82 Development and Activities of Roots of Crop Plants. 



depths are progressively drier westward. Abundant moisture was present at 

 all levels at Lincoln; the soil below 1 foot was quite dry at Phillipsburg, 

 while no available moisture occurred below 3 feet at Burlington. However, 

 at all stations the surface soil had been fairly moist during the period, and 

 undoubtedly the limiting factor to growth was temperature. 



At Lincoln the mean temperature for April was 53.9° F., at Phillipsburg 

 54.2°, and at BurUngton 50.4°. The temperature at Lincoln fell below 

 freezing on 6 days (latest April 17) during April, at PhilUpsburg on 7 days 

 (latest April 26), and at Burlington on 13 days, including April 28. The crops 

 at the latter station had been damaged somewhat by frost. The soil-tem- 

 perature to depths of 4 feet on April 28 to 30 are given in table 26. These 



data show that the drier soils at Phillipsburg were warmer at all depths than 

 those at Lincoln, while the Burlington soils were much colder than at either 

 of the other stations. 



By May 18 to 21 the wheat and barley at the several stations had reached 

 the stages of development shown in plate 5. The condition of the oats in 

 the various plats at this time is shown in plate 6. Judging from general 

 crop conditions, the growing-season at Phillipsburg was at least a week later 

 that than at Lincoln, while that at BurUngton was perhaps 3 weeks later. 

 A summary of crop development is given in table 27. At both Phillipsburg 



Table 27. — Crop development at the several stations, May 18 to 21, 1921. 



