814 EXPERIMENT STATION RECORD. 



The author further discusses gravitational water and soil drainaj;e, reviewing 

 the worlc of otliers bearlu}^ on the subject and i)ointlng out particularly the 

 importance of soil drainage in regulating the soil moisture content, soil aera- 

 tion, soil leniperature, and tlie physical condition of tlie soil. 



Effects of variations in moisture content on certain properties of a soil 

 and on the growth of wheat, F. S. IIabbis (New York Cornell 8ta. Bui. 352 

 (191 Jf), pp. 805-868, fig. i).— The worlc of others relating to the subject is 

 briefly reviewed and greenhouse vnd laboratory experiments with wheat plants 

 grown in pots containing clay loam soil subjected to different moisture and 

 fertilizer treatments, and studies of certain properties of cropped and uncropped 

 soils standing for long periods under these conditions are reported. 



It was found that the cropped soil was more compact than the uncropped 

 and the volume of the soil decreased as the moisture content increased. Fer- 

 tilized soils with crops were more compact than unfertilized soils. Floccula- 

 tion was greater in cropped than in uncropped soils and was greater with a 

 medium degree of soil moisture than with a very large or very small degree, 

 the least flocculation occurring in the very wet soil. Flocculation was in- 

 creased by fertilizers, especially those containing little sodium nitrate. The 

 nitrate content was always greater in uncropped than in cropped soil and in 

 soils to which nitrate fertilizers had been added, and was greater with 30 per 

 cent moisture than in a drier or a wetter soil. Soil constantly saturated 

 with moisture contained practically no nitrates. The nitrite content of the 

 soils was always low but was higher in the uncropped soil than in the cropped, 

 and was higher where high nitrogen fertilizers had been added. The ammonia 

 content, while never great, was always higher in cropped than in uncropped 

 soils, was highest where a high nitrogen fertilizer was used, and was not much 

 affected by the soil moisture. The ratio of soluble salts to nitrates was always 

 higher in cropped than in uncropped soil. 



While not definitely determined, the number of bacteria in the soil was 

 usually greater with 15 than with 30 per cent moisture and was slightly greater 

 in unfertilized than in fertilized soil. The easily soluble phosphoric acid was 

 always higher in the nnci-opped than in the cropped soil, higher in the fer- 

 tilized than in the unfertilized soil, and varied irregularily with the soil 

 moisture. 



Wheat matured sixteen days earlier with 20 per cent moisture than with 

 either 11 or 45 per cent and a well-balanced fertilizer caused an earlier maturity 

 than one with high nitrogen or no fertilizer. Tillering was promoted by high 

 moisture and by fertilizers. Plants were able to stand excessive moisture 

 better when young than when older and mildew attacks were severest on 

 plants growing with high moisture and a high nitrogen fertilizer. 



" The number of nodes per culm was least with a medium, and most with 

 the very high, soil moisture. The length of culms and of heads increased with 

 the moisture up to 37i per cent, after which both decreased. The heads were 

 proportionately longer in the dry than in the wet soil. The quantity of moisture 

 during the early growth, more than at any other time, determined the head as 

 well as the culm length. Fertilizers increased the number of nodes i>er culm, 

 as well as the length of culm and of head." The number of kernels of wheat 

 per pot and the quantity of straw increased with the fertilizei's, and with the 

 soil moisture up to 37^ per cent, above which it decreased. The number of 

 kernels per head was gi-eatest on the soil with a medium amount of moisture 

 but the weight of 100 kernels was greatest on the very dry soil and least on 

 the very wet. There was proportionately more grain than straw when the 

 soil moisture was low during the early stages. Proportionately more of the 

 dry matter in wheat had been produced by the boot stage in the dry soil than 



