1918] FIELD CROPS. 227 



ments of plants enibi'ucing experiiueuts with different field crops grown in 

 galvauized-iron tanks from 1911 to 1913, inclusive, in field plats from 1912- 

 1914, inclusive, and in sand cultures to which were added nutrient solutions 

 of varying concentration. Considerable tabulated data are present showing 

 the water requirenionts of crops under field conditions. The results are de- 

 [)icted by gnqjlis. Adilitional data show the effect upon the water require- 

 ments of plants of the following factors: Kind of crop, percentage of ash in 

 plants, concentration of the nutrient soil solution, fallowing, individiial plant 

 food elements, alkali salts, previous cropping, variety, stage of development, and 

 percentage of capillary saturation. The conclusions reached have been sum- 

 marized as follows : 



" The numerous conditions surrounding plants that influence their growth 

 and water requirement and the adaptability and habits of the plant to meet 

 these conditions make it impossible to give any definite water requirement for 

 any plant, or even to give the relative order in which a given number of 

 varieties will stand in respect to this factor. The average water requirement 

 [pounds of water required to produce a pound of dry matter] of 6 cereal crops 

 was 312, and for 4 legumes. 429. The daily amount of water transpired by 

 wheat, corn, oats, and peas increa.sed until about the beginning of the ripen- 

 ing period ; from this time there was a gradual decrease up to maturity. 

 The depth to which field crops took moisture was : Wheat, 9 ft. ; oats, 8.5 ft. ; 

 barley, 8 ft. ; peas, 6 ft. ; millet, 5.5 ft. ; corn, 5 ft. ; beans, 5 ft. The crops 

 that took the soil moisture from the greatest depth also had the greatest 

 water requirement. Tanks proved to be equal to field plats in determining 

 the water requirements of plants. The ash content of different plants in- 

 creased with the increased water requirement. 



" Plants grown in culture solutions varying in concentration from 0.01 to 

 0.1 per cent increased in total dry matter produced and decreased in water 

 requirement. The average of 3 trials, a 0.01 per cent concentration gave a 

 growth of 3.152 gm. of dry matter and a water requirement of 729; in a 0.1 

 per cent concentration, 39.2226 gm. of dry matter and a water requirement 

 of 381. The percentage of roots in the total dry weight decreased from 43.2 

 per cent in a 0.0125 per cent concentration to 17.3 per cent in 0.1 per cent con- 

 centration of a nutrient solution. In like manner the water requirement was 

 reduced from 605 to 262, respectively. The above results indicate that weak 

 soil solutions cause an increased root development in plants. 



" The water requirement of wheat was 34 per cent less, and for beans 19 

 per cent less, when grown on summer-fallowed soil than when grown on cropped 

 soil. 



" When any of the essential plant food elemepts — nitrogen, potassium, phos- 

 phorus, and calcium — were reduced to 0.02 per cent and 0.01 per cent of that 

 contained in a normal solution used in culture solution work in this bulletin, 

 the reduction of calcium and potassium made good growths and nitrogen and 

 phosphorus poor growths. The water requirement was increased in each case 

 except when calcium was deficient. When nitrogen was reduced to 0.01 per 

 cent of the normal solution, 43.2 per cent of the total di'y matter produced 

 was roots. When calcium was reduced to 0.01 per cent of the normal solution, 

 only 10 per cent was roots. Consequently a soil with a low nitrate content 

 causes a plant to develop an abnormally large root system. Increasing the 

 concentration of a complete culture solution by addition of alkali salts, viz. 

 sodium carbonate, sodium sulphate, and sodium chlorid, decreased the water 

 requirement until the solution became so concentrated to inhibit growth. 



" The water requirement of wheat was less when grown on soil that had 

 grown legumes and intertilled crops the previous season than the soil that 

 had grown cereals. The difference obtained in the water requirement due to 



