California Crop Fertilization Guidelines

UC Davis
A collaboration between CDFA, FREP and UC Davis

Onion Nitrogen Uptake and Partitioning

The Fertilization guidelines can also be found on the UC Davis Nutrient Management website .

Seasonal N Uptake

Season N Uptake Curve Graph

Nitrogen accumulation in the bulbs and tops of intermediate day (open squares) and long-day (diamonds) varieties of fresh market onions grown in the high desert near Lancaster, CA. Yields were approximately 828 and 700 cwt/acre, respectively. Uptake was very slow for the first half of the season, until the early bulbing stage. Uptake was steady during bulb development until early maturity, at about 3.1 lbs N/acre/day for the intermediate variety and 1.7 lbs N/acre/day for the long-day variety [2].

Nitrogen Partitioning

Nitrogen partitioning pie chart

Nitrogen distribution in fresh market onions grown near Lancaster, CA. Values represent the means of two intermediate-day varieties and one long-day variety [1].

Nitrogen Removed at Harvest

Nitrogen removed at harvest with onion bulbs. The overall average is weighted for the number of observations in each trial. More information can be found here [3].

Location Years Removal (lbs N/ton fresh weight) Source
    Mean Range  
Lancaster, CA 2013-14 3.42 2.97 - 3.92 [2]
Salinas, CA 1961 5.41 4.83 - 6.29 [7]
India 2012 4.89 3.1 - 6.16 [5]
Various   3.60 1.6 - 4.8 [4]
Various   3.52 2.53 - 3.81 [6]
Weighted Average 3.94 1.6 - 6.29  

The amount of N removed per unit of yield is higher for onion varieties with a high percentage of dry matter. However, because yields are higher for onions with less dry matter, total N removal may not differ.



  1. Biscaro, A., Cahn, M., 2014. Improving irrigation and nutrient management . Garlic and Onion Symposium, Tulare, California, Feb 10, 2014.
  2. Biscaro, A., Cahn, M., Smith, R., Hartz, T., 2014. Nitrogen, phosphorus and potassium uptake patterns of freshmarket onion production in southern California. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America (ASA, CSSA, and SSSA) International Annual Meetings, Long Beach CA. Complemented with unpublished data.
  3. Geisseler, D., 2016. Nitrogen concentrations in harvested plant parts -A literature overview. Report to the Kings River Watershed Coalition.
  4. Howard, F.D., MacGillivray, J.H., Yamaguchi, M., 1962. Nutrient composition of fresh California-grown vegetables. California Agricultural Experiment Station, Bulletin No. 788, California Department of Agriculture.
  5. Pradhan, R., Pattnaik, A. K., Tripathy, P., Mallikarjunarao, K., Sahoo, B. B. Lenka, J., 2015. Influence of sulphur fertilization on nutrient uptake of onion (Allium cepa L.). Journal Crop and Weed 11, 134-138.
  6. United States Department of Agriculture Food Composition Database.
  7. Zink, F.W., 1966. Studies on the growth rate and nutrient absorption of onion. Hilgardia 37, 203-218.