A collaboration between

Acknowledgments

Acknowledgments

Funding provided by:

Guidelines and Webpage Design:

Daniel Geisseler, Ph.D.; Cooperative Extension Specialist in nutrient management; Department of Land, Air and Water Resources, University of California, Davis

Reviewers:

Richard Smith; Farm Advisor; University of California Cooperative Extension Monterey County

William R. Horwath, Ph.D.; Professor of Soil Biogeochemistry and James G. Boswell Endowed Chair in Soil Science; Department of Land, Air and Water Resources, University of California, Davis

Support:

Amadou Ba, Ph.D.; Branch Chief Feed, Fertilizer, and Livestock Drugs Regulatory Services, California Department of Food and Agriculture

Amrith Gunasekara, Ph.D.; Science Advisor to the Secretary; California Department of Food and Agriculture

Last Update: September, 2015

Additional Information:

Cauliflower Nitrogen Uptake and Partitioning

Cauliflower Production in California

California Fertilization Guidelines

Cauliflower

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Preplant

Sowing
Tansplanting

Rosette
Stage

Head
Development

Harvest

Even though splitting N applications has not always been found to be superior to applying all N at planting ^[N4], split applications should be preferred because, high pre-plant or starter application rates considerably increase the risk of nitrate leaching below the root zone.

In a study on the Central Coast, Welch and coworkers ^[N32] found that a single ammonium sulfate application at planting as was less effective than split applications. Addition of nitrapyrin, a nitrification inhibitor, was equally effective as split applications. Split applications also increased N uptake and yield in a Danish study ^[N29].

Application Rate

The required N rate depends on soil nitrate content. Several studies carried out in commercial fields of cauliflower and other cool-season vegetables on the Central Coast found that when the pre-sidedress soil nitrate-N level is above 20 ppm, no fertilizer N is necessary ^{[N7,
N10]}. If the nitrate-N concentration in the soil is below 20 ppm, only enough N to increase soil available nitrate-N to 20 ppm is needed. Approximately 4 lbs N/acre need to be added to increase the soil nitrate level by 1 ppm ^[N12]. As an example, when the soil nitrate-N concentration is 15 ppm, 20 lbs N/acre are needed to increase the level to 20 ppm. Contact your local farm advisor for more information.

Crops produced from late fall through early spring generally require more fertilizer N because the residual soil N content tends to be lower during this period compared to the summer months ^[N9]. When leaching losses are minimized, the seasonal N application rates for cauliflower should not exceed 180-240 lbs/acre for winter and spring production and 150-180 lbs/acre for summer and fall production ^[N9].

These application rates are in line with studies from Europe, where optimum yields were produced with a total N availability ranging from 200 to 240 lbs N. The available N included fertilizer N plus pre-plant nitrate-N in the top two feet of the soil profile ^{[N4, N19, N29]}.

Studies carried out in Arizona found that marketable yields ranging from 200 to 260 cwt/acre were achieved with 300-360 lbs N/acre ^{[N23, N26, N27]}. However, in one of the studies with cauliflower produced with subsurface drip, the residual soil nitrate N in the top three feet of the profile after the harvest of the cauliflower generally was between 135 and 180 lbs/acre. This amount does not include N leached during the cropping season and N in residues remaining in the field ^{[N26,
N27]}.

CropManage

Mode of Application

Subsurface band

Everaarts and de Moel ^[N4] reported that placement of fertilizer in a band 2 inches to the side of the row and 2 inches below the soil surface tended to slightly increase cauliflower yield compared to a broadcast application. However, in Oregon, Hemphill and Hart ^[N14] found that band applied in-season N resulted in significantly lower yield and mean head size than when the N was broadcast.

Fertigation

In drip-irrigated fields, N can be applied through the drip system ^[N17].

Surface band

A surface band application of an ammonium nitrate solution between rosette stage and harvest serves as contact herbicide against broadleaf weeds and as a N source ^[N28]. The waxy cuticle that cauliflower and other cole crops develop once they have at least three true leaves prevents damage to the crop, unless the plants are very wet ^[N28]. A shielded spray should be used to avoid spraying the growing point or emerging new leaves of the broccoli plant ^[N28].

Agamalian ^[N1] found that topical applications of 50 to 60 gallons per acre of undiluted 20% ammonium nitrate were effective in killing weeds. Ammonium thiosulfate was also effective in killing weeds, while the results with urea/sulfuric acid solutions were variable ^[N1]. The amount of N in these applications is equivalent to 105-125 lbs N/acre. Therefore, such high topical applications should only be used when the amount of N applied is needed by the plants at the time of application. The N applied must be integrated into the N fertilization program.

Foliar N

Little information on the effect of foliar N application is available.

Time of Application

Fertilizer Type

N in Cauliflower Residues

Phosphorus (P₂O₅)

Soil Test

Tissue Analysis

Leaf Analysis

Sampling

Interpretation of Test Results