6 



BULLETIlir 1120, U. S. DEPARTMENT OF AGRICULTURE. 



10 a. m. to 4 p. m. This typical arrangement of plats is represented 

 diagrammatically in Figure 1. 



Experimental plats of the kind described were sown at Fargo on 

 May 22 (plat A), June 9 (plat B), June 27 (plat C), and July 18 

 (plat D) . In plat A the shades unfortunately were not put in position 

 until after canker had occurred. Canker occurred in plat A, not in 

 plat B, to a slight extent in plat C, and not in plat D. Similar 

 plats were sown at Mandan, N. Dak., on April 28, June 11, and July 1, 

 except that where sand was applied at Fargo the soil was compacted 

 at Mandan. Dry weather, cutworms, and grasshoppers made the 

 results at Mandan unworthy of consideration. 



While the canvas shades unfortunately were not put in position 

 in plat A at Fargo until after canker had occurred on June 16, the 

 presence and absence of weeds in different parts of the plat served 

 much the same purpose in varying the amount of shade. Rows 1, 

 2, and 3 had been carefully weeded, while the rest of the plat was 

 rather weedy. It was at once strikingly evident that by far the 

 most canker occurred where the young flax plants had not been shaded 

 by weeds or by the nurse crops. The data from this experiment 

 are given in Table 2, showing a summary and comparison of the 

 percentages of canker under different conditions. 



Table 2. — Results of experiments conducted at Fargo, N. Dak., to determine the effect 

 of various types of shading of flax in sanded and unsanded ground on plat A, sown on 

 May 22, 1919. 



[Data on the occurrence of heat canker of flax recorded on June 18, 1919.] 





Without sand on surface. 



Surfaced with sand. 





Num- 

 ber of 

 plants 

 in row. 



Plants cankered. 



Num- 

 ber of 

 plants 

 in row. 



Plants cankered. 



Conditions as to shading. 



Num- 

 ber. 



Per cent. 



Num- 

 ber. 



Per cent. 





Actual. 



Aver- 

 age. 



Actual. 



Aver- 

 age. 



No shade: 



Row No. 1 



469 

 411 



188 



329 

 461 

 361 

 355 

 147 

 189 

 308 



637 

 352 

 390 

 379 

 322 

 396 

 348 



216 

 168 

 70 



34 

 34 

 25 

 10 

 10 

 33 

 5 



19 

 16 

 10 

 11 



40 

 9 



8 



46.0 

 40.9 

 37.2 



10.3 

 7.4 

 6.9 

 2.8 

 6.8 



17.5 

 1.6 



3.0 

 4.5 

 2.6 

 2.9 

 12.4 

 2.3 

 2.3 



I 41.4 

 7.3 



4.3 



f 480 

 \ 467 

 [ 277 



f 574 

 433 

 198 

 159 

 80 

 288 

 115 



f 333 



482 

 407 

 236 

 188 

 119 

 118 



179 

 80 

 21 



18 

 17 

 10 

 6 



2 

 7 

 4 





 19 

 2 

 1 



6 

 5 



1 



37.3 

 17.1 

 7.6 



3.1 

 4.0 

 5.1 

 3.8 

 2.5 

 2.4 

 3.5 







4.0 

 .5 

 .4 



3.2 



4.2 

 .9 



\ 



Row No. 2 



\ 20.5 



Row No. 3 



1 



Shaded by weeds: 



Row No. 4 





Row No. 5 





Row No. 6 





Row No. 7 



i 3.5 



Row No. 8 





Row No. 9 





Row No. 10 





Shaded by weeds and grain: 



Row N(5. 11 





Row No. 12 





Row No. 13 





Row No. 14 



i 1.9 



Row No. 15 





Row No. 16 





Row No. 17 









