SOILS — FERTILIZERS. 421 



week, until during the fourth week the oxidation became so slow as hardly to 

 be distinguished from the soil carbon. The decrease in oxidation of excrement 

 was less rapid, but still marked. Humic acid was very resistant toward the 

 oxidation processes. The relative powers of soils to oxidize excrement (oxida- 

 tion capacity) . . . varied comparatively little with most of the soils, but was 

 low with three of 17 soils. There are decided differences in the oxidation of the 

 soil carbon in the different soils. The relative oxidation of the soils tested 

 (based on equal nitrogen) was 130 for three soils containing less than 0.04 per 

 cent nitrogen, compared with 81 for six soils containing 0.05 to 0.099 per cent 

 nitrogen, and 42 for six soils containing over 0.1 per cent nitrogen. The soils 

 containing the least nitrogen appear to carry their carbon in a more easily oxi- 

 dized condition. Soils when almost dry oxidized organic matter rapidly. 

 Oxidation in a saturated soil depends upon the character of the soil and the 

 way in which the water is added. The oxidation may be very low or moderate, 

 Carbonate of lime had little or no effect upon oxidation in the soil tested." 



Effect of additions on availability of soil phosphates, G. S. Fraps ( Texas 

 Sta. Bui. 178 {1915), pp. 15). — Pot experiments with six soils, including fine 

 sandy loam, fine sand, and clay, to determine the effect of additions of precipi- 

 tated calcium carbonate and of organic matter as ground corncobs, sawdust, and 

 starch on the assimilation of the soil phosphates by corn, millet, mustard, and 

 Kafir corn are reported. 



It was found that when nitrogen and potash were supplied, as nitrates of 

 soda and ammonium and sulphate of potash the addition of calcium carbonate 

 at the rate of 5 tons per acre increased the size of the crop and the amount of 

 phosphoric acid withdrawn from the soil phosphates on the six soils tested. 

 The effect of the lime was small at first, but usually increased with succeeding 

 crops. The addition of starch, sawdust, or cobs had some effect on the crop 

 in two soils, but little with the other four soils. "With the six soils v/hich 

 gave up phosphoric acid equal to 5 to 18 bu. of corn per acre per crop, the 

 addition of carbonate of lime caused an increase in the quantity of phosphoric 

 acid taken up equal to 3 to 7 bu. per acre per crop. The vegetable matter in 

 three cases caused a gain in phosphoric acid taken up equal to 2 or 3 bu. corn 

 per acre. The presence of carbonate of lime or of vegetable matter may bring 

 about differences in the quantity of phosphoric acid assimilated by plants from 

 soils, containing equal quantities of active phosphoric acid. No relation can 

 be traced between the additions and the phosphoric acid content of the crops. 

 When the crops are unusually small, the phosphoric acid content usually runs 

 higher than the average." 



The additions of calcium carbonate and organic matter and the phosphoric 

 acid removed by the crops had practically no effect upon the quantity of active 

 phosphoric acid remaining in the soil at the end of the experiments. " The 

 phosphoric acid taken up by the plants was evidently drawn largely from the 

 more insoluble phosphates." 



Fate and effect of arsenic applied as a spray for weeds, W. T. McGeorgb 

 {U. S. Dept. Agr., Jour. Agr. Research , 5 (1915), No. 11, pp. 459-463) .—Con- 

 tinuing work previously noted (E. S. R., 33, p. 623), studies were made at the 

 Hawaii Experiment Station to determine the fate of sodium arsenite when 

 applied to ferruginous red and brown clays and to a highly organic silt soil 

 as a spray for weeds. 



It was found that the fixation of the arsenic in the surface soil involves 

 chemical reactions consisting of " a replacement or solution of iron, calcium, 

 magnesium, and humus, owing in part to a hydrolysis of the sodium arsenite in 

 solution, also a combination with the dibasic and tribasic elements to form the 

 difficultly soluble arsenites or arsenates." 



