 

 it, each with its own peculiar habit of growth, and consequent varying range and 

 power of food-collection, it will not appear surprising that different species are 

 developed according to the manure employed; and, this being so, that the charac- 

 ter and amount of the constituents taken up from the soil by such a mixed herb- 

 age should be found much more directly dependent on the suppUes of them by 

 manure than is the case with a crop of a single species growing separately. 



"In further illustration it may be mentioned that, not only does the per- 

 centage of nitrogen in the dry substance of the produce of the different plots 

 vary considerably, but the average annual amount of it assimilated over a given 

 area is more than three times as much in some cases as in others. Again, the 

 percentage of potash in the dry substance is three times as much in some cases 



