Abstract
Organic and conventional production are common in horticulture crops and each system may exert a different influence on the soil ecosystem, particularly the nematode community. Crop nutrient rate is an important choice in both production systems. The objectives of this study were to assess the impacts of (i) organic and conventional production systems and (ii) nutrient rate in both systems on the nematode community in carrot production. To investigate these objectives, field studies in organic and conventional production – which included fumigation with 1,3-dichloropropene – were conducted in North-Central Florida. In both production systems, nutrient rate treatments were 168, 224, 280, 336, and 392 kg N/ha. Poultry litter was the nitrogen source in organic production whereas synthetic, inorganic fertilizer was used in conventional production. All nematode trophic groups were consistently more abundant in organic than conventional production. The nematode community was more diverse and had greater trophic structure in organic production. Greater rates of organic nutrients increased enrichment opportunists (bacterivores and fungivores), but inconsistently across years. Conventional production had similar results except that only moderate nutrient rates increased fungivore abundances. Extreme enrichment opportunists (Rhabditis spp.) drove bacterivore trends in organic production whereas moderate enrichment opportunists (Cephalobus spp.) drove trends in conventional production. Nutrient rates did not affect omnivore-predators, herbivores, nematode community diversity, or structure in either system. In summary, type of production system, organic or conventional, exerts a strong influence on the nematode community, but nutrient rate has less consistent effects in horticulture production.
Highlights
Carrot (Daucus carota spp. sativus) production is an important industry in the United States, planted to 28,207 ha with a total crop value of $716 million (USD) in 2020 (NASS-United States Department of Agriculture (USDA), 2021)
The nematode community is known to be sensitive to many agricultural practices such as pesticide application (Grabau et al, 2020; Watson and Desaeger, 2019), tillage (Grabau et al, 2018; Neher et al, 2019), and crop rotation (Grabau and Chen, 2016), so it could be useful for assessing impacts of organic and conventional systems on the soil community
The maturity and channel indices were each decreased in organic relative to conventional production (Fig. 3)
Summary
Carrot (Daucus carota spp. sativus) production is an important industry in the United States, planted to 28,207 ha with a total crop value of $716 million (USD) in 2020 (NASS-USDA, 2021). Free-living nematodes include a wide range of trophic groups – including fungal-feeders, bacteria-feeders, predators, and omnivores (Ferris et al, 2001; Yeates et al, 1993) They can contribute directly to soil productivity through services such as pest suppression (Khan and Kim, 2005), nutrient cycling (Holajjer et al, 2016; Trap et al, 2016), and redistribution of microbes in the soil profile (Jiang et al, 2018). Among nematode community research in more intensively managed crops – typically tomatoes – in warm climates, fumigation is often not included (Berkelmans et al, 2003; Briar et al, 2011; Sanchez-Moreno et al, 2009), fumigation is a universal practice in Southeast conventional vegetable production. This flush of resources may favor extreme colonizers or R-strategy adapted organisms that increase rapidly in response to resources
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