^ KOTES AND ABSTRACTS. 465 



systematic study. The moveiiient of water in the soil and the rate of 

 loss of soil water are influenced by numerous factors, and the value of 

 these factors needs to be determined for a variety of soils. It is not 

 even certain that surface cultivation will check evaporation from every 

 soil, for one kind of soil has been found which invariably loses more 

 water when cultivated than when left sun-baked. It is thought that 

 plants cannot regulate the amount of water that they take from the soil, 

 but, other conditions being the same, the larger the quantity of water 

 presented to the plant roots the greater the amount used. Hence it is 

 necessary to deternhne the optimum percentage of water that should be 

 found in various kinds of soil after each irrigation, keeping in mmd both 

 the rate of assimilation and that of transpiration, the latter being in- 

 fluenced by t]ie composition of the soil itself, so that the number of 

 pounds of water required for the production of one pound of diy matter 

 is increased or diminished according to the available plant food. Cer- 

 tain experiments have shown that the available soil fertility set free 

 during one season by persistent hoeing has largely reduced the amount 

 of water required for each pound of ihy matter — in one case by nearly 

 -0 per cent. ; that two or more years of fallowing have reduced the 

 water cost of dry matter by one-half or more ; and that the addition of 

 commercial fertilizers to somewhat infertile soils has "made it possible 

 to grow^ crops with very much smaller amounts of water than before. 

 The bacterial life of the soil, as affecting fertility, is also strongly in- 

 fluenced by irrigation, and it seems to have been proved that the periodic 

 application of irrigation water does affect definitely the production and 

 distribution of nitrates. 



The investigations necessaiy to determine the relations between 

 plants and water under conditions of irrigation are very complex. In 

 general, it has been foimd that with little irrigation water much more 

 grain, potatos, sugar-beets, and other crops, is produced per inch than 

 with larger quantities of w^ater, the crop-producing value of w^ater appear- 

 ing to get less up to a definite limit, beyond w^hich an actual diminu- 

 tion of crop may result. It is estimated that the more moderate use of 

 water, according to the finding of the experiments already conducted, 

 would double or treble the irrigation area wuthout adding to the storage 

 and conduction of water for the purpose. Not only the total yield of 

 the crop but its quality and manner of growth may be influenced. The 

 time of maturing may be delayed or hastened; the relative proportions 

 of plant parts — leaves, roots, stems, and seeds — may be varied, as well 

 as the composition of the plants. It w^as found some years ago at the 

 Utah station that by regulating the amount of water applied to wheat 

 on a certain shallow soil the proportion of protein m tlie grain was raised 

 from about 15 to 26 pei" cent., though it is thought such a greaL 

 variation can only be accomplished under unusual conditions. 



It is. pointed out that to carry out irrigation investigations success- 

 fully needs the services of skilled men trained m various branches of 

 science. — A. P. 



VOL. XXXVII. H H 



