Spatial and Temporal N Management for Irrigated Vegetable Production Systems

Crops: Apples Broccoli Cauliflower Celery Lettuce
4R Practices: Rate Time Place

Lead Researcher:

Dr. Charles Sanchez


University of Arizona

Start Date: 2019

End Date: 2022

Collaborating scientists and universities

  • Dr. Pedro Andrade-Sanchez, University of Arizona

Project Summary

Intensive vegetable production in the desert receives large annual applications of nitrogen (N) fertilizers. Soils in the southwestern United States are generally low in organic matter and amounts of N applied range from 200 to 400 kg/ha. Crop recoveries are less than 50%. There are numerous possible fates of fertilizer applied N in addition to the desired outcome of crop uptake. Over the past 15 years, researchers with the University of California and University of Arizona have developed strategies for efficient nutrient management. For N, these practices include fertilizer timing, pre-side dress plant and soil testing, and improved irrigation management. However, these guidelines have been applied to uniform management schemes in spite of the fact that fields often show considerable variation in soil properties. In-field soil textural variation is a significant factor affecting the mobility and availability of N. The prospect of variable rate (VRT) pre-plant and in-season N fertilizer application has not been evaluated in desert vegetable cropping systems. Certainly, varying N fertilizer applications by soil management zone makes sense. Further, emerging optical sensor technologies expand opportunities for in-season N management. We have evaluated VRT for pre-plant P fertilization in the desert. However, data exploring the potential for using VRT for N management is limited.

Studies conducted within Bard Water District, Yuma County Water Users Association, and Yuma Irrigation District in 2019-2020.

Project Goals:

  • Develop economically viable and effective sampling protocols to generate prescription maps for the variable rate pre-plant and in-season application of N comparing soil and plant sampling.
  • Compare variable rate N application to current methods and evaluate alternative economic outcomes.
  • Evaluate and test methods to augment zone-based management with optical sensors.

Project Results:

  • In the first year of this study, broccoli and iceberg lettuce yields were optimized with variable rate technology using soil-based zones.
  • Utilizing variable rate side-dress nitrogen applications, broccoli and iceberg lettuce yield per pound of nitrogen applied was optimized.

Annual Reports