Activity 12

Development of an organically managed baby greens production system: a multidisciplinary approach

Problem Statement

The organic production of baby green vegetables in muck soil presents multiple challenges, especially the management of weeds and insect pests. This project evaluated various production systems to optimize yields while managing these problems.

Objectives

1. Quantify the impacts of cover crops and organic fertilizers on yields
2. Determine the redheaded flea beetle trapping potential of various attractive plants and quantify the damages on spinach crop
3. Establish relationships between meteorological data (air and soil temperatures, soil moisture) and weed emergence to develop emergence models and improve delayed seedingass, stale seedbed and seedbed preparation practices
4. Assess the effectiveness of mechanical weed control equipment (cage weeder, bar arrow) and bioherbicides in delayed seeding and stale seedbed
5. Determine optimal irrigation conditions to promote weed emergence before leafy greens are planted
6. Assess the effectiveness of bioinsecticides used alone or in combination with natural predators on pest populations
7. Assess the impact of production systems on the incidence of plant diseases and the effectiveness of the control strategies adopted

Methods

Two sites were established in 2018 and 2019 at IRDA's Organic Agriculture Innovation Platform in St-Bruno-de-Montarville, Quebec.

At site 1, consecutive cycles of green romaine lettuce and spinach were established. Nine treatments combining different cover crops and fertilization methods were repeated 3 times in the field for a total of 27 experimental plots. Four combinations of trap plants were also integrated in the design to evaluate their attractive potential on the redheaded flea beetle. Lettuce and spinach yields, as well as the number and biomass of weeds were determined at harvest for each plot.

At site 2, crops of red curled lettuce (2018), red romaine (2019) and arugula (2 years) were produced. The design included three types of cover crops in main plots repeated three times in the field. For each main plot in 2018, six treatments of mechanical weeding combined or not with bioherbicides were evaluated, for a total of 54 experimental plots with weed monitoring. The effectiveness of weeding practices was determined at each pass and at harvest, by counting weeds in each plot, and by measuring weed biomass and crop yields. Integrated into these plots, three treatments including bioinsecticides and natural predators as well as a control were repeated six times in the field, for a total of 18 plots with insect monitoring.

At the edges of Site 2, weed emergence modelling collected preliminary data on weed emergence dynamics based on the time of year soil preparation takes place.

Results and conclusions

At Site 1, combining the two-year trials, lettuce yields were significantly higher with fertilization including compost, while pelleted poultry manure increased spinach yield.

The irrigation trigger guideline determined with the "turning point" approach was established at values between -25 and -30 kPa for green romaine lettuce, under the conditions of the study (soil, biomass and weeds). Water losses due to evaporation and withdrawals from romaine lettuce and spinach crops mainly occurred in the first ten centimeters of the soil. The positioning of the tensiometer should therefore not exceed this depth for nearly 75% of the growth period for romaine lettuce, while it could be maintained at 10 cm for the entire season with spinach.

The cover crop had no effect on lettuce and spinach yields. The presence of cover crops or the fertilization method had very little impact on weed populations.

Finally, the trap crops incorporating several species were more attractive than the one including only amaranth. The presence of weeds and the lack of water had a significant negative effect on the germination of attractive plants. It is therefore important to apply good weed management and irrigation in order to use trap crops as a control method.

At Site 2, the results of the two seasons demonstrated the importance of adjusting mechanical weeding equipment, particularly the bar harrow. In 2019, the density of weeds in plots weeded with the bar harrow was approximatively 23% lower. Irrigation also played an important role in stimulating weed emergence during the period of stale seedbed. However, in this study, one irrigation was as beneficial as two irrigations. In addition, plots irrigated once or twice had a similar amount of weeds at crop harvest. Finally, the use of bioinsecticides or bioinsecticides combined with natural predators did not demonstrate statistically significant effects on harvest damage for red curled lettuce and arugula. The use of natural predators may be of interest in cases where there is no registered plant protection product.

Future research

More testing is required to consolidate the trends observed following the two years of the study, particularly with regard to the use of natural predators, the impact of irrigation on weeds during stale seedbed and to calculate crop coefficients (link between water withdrawal and evapotranspiration). More data is also required to refine weed emergence models.

Research team

Contributing partners

Vert Nature  

Agriculture and Agri-Food Canada

Last updated: January 2022

Tthe Organic Science Cluster program is led by the Organic Federation of Canada in collaboration with the Organic Agriculture Centre of Canada at Dalhousie University. Organic Science Cluster 3 is supported by funding from the AgriScience Program under Agriculture and Agri-Food Canada’s Canadian Agricultural Partnership (an investment by federal, provincial, and territorial governments) and over 70 partners from the agricultural community. More information about the Organic Science Cluster Program can be found at, www.dal.ca/oacc/OSC.