Essential Plant Nutrients

Bonnie Nowicki

Happy January 2023, dear Quail Creek residents. I wish to focus this article on three plant elements: nitrogen, phosphorus, and potassium. You know, those three numbers you see on bags of fertilizer. I referred to my Arizona Master Gardener manual to guide this review. Let’s start with basic soil. Arizona soils typically contain very low levels of organic matter, usually less than one percent by weight. The subsoil can include hardpan, or caliche, a naturally occurring layer cemented with calcium carbonate (lime) that is common in desert soils. Most soils in Arizona are considered highly alkaline and have a pH of between 7.5 and 8.5. Values below seven constitute the acid range of the scale.

Nitrogen is an essential nutrient that supports all life and is used in large quantities by the plant. Nitrogen deficiency shows up as a general chlorosis (or yellowing) of the plant leaves. A little “ammonium”—nitrogen fertilizer will be taken up quickly by the plant’s roots. Excessive fertilizing with “nitrate”—nitrogen inhibits root growth and weakens plants, even though they look lush and green. Too much can also delay or prevent flowering.

The macronutrient phosphorus is ideal for flowering and fruit growth. It’s the energy element. Growth is stunted and quality and yield is decreased if a plant develops a phosphorus deficiency. When applying extra phosphorus, use only when the temperature is 68 to 75 degrees.

Potassium activates many key enzymes for plant growth and reproduction. Potassium is the health element. A deficiency appears as browning of leaf margins and sometimes spotted leaves. It results in watery fruit and poor shelf life. A little potassium sulfate will quickly solve the problem. Please remember, balance is key when applying any nutrient. Test your soil with a pH meter probe prior to applying fertilizers.

This new year marks the beginning of my fifth year writing these gardening articles exclusively for the Quail Creek Crossing. As a Master Gardener, this exercise in learning and sharing is important to me. You can read any of my past articles on just search Bonnie Nowicki. This winter, dream big and plan an exciting addition to your landscape.