106 J. Kk. TAYUOR. 
Soil Nitrogen.—The amount of nitrification of the soil’s. 
own nitrogen is important as showing the capacity of a 
soil to nitrify its reserve of complex nitrogen compounds 
and gives us an idea of what it is capable of doing with 
optimum field conditions. Reports from other countries 
show as much as 387 of this soil nitrogen nitrified and as 
little as a trace, but for average semi-arid soils the amount 
is roughly up to 6%. Hall at Potschefstroom reports an 
average of up to 57% for fifty-four soils, California from a 
trace to 267, an average of 3—67, Colorado 6/ and so on. 
Granting now that the soil we are dealing with is typical 
of a large wheat district the amount of nitrification is 
quite low. The maximum amount for each soil is Grass, 
2°2%; Lucerne, 2°8%; PA, 2°15%; PB, 2°2%; PO, 1°9%; PD, 
1°8%; or in round figures 40 - 50 tbs nitrates in four weeks 
of optimum conditions. 
Summary. 
Some points of interest in the preceding pages may be 
tentatively emphasised not as indisputable facts but as 
useful for any continuation of this or similar experiments, 
(1) Judged by the failure of the soil to respond to nitro- 
genous fertilisers, the crops grown on it are usually 
sufficiently supplied with nitrates. The experiments 
indicate, however, that it would be improved from a physical 
as well as a chemical and biological point of view, by 
liming and the introduction of organic matter. 
(2) The moisture content is a Jesson in fallowing. The 
cultivated fallow designated PC has not shown out as well 
as might be expected, but this was due largely to neglect 
to cultivate at a critical time, viz. October, November, 
and January. It is not improbable that with care’ and 
proper treatment not less than 8% could have been stored 
in the surface soil and the. subsoil was shown in March to. 
be holding 12% water. All the other soils were very low,, 
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