Evaluating solarization and cultivated fallow for johnsongrass (sorghum halepense) control and nitrogen cycling on an organic farm

Derek M. Law, Victoria Bhavsar, John Snyder, Michael D. Mullen, Mark Williams

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


A two-year field study evaluating efficacy of two weed control techniques on the noxious weed johnsongrass (Sorghum halepense L. Pers.) was conducted in Lexington KY. The weed control treatments were soil solarization, accomplished by covering the soil with clear plastic for 8 weeks, and cultivated bare fallow. Both treatments, along with a control treatment (mowing), were applied during the summers of 2003 and 2004 to a field heavily infested with johnsongrass (40–50% coverage). Effects of solarization on soil microbial activity and nitrogen (N) cycling were also evaluated. In both years, half of each treatment plot was lightly tilled 8 months after initial treatment application, and johnsongrass populations were characterized 2 months later. At the end of the experiment, the solarized-untilled treatment had lower johnsongrass populations than the cultivated-tilled and control treatments. Shallow tillage resulted in significantly more johnsongrass in the cultivated treatment in 2003, and in both cultivated and solarized treatments in 2004, compared with their untilled counterparts. At the conclusion of the experiment the johnsongrass populations were considerably reduced in both treatments compared with the original infestation. Solarization resulted in significant increases of both NH4-N and NO3-N in the soil during the time the plastic was in place, likely due to release of labile NH4-N from soil microbial biomass and subsequent nitrification. Substrate-induced respiration rates were also reduced during solarization, indicating a reduction of microbial biomass. However, these soil indicators were not persistent and should not prohibit the use of this weed management technique by organic growers.

Original languageEnglish
Pages (from-to)175-191
Number of pages17
JournalBiological Agriculture and Horticulture
Issue number2
StatePublished - 2008

Bibliographical note

Funding Information:
This article is no. 08-11-055 of the University of Kentucky Experiment Station and is published with the approval of the Director. This research was partially funded by the New Crop Opportunities Center at the University of Kentucky through a USDA Special Grant.

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Horticulture


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