Tem­per­a­ture In­ver­sions

Successful Farming - - CROPS -

Tem­per­a­ture in­ver­sions can fuel off-tar­get dicamba move­ment.

Dur­ing the day­time, warm air rises when sun­light hits the ground. Mean­while, cool air comes down, hit­ting the warm air. When this hap­pens, wind re­sults, which keys air cir­cu­la­tion. At night, air pat­terns flip-flop, with cool air at the bot­tom and warm air on the top. This cre­ates a sta­ble en­vi­ron­ment that traps any pes­ti­cide par­ti­cles in a sus­pended air mass.

When this air mass en­coun­ters a hor­i­zon­tal wind, those par­ti­cles move some­place. At its worst, the trapped pes­ti­cide can land in the mid­dle of a mul­ti­t­hou­sand­dol­lar-per-acre field of fruits or veg­eta­bles.

In­ver­sions are com­mon, oc­cur­ring any­where sun hits the sur­face of the soil, says Mandy Bish, Univer­sity of Mis­souri (MU) se­nior re­search spe­cial­ist. MU re­searchers have found in­ver­sions set­ting up at 5 or 6 p.m., a time when many ap­pli­ca­tors are still spray­ing.

Bish says fac­tors as­so­ci­ated with in­ver­sions in­clude:

• Clear night skies

• No wind

• Morn­ing dew or frost

• Low-ly­ing fog, which is an in­di­ca­tor of an in­ver­sion.

“If you spray the night be­fore you see the fog, it is not the best in­di­ca­tor,” Bish says.

Though not fool­proof, smoke bombs are one way to de­tect tem­per­a­ture in­ver­sions. Smoke bombs set off at 4 p.m. by MU sci­en­tists showed fairly rapid dis­per­sal. Ones set off at 7:30 p.m. lin­gered ap­prox­i­mately 50 sec­onds, which in­di­cates in­ver­sion pres­ence, she says.

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