Junk 1908.] 



551 



Scientific Agriculture. 



that'from earth was 17*9 inches, and from 

 sand only 3*7 inches. The velocity of the 

 wind, too, has a great effect ou the 

 amount of evaporation. It has been 

 observed that with a velocity of 5 miles 

 per hour, the evaporation was 2*2 times 

 that form one iu quiet air; 10 miles per 

 hour, 3 - 8 times ; 15 miles, i'9 times ; 20 

 miles, 57 times ; 25 miles, 01 times ; and 

 30 miles, 6'3 times. 



Murungan, May 12, 1908. 



NOTES ON HUMUS AND THE BEST 

 MEANS OE SUBELYTINLr IT. 



By P. B. Guthrie. 

 Over that considerable portion of the 

 State's arable land ou wincn the rainfall 

 is limited or uneven, the need of retain- 

 ing within the soil whatever moisture is 

 received as ram is one of paramount 

 importance in tne treatment or tne laud. 

 The maintenance of the soil's fertility in 

 these areas becomes iaigely a question of 

 conserving this sometimes scanty supply, 

 and soil treatment having for its object 

 suitable means of maintaining the most 

 favourable conditions as to moisture will 

 claim the most serious consideration of 

 the farmer. 



As the land taken into cultivation 

 gradually extends so as to include more 

 and more of the area within the belt of 

 reduced rainiall and approaching to 

 semi-arid conditions, this question oi the 

 conservation of soil moisture becomes of 

 increasing importance. 



It far exceeds in importance the ques" 

 tion of manuring, and it is safe to say 

 that unless the conditions as to moisture 

 are satisfactory, the application of 

 manures is not likely to be of any benefit, 

 and the money expended on their use is 

 practically thrown away. 



Apart from the question of cultivation 

 and drainage, the maintenance of the 

 best conditions as to water within the 

 soil depends to a very large extent upon 

 the presence of humu^. Humus, which 

 is derived from the gradual decay of 

 animal or vegetable matter within the 

 soil, is one of the most important of the 

 soil's constituents, and any variation in 

 its amount affects profoundly the value 

 of the soil for agricultural purposes. 



Functions op Humus. 

 The presence of humus in the soi^ 

 increases the fertility in the following 

 ways :— 



In the first place it absorbs and retains 

 moisture in the soil, and prevents surtace 

 evaporation. A surface soil, fairly rich 



in humus exercises much the same in- 

 fluence on the underlying soil as does a 

 mulch of dead leaves or' other vegetable 

 matter. During the dry spells and under 

 the influence of the hot winds usually 

 prevalent under such conditions, the loss 

 of moisture from the soil by surface 

 evaporation is enormous, and in soils 

 destitute of humus this loss is so rapid as 

 to result in the drying up of the soil and 

 the wilting of the crops. The final result 

 of such conditions is the formation of 

 scalded spots and the complete removal 

 of the fine surface soil in the form of 

 dust. 



The humus in the soil is the ingredient 

 which is most subject to alteration and 

 destruction, and under dry conditions it 

 is more or less rapidly destroyed. As 

 soon as it has lost its moisture and be- 

 come dry it is rapidly burnt out by the 

 combined action of sun and air. So that 

 it is exactly in those circumstances 

 where its presence is most essential that 

 it is most liable to destruction, and the 

 necessity for renewing it most urgent. 



The presence of humus in the oil also 

 tends to improve the texture of the soil, 

 lightening it and loosening it, and 

 preventing compaction of the surface, 

 so that it is of special value in the ameli- 

 oration of stiff soils. 



It is the principal source of nitrogen 

 in the soil, and by its decay under the 

 influence of soil organisms, ammonium 

 salts and nitrate are produced, which are 

 the forms in which this important ele- 

 ment is assimilated by the plant. It is 

 of interest to remember that the humus 

 of arid or semi-arid regions is richer in 

 nitrogen than that of the moister dis- 

 tricts. This is a point of great import- 

 ance with reference to the potential 

 fertility of these soils. In point of fact 

 from a variety of causes acting together, 

 the soil of the dry climates are richer in 

 plant food of all kinds than are the soils 

 in regions of greater rainfall, conse- 

 quently nothing but the absence of water 

 prevents these from being extremely 

 reproductive. There is, therefore, no 

 problem which exceeds in importance 

 that of retaining in the soil the little 

 moisture that it receives, and any oper- 

 ation that exceeds in arresting even par- 

 tially the unavoidable loss of that moist- 

 ure deserves the highest consideration. 



Methods op Supplying Humus. 

 There are three ways of supplying 

 humus to soils in need ot this constituent, 

 namely, by the application of generous 

 additions of farmyard manure (in cases 

 where this is available), by the applica- 

 tion of compost manure, and by green- 

 manuriug, or the ploughing under of a 



