VALOR AGREGADO

of their development under the influence of other conditions; and it is to be observed, as would be expected, th a t in all the cases of high amounts of silica in the crops, it was where the gramineous herbage was forced into prominence under the influence

of liberal supplies of both nitrogen and mineral constituents. I t is, however, obvious

th a t there was more silica where the nitrogen was given as nitrate of soda, than

where it was applied in corresponding amount in ammonium-salts. There is also, in

the crops of the third group, with mineral manure alone, more silica where soda was

included than where it was not. In reference to this point it will be remembered

th at, in the detailed discussion of the percentage composition of the ashes, attention was several times called to the fact that, in comparable cases, an increased percentage of silica was generally associated with an increased percentage of soda.

Nitrogen :—Of nitrogen, the average annual amount in the crops ranged, in the first group, from 34 lb. on plot 3 without any manure, to 50 lb. on plot 2, where

farmyard manure had been applied during the first 8 of the 18 years, and to 61 lb. on plot 1, where besides the residue of farmyard manure previously applied, 43 lb. of nitrogen were annually supplied as ammonium-salts.

In the second group, to which nitrogenous manures alone were applied, the annual yield of nitrogen in the first crops was from 55 lb. on plot 5 with 86 lb. of nitrogen as ammonium-salts ; to 64 lb. on plot 15 with the same amount of nitrogen applied but as nitrate of soda; and to 56 lb. on plot 17 with only half the quantity (43 lb.) annually supplied as nitrate of soda.

To the plots of the third group, mineral manure was annually applied, but no nitrogen; and the annual yield of nitrogen in the first crops was 35 lb. on plot 4-1 with superphosphate of lime alone, 58 lb. on plot 7 with the full mineral manure including potash, by which the highly nitrogenous leguminous herbage was much

encouraged, and the grasses became stemmy and matured. P art of the increased

amount of nitrogen in the crops under the influence of the mineral manure including potash was, as shown by analyses of the surface-soil, derived from the stores of the soil itself; and part by fixation, as shown by the presence of nodules on the roots of

the leguminous plants. The yield was, however, compared with th at on plot 7,

reduced to an average of only 48 lb. over the 18 years on plot 8, from the manuring of which potash had been excluded during the last 12 of the 18 years. The reduction was from 61 lb. over the 6 years with potash, to 42 lb. over the 12 years without it, and it was associated with a great reduction in the amount of leguminous herbage, and a great reduction in the amount and character of the grasses, but an increase in the amount of miscellaneous herbage.

In the fourth group, where the nitrogenous and mineral manures were used together, the average annual yield of nitrogen in the crops was 74 lb. on plot 9, with 86 lb. supplied per acre per annum as ammonium-salts; 70 lb. on plot 14, with the same amount applied, but as nitrate of soda; 65 lb. on plot 16 with half the quantity as nitrate of soda; and 106 and 109 lb. on plots 11-1 and 11-2, where the

excessive amount of 158 lb. of nitrogen was on the average annually supplied. I t should he added, th a t to each of the above plots the same complex mineral manure was annually applied ; excepting th a t on plot 11-2 artificial silicate was supplied in addition. On plot 4-2, on the other hand, with ammonium-salts and superphosphate, h u t no potash, soda, or magnesia, and accordingly by far the smallest produce within the group, scarcely any leguminous herbage, and characteristically dark green and imm ature leafy produce, the average annual yield of nitrogen was also the lowest

within the group, namely, 58 lb. There was, therefore, three times as much nitrogen

in the crop over a given area where it was very abundantly supplied, as where no manure was used ; and there was nearly twice as much as where the complex mineral manure was used alone.

Looking a t the results from another point of view, it is of interest to notice th a t where 86 lb. of nitrogen were annually applied as ammonium-salts alone (plot 5), the average amount of nitrogen in the first crops was 55 lb., but where the same amount of ammonium-salts was used in conjunction with the complex mineral manure including

potash (plot 9), the amount of nitrogen in the produce was 74 lb. Again, when the

same amount of nitrogen was applied as nitrate of soda (plot 15), the annual yield ol nitrogen in the crop was 64 l b .; but when the nitrate was used with the complex mineral manure including potash (plot 14), the yield in the crop was 70 lb.

Lastly, the figures quoted show, th a t where nitrogen was applied as manure, a large amount of th a t supplied remained unrecovered as increased yield in the crop.

The Non-nitrogenous substance:—The mode of estimating the non-nitrogenous substance has been explained, and it is adm itted th a t the results are only approxi­

mations to the tru th . Still, they have considerable significance. Thus, when

ammonium-salts alone supplying 86 lb. of nitrogen per acre per annum were used (plot 5), the estimated annual yield of non-nitrogenous substance in the removed crop was 2065 lb. W hen the same amount of ammonium-salts was used with superphosphate (plot 4-2), the yield was 2487 lb., or 422 lb. more ; but when used with superphosphate, and potash, soda, and magnesia (plot 9), the yield was 3996 lb., showing therefore a further increase of 1509 lb. ; or a total increase of 1931 lb. compared with the yield by the ammonium-salts alone. Again, when the same amount of nitrogen was applied as n itrate of soda (plot 15), the yield of non-nitrogenous substance was 2742 lb. ; but when the same amount of nitrate was used with the mixed mineral manure, including

potash (plot 14), it was 4546 lb., or 1804 lb. more. Lastly, when the ammonium-

salts were applied with the mixed mineral manure including potash, over 6 years (plot 10), the annual yield of non-nitrogenous substance was 4261 lb .; but when over the next 12 years potash was excluded from the manure, the yield was only 3314 lb.— or 947 lb. less.

There can be no doubt th a t the luxuriance, or vegetative activity, is intimately

associated with the amount of nitrogen available and taken up. Further, it may be