22 BULLETIN 169, U. S. DEPARTMENT OF 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 killirig 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 
