Recovery of 15N Labeled Nitrogen Fertilizer by Fertigated and Drip Irrigated Greenhouse Vegetable Crops

Abstract

The stable isotope ¹⁵N was used to assess the recovery of mineral N fertilizer applied to fertigated and drip-irrigated spring muskmelon and autumn-winter sweet pepper crops grown in greenhouse soil plots. They received 92–96% of mineral N fertilizer as NO₃⁻. ¹⁵N-labeled Ca (NO₃)₂ fertilizer was applied to crops during vegetative growth and fruit production phases. Crops were grown with either conventional management or combined improved N and irrigation management. Improved management for both irrigation and N was based on the combined use of models, to estimate crop requirements, and of monitoring of soil parameters. In sweet pepper, from conventional management, ¹⁵N recoveries from the ¹⁵N applications made during vegetative growth and fruit production were 66% and 58%, respectively. With improved management in sweet pepper, the corresponding ¹⁵N recoveries were 82% and 77%. In muskmelon, ¹⁵N recoveries from conventional management from the ¹⁵N applications made during vegetative growth and fruit production were 71% and 42%, respectively. With improved management, the corresponding ¹⁵N recoveries were 68% and 44%, respectively. The results demonstrated that combined drip irrigation and fertigation systems with frequent irrigation and N fertilizer application can have very high recovery of applied N fertilizer, of 77–82%.