Nutrient Carryover A Drought Year Concern

October 24, 2012 07:24 AM
 

Experts from Purdue University advise growers to watch for excessive nutrient carryover in this drought year soil profile. This can damage crops that follow on these plots, and it is advised that growers consider what they applied during the dry summer before replanting.

With little rain across most of the growing regions of the nation this summer, any nutrient left in the soil will not have had the chance to dissipate as in a normal growing season.

"The largest concern this year is the carryover of atrazine and subsequent injury on wheat," Bill Johnson said. "It is off-label to plant any crop other than corn or sorghum during the same calendar year of an atrazine application."

Labels vary on exact rotational restrictions, but most atrazine premix labels range 14-15 months.

Wheat can also be injured by fomesafen applied to soybeans postemergence. Rotational restrictions lie in the 4-5 month range on this, but again, with the dry soil this year, nutria will have dissipated at a slower rate -- proceed with caution.

Purdue extension weed specialist Travis Legleiter cautions that producers in these dry areas should be aware of the danger of atrazine and HPPD inhibitors to carry-over into spring planted soybeans, especially in high pH or high clay content soils. Legleiter also warns of the potential for imidazolinone chemistry carryover into spring-planted corn.

The report offers two options for zeroing in on this potentially harmful carryover. The first is a bioassay of the soil. This process collects suspect soil samples and plants susceptible crop seeds in that soil. As the plants grow, the effects of carry-over in that soil can be noted in the emerging plants. This can be done either in containers or in the actual field.

The second option they offer is to have soil samples evaluated in a commercial lab. This method also yields solid answers, but tends to be a little more expensive.

"Both bioassays and lab analysis should either be done in late fall or early spring to allow for maximum herbicide degradation and provide a more representative result of potential injury at planting," Legleiter said.

More information about conducting bioassays and a list of commercial soil labs are available in the Oct. 12 edition of Purdue Extension's Pest and Crop Newsletter at http://extension.entm.purdue.edu/pestcrop/2012/issue26/index.html#indiana.


 

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