10 



BULLETIN 453, U. S. DEPARTMENT OF AGRICULTURE. 



At Haugan the acid has been used for three years and damping-off 

 has been practically abolished in the beds treated. These three 

 nurseries differ from the preceding three in that the soil is heavier 

 and there is no need of any extra watering in order to prevent chem- 

 ical injury to the seedlings. 



At a seventh nursery an entirely different condition was encoun- 

 tered. The seed beds were located on a rather heavy soil near 

 Garden City, Kans. This soil effervesced vigorously when treated 

 with acid, yielding 0.23 per cent of carbon dioxid from the surface 

 soil and over 1 per cent from the subsoil in a test made by the Bureau 

 of Soils. Acid treatments had no effect on damping-off in this soil, 

 owing presumably to the high carbonate content and consequent 

 alkalinity which the effervescence indicated. Tests with copper 

 sulphate, one-fourth- ounce per square foot, and zinc chlorid, one-half 

 ounce per square foot, showed that both these and heavier treatments 

 were effective against damping-off. The results are given in Table II. 



Table II. — Control of damping-off of pines by one-fourth to three-fourths ounce copper 

 sulphate and one-half to one ounce zinc chlorid per square foot of seed bed, Garden City, 

 Kans. 



Species and time of sowing. 



Pinus austriaca: 

 Spring 



P. banksiana: 

 Fall 



Spring. 



Disinfectant. 



Num- 

 ber of 



rate 



tests. 



Copper sulphate...' 

 None 



Zinc chlorid. 

 None 



Copper sulphate. 

 Xone 



Zinc chlorid. 

 Xone 



'Copper sulphate.. 

 Xone 



Zinc chlorid. 

 [None 



(Copper sulphate 



Average, fall and spring. . i and zinc chlorid. 



Xone 



P. ponderosa: 

 Fall 



[Copper sulphate. 

 Xone 



Zinc chlorid. 

 Xone 



Spring. 



[Copper sulphate. . . 

 Xone 



Zinc chlorid. 

 None 



(Zinc chlorid and 



Average, fall and spring. . i copper sulphate. 



|Xone 



Absolute results. 



Ger- 

 mina- 

 tion. 



Death Final 

 perhun-i stand 

 dred I based 

 seed- on seed 

 lings 



Perct. 



r 40. i 



{ 15.8 



f 37. 5 

 [ 19.5 



r 27.i 



{ 2,5.9 



f 30.7 

 i 23.7 



f 16.6 

 I 11.6 



f 37. 5 

 I U.2 



28.0 

 18.9 



46.1 

 40.9 



42.9 

 36.6 



58.1 

 50.9 



61.3 



52. 7 



52.1 

 45. 3 



59.0 

 91.0 



99.0 

 10C.0 



35.2 

 62.3 



27.6 

 69.0 



67.0 



20.0 

 66.0 



37.7 

 66.1 



Perct. 



21.3 



1.3 



16.1 

 7.6 



21.0 

 5.8 



9.0 

 6.3 



28.9 

 6.4 



18.8 

 6.5 



Relative results. 



Ger- 



mina- Death, 

 tion. 



Final 

 stand. 



254 

 100 



102 

 100 



1 05 

 100 



130 

 100 



143 

 100 



264 

 100 



148 

 100 



65 



100 



00 



11 ill 



56 

 100 



40 

 100 



101 

 100 



30 

 100 



57 

 100 



20.1 

 59.8 



34.8 

 16.0 



113 

 100 



34 

 100 



16.1 

 57.4 



33.1 

 18.1 



117 

 100 



28 

 100 



24.0 

 45.1 



42.2 

 28.7 



114 

 100 



53 

 100 



bll.8 



6 39.1 



46.6 

 31.0 



116 

 100 



30 

 100 



18.0 



39.2 



115 



36 



50.4 



23.5 



100 



100 



100 





212 

 100 



100 



143 

 100 



452 

 100 



217 

 100 



1S3 

 100 



147 

 100 



1.50 

 TOO 



167 

 100 



a No expression possible. 6 The damping-off percentage was determined in but five of the six tests. 



