Ground cover management and farmyard manure effects on soil nitrogen dynamics, productivity and economics of organically grown lettuce (Lactuca sativa L. subsp. secalina)

Ground cover management and farmyard manure (FYM) management have important roles in organic lettuce production. However, there is not enough information about their combined effects. In order to assess the effects of individual and combined ground cover and FYM management on soil mineral N (NH4-N and NO3-N) dynamics, lettuce yield and economics in organic farming, a two-year field experiment was conducted on a certified organic farm in Kisač (Vojvodina, Serbia). The experiment had a two-factorial split-plot completely randomized block design. FYM was applied on the half of the experimental field as a whole-plot factor, while ground cover management included the following four treatments: (I) control, without ground cover management (Ø); (II) hoeing (H); (III) agrotextile cover; (IV) straw mulch (SM), which were applied on split plots. The applied SM and AT increased soil moisture by 12.83 and 3.73%, respectively, compared to the control treatment. FYM increased soil mineral N concentration, the lettuce fresh matter (FM) yield and nitrate concentration in lettuce. However, nitrate concentration in lettuce in all treatments was below the limit required by the European Commission (EC) (2001). The highest lettuce yield was obtained by AT (39 122 kg), followed by SM (33 925 kg), and it was higher with FYM application by 16.85%. Hoeing did not positively affect the yield, probably due to its negative effect on soil moisture. Additional profit was higher with FYM, showing the following decreasing order: AT>H>SM>Ø. However, value/cost ratio (VCR) was in the order Ø>H>SM>AT on FYM fertilized plots. FYM application led to higher lettuce yield and higher profit and VCR. In case a farm does not have FYM, SM is the best alternative due to its positive effect on the yield and low investment costs.