Soils to be fumigated
with Methyl bromide, Chloropicrin, and Telone II (1,3-dichloropropene)
mixtures should be specially prepared to insure the grower of a satisfactory
job. The soil prep guidelines listed below will help insure a
successful fumigation. If you have any questions regarding soil prep,
please contact your Trical representative.
Application Timing
Methyl bromide,
Chloropicrin, and Telone® II can be
applied at any time of the year when soil conditions permit.
Conditions that allow rapid diffusion of the fumigant as a gas through the
soil normally give the best results. These fumigants do not provide
residual control of soil pests and are used as a preplant application.
Below are soil preparation, moisture, and temperature parameters that should
be followed at time of treatment. Failure to meet these conditions may
result in unsatisfactory product performance.
Soil Prep
Plant residue from
previous crops should be worked into the soil to allow for decomposition
prior to fumigation. Plow or rip the soil to the depth to which effective
treatment is desired. The soil should be worked to minimize any clods.
Some soils will need to be roto-tilled. Common soil prep mistakes include
delaying soil prep until the last minute, not allowing plant debris time to
break down. Another mistake is working soil when it is too wet. This
compacts the soil and creates clods that the fumigant cannot penetrate.
Soil Moisture
Fumigants perform very
poorly in wet soils. Excessive soil moisture
restricts fumigant movement.
Soil conditions that are ideal for discing and tilling are ideal for
fumigation. Work the soil just prior to fumigation to bring moisture to the
soil surface and to secure a seed bed condition. Dry soils can also reduce
fumigation effectiveness. There should be sufficient moisture in the soil
for seed germination. It may be necessary to irrigate prior to working the
soil or prior to fumigation.
Soil Temperature
Methyl
bromide/Chloropicrin applications work best when soil temperatures are
between 50º F and 80º F at the depth of injection. Below 50º F higher
dosages may be required. Do not fumigate below 42º F. Telone®
II combinations may be applied at soil temperatures between 40º F and 80º F.
The lower the soil temperature, the longer the planting interval following
fumigation.
Dosage and Application Technique
The pest to be
controlled, degree of control desired and crop to be planted will determine
the best fumigant to use, dosage and application technique. A soil sample
can be taken and tested for nematodes and/or pathogens prior to the
application. Crop history is also a good indicator of soil pest problems.
Consult with your Trical representative to develop a fumigation plan.
Exposure
For tarped applications, leave the tarp on for 5 days for a methyl
bromide/Chloropicrin application. Cut each tarp panel on the 6th day
and remove on the 7th. For Telone® II
mixes leave the tarp on for 7 days. Cut on the 8th day, and remove on
the 9th. In all cases do not remove the tarp if fumigant odor is
evident.
For non tarped
applications of Telone® II mixtures, the
soil should be packed and left undisturbed for 10 to 14 days following
fumigation. In some instances a cover crop may be direct seeded near
the surface after 7 days. A longer undisturbed interval may be
required if the soil becomes cold or wet.
Fertilization
Fumigation may
temporarily raise the level of ammonium nitrogen and soluble salts in the
soil. This is most likely to occur on soils that are cold, wet, acidic, or
high in organic matter. To avoid ammonia injury and/or nitrate starvation
avoid using fertilizers containing ammonium salts and use only fertilizers
containing nitrates until after the crop is well established and soil
temperature reaches 65° F.
Avoid excessive manuring of soil. Liming of highly acidic soils before
fumigation stimulates nitrification and reduces the possibility of ammonia
toxicity. Phosphorous and micronutrients may become deficient
following fumigation and may need to be applied before planting.
Planting
To avoid phytotoxicity,
allow the fumigant to dissipate completely before planting the crop.
For methyl bromide or methyl bromide/Chloropicrin mixtures under tarp,
normally, the soil can be planted 10 to 14 days after fumigation without
damage to crops. For Telone® II
or Telone® II/Chloropicrin mixtures under
tarp, 1 week is recommended for every 10 gallons per acre applied before
planting after a 7 day exposure interval. For non tarp applications
using Telone® II or Telone®
II/Chloropicrin mixtures, 1 week is recommended for every 10 gallons per
acre applied before planting after a 7 to 10 day exposure interval. If
after this time, an odor of the fumigant is detectable, working the soil
will assist is hastening dissipation. Do not plant if the odor of
these fumigants is present.
Mycorrhizal Fungi
Under certain
conditions, crops requiring Mycorrhizal fungi may be adversely affected by
soil fumigation. Trical makes no guarantee that crops planted in fumigated
soil will not have this problem. In the event of nutrient deficiencies
related to fumigation of Mycorrhizal fungi, the grower should apply
appropriate nutrients.
NOTE CAREFULLY: Before fumigation, soil
sampling for the type and quantity of pests present is recommended. A
successful fumigation cannot be expected to eradicate pests completely.
Therefore, post treatment sampling is recommended to determine the need for
additional pest management practices.
