156 Journal of A gricultural Research vol. xxi, NO. 3 



solubility of ferric phosphate. The other soils on which chlorosis occurred, 

 however, did not give any such high phosphorus analysis. The fact that 

 the solubility of ferric phosphate is sufficient to make it a good source of 

 iron in water-culture experiments prevents any probability of a relation 

 between the amount of phosphorous found by analysis and the availability 

 of iron. 



All the analyses indicated normal quantities of iron. The results are 

 in agreement with the general experience that acid-digestion soil analyses 

 yield little information of value from the plant physiological or patho- 

 logical standpoint. Petrographic examination by the United States 

 Bureau of Soils of the Pocatello soil and of the nursery soil which con- 

 tained carbonates without chlorosis gave no clue to the difference be- 

 tween the plants on them. Acidity determinations by Dr. L. J. Gillespie, 

 of the Bureau of Plant Industry, showed a P H of 7.8 for the Pocatello soil 

 and 8.4 for the nursery at which there were carbonates but no serious 

 chlorosis. The main facts to be drawn from the examination of the soils 

 of the different stations was that all the soils on which chlorosis occurred 

 contained carbonates and that two of them were underlaid with lime- 

 stone. 



Analysis by the United States Bureau of Chemistry of the water supply 

 showed 320 mgm. of bicarbonic acid (HCO 3 ) per liter of water at the 

 Pocatello Nursery, and practically no other anions, while at the nursery 

 at which there were soil carbonates but no chlorosis there were reported 

 1 80 mgm. of bicarbonic acid per liter, as against 450 mgm. of sulphate (SO 4 ) 

 per liter. This is of some interest in connection with the difference in 

 the amount of chlorosis at the two places, as the arid conditions made 

 necessary the application of considerable amounts of water to the nursery 

 beds during warm weather. The soil solutions during the periods of 

 greatest growth must, therefore, have been influenced to a considerable 

 extent by the character of this water. It was noted at the Pocatello 

 Nursery that the chlorosis was more prevalent in beds which had been 

 under nursery management for several years than in beds which had just 

 been included in the nursery area and had therefore received less of the 

 water. 



KIND AND EXTENT OF INJURY 



At the Pocatello Nursery there was so much chlorosis and the growth 

 of affected stock was so unstisfactory that a detailed study of it was 

 undertaken. The nursery is at an elevation of 5*200 feet, well below the 

 lower limit of natural coniferous forest growth in this region. Precipita- 

 tion for the period during which the nursery is usually free from snow 

 (April to October, inclusive) averaged but 11.2 inches for the years 1909 

 to 1917, inclusive. The days are warm and the nights cool during the 

 growing season, only 2^ months being entirely free from killing frost. 

 The soil is a rather heavy black silt loam; composite samples from 8 to 10 



