1020] SOILS — FERTILIZERS. 121 



li'iiipiM-ntiire of 33" was (>l)serve<l on May 27, however, and thoufih noi so 

 nM-orded, doubtless a killing frost occurred in low places. There was a lislit 

 frost on June 30 that caused some damage to the more tender crops. Tliere 

 were several frosts in Scpfeiuher, the (irst tenipei'ature of 32°, or lower, being 

 recorded on September (>. (Juite tender plants s^irvived these frosts, however, 

 and were not killed until ()ctol)er 10. 



" Tlie annual i»re<iititalion, 12.38 in., was 1.3S in. above normal; nearly 70 

 per cent of the total amount occurred between April 1 and September .30. The 

 month of May was dry, the precipitation being nearly 1 in. below normal. 

 Most of the other months except .January were nearly normal or slightly above. 

 The precipitation in July was exceptionally high, due to a single 2-hour storm 

 during wliicli 1.72 in. of water fell. Coming in such a short time, a large pro- 

 portion of this water ran off into the streams and thus was of no benefit to 

 the crops." 



SOILS— FERTILIZERS. 



Soil and fertility investigations, A. G. McCall et at.. {Maiifland Sta. Rpt. 

 Ifil!), pp. A'H-XXI). — A number of studies at the station are summarized. 



-Vii investigation of the nutrient requirements of wheat, buckwheat, and soy 

 l»eans in sand and soil cultures to determine the best proportion of nutrient 

 for the first 30 days of their growth period, and for two additional periods for 

 wheat up to maturity, showi'd that the mineral food requirements of the 

 wlieat plant during the .second growth period are substantially the same as 

 for the first 30-day period. liesults for the final growth period indicate that 

 there is an increase in the physiological requirements for magnesium during 

 the late stages in the development of the wheat plant. During the first growth 

 I)eri(td the proportion of nutrii-nt salts that gave the highest growth rate for 

 wheat also gave the highest growth rate for soy beans. Recent results 

 strongly .suggest that the physi(»logical i)roperties of a solution are not deter- 

 mined .solely by the ionic proportions, but are conditioned as well upon the 

 molecular combinations that may exist in the nutrient solution. 



A study of the hourly and daily fluctuat4on in the temperature of tlu; .soil 

 at 3, G, and 24 in. below a bare surface and below a blue grass sod, covering 

 a period of two years, showed that during very severe periods of cold weather 

 when the ground was covered with snow there was a very marked difference 

 in the temperature of bare and of cropped .soil. On December 30, 1917, with the 

 air temperature — 12° F., the temperature at a depth of 3 in. under cropped 

 soil was 31°, while at the same depth under bare soil the temperature went down 

 to 22°. On January 1, 1918, with an air temperature —8°, the temperature 

 under cropped soil was 30°. and under bare .soil surface 21°. It is considered 

 evident that wheat seeded early enough to make a good growth befor(> severe 

 weather will have a nuich better chance to survive than wheat seeded late. 



An investigation of the factors affecting th'> availability of the potassium 

 (•«ni|)onn(ls of the .soil showed that the addition of lime in the form of <'alcium 

 carbonate decreased the solubility of the soil potassium, Avhile th(> addition of 

 calcium oxid slightly increased the availability of potassium compounds. The 

 iiddition of sodium chlorid very greatly increased the solubility of potassium, 

 while gypsum or calcium sulphate had no appreciable effect. In another series 

 of exi)eriments green sand was composted with sulphur and manure in various 

 combinations and supplied with sulfofying Imcteria. An analysis of the water 

 extract from these composts was made from time to time over a period of 23 

 weeks. In certain of these composts it was found that more than 40 per 

 cent of the total potassium present iu the mixture had been made water- 



k 



