18 



BULLETIN 42, U. S. DEPAETMENT OF AGRICULTURE. 



The experiments with the different soils recorded above were made 

 at different times of the year and, as the action of the manganese and 

 growth of the plants might be influenced by some climatic conditions, 

 an experiment was next made in which both poor and good soils 

 were simultaneously tested. Six soils of different character were 

 selected. 



Three of these soils were very poor and unproductive and three 

 were good productive soils. Soils Nos. 1, 2, and 3 are unproductive. 

 Soil No. 1 is a sandy clay collected from a park where the lawn was 

 very poor. No. 2 is a sandy loam soil from a cultivated field. No. 3 

 is a clay loam taken from under a tree, where repeated attempts to 

 grow a lawn had failed. 



Soils Nos. 4, 5, and 6 are productive soils taken from fields which 

 were growing good crops. No. 4 is a loam, No. 5 a sandy loam, and 

 No. 6 a silt loam. 



Extracts were made and plants grown in each at the same time. 

 Manganese in the form of chloride and sulphate were used in amounts 

 of 20 and 50 parts per million of the element manganese. The 

 experiment was conducted from April 5 to April 19. The results 

 are given in Table X. The growth and oxidation are compared with 

 the untreated soil extract in each case. 



Table X. — Effect of manganese on oxidation and growth in unproductive and productive 

 soil extracts. Results expressed in relative oxidation and growth. (Untreated = 100.) 





Unproductive soils. 



Productive soils. 





1 



2 



3 



4 



5 



6 



Treatment. 



Sandy clay. 



Sandy loam. 



Clay loam. 



Loam. 



Sandy loam. 



Silt loam. 





1 



o 

 u 



O 



a 



o 



■•§ 



-a 



•a 



o 



O 



o 



o 



•a 



o 



o 



u 

 O 



H 



o 



O 



o 



A 



o 



% 



o 



O 



a 



.g 

 +^ 



C3 



o 



o 



a 



"3 

 2 



o 





100 

 126 

 119 

 130 

 137 



100 

 142 

 156 

 135 

 172 



100 

 102 

 101 

 114 

 107 



100 



111 



118 

 120 

 130 



100 

 112 

 122 

 114 

 108 



100 

 180 

 190 

 130 

 127 



100 

 99 

 76 

 94 



98 



100 

 180 

 175 

 130 

 135 



100 

 90 

 93 

 96 

 88 



100 

 125 

 156 

 142 

 160 



100 

 106 



76 

 100 



83 



100 



Extract+MnCl 2 , 20 parts 



150 



Extract+HnCl 2 , 50 parts 



132 



Extract+MnS0 4) 20 parts 



100 



Extract+MnSO*, 50 parts 



114 







The results of this test substantiate those of previous experiments. 

 The effect of the manganese on the unproductive soils was to increase 

 the oxidation and growth. There was an increase with both salts of 

 manganese and both concentrations. This, however, is reversed in 

 the case of the productive soils. The oxidation is increased with each 

 of the solutions, while the growth was depressed. The effect of exces- 



