June 27, 2018
Now that it's summer, you may be asking the age-old gardening question "To fertilize or not to fertilize?" Plants do need nutrients to not only maintain existing leaves, roots, flowers or fruits, but also to develop new ones. But is this the time to fertilize?
The three primary plant nutrients are nitrogen, phosphorus and potassium. Nitrogen is the main nutrient that supports plant growth. It makes plants green and leafy. Provided at the right time and in the proper amounts, nitrogen can give plants the kick-start they need to produce a bountiful harvest. Be careful, though – too much nitrogen can cause plants to grow too fast and become leggy, and it can interfere with flower and fruit development in vegetables such as tomatoes and cucumbers. Phosphorus is the nutrient that supports root, flower and fruit development but it also supports plant growth. Too little phosphorus may cause stunted growth and reduced yield. Potassium is required for overall plant development. Timing of application and application amounts of these nutrients are important because nitrogen, phosphorus or potassium applied in excess can be leached into groundwater and pollute our waterways.
It may not be necessary to fertilize much in the summer. When we add fertilizers to our soil, the nutrients are held on organic matter particles. The organic particles act like a pantry, holding on to the nutrients that plants use for growth. How do you keep more plant nutrients in the soil? Add organic matter to increase shelves in the soil pantry. By increasing the amount of organic matter in your soil, you increase your soil's ability to hold on to the nutrients until your plants are ready to use them. The organic matter slowly supplies nutrients as plants need them. Soils that don't have much organic matter can't hold onto soil nutrients very well. When you apply fertilizers to these low-organic-matter soils, much of the fertilizer washes away when you water.
Avoid fertilizing lawns now that the temperatures are high except with slow release or organic fertilizers. The lush growth fast release fertilizers such as 21-0-0 or traditional lawn fertilizers encourage is highly susceptible to diseases and heat stress. Slow release fertilizers release their nutrients gradually. They maintain good color and health of the lawn, but don't make the lawn grow rapidly.
For information on specific vegetables' nutrient needs during summer, read "Fertilizing Your Vegetable Garden," by Dr. Heidi Kratsch, Horticulture Specialist, University of Nevada Cooperative Extension, http://www.unce.unr.edu/publications/files/ho/2010/fs1068.pdf.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita, University of Nevada Cooperative Extension. She can be reached at firstname.lastname@example.org.