Amending soil with used cooking oil to reduce nitrogen losses after cole crop harvest: a 15N study

Nitrogen cycling and management in intensive horticultural systems

“…Congreves et al (2014) found broccoli roots contained 21 kg N ha -1 , and including roots in calculations increased plant fertilizer use efficiency estimates by 2 % (from 52 to 54 %). Based on the 15 N work by Congreves et al (2014), a shoot to root ratio of 19:1 may be used by researchers to estimate total plant uptake and fertilizer N recovery in broccoli production. Despite low C:N ratios for broccoli roots (26), Congreves et al (2014) suggested it remained mostly as organic N after crop harvest and therefore had a low risk for N loss.…”

“…However, with a 15 N tracer, broccoli biomass (not including roots) recovered 52 % of fertilizer N . The 15 N tracer study by Congreves et al (2014) suggested that broccoli plants contained 25 % more fertilizer-derived N (not including roots) than previously thought using common nontracer indices, such as NUE or apparent N recoveries. Thus, the accuracy of estimating NUE has important implications for assessing risk of N losses.…”

“…Without the use of a 15 N label, researchers have found mean NUE of 47-31 % for broccoli and cauliflower, respectively (Table 4). Similarly for broccoli, a NUE of 27 % was calculated in a study by Congreves et al (2014), using a common NUE index without a 15 N label (Van Eerd 2007) (i.e., (plant N content in fertilized treatment -plant N content in unfertilized treatment) 7 amount of N fertilizer applied). However, with a 15 N tracer, broccoli biomass (not including roots) recovered 52 % of fertilizer N .…”

Alternative Management Practices Improve Soil Health Indices in Intensive Vegetable Cropping Systems: A Review

“…The breadth of amendment types that were studied reflects the diversity of organic carbon material available for potentially improving soil health; ranged from various types of composts (plant-based, manure, or vermicompost) (e.g., Morra et al, 2010), to biochar (e.g., Dumontet et al, 2017), and to used cooking oil (e.g., Congreves et al, 2014). There were also a variety of intended purposes for applying these amendments to soils in vegetable production, such as hypothesized improvements in soil organic matter levels (Morra et al, 2010), potential enhancements in microbial diversity (Dumontet et al, 2017), and reductions in postharvest N losses (Congreves et al, 2014). Although relatively few studies focused on the soil physical aspects of soil health, when physical attributes were reported, there was a general improvement (Figure 3) including: decreased soil bulk density (0.79 RR), increased soil porosity (1.28 RR), and increased soil moisture (1.22 RR).…”

“…In some cases, greater inorganic concentrations after amendment applications were interpreted as beneficial for soil health, i.e., greater nitrate availability for plant growth (Ninh et al, 2015), but in other cases it was interpreted as increased potential for nutrient losses with a negative impact on the environment (Evanylo et al, 2008). A number of studies explored how carbon amendments immobilize inorganic nitrogen during periods when there is a high risk of nitrogen loss (Congreves et al, 2013(Congreves et al, , 2014Congreves and Van Eerd, 2015). A finerscale understanding of how amendments influence the temporal dynamics for soil inorganic nitrogen availability is key for linking its influence to aspects of soil health i.e., enhancing nutrient reservoirs for plant growth, improving nitrogen sequestration for mitigating losses to the environment, and the balance between these soil functions, etc.…”