June 12, 1914] 



SCIENCE 



861 



is essential to the preservation of moisture 

 and the supplying of fertility. 



There is little doubt that the earth mulch, 

 a preparation for erosion, does make the fertil- 

 ity more available, and does cheek evapora- 

 tion. We need much more knowledge than 

 we now have as to whether or not the same 

 results may not be obtained by the application 

 of mineral or other chemical fertilizers, which 

 will increase natural vegetation, which will 

 therefore increase humus, and the natural 

 water-holding power of the soil. Eather con- 

 vincing evidence as to the efficacy of this 

 latter method is to be had in the sod mulch 

 orchards under the care of the Ohio Agricul- 

 tural Experiment Station, and also in the 

 variation of crop yields in rich and poor lands 

 in a dry season in the Berber villages of 

 Northern Algeria. At the present moment the 

 idea of the maintenance of fertility and a 

 good crop yield without tillage is so unortho- 

 dox that almost no experiment stations in the 

 United States will look at the subject with 

 respect, yet in it lies great possibility of the 

 extension of tree-crop agriculture to large 

 areas of land where cultivation is difficult and 

 is almost synonymous with erosion unless 

 careful terracing shall be worked out. 



The actual holding of water upon the ground 

 until it sinks in is an aspect of the matter 

 well worthy of extensive investigation. The 

 mangum terrace, which is so efficient in taking 

 water away from a hillside without erosion, 

 can doubtless be enlarged and made absolutely 

 horizontal so that it will keep the water where 

 it falls, after the practise of Colonel Freeman 

 Thorpe, of Hubert, Minnesota. This is a 

 practise worthy of much experimentation, and 

 one which fits peculiarly into the tree-crop 

 idea. It is doubtless true that in many local- 

 ities the water standing behind the horizontal 

 mangum terrace would injure wheat, clover 

 and other small crops. On the other hand, 

 there seems to be little reason to anticipate 

 that it would injure trees that stood upon the 

 terrace and had their roots beneath the reser- 

 voir of water, which might stand and freeze 

 for considerable periods with no injury to the 

 tree, which would get the water when it soaked 



into the ground. This has been proved suc- 

 cessful for 20 years in a Pennsylvania apple 

 orchard. 



This practise has been worked out for many 

 decades in the olive orchards of Central Tunis 

 around Sousse, and it unquestionably can be 

 utilized with tree crops in many parts of the 

 United States. Its limitations must be defined 

 by experimentation, which may also find aids 

 in the growth of deep-rooting annual plants 

 to increase porosity and absorbing power of 

 the soil. 



There also appears to be no reason why this 

 mangum terrace might not be modified into 

 a series of basins that would hold near each 

 tree the water that fell near it, and thus prac- 

 tically apply the methods of the California) 

 water economizing irrigators. Such prepara- 

 tion of the soil would be efFective for many 

 years and would therefore be less expensive 

 than annual cultivation. 



An efl^ect of this holding of water where it 

 fell would be the absolute stoppage of a loss of 

 fertility that results from the washing away 

 of incrustations of soluble salts deposited 

 through the evaporation of earth moisture at 

 the surface. The effectiveness of this process 

 in bringing earth salts to the surface is well 

 known. It has given us our alkali soils, but 

 we owe it to Colonel Freeman Thorpe to call 

 our attention to its surprising effectiveness as 

 an agency in fertility loss where water is al- 

 lowed to run off of the surface. This factor 

 alone may be found worthy of all the effort 

 necessary to hold water where it falls. 



m. CONCLUSION 



If the economic botanists and plant breeders 

 can give us a series of new cropping trees 

 which will furnish new foods for both man 

 and beast, we will have an economic factor 

 which will combine a number of forces, be- 

 cause it helps to meet a number of needs. It 

 will greatly stimulate food production, also 

 wood production. Through the development 

 of the plowless agriculture and terrace water 

 holding, we will have conservation of the soil 

 and of fertility. We will also have in this 

 combination the greatest of all forces yet 



