Effects of mulching on above and below ground pests and beneficials in a green onion agroecosystem

• Effects of organic, living and solarization mulch were evaluated on green onion.
• Organic mulch and insectary borders increased beneficial, but reduced arthropods pests.
• Solarization suppressed weeds and initial population of plant-parasitic nematodes.
• Sunn hemp in no-till or solarization system reduced the incidence of purple blotch.
• Green onion yield was greatest in sunn hemp organic mulch systems.

In 2013 and 2014, different mulching systems were investigated for their potential to suppress above and below ground pests, and enhance beneficial arthropods and soil health in green onion (Allium cepa) plantings. Three types of mulch systems (organic, living and solarization mulch) were evaluated and compared. Green onions were grown in four pre-plant treatments: (1) organic mulch generated by flail mowing a sunn hemp (Crotalaria juncea) cover crop (SH) followed by a no-till cropping system, (2) soil solarization (Sol), (3) sunn hemp-solarization mulch in which the sunn hemp was incorporated into the soil followed by soil solarization (SHSol), and (4) bare ground with insecticides (BG). Sol, SHSol and BG were practiced in conventional tilled system. SH (in 2013 and 2014) and SHSol (in 2014) treatments included strips of buckwheat and cowpea along the crop border to serve as living mulch or insectary plants. Green onion plants in SH had lower thrips and leaf miners damage than other treatments in both study years. When insectary borders were added to SHSol in 2014, thrips and leaf miners damages were also reduced in SHSol compared to Sol and BG. Incidence of purple blotch was reduced in SH and SHSol treatments in 2014. The SH treatment contained an increased abundance and richness of detritivores, predatory arthropods, parasitoids and beneficial free-living nematodes (particularly bacterivores and fungivores). Although weeds and initial populations of plant-parasitic nematodes were lower in solarization (Sol, SHSol) than other treatments, green onion yield was greatest in SH organic mulch systems in both study years. Overall, the integration of surface organic, living and solarization mulches into a green onion agroecosystem provided multiple ecosystem services including suppression of above and below ground pest organisms.

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