1^10] SOILS — FERTILIZERS. 219 



phate used In various combinations with monopotassium phosphate, calcium 

 carbonate, magnesium sulphate, and ferrous sulphate upon the germination 

 and growth of barley grown in pots containing sea sand or Sassafras light sandy 

 loam soil. The sand and soil were maintained at different moisture contents 

 representing 20, 40, 60, and 80 per cent of their water-holding capacity. The 

 effect of different amounts of potassium chlorid, sodium chlorid, sodium nitrate, 

 calcium sulphate, aluminum sulphate, and sodium silicate upon the main fer- 

 tilizer treatment was also studied. In many cases the osmotic concentration 

 of the nutrient solutions was determined both before and after application to 

 the sand or the soil. Observations were also made on the effect upon the 

 germination of barley of the different moisture contents noted above, and of 

 10 and 15 per cent of the water-holding capacity for both the sand and soil and 

 in addition for Sassafras medium silty loam, Elkton clay loam, and muck. Con- 

 siderable data are presented in tabular form and fully discussed. The results 

 are summarized as follows : 



The moisture content of the soil has a very marked influence on the growth 

 and development of plants. In the sand cultures the plant yield increased with 

 an increase in moisture content from 20 to 80 per cent of the water-holding 

 capacity of the sand. In the soil the plant yield increased with an increase 

 in moisture content up to GO per cent, while a further increase in moisture 

 brought a considerable decrease in the yield of dry matter of barley. Plant 

 growth in both the soil and sand maintained at a moisture content equivalent 

 to 20 per cent of saturation was very small, and had no direct relation to the 

 water present, as compared with the series of the higher moisture content. 



With a constant moisture content in the sand, the plant yields increased with 

 an increase in the application of ammonium sulphate, calcium carbonate, or 

 monopotassium phosphate, the response to the applications of these salts in the 

 amounts used being in the order named. In the Sassafras light sandy loam a 

 similar response to applications of nitrogen was observed, but not to those of 

 lime and very little to those of phosphorous. Differences in plant growth with 

 various moisture contents were attributed to two factors, the total plant food 

 remaining the same: (1) Differences in concentration of the soil solution and 

 (2) aeration of the soil. 



The osmotic concentration of the soil solution increased with a decrease in 

 the moisture content of sand or soil, but the changes were not proportional to 

 one another. The change in the osmotic concentration of the soil solution with 

 the change in water content from one series to another was greater than the 

 change in the osmotic concentration of the soil solution due to the different fer- 

 tilizer treatments with the water content the same. In cultures with the 

 moisture content corresponding to SO and 60 per cent of the water-holding 

 capacity, the osmotic concentration of the soil solution varied from 0.7 to 1.5 

 atmospheres in the sand and from 0.31 to 0.85 atmosphere in the soil. With a 

 moisture content corresponding to 40 per cent of the water-holding capacity 

 the corresponding values for sand were 1.2 and 2.6 atmospheres, and for soil, 

 1.7 and 2 atmospheres. With 20 per cent of the water-holding capacity the 

 maximum and the minimum values in sand were 3.6 and 6.2 atmospheres, and 

 in soil, 7.5 and 9.4 atmospheres, respectively. The osmotic concentration of the 

 soil solution following the normal application of a fertilizer is not deemed 

 great enough to influence plant growth, providing the moisture content of the 

 soil is at its optimum (about 60 per cent of saturation), becoming an im- 

 portant factor only when this is considerably reduced (40 per cent of the satu- 

 ration or lower). 



On adding the nutrient solution to the soil its osmotic concentration de- 

 creased, as measured by the cryoscopic method, if the moisture content of the 



