108 Development and Activities of Roots of Crop Plants. 



container, was fastened in place. Before putting the wooden strips in posi- 

 tion, however, pieces of oilcloth were inserted under them in such a manner 

 that one end extended an inch or two under the wax seal, while the other Uned 

 the inside of the opening between the strips and came up through the roof, 

 upon which it was folded back and tacked down. This gave a smooth surface 

 against which the plants might later be blown back and forth free frdm injury 

 during windy weather (plate 12 b). In case of the potatoes, a rectangular 

 opening about 3 by 4 inches was left in the roof. Similar modifications from 

 that described were also made for the corn and wild grasses, the latter being 

 planted as sods. A small amount of earth was placed in the opening thus 

 left, the crop planted, and a mulch of about an inch of dry sand added to check 

 water-loss. Both barley and potatoes were planted on April 1, the halves of 

 two potatoes being placed in the soil of each of the several containers at a depth 

 of about 4 inches. The barley, as usual, was planted thickly and later thinned 

 to the desired stand. 



Table 39. — Loss of water and nitrates April 1 to May 25. 



1 The gain by nitrification has been calculated here, as in the following tables, from data 

 obtained from the control container (see table 41, p. Ill), on the assumption that the increase 

 by nitrification varied directly with the time. 



After the soil had been replaced about the containers in the trench and 

 ridged up in such a manner as to insure drainage away from them, barley 

 was planted thickly on both sides of the row of containers and in this manner 

 field conditions were approximated (plate 12). During the hotter part of 

 the season the wooden roofs were covered with a mulch of straw to lessen the 

 intensity of the heat. Brome-grass was sowed about the containers in which 

 wild grasses were growing, while the corn was placed in tho middle of a small 

 corn-field. 



As pointed out on page 88, weather conditions were very favorable for 

 rapid development of the crops, the ripening of the small cereals occurring 

 at least two weeks earher than normally in eastern Nebraska. The average 

 dail}' temperature, humidity, and evaporation are shown in figure 41. 



