228 EXPERIMENTAL FARMS 



5-6 EDWARD VII., A. 1906 



suits show a marked decrease in the percentage of nitrogen in the cultivated lands. 

 One series may suffice. Regarding the cultivated soil, we possess a complete and au- 

 thenticated record of the cropping and fallowing since the prairie was first broken, 

 22 years ago. It had home six crops of wheat, 4 of barley, and 3 of oats, with fallows 

 (9 in all) between each crop since 1887. No manure had ever been applied. The 

 pample of virgin soil for comparison was taken from an adjacent area that had never 

 been cultivated, the point of collection being about 120 feet distant from where the 

 cultivated soil sample was taken. Both samples were of a composite character and 

 every precaution taken to have them thoroughly representative. It may, further, be 

 added that there is every reason to suppose that the soil over the whole area examined 

 was originally of an extremely uniform nature; in other words, that at the outset the 

 nitrogen content was practically the same for the soils now designated as virgin and 

 cultivated respectively. The results of the investigation are given in the following 

 table : — 



Nitrogen. ' 



Per cent. Lbs. per acre. 



Virgin soil to a depth of 4 inches -409 3,824 



Cultivated soil to a depth of 4 inches -257 2,402 



Difference, or loss due to cropping and cul- 

 tural operations -152 1,422 



Virgin soil, to a depth of 8 inches -371 6,936 



Cultivated soil to a depth of 8 inches -253 4,730 



Difference, or loss dvie to cropping and cul- 

 tural operations '118 2,206 



Though in all probability the virgin soil has gained somewhat in nitrogen during 

 the period of 22 years, for that is the tendency with soils in sod, the increase could 

 not have been such as to materially affect the deduction that a very considerable de- 

 pletion of soil nitrogen has followed the practice of continued cropping with grain 

 and fallowing. The results show that the cultivated soil is to-day still very rich, yet 

 compared with the untouched prairie it is seen to have lost one-third, practically, of 

 its nitrogen. This is highly significant. Humus and nitrogen must be returned, either 

 as manure or by the occasional growth of certain enriching crops, or fertility will 

 inevitably decline. The productiveness of many of our soils is due largely to the 

 accumulation of centuries, but these stores of plant food may be and are in many places 

 being unduly dissipated through irrational methods and with even our best soils it 

 cannot be many decades before decreased yields will show the necessity of occasionally 

 replenishing the soil's hvimus and nitrogen. 



The work of the experimental farms during the past fifteen years has shown that 

 wherever climatic conditions allow, this replenishing of humus and nitrogen, this 

 maintenance, and indeed increase, of fertility may be most readily and economically 

 accomplished through the growth of one or other of the legumes — a family of plants 

 possessing the unique and valuable property of appropriating the free nitrogen of the 

 atmosphere. In establishing the manurial value of the legumes, the nitrogen-content 

 of a number of those more commonly advised from the standpoint of soil enrichers 

 has been determined. The results of these analyses are to be found in several of the 

 past reports of this Division. Evidence has also been brought forward by determining 

 the yields of various farm crops following the growth of clover or other legume. The 

 data that we have accumvilated on this important subject are voluminous, but they all 

 point in the same direction — the increase of productiveness following the growth of 

 the legume. 



