8 



was 4^ bushels in 1879. Other yields have been 21^ bushels in 1854, . 

 20 in 1857, only 5^ in 1853, and only 8-9 bushels in 1867, 1875, 1876, 

 and 1877. 



In the lower division of the table (I.) the average produce is given for 

 each four years, each eight years, each sixteen years, and for the thirty- 

 two years from 1852 to 1883 inclusive; also for the whole period of 

 forty years. Without manure, the average annual produce over the 

 four-year periods was 14^, 17^, 14^6, 12^, 13^, 10^,8^, and 12^ 

 bushels; over the eight-year periods, 16}^, 13^, 12^, and io}4 ', over 

 the sixteen-year periods, 14^5 and u^j ; over the thirty-two years, 13^, 

 and over the forty years, 14 bushels. With such wide variations due to 

 season, it is very difficult to estimate the rate of decline due to exhaus- 

 tion. Excluding the very bad seasons, the decline due to gradual ex- 

 haustion is reckoned at from one-fourth to one-third of a bushel per 

 acre per annum. 



It is estimated that over a period of thirty years the unmanured plot 

 yielded an average of 18.6 Ibs. of nitrogen per acre per annum in the 

 crop, and lost a minimum of 10.3 Ibs. in drainage, in all 28.9 Ibs.; whilst 

 on the mixed mineral manure plot (5), it is estimated that the crop re- 

 moved an average of 20.3 Ibs. of nitrogen, and that at least 12 Ibs. were 

 lost by drainage, or in total 32.3 Ibs. Further it is estimated that the 

 soils lost to the depth of twenty-seven inches about two-thirds of these 

 amounts; leaving, say, 10 Ibs. more or less to be otherwise accounted 

 for. Of this, the rain, etc., would supply 5 Ibs., or perhaps rather more, 

 and the seed about 2 Ibs., so that there is but little to be provided from 

 all other sources. Lastly, as at the commencement the soil was, agri- 

 culturally speaking, exhausted, the nitrogen supplied by it would be 

 largely due to old accumulations. 



SECOND. FARM-YARD MANURE EVERY YEAR. 



In the application of farm-yard manure every constituent is supplied 

 in excess. The highest yields of the series of years were 44 bushels in 

 1863,41^ m 1868,41^ in 1857, and 41^6 in 1854. The lowest yields 

 were 16 bushels in 1879, 19^ in 1853, 20^ in 1844, 23^ in 1876, and 

 24^ in 1877. 



The average produce per acre per annum over each of the five eight- 

 year periods was, 28, 34^, 35^, 35^, and 28^ bushels. Excluding 

 the first eight years, and several of the recent very bad seasons, the 

 average produce is about 35 bushels per acre per annum. 



On the farm-yard manure plot, the first nine inches of soil show a 

 great accumulation ; it is nearly twice as rich in nitrogen as any other 

 plot, yet this richness is not proof against bad seasons ; nor are the 

 highest amounts of produce in the field obtained on this plot. 



Thus, without manure, or with mineral manure alone, there is a grad- 

 ual decline in yield, and with this a marked reduction in the nitrogen of 

 the soil. With farm-yard manure, on the other hand, there is great ac- 

 cumulation, and yet not the fullest crops, a large proportion of the con- 

 stituents becoming very slowly available. 



The next question is, which constituents of farm-yard manure are tht 

 most effective for wheat in this agriculturally exhausted rather heavy 

 soil, with a raw clay subsoil. The first illustrations on this point will be 

 drawn from Table II. 



