54^ Journal of AgncuUitre , Victoria. [lo Sept., 19 12. 



•or from an absence of lime, moulds, fungi, and harmful types of bacteria 

 flourish to the exclusion of the useful forms. 



Summing up, we may say that a soil, to be fertile, must be satisfactory 

 from three i)oints of view : — 



{a) It must contain a sufficiency of plant food in a ])roperly 



assimilable form. 

 {b) It must possess a satisfactory physical constitution, i.e., be 

 of good texture, mellow, well drained, retentive of moisture, 

 and good capillary power, 

 (c) It must be in good biological condition, so that free plav may 

 be given to the development of those bacteria which work 

 for the advantage of the crop. 

 Formerly, the importance of the chemical aspect of the question was 

 greatly exaggerated. To-day it is recognised that many important problems 

 •connected with the treatment of soils and manuring of crops, which 

 iiitherto have been incapable of explanation bv the chemist, may, in the 

 near future, be satisfactorily explained by the biologist. 



Manuring. 



The object of manuring is to supplement the supplies of plant food 

 in the soil to such an extent as to enable a full crop to be grown. 



The substances requiring special attention are those in which the soil is 

 likely to be deficient, namely, nitrogen, phosphoric acid, and potash. 



Occasionally, however, manures are applied with a view of improving 

 the physical and biological condition of the soil rather than augmenting 

 the supplies of plant food. This is the case when soil amendments, such 

 -as lime, gypsum, and green manures, are used. 



If the soil is deficient in any one of the necessary ingrerlients, no 

 amount of tillage can put it into good " heart;" and, as the yield of the 

 -crop is governed by the amount present of the most deficient soil ingredient, 

 it is imperative that the deficiency be made good by the direct applica- 

 tion of fertilisers if satisfactory crops are to be obtained. 



How TO Determine Soil Deficiencies. 



In view of the fact that soils vary very considerably in their chemical 

 •composition, it is most important that every farmer should be able to 

 •determine for himself in what elements his soil is deficient. It has already 

 been observed that chemical analysis is of little value for this purpose. 



The most practical method of determining the soil requirements is 

 ■establishment of a simple set of experimental plots. By this means, the 

 farmer puts questions to the soil, and the answers to the questions are 

 indicated by the amount of growth and the yield of the crop for each 

 :separate treatment. 



A simple and effective scheme is to arrange for the sowing of a series 

 of plots at seed time with the following treatment : — (a) No manure ; 

 ■{h) phosphates alone ; {c) nitrates alone ; {d) potash alone ; {e) phosphates 

 jnd nitrogen; (/) phosphates and potash; {^ phosphates, nitrogen, and 

 potash. If the growth and development of these be carefully observed, 

 and the yields from each separately determined, the experiments will be 

 able to determine what class of manures is likely to prove profitable under 

 his particular conditions. On badly drained, sour soils, lime supplemented 

 3jy phosphates, should be included. Having determined which ingredient 

 is deficient in his soil, the farmer may now proceed to determine, in a 

 similar manner, the most profitable and economical form in which this 



