400 CARNEGIE INSTITUTION OF WASHINGTON. 



The root extent at each station varied but slightly from year to 

 year. With all crops it was greatest in the mellow loess at Peru, and 

 least in the compact silt-loam at Burlington. At Peru the smaller 

 cereals reached depths of 6 to 8 feet, potatoes 4 to 4.5 feet, and corn 

 7 to 8 feet. At Burlington the hard-pan at a depth of 2.7 feet deter- 

 mined the limit of root extent. The lateral spread of roots in these 

 drier soils was marked, and especially their development near the sur- 

 face. Alfalfa was greatly branched in this environment, although in 

 moister soils it normally has a pronounced tap-root free from large 

 branches. In general, root extent at Phillipsburg was somewhat 

 greater than at Lincoln, probably to be accounted for by exceptional 

 seasonal rainfall. 



Experiments have been carried out with barley, potatoes, corn, and 

 certain native grasses to determine the absorption of water and nitrates 

 at different levels throughout the period of growth. Cylindrical con- 

 tainers, 2 to 4 feet in diameter and 2.5 to 5 feet deep, were filled with 

 soil and subsoil of known physical and chemical composition taken 

 from the crop plats in such a manner that the soil had the same relative 

 position it occupied in the field. Before filling the containers the soil 

 from each level was thoroughly mixed, brought to the desired water- 

 content, and certain levels impregnated with NaNOs at the rate of 400 

 parts per million, based on the wet weight of the soil. The soil was 

 separated into layers a foot or less in thickness by means of a wax- 

 seal consisting of 85 per cent paraffin and 15 per cent petrolatum, 

 which was melted and poured upon the soil quite hot. This seal 

 prevented the movement of water and solutes from one level to another, 

 and was easily penetrated by the roots, as shown by their distribution 

 in the soil-mass, as well as by the normal growth of the plants in 

 comparison with those grown in unsealed containers and experimental 

 plats. Barley was grown thickly in a row across the containers, and 

 corn and potatoes in hills in the center, the stems extending through 

 openings in the sloping wooden cover. The containers were placed in 

 trenches in the field and the crops grown about them in such a manner 

 as to simulate normal field conditions. The results thus far obtained 

 show conclusively that crops absorb water at all levels to which 

 roots penetrate, and barley, for example, in quite as large amounts 

 from deeper as from surface soils. Similar results are indicated in 

 regard to nitrates. 



Plant Production Quadrats, by J. E. Weaver. 



The study of the effect of climate upon the production of natural 

 vegetation, begun m 1920, has been continued during the present 

 season at the several transplant and crop stations. The usual method 

 employed was to select 10 or more meter-quadrats in typical undis- 

 turbed areas in the climax vegetation. The height and density of 



