456 Journal of A f/riri//fii/r, Victoria. ["10 Aug., 1916. 



Now contrast this with the amount removed by a 30-bushel wheat 

 crop. If the grain is carted off the farm, and the straw burnt in situ, 

 or ploughed in, a 30-bushel crop of grain will remove — 



Nitrogen, 34 lbs. 

 Potash, 9.3 lbs. 

 Phosphoric acid, 14.2 lbs. 

 Lime, 2 lbs. 



These figures should give some idea of the tremendous foraging power 

 of lucerne. The worst plot on the Experimental Field at Werribee in 

 two years removed from the soil — 



9 times as much nitrogen as a 30-bushel wheat crop. 



36 times as much potash as a 30-bushel wheat crop. 



172 timesi as much lime as a 30-bushel wheat crop. 



4.5 times as much phosphoric acid as a 30-bushel wheat crop. 



Now, experience has shown that wheat lands are generally deficient 

 in phosphoric acid, and that superphosphate must be sown with the 

 seed if profitable crops are to be reaped. What then must we say of 

 a crop which uses up every two years enough phosphoric acid to supply 

 the needs of nearly five 30-bushel wheat crops? And since phosphoric 

 acid is the most deficient plant food in our Australian soils, it follows 

 that the fertilizers applied should contain a substantial amount of 

 phosphates. 



There are now verv few wheat farmers in Victoria who fail to apply 

 phosphatic manures with everv crop of wheat they sow. Experience has 

 taught them that phosphates are absolutely essential for successful 

 cropping. How much more essential should it be to apply an occasional 

 dressing of phosphates to an established lucerne crop, grown in many 

 cases on worn out wheat lands. 



It will be seen, too, that lucerne makes a heavy drain on the potash 

 supplies of the soil. Victorian soils, however, are generally well sup- 

 plied with potash, and the average wheat soil contains at least 2 per 

 cent., or 7,000 lbs. of potash for each acre-foot of soil. The subsoils 

 are even richer. Only a small portion (possibly not more than 1 per 

 cent, of the total potash in the soil) is available for the use of the crop 

 at any given moment. The use of such soil amendments as lime, gypsum, 

 and ground limestone, helps to liberaJte some of the insoluble phosphates 

 and potash of the soil, and this explains the increased returns of lucerne 

 following the use of dressings of lime. 



Regarding the nitrogen supply, the lucerne plant is, of course, able 

 to draw on the supplies of nitrogen from the air, and probably the 

 greater part of the nitrogen gathered by the plant comes from this 

 source. Of- course, if the whole of the crop is removed in the form of 

 hay, then the drain on. the nutrients of the soil is considerable. If the 

 lucerne is grazed, however, or consumed on the farm by live stock and 

 the drippings returned as top dressings, approximately one-third _ to 

 one-half of these nutrients are returned to the soil, the balance being 

 utilized to maintain the animals, and build up muscle, flesh, and bone. 



These figures are certainly striking, and they explain why oM lucerne 

 fields are so productive for some years after their renovation. It is 

 particularly noticeable on the irrigation settlements, where old lucerne 

 fields are broken up and sown with forage and grain crops prior to re- 

 sowing down with lucerne. The large quantities of nutrient material, 



