Jmi. 2,1920.] Agricultural Gazette of N.S.W. 29 



Soil Improvement for Maize. 



I — Manures and Fertilisers. 



H. WENHOLZ, B.Sc. (Agr.), Inspector of Agriculture. 



The improvement of the soil for maize-growing is a question that is yearly 

 becoming of more importance. The time has passed in most districts when 

 " the face of Mother Nature can be tickled and she will laugh herself into 

 a bounteous crop," and the 100-bushel yields which the early settlers 

 obtained by hoeing the maize in between the stumps on newly-felled scrub 

 lands are less frequently heaid of. 



The maize grower of to-ilay kno-^s that in order to get hea\y yields he has 

 to use the best methods of seed selection and cultivation, but the improve- 

 ment or maintenance of soil fertility is even more important. Every farmer 

 who has handled virgin soil must ha\e observed the change produced in it by 

 continued cultivation. The mellow tilth, the moisture-retaining capacity, and 

 the fertility give place to a soil which becomes heavier, which dries out 

 more quickly, and bakes and cracks more easily, turning over in big hard 

 lumps and clods when ploughed. It is only by a study of the cause for this 

 change and of what materials this virgin soil has lost, that any successful 

 attempt can be made to restore it to its former likeness. 



The first examination reveals that the greatest loss is that of organic matter 

 or humus. The accumulation of vast quantities of leaf mould in the forest 

 or scrub during thousands of years has added large amounts of organic matter 

 to the soil, which begin to disappear when the soil is cultivated. It is now 

 known that the aeration of the soil by cultivation oxidises the organic matter 

 eventually into a form (particularly nitrates) in which it can be made use of 

 by plan*:s as food material, and that at the same time this oxidised organic 

 matter loses its capacity for retaining moisture. Cultivated crops like maize, 

 root crops, &c., which are grown in drills, therefore consume this organic 

 matter more quickly than wheat and bioadcast crops which are not cultivated. 

 It is easy to see, then, why the continued cultivation of maize or potatoes, 

 although grown on land which was originally very fertile, depletes the soil 

 of its virgin fertility more quickly than most other crops. It has been 

 calculated that land cultivated for thirty years has lost 30 to 35 per cent, of 

 its organic matter. In addition to the loss of organic matter, a crop of 

 maize removes from the soil larger amounts than most other crops of the 

 chief materials of plant food — nitrogen, phosphoric acid and potash. 



The three chief means of restoring or making good these losses of organic 

 matter and plant food are (1) rotation of crops ; (2) cover cropping and green 

 manuring ; and (3) the application of manures and fertilisers. On some 

 alluvial soils on the banks of streams, a flood deposit of rich silt makes good 

 this loss naturally ; but in many cases, partly because of efi'orts made to 



