432 



Soil investigations, F. H. King (pp. 189-20G).— The iinportanco 

 of investigations in the physics of the soil has led to the ai)poiutnient 

 of an agricultural physicist at this station. 



The work in soil physics which has been coniraenced, relates, among other qnes- 

 tions, specifically to the following : 



(1) To what depth below the snrface is the water contained in tlie soil drawn upon 

 by plants? 



(2) What is the amount of water the available depth of soil is capable of storing ? 



(3) How much of the waters stored in our soils dill'erent kinds of cultivated plants 

 can use and yield average crops? 



(4) What is the amount of water a given soil must contain at the beginning of the 

 growing season, supjilemented by our average summer rain fall, to give an average 

 yield? 



(5) When the amount of stored water in the spring is above or below that best 

 suited to plant growth, what distribution of crops and what sort of tillage will yield 

 the largest returns ? 



(G) What volume of air various soils should contain to give the largest yields with 

 diflerent varieties of cultivated plants ? 



(7) Do our present methods of tillage impart the desired porosity to soils ? 



(8) Influence of difterent methods of tillage on soil temperatures. 



(i)) Influence of our various methods of tillage on the rate of evaporation. 



(10) Whether one variety of corn, for example, requires more water than another 

 to produce a pound of dry matter. 



The aim in approaching these questions has been to make each case definitely a 

 field study with soils undisturbed, except by the operations of tillage, using labora- 

 tory methods only as checks on field work and as suggestive of lines of procedure. 



Soil water. — On the basis of investigations by Hellriegel in Prussia, 

 it is estimated that the amount of water required by a crop of corn is 

 nearly 12 inches of rain-fall, which is more than one third of the year's 

 rain-fall at the station, and within 3 inches of the rain-fall during the 

 months of May, June, Julj^, and August, that being 15 inches. The 

 need of more definite knowledge regarding soil water is urged as follows : 



Since soils may contain either too much or too little moisture, for the best results 

 in plant growth it is evident that before methods of tillage, intended either to 

 diminish or conserve the amount of water contained in the soil at any time, can be 

 intelligently applied, many A'ery fundamental facts aud principles need to be better 

 understood. 



Just as in stock feeding it is important to know how many pounds of this or that 

 combination of food stufts are required to produce a pound of mutton, pork, or beef, 

 so in plant feeding it is equally important to know how many pounds of water on 

 this or that kind of soil are required to produce a pound of clover, corn, oats, or 

 potatoes. 



More knowledge is needed as to the storage capacity for water of our soils in their 

 natural conditions and positions ; as to the jier cent of this water available for differ- 

 ent crops in the production of good yields; as to the depth below the surface difit'ereut 

 plants can utilize soil water ; and as to the best methods of reducing the amount of 

 soil water when the soil contains too much, and of c:onserving it when the stock is 

 below the average needed. 



If we knew very definitely the amount of water our difiereut varieties of soil should 

 contain at the beginning of the growing season, when supplemented by the mean 

 ijummer rain-fall, to bring goodcrop yields, it would be a simple matter for any farmer 

 to determine whether the water present in his soils was above or below the amount 



