416 REPORT — 1873. 



The quantity of effluent water measured was 470,552 tons as against only 

 195,536 tons last year. This is to be accounted for partly by the greater 

 dilution by rain, indicated by a difference of 0-01 of nitrogen per 100,000 

 parts in the composition of the effluent water, but principally by the fact 

 that the extra drainage alluded to in the last Report has been carried out. 

 Although, therefore, the effluent water this year shows less total nitrogen per 

 100,000 parts, yet the absolute quantity contained in it amounted to i 

 instead of -^ of the absolute quantity distributed over the farm. 



Tables IV. to VI. are similar to the corresponding Tables of last year, and 

 are subject to the same qualifications with regard to the quantities of sewage 

 applied to the various crops and plots ; that is to sa^^ that the means available 

 for the measurement of the quantities of sewage and effluent water only 

 rendered possible the actual measurement of the total daily quantities, the 

 details professing to show approximately the quantities applied to the 

 individual crops and plots being merely calculated numbers obtained from 

 the daily totals by breaking these up in proportion to the areas irrigated each 

 day. The chief value of these figures is to show the desirability of obtaining 

 such details with precision. This, however, would require a numerous staff 

 of trained chemical and engineering assistants, and also the expenditure of a 

 considerable sum of money in apparatus, and in isolating, by means of sunken 

 barriers of concrete, the individual plots. 



By comparing Tables V. and VI. of this year with Tables V. and VI. of 

 last year, it will be found that the total produce taken off the farm during the 

 year ending March 2-lth, 1873, was 1704 tons against 2714 for the pre- 

 ceding year. This was due partly to the fact that tlie area in standing crop 

 on March 24th, 1873, was 87-62 acres against 4049 acres on March 24th, 

 1872 (see Table VIT.), and partly to the fact that there were 26-18 acres of 

 cereals in the j'ear now recorded, against 0-9 of an acre in the previous year. 

 The nitrogen recovered in the ci'ops taken off the land for the year under 

 review is estimated at 15,704 lbs. as against 19,067 lbs. for the preceding 

 year. This smaller quantity recovered out of a larger quantity applied is 

 obviously due to the same causes which affected the weight of crops. 



The nitrogen escaping in the effluent water is estimated at 11,973 lbs., as 

 against 5024 lbs. in the previous year. This increase is due to the additional 

 drainage of the farm giving a larger measured quantity of effluent water as 

 before explained, namely 470,552 tons as against 195, .536 tons. 



The amount of nitrogen unaccounted for (that is to say, accumulated in 

 the standing crops and top soil, washed into the subsoil, or lost) is the differ- 

 ence between that applied in the sewage (60,438 lbs.) and the sum of the 

 quantities recovered in the crops (15,704 lbs.) and escaping in the effluent 

 water (11,973 lbs.) — namely, 32,701 lbs., as against 22,404 lbs. unaccounted 

 for in the previous year. 



These quantities, expressed in percentages, show that of every 100 parts of 

 nitrogen distributed over the farm in the sewage, 26 were recovered and 

 taken off the farm in crops, 20 escaped in the effluent water, and 54 remained 

 in the standing crops, in the soil, or in the subsoil, or were lost. 



This nitrogen balance-sheet shows that the results of an experiment in 

 agricultural chemistry over so extended an area, and with so great a variety 

 of crops, can only give true averages if condiicted over a lengthened series of 

 years ; for the produce of the farm was in many respects moi-e satisfactory in 

 the year now recorded than in the preceding one, liaving regard to the amount 

 of cereals grown and the crops left standing, and yet at first sight it appears 

 the reverse. 



