10 



BULLETIN 453, U. S. DEPARTMENT OF AGRICULTURE. 



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

 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. 





Disinfectant. 



Num- 

 ber of 

 sepa- 

 rate 

 tests. 



Absolute results. 



Relative results. 



Species and time of sowing. 



Ger- 

 mina- 

 tion. 



Death 

 per hun- 

 dred 

 seed- 

 lings. 



Final 

 stand 

 based 

 on seed 

 sown. 



Ger- 

 mina- 

 tion. 



Death. 



Final 

 stand. 



Pinus austriaca: 



[Copper sulphate... 



Izinc chlorid 



(Copper sulphate... 

 None 



Izinc chlorid 



} 2 



} ' 



} ^ 



} ' 

 } * 

 } 2 



Perct. 

 f 40.1 

 \ 15.8 



f 37.5 

 \ 19.5 



/ 27.1 

 \ 25.9 



/ 30.7 

 \ 23.7 



/ 16.6 

 \ 11.6 



/ 37.5 

 \ 14.2 



59.0 

 91.0 



99.0 

 100.0 



35.2 

 62.3 



27.6 

 69.0 



67.8 

 67.0 



20.0 

 66.0 



Perct. 



21.3 



1.3 



.5 

 



16.1 

 7.6 



21.0 

 5.8 



9.0 

 6.3 



28.9 

 6.4 



254 

 100 



192 

 100 



105 

 100 



130 

 100 



143 



100 



264 

 100 



65 

 100 



99 

 100 



56 

 100 



40 

 100 



101 



100 



30 

 100 



1,638 



100 



P. banksiana: 



Fall 



00 



(a) 



212 

 100 





362 

 100 





(Copper sulphate... 



143 

 100 





I Zinc chlorid 







452 

 100 





(Copper sulphate 

 i and zinc chlorid. 





Average, fall and spring. . 



28.0 

 18.9 



37.7 



66.1 



18.8 

 6.5 



148 

 100 



57 

 100 



289 

 100 





(Copper sulphate. . . 



} 2 

 } 2 

 } 8 



} « 





•P. ponderosa: 



/46.1 

 \ 40.9 



f 42.9 

 \ 36.6 



/58.1 

 \ 50.9 



/61.3 

 \ 52.7 



20.1 

 59.8 



16.1 

 57.4 



24.0 

 45.1 



6 11. S 

 6 39.1 



34.8 

 16.0 



33.1 

 18.1 



42.2 

 28.7 



46.6 

 31.0 



113 

 100 



117 

 100 



114 

 100 



116 

 100 



34 



100 



28 



100 



53 

 100 



30 

 100 



217 

 100 



Fall 



Zincchlorid 







1S3 

 100 





(Copper sulphate. . . 



147 



100 





I Zinc chlorid 







150 

 100 





(Zinc chlorid and 

 \ copper sulphate. 





Average, tall and spring. . 



52.1 

 45.3 



18.0 



50.4 



39.2 

 23.5 



115 



100 



36 

 100 



167 



100 











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



