6o 



Journal oj Agricultural Research 



Vol. III. No. I 



Table XXXIV. — Summary of ■water-requirement determinations at Akron, Colo., in 

 1911, 1912, and igi3, based on the production of dry matter — Continued 



Botanical name. 



Num- 

 ber 

 of ob- 

 serva- 

 tions. 



Water requirement. 



Of species or 



variety. 



Mean 

 of 



Genus. 



OTHER CROPS — continued. 



Legumes — Continued . 



Alfalfa, Peruvian, S. P. I. 



30203. 

 Alfalfa, Grimm, A. D. I. 



E-23-20-52. 

 Alfalfa, yellow-flowered. . 

 AUalfa, Grimm, S. P. I. 



25695- 

 Grasses: 



Wlieat-grass 



Brome-grass 



NATIVE PLANTS. 



Tumble weed 



Pigweed 



Piuslane 



Grass, buffalo 



Thistle , Russian 



Grass, buffalo and grama. 



Cocklebur 



Gum weed 



Sage , mountain 



Sunflower f Akron) 



Sunflower (sand hills) . . . 



Sunflower 



Lamb's-quarters 



Marigold, fetid 



Ragweed, western 



Wheat-grass, western 



Medicago sativa . 

 ....do 



Medicago falcata. 

 Medicago sativa. . 



Years. 



Agropyron cristatum. 

 Bromus incrmis 



Amaranthus graecizans. . 

 Amaranthus retroflexus . 



Portulaca oleracea 



Bulbilis dactj'loides 



Salsola pcstifer 



Bulbilis dactyloides 



,Bouteloua gracilis 



Xanthium commune 



Grindelia squarrosa 



Artemisia frigida 



Helianthus petiolaris 



do. 

 Helianthus annuus. 

 Chenopodium album. 

 Boebera papposa. 

 Ambrosia artemisifolia. 

 Agropyron Smithii. 



65i±i2 



844±8 



865±i8 

 963 ±9 



7o5±27 

 I, oi6±26 



277±4 

 297 ±4 

 292 ±11 

 3o8±i7 

 336±S 

 389±i2 



432 ±13 

 608 ±23 

 6i6±i8 

 774±2o 

 S70±ii 

 705 ±8 

 801 ±41 

 881 ±26 

 948 ±86 

 i,o76i:29 



831 



861 



287 



292 

 308 

 336 



389 



432 

 608 

 616 



683 



801 



881 



948 



I, 076 



The results given in the summary table (Table XXXIV) therefore 

 represent the water requirement of the plants for years similar to 191 1 

 and 1 91 3, when grown in a screened inclosure, which reduces the solar 

 radiation to 80 per cent of its normal value. According to measurements 

 made with wheat, alfalfa, and cocklebur, the removal of the inclosure 

 would increase the water requirement as given in the table by 25 per 

 cent. The plants grown outside the inclosure were isolated and freely 

 exposed, while plants under field conditions mutually protect and shade 

 one another to some extent. Comparison with wheat plants grown in 

 pots sunk in trenches indicates that the inclosure measurements, at 

 least in the case of wheat, are less than 10 per cent below the water 

 requirement of plants exposed under field conditions. 



The measurements in Table XXXIV represent the relative water 

 requirement of the different plants tested, subject to the limitations 

 imposed by the difference in the growth period of the plants. The 



