10 Aug., 1916.] Lucerne Manurial Tests. A5I 



particularly nitrogen, accumulated by the lucerne roots during the time 

 it occupied the ground, are gradually made available to these crops. 

 This reserve of plant food, together with the amount normally supplied 

 by the soil, is sufficient to provide for the demands of the heaviest 

 crops. Crops like sorghum, ambercane, imphee, maize, &c., grow par- 

 ticularly well. . 



One other point needs to be mentioned. Most farm crops secure 

 their mineral nutrients from near the surface. Lucerne, on the other 

 hand, can penetrate the soil to a great de])th. At Bacchus Marsh and 

 Tamworth the roots have been traced to a depth of 30-35 feet. 



Near Tamworth, New .South Wales, many old paddocks of lucerne 

 have been undermined by the eroding action of the Peel and the Cock- 

 burn rivers, and the root system to a depth of 30 feet exposed to full 

 view. 



Though the total amount of plant food removed per acre by lucerne 

 is considerable, it must be borne in mind that a goodly quantity of tins 

 material is gathered from regions inaccessible to the roots of ordinary 

 farm crops. 



The reader will see that the lucerne crop makes a heavy drain on the 

 mineral constituents of the soil. He may infer that lucerne is an ex- 



Fig. 5. — Cutting Crops on Lucerne Manurial Plots, State Research 

 Farm, Werribee. 



Iiausting crop, and that its continual growth will deplete the soil of its 

 fertility. There is no doubt that lucerne, as compared with cereal 

 -crops, does make heavy calls on the soil; but the old adage " One cannot 

 eat the cake and have the cake " applies here. A large crop of high 

 nutritive value cannot be Drcdueed without removing from the soil large 

 c|uantities of plant food. 



The amount of plant food removed from the soil by any given crop 

 is, roughly, proportionate to the size of the crop. The skilful cultivator 

 endeavours to raise as big a crop as possible, and recognises that the 

 larger the crop, the more the necessity for replacing some of the 

 nutrients removed by the crop. 



Large Amount of Plant Food Stored Up in Lucerne Roots. 



It may be of interest in passing to briefly indicate the amount of 

 plant food stored up in the lucerne roots. A number of lucerne plants 

 were grown at Rutherglen during 1914-15 in deep pots to gather infor- 

 mation as to the ratio of root development to overhead growth, and 

 tlie amount of plant food stored up by me roots. 



