1918] SOILS FERTILIZEES. 323 



It was found that " nitrification in normal soil is stimulated by small amounts 

 of sodium chlorid. sodium sulphate, and magnesium sulphate, and large amounts 

 of calcium carbonate. These salts become toxic, however, at certain points, 

 which uudoubtedty vary in different soils. With this soil in laboratory tests 

 the toxic point was 0.02 per cent sodium chlorid, 2 per cent sodium sulphate, 

 and between 1.5 to 6 per cent calcium carbonate. The toxic point for mag- 

 nesium sulphate was not determined. Nitrification in alkali soil was increased 

 by small amounts of sodium bicarbonate, sodium carbonate, and calcium car- 

 bonate. Calcium sulphate had no effect. These salts became toxic in this soil 

 at 0.3 per cent for both the sodium carbonate and bicarbonate and at 6 per cent 

 for the calcium carbonate. The addition of calcium sulphate with the sodium 

 carbonate and bicarbonate, in the proper amount to react with them, prevented 

 any toxic effect from the largest amount used. 



" The tests in the greenhouse soils checked very closely with the laboratory 

 studies in the case of the alkali soils. In the normal soils the agreement was 

 likewise good, except in the case of sodium sulphate. That salt became toxic 

 according to these tests at a concentration of 0.5 per cent. This is a very 

 much lower toxic point than was noted above but nearer that found by otbers. 

 The effects on the crop grown in normal soil of the alkali salts, with the excep- 

 tion of the sodium sulphate, were very similar to the effects on nitrification in 

 both laboratory and greenhouse tests. Increases were secured with sodium 

 chlorid, magnesium sulphate, and calcium carbonate, but sodium sulphate 

 caused a depression in crop and in nitrification in the greenhouse soils. All 

 the salts together had no effect. In general, it seems that nitrification and 

 crops are very similarly affected by alkali salts. 



" Crops refused to grow in the alkali soil, but the injurious factor was 

 evidently not an excess of sodium bicarbonate or carbonate, as additions of 

 these salts increased nitrification in the soil. The injurious factor was likewise 

 evidently not calcium carbonate, for that compound stimulated nitrification in 

 the alkali soil." 



Reclaiming- niter soil in the Grand Valley; E. P. Sandsten {Colorado Sta. 

 Bui. 235 {1911), pp. 3-8, figs. 4).— Field tests of methods for the correction and 

 reclamation of abandoned niter land in the orchard areas of the Grand Valley 

 of Colorado led to the conclusion that flooding gave the quickest results, 

 especially on well-drained lands. While the corrugating system of irrigation 

 (letting water run for 36 hours in furrows made close together after seeding 

 the land) appeared adequate for soils in the first stages of niter poisoning, it 

 was found to be slower and in the long run more expensive than flooding on 

 land made unproductive by excessive niter. The results emphasize especially 

 the necessity for good drainage in reclaiming niter soils. 



It was also found that cover crops alternating with clean culture tended 

 to check niter poisoning in bearing orchards. 



Soil survey of Harnett County, N. C, R. C. Jubney and S. O. Pekkins {U. S. 

 Dept. Agr., Adv. Sheets Field Oper. Bur. Soils, 1916, pp. 37, fig. 1, map 1). — This 

 survey, made in cooperation with the North Carolina Department of Agricul- 

 ture, deals with the soils of an area of 880,800 acres in the east-central part 

 of North Carolina, lying mainly in the Coastal Plain but with part of the north- 

 western section of the county in the Piedmont. The topography of the county 

 varies from flat and gently undulating to rolling, hilly, and broken. The area 

 is well drained with the exception of the flatwoods section and some of the 

 first bottom lands. 



The soils of the county are derived from unconsolidated sands and clays 

 of sedimentary origin in the Coastal Plain section and from igneous and 

 45967°— 18 3 



