22 BULLETIN 169, U. S. DEPARTMENT OP AGRICULTURE. 



0.5 ounce of ammonia eight days before sowing, suffered no injury. 

 In this case the heavy acid treatment would probably have resulted 

 in injury had not the ammonia been applied. 



From the practical standpoint, the prevention of injury from acid in 

 pine seed beds by the use of neutralizing agents at this nursery is not a 

 success, because beds so treated are often as badly infested by para- 

 sites as beds which have received no disinfectant treatment. The 

 action of heavy applications of lime on the beds is also somewhat in 

 question. Amounts up to 0.5 ounce per square foot, as used in the 

 neutralizing work, have, however, been used alone without any bad 

 effect. In one case 0.73 ounce per square foot (equivalent to 1 ton per 

 acre) used on jack-pine beds at or before seeding in two different 

 series was followed by a serious decrease of germination, and in the 

 other case by a marked increase in the number dying after the seed- 

 lings came up. Whether the effect was a direct injury to the seed- 

 lings or a stimulation of the parasites which attack them was not 

 determined. 



The effect on weeds of acid followed by lime is also shown in Table 

 V. Much injury to weeds occurred despite the neutralization several 

 days later of two-fifths of the acid applied. However, it is quite 

 certain, especially in the case of series 504, plat E, that much more 

 injury would have occurred had not the lime been applied. Three- 

 fourths as much acid applied to another plat in this series at about the 

 same time, and not followed by lime, prevented the growth of angio- 

 sperms on the plat. The extremely rapid growth of the weeds on the 

 acid-lime plats a few weeks after the application of the lime indicates 

 that most of the remaining acid had been broken down by the lime. 

 If enough lime had been used to neutralize one-half or three-fifths 

 of the acid applied, it is entirely probable that all of the acid remaining 

 at the time of the lime application would have been broken down and 

 the soil rendered entirely safe for sowing any crop plant desired. 

 Because the lime applied was not sufficient to take up at once all the 

 acid remaining in the soil at the time of application, as indicated by 

 the injury to the pines in series 507, plats M and O, the question as to 

 whether the acid prevented weed growth largely by killing dormant 

 seed or entirely by killing germinating seed, as with the pines, remains 

 undecided. 



Ammonia, 0.469 ounce per square foot, was used in 3 pints of water 

 a few days after the application of 0.750 ounce of acid, with watering 

 sufficient to prevent injury to jack pine even on unneutralized acid 

 plats. Examination approximately 45 days after the ammonia appli- 

 cation showed an entire absence of weeds on the acid-ammonia plat, as 

 on the acid plats, while the four checks all contained plants of grass, 

 Mollugo, Amaranthus, and Portulaca. For 37 days after the ammonia 

 was applied 0.562 ounce of acid followed by 0.5 ounce of ammonia five 



