Guide for Fertilizing Vegetables
The authors are H. W. Otto, University of California Farm Advisor in Orange County; Roy Branson, Soils and Water Specialist, University of California, Riverside, retired; Kent Tyler, Vegetable Specialist, University of California San Joaquin Valley Agricultural Research and Extension Center., Parlier.
Contributors: Oscar Lorenz, Professor of Vegetable Crops, University of California, Davis; Keith Mayberry, University of California Farm Advisor in Imperial County; James Quick, Technologist, University of California, Davis; Ronald Voss, Vegetable Specialist, University of California), Davis.
CAUTION: INFORMATION IS PRESENTED AS A GENERAL GUIDE. THIS IS NOT AN OFFICIAL UNIVERSITY OF CALIFORNIA RECOMMENDATION FOR EXACTLY HOW TO FERTILIZE A SPECIFIC FIELD.
This publication can't tell you exactly how to fertilize for all soils, fertilizers, temperatures, application methods, irrigation systems, varieties and cropping patterns in all possible combinations. So guidelines in this publication may need to be modified under certain conditions and from season to season. Where guidelines are very much different from your standard practice, use the guidelines for several small test strips in fields. Compare results with your regular practice for a few seasons.
Fertilizer guidelines are based primarily on University of California research. Where California data is lacking, information has been supplemented by carefully selected field research and experience from other areas. This supplemental information is expected to be useful for trial in California, either because of widespread agreement among research findings in different regions, or because of the nature of the information itself.
To simplify information, trade names have been used. No endorsement of named products is intended, nor is criticism implied of similar products which are not named.
Note: Soil and plant analysis reports must be interpreted with care! Be sure you work closely with your farm advisor when interpreting soil or plant tissue tests.
Certain nutrients applied either to the soil or as a foliar spray, may cause plant injury if used at the wrong stage of development or under adverse weather or soil conditions. Injury may also result from excessive amounts of the wrong fertilizer source, improper placement, or from mixing incompatible materials. When using foliar applied nutrients, plant injury can be caused by inert ingredients, such as wetters, spreaders, emulsifiers, diluents and solvents.
Since formulations are often changed by the manufacturer, and since varieties grown, weather, or crop condition can change, it is possible that plant injury may occur, even though no injury was noted in other seasons.
Fertilizing Vegetables: Summary For Most Crops
If your soils are typical of many vegetable farms that have been fertilized for years, soil tests for phosphorus and potassium are high. On such soils no phosphate or potash fertilizer is useful except for a small amount of ammoniated high-phosphate starter at planting.
Later only nitrogen fertilizer is sidedressed as needed by the crop. Do not sidedress with fertilizers containing phosphorus or potash.
Every few crops, you can apply extra phosphate if soil tests warrant. Certain micronutrients are sometimes added if soil or plant tests show a need.
You may apply manures to supplement commercial fertilizer if you wish to use them; but apply no more than necessary. (Overdoses can be harmful.) This is a general summary. For details, see each crop in pages that follow.