131-4 Influence of Used Cooking Oil On the Fate of Broccoli Crop Residue-Derived 15N in the Autumn.
See more from this Division: S04 Soil Fertility & Plant NutritionSee more from this Session: Divisions S4/S8 Graduate Student Oral Competition - Managing Inorganic and Organic Nutrient Sources to Improve Efficiency and Minimize Losses
Monday, October 22, 2012: 10:55 AM
Duke Energy Convention Center, Room 207, Level 2
Cole crops can pose a high risk of N losses after harvest due to the substantial quantities of N in crop residue (191-304 kg N ha-1) which rapidly mineralize. Previous field and laboratory studies have found lower soil mineral N with the application of 5 Mg ha-1 used cooking oil after broccoli harvest. However, the quantity of residue-derived N must be separated from indigenous soil N or N fertilizer to accurately assess reduction of crop residue-derived N losses. Thus, a 15N tracer study was conducted to label broccoli plants from early and late crop production to assess the fate of broccoli crop residue-derived N after harvest, with and without the application of used cooking oil. In spring 2011, 5% atom excess enriched 15N urea fertilizer (at 342 kg N ha-1) was incorporated in the top 15 cm soil in 1.35m2 micro-plots prior to broccoli transplanting. Seasonal management followed typical grower practices. At harvest, plant parts (head, leaves, stem, roots), rhizosphere soil, and soil samples were collected. After harvest, two treatments were established: (1) a crop residue incorporated control and (2) crop residue incorporated with used cooking oil. Soil samples were collected twice throughout autumn. Minimal fertilizer N losses occurred during the broccoli growing season but a significant amount of fertilizer-derived N (54%) remained in the field as above-ground crop residue (leaves and stem). In early harvested broccoli only, used cooking oil resulted in significantly lower (by 45 to 68 %) mineral 15N- and quantifiably higher (by 80%) microbial biomass 15N-derived from crop residue, suggesting immobilization during autumn after early- but not late-broccoli harvest. Environmental conditions later in autumn may have limited immobilization of crop residue-derived N. Thus, the application of used cooking oil may be a beneficial N management practice for cole crop producers to minimize N losses, particularly after early-harvested broccoli.
See more from this Division: S04 Soil Fertility & Plant NutritionSee more from this Session: Divisions S4/S8 Graduate Student Oral Competition - Managing Inorganic and Organic Nutrient Sources to Improve Efficiency and Minimize Losses