No. 2, September, 1920) SOIL SCIENCE 303 



are short and mild while the summers are long and hot. Two-thirds of the 17 inches of rain 

 fall during the summer months. The growing season is aboul 216 days. A great variety of 

 cnips may be grown. Marlboro ( lounty is one of the best developed count ies agriculturally 



of the state. Many different soil types occur, (hose of the coastal plain being extensively 

 farmed and mostly to cotton. While the terrace soils along the Pee Dee River are cropped, 

 the bottom lands yet remain to be developed. Corn, cowpeas, wheat and oats do well. Pea- 

 nuts yield splendidly on all soils. The first bottoms are fine grass lands and offer splendid 

 opportunities for cattle raising. — Crops are not very often grown in rotation and the land 

 is running down. Const ant ly increasing amounts of fertilizer are necessary. Complete mixed 

 fertilizers are most generally purchased. Some nitrate of soda is used as a top dressing. Lime 

 although needed has not come into general use. — H. O. Buckman. 



2319. W atkins, W. I., E. D. Fowler, H. I. Cohn, J. A. Macklis, and H. H. Krube- 

 kopf. Soil survey of Texas County, Missouri. Advance sheets, Field Operations Bur. Soils, 

 U. S. Dept. Agric. 1917: 5-36. 1 fig., 1 map (colored). 1919. — For character of report see Bot. 

 Absts. 5, Entry 2316. 



MOISTURE RELATIONS 



2320. Harding, S. T. Relation of the moisture equivalent of soils to the moisture proper- 

 ties under field conditions of irrigation. Soil Sci. 8: 303-312. 6 fig. 1919. — A comparison was 

 made of the moisture equivalent with the critical moisture points of soils under actual field 

 conditions of irrigation practice. The results include over 9000 individual moisture deter- 

 minations and 136 determinations of moisture equivalent varying from 4.1 to 37.6. The max- 

 imum field capacity, the normal field capacity, soil moisture before irrigation, and soil mois- 

 ture at permanent wilting of the crop were studied. Expressed as per cent of the moisture 

 equivalent the moisture at the time of permanent wilting alone shows a linear relationship 

 with the moisture equivalent. This for the surface foot is about 15 per cent less than that 

 given by the formula of Briggs and Shantz. — W. J. Robbins. 



2321. Knapp, George S. Winter irrigation for western Kansas. Kansas Agric. Exp. Sta. 

 Cire. 72. 8 p. Jan., 1919. 



METHODS 



2322. Bear, Firman E., and George M. McClure. Sampling soil plots. Soil Sci. 9: 

 65-75. 4 fi-9- 1920. — -The composite from a one-twentieth acre plot should be made up of 20 

 samples, each 12 inches in depth and uniformly distributed over the plot. — W. J. Robbins. 



2323. Gardner, Willard. A new soil elutriator. Soil Sci. 9: 191-197. 2 fig. PI. 1. 

 1920. — An elutriator for the mechanical analysis of soil is described and figured. — W. J. 

 Robbins. 



2324. Gillespie, L. J. Colorimetric determination of hydrogen-ion concentration without 

 buffer mixtures, with especial reference to soils. Soil Sci. 9: 115-136. 1 fig. 1920. — A simple 

 method is described for the colorimetric determination of the hydrogen-ion exponent with- 

 out the use of buffer mixtures. The method also provides for the elimination of errors due to 

 the turbidity of the solution in which the determination is made. Each color standard con- 

 sists of two test tubes, one tube containing 5 cc. of dilute acid, the other 5 cc. of dilute alkali. 

 The tubes together contain 10 drops of indicator solution, the 10 being divided between the 

 alkaline and acid tubes in various "drop ratios." To 10 cc. of the unknown solution, 10 drops 

 of the indicator solution are added and compared with the two color standards by means of 

 a simple comparator. A table is given of the pH for each drop ratio of the indicators used 

 which cover a range of P H 3.1 to P H 9.75. Soil extracts, water clear, were prepared by the 

 use of colloidal iron solution as a precipitant and pH measurements of the water extracts of 

 nine soils prepared by this method gave the same results as were obtained by the usual 

 methods. — W. J. Robbins. 



