Influence of Management Practices on Lettuce Yield and Weed Population in Organic Production, Poster Board #065

Management practices can vary significantly in organic crop production systems depending on the selection of inputs. The impact of different management practices on crop production is also affected by site-specific conditions. In this study, the use of cover crops, plastic mulch, and no-till was evaluated in organic lettuce production in sandy soils in north central Florida. Sunn hemp and sorghum-sudangrass were grown during Aug. to Oct. 2011 and terminated using a roller-crimper prior to fall production of ‘Tropicana’ green loose leaf  lettuce in a certified organic field at the Plant Science Research and Education Unit in Citra, FL. Five treatments with different management practices were established before the organically grown lettuce seedlings were transplanted into the research plots: 1) without cover crops and plastic mulch, tilled; 2) without cover crops but with plastic mulch, tilled; 3) with cover crops and plastic mulch, tilled; 4) with cover crops but without plastic mulch, tilled; and 5) with cover crops, no-till. A randomized complete-block design was used with 4 replications and 48 lettuce plants per treatment in each replication. Lettuce yields and weed populations were assessed. Establishment of lettuce plants was poor in the no-till plots primarily due to the high population of annual grass weeds at planting. The total marketable yields of lettuce were significantly higher in treatments with plastic mulch than those in the treatments without plastic mulch. Moreover, the no-till treatment had the lowest lettuce yield of all the treatments. Weed population assessment was conducted following the lettuce harvest. A 0.4 m² quadrat was used for estimating the populations of annual and perennial grass weeds, annual and perennial broadleaf weeds, and nutsedges. Results showed that the populations of grass and annual broadleaf weeds did not differ significantly among treatments. Treatments without plastic mulch and the no-till treatment resulted in significantly higher populations of perennial broadleaf weeds than the treatments with plastic mulch. A similar trend was observed when comparing the population of nutsedges among treatments. Regrowth of sunn hemp and sorghum-sudangrass was also noted with the no-till treatment. Considering the poor establishment of lettuce plants in the no-till plots, the use of strip tillage may be a more appropriate option than no-till to reduce the incidence of interference with the lettuce crop.