How to Recognize Phosphorous Deficiencies in Your Vegetables

Phosphorous is one of the three primary nutrients required by plants in relatively large quantities and is essential for cell division, strong stems, and good root development. Phosphorous is also the most important nutrient for seedlings when they are growing quickly. If it is deficient in the soil, or simply unobtainable by the plants, then your vegetables will suffer visible symptoms of phosphorous deficiency. This article will identify the common symptoms of phosphorous deficiencies, explain common causes, list the best sources of phosphorous, and explain how to correct problems.

Difficulty: Moderately Easy

Instructions

1. Symptoms
   
   Initial symptoms of phosphorous deficiency are not very distinctive or dramatic. Typically it shows up as a red or purple tint on leaves. The first time I grew tomato seedlings I was delighted with the beautiful, delicate purple hue of their young leaves. I thought that was simply the way they looked. Only later did I realize they were suffering from a classic case of phosphorous deficiency. Later on symptoms may manifest themselves as leaf bronzing and mottling; thin stems; stunted, slow growth; and poor fruit set.

2. Common Causes
   
   Phosphorous readily combines with iron and aluminum to form insoluble phosphates, so even if it is present in the soil it is mostly unavailable to plants, whose roots can only absorb a soluble mix of phosphorous ions and water. So the problem is usually not a soil deficiency but rather getting the soil to release the phosphorous. Maintaining proper soil pH is also important because phosphorous only becomes available when the soil is close to neutral.

3. Sources and Remedies
   
   If is difficult to deal with a phosphorous deficiency because it is so slow to release and become available to plants. It is frequently recommended that you provide seedlings as much phosphorous as you can to fuel their rapid cell division and growth, and to get a good jump on root system development. Plants with vigorous root systems can forage farther and deeper so they have a better opportunity to locate available phosphorous once planted out.
   
   The most common organic fertilizer that supplies phosphorous is rock phosphate. The finest ground variety is known as colloidal phosphate, which becomes available to plants the fastest. Unlike other amendments, you can’t use too much rock phosphate so don’t skimp.
   
   There are two quick fixes for deficiencies. One is to foliar feed plants weekly with fish emulsion until symptoms abate. You can also try making bat guano or worm casting “tea” and applying it as a soil drench. Use this in conjunction with a top dressing of bonemeal, which is phosphorus rich. Be sure to thoroughly “water in” the top dressing.
   
   For a long term fix mix rock phosphate or aged poultry manure into the soil and your compost pile in the fall. This gives the micro herd time to work its magic and also leaches some of the nitrogen out of the poultry manure, which is often too nitrogen “hot” to use in the spring.

Tips & Warnings

• There is a link under Resources to a website with color picture of plants suffering from phosphorous deficiency.
• There is also a link to a website with a comprehensive deficiency symptom chart that also provides remedies.

Resources

• How to Apply Solid Fertilizer to an Organic Garden
• How to Apply Liquid Fertilizer to an Organic Garden
• Color Pictures of Mineral Deficiencies in Plants
• Nutrient Deficiency Symptoms Chart
• How to Recognize Nitrogen Deficiencies in Your Vegetables

[susanhorton72]

on 10/17/2009 You are quite knowledgeable about the subject. Your article is further proof that the correct ph balance is important for all life.

[billips]

on 10/1/2009 Great information to store away for next growing season - will definitely be watching for phosphorous deficiencies in my vegetables - 5* - B.