One of the steps many homeowners take each spring to ensure that they have a quality lawn is to apply fertilizer to their lawn. After all, our turf has specific nutrient requirements and by putting out the right amount of fertilizer we can correct any nutrient deficiencies that may be present in the soil and maintain that high quality landscape. However, before we apply any fertilizer (be it organic or not) to our lawn we need to have a recent soil test to make sure we are not over doing it. Just like no one should ever add oil to their crank case without pulling the dip stick first, no one should ever add fertilizer to their lawn without having some idea of what their soil’s nutrient level is. The only way to do that is with a current soil test. 

From a healthy lawn stand point, excessive phosphorus build-up in the soil can lead to deficiencies in iron and zinc. Deficiencies of these nutrients will cause yellowing of turf grass. High levels of nitrogen can also promote fungal problems like take-all patch in St. Augustine lawns. 

Excess nutrients in our soils have the potential to runoff, enter storm water, and become directly discharged into our area receiving waters such as Corpus Christi Bay. In fact, it has been estimated that 45% of rain on our lawns is lost to surface water runoff. Along with the water coming off our lawns we lose around 32 lbs of soil per 1,000 square feet of lawn. This soil lose comes from our nutrient rich topsoil layer, and once it has reached our receiving waters can become a pollutant. 

The over-enrichment of water with nutrients is called eutrophication. The presence of too many nutrients causes the rapid growth of algae and aquatic plants. When these large masses of algae and plants die, the bacteria that decomposes them uses up all of the available dissolved oxygen in the water which can cause large fish kills and other threats to aquatic life. 

For these reasons, soil testing and applying recommended amounts of fertilizer are the best way to protect the environment and maintain a healthy lawn. Therefore, appropriate use of lawn fertilizer is essential to ensure a high quality lawn and protect the environment. To aid homeowners in maintain their lawns and to help protect our water resources, the City of Corpus Christi has partnered with AgriLife Extension in Nueces County to offer a FREE soil testing program to residents of Corpus Christi ponce again. Residents may participate now through March 4, 2016. Non residence can also submit samples through our soil testing lab in College Station with minimal cost. 

Over the last 5 years, well over 800 soil samples have been submitted thought the campaign. What we can see from the results of these; is that soil fertility varies widely likely based on the pervious fertility practice of the homeowner. Across the board 65% of the samples come back suggesting that some nitrogen be applied to the lawn. Only 27% of the samples come back with a suggesting a phosphorous application. And 7% of the samples suggested applying potassium. When we separate out samples submitted from zip codes with predominantly sandy soil, we see an increase in the amount of samples suggesting applications of additional nitrogen (71%), phosphorous (43%), and potassium (43%). This is expected, because our sandy soils do not have the nutrient holding capacity that a clay soil does.

Other trends in soil results can be seen, as well. For example, in the first year of the soil testing campaign 20%, 50%, and 48% of the samples submitted were categorized as having very high levels of nitrogen, phosphorous, and potassium, respectively. In 2014, 9%, 53%, and 60% of the samples submitted were categorized as having excessively high levels of nitrogen, phosphorous, and potassium, respectively. This is a strong indication that homeowners need to take a second look at their lawn fertilization program. In most cases, nitrogen is all that likely needs to be applied and should not exceed 1 lb of nitrogen per 1,000 square feet. But again, following the recommendations of a good soil test is the only way to know you are doing your best for your lawn and the environment. 

For more information or publications on lawn management and soil fertility contact the Texas A&M AgriLife Extension Service – Nueces County office at 361.767.5223 or go to http://nueces.agrilife.org.