228 EXPERIMENT STATION RECORD. [Vol.38 



variety in spring wlieat is small. Tliere is a decrease in the water require- 

 ment of wheat and oats with increase in age. 



"The percentage of caj)illary saturation of the soil in which plants are 

 grown Is not an important factor in the water requirement of plants, provided 

 the percentage of moisture is maintained considerably above the wilting point. 

 The results of these investigations indicate that any condition wiiich disturbs 

 the normal life processes, be it soil, atmospheric, or pathological, increases the 

 water requirement to just such a degree as it depresses the normal functionings 

 of the plant." 



A bibliography of 27 titles is appended. 



A new method for harvesting small grain and grass plats, A. G. McCall 

 (Jour. Amcr. Soc. Agron., 9 (1911), No. S, pp. 138-11,0, figs. 2).— A device for 

 harvesting small grains and grasses in varietal and soil fertility tests is de- 

 scribed and illustrated. The apparatus was constructed and used at the Mary- 

 land Experiment Station, where small areas of wheat and timothy plats were 

 harvested, giving results which checked satisfactorily with records obtained 

 from harvesting and thrashing entire plats. 



[Report of field crops work in Nebraska] (Nehraska Sta. Rpt. 1916, pp. 

 XV-XVII). — Water requirement investigations were continued through 1916, 

 employing 425 potometers, and the relation of soil, climatic, and crop characters 

 to the use of water by crops studied. Some of the more important conclusions 

 arrived at are as follows : 



" Transpiration is essentially evaporation. Changes in climatic conditions 

 affect somewhat similarly the rate of water loss from a corn plant and that 

 from a shallow physical free water surface. Variation in the water lequlre- 

 ment from day to day is very marked. Occasionally this daily variation 

 amounts to 300 or 400 per cent in successive days. The maximum variation 

 observed in 2 successive days has been 600 per cent. On days of extreme tem- 

 perature in very dry years there may be an atmospheric demand of 10 lbs. of 

 water from a single average corn plant during 24 hours. ... In a compara- 

 tively short time the corn may receive injuries from which it never fully 

 recovers. Bearing this in mind it is evident that a period of brief duration 

 may affect yields more than the annual amount of rainfall. 



"A marked variation exists in the water requirement of different years, due 

 to natural climatic differences. There is a rather consistent relationship in the 

 relative seasonal variations between (1) transpiration per unit of dry matter. 

 (2) transpiration per unit of leaf area, and (3) evaporation from a free water 

 surface. There is no such thing as a definite water requirement which is 

 constant for any one kind of crop. A reduction in soil-moisture content below 

 the optinnnn during three years i*educed the water requirement per pound of ear 

 corn 4.3 per cent and per pound of total dry matter 7.9 per cent. This reduc- 

 tion in water requirement was, however, accompanied by 37.3 per cent reduced 

 stalk yield, 28.5 per cent reduced yield of ear corn, and 30.7 per cent lower 

 yield of total dry matter. . . . 



"An increase in the soil-moisture content above the optimum during three 

 years increased the water requirement per pound of ear corn 13.5 per cent and 

 per pound of total dry matter 8.2 per cent. This increase in water requirement 

 was accompanied by 11.3 per cent reduced stalk yield, 21.1 per cent reduced 

 yield of ear corn, and 1G.7 per cent lower yield of total dry matter. . . . 



" The water requirement per pound of dry matter is much larger in an infer- 

 tile soil than in a fertile .soil. Increasing the fertility of the soil reduces the 

 water requirement for grain production and for total dry matter. An appli- 

 cation of manure has a much greater effect upon an infertile than upon a 



