118 EXPERIMENT STATION RECORD. 



was important for the yield of both grain and straw; 70 mm. (2.75 in.) was 

 the normal precipitation for the month. 



As compared with precipitation, the temperature in the chernozem region 

 appears to be as a rule a secondary factor, although extremes of temperature 

 may occasionally prove fatal to the yield. The mean temperature and the 

 length of the period from seeding to heading exerted a certain influence on the 

 yield of straw. Good yields of grain were obtained under greatly varying 

 mean temperatures and sums of temperature. In general a low mean tem- 

 perature (5-6° C.) during the period of germination and a moderate mean 

 temperature (11-13°) during the later stages of growth was favorable to the 

 yield of grain and especially of straw. A mean temperature higher than 17° 

 during the period from sprouting to heading affected unfavorably the yield of 

 straw and endangered the yield of grain. A moderate mean temperature dur- 

 ing the period from sprouting to heading (15-16°) and its consequent long 

 duration (more than 50 days) were found to be necessary for a good yield 

 of straw; a high mean temperature during this period (18° and higher) and its 

 consequent short duration (less than 45 days) though not injuring the yield of 

 grain, all other conditions being favorable, caused a failure of the straw. 

 Frosts, even when heavy and frequent (to — 10° at the surface of the soil) in 

 the first period did no harm, but frosts (to — 5°) in the second period endangered 

 the yield of grain. Hot days with mean daily temperatures of 24° and higher 

 and with maximum temperatures of 30° and higher in the intei'val of time 

 from earing to the milk stage endangered the yield of grain, especially a 

 number of such days in succession. A similar temperature after the milk 

 stage may cause the falling out of the grain. 



The relation of the yield of apples to precipitation during 1901 to 1908, 

 K. I. Semadeni and W. K. Gauer (Trudiii »SV7.sA-. 7\7/o~. Met.. 1909. \o. .7, /, p/>. 

 20-26). — The observations were made on an estate near the city of Chernigov, 

 51° 37" north latitude and 31° 1' east longitude from Greenwich, and about 

 150 meters above sea level. The soil is a clay. 



During the 6 years under observation good and bad yields of apples alternated. 

 The general conclusions of the author follow: (1) The size of a full crop (good 

 yield) is in direct correspondence with the amount of i)recipitation during the 

 vegetation year preceding the crop; (2) in like corresi)ondence with the i)re- 

 cipitation are the short crops (bad yields) ; (3) the chief role is played by the 

 precipitation during the preceding period of vegetative activity (from the 

 thawing of the soil in the spring to its freezing in the beginning of the winter). 



The minimum temperature of the lower layers of the air, T. P. Wangen- 

 HEiM (Trudui Selsk. Khoz. Met., 1909, No. 5, I, pp. 27-35, figs. 3).— Since the 

 life of a great majority of the field and garden plants is passed between the height 

 of 10 cm. (about 4 in.) from the ground and the surface of the soil the author 

 deemed it vei-y important to study the temperature of this layer of air. 



He concludes that immediately over or at the surface of grass (10 cm. from 

 the surface of the soil) there is a considerable lowering of the temperature as 

 compared with that of the air in the instrument shelter at a height of 3.74 

 meters as well as with that of the surface of the soil on black fallow ; at the 

 10 cm. level the coming of frosts was observed when no fi-eezing could be 

 detected at the other levels. This lowering of the temperature takes place in 

 the evening and night, in the complete absence of dew or other moisture on the 

 plants, and at a time when there is increased radiation, this inclines the 

 author to the opinion that it is due to increased radiation and not to increased 

 evaporation. 



Moisture and temperature of the air on mountains and in the free atmos- 

 phere, J. Schubert {Met. Ztschr., 26 {,1909), pp. 390-396; Verhandl. Dent. 



