re: 2023 Lawn Thread - Helpful Tips, Q&A, general discussion

Fertilization:
Main reason to fertilize is to provide a nitrogen source to your lawn as that is what is depleted with each season.

On each bag you’ll see a set of 3 numbers separated by dashes(N-P-K) which represent the ratio of Nitrogen, Phosphorus, and Potassium in each bag. If you have a 30lb of fertilizer at a ratio of 26-0-0, then you’ll put down 7.8 lbs of nitrogen if you applied the whole 30lb bag to your lawn. If your lawn is 5000 sq. ft and you distributed it evenly, then you’ve applied 1.56lbs of nitrogen per 1000sq. Ft.

A better way to do the calculation - if you’re aiming for 0.5lbs of nitrogen per 1000 sq ft, then divide 50 by the first number to give you the pounds of product to apply. For 1.0 lb/1000 sq. ft divided 100 by the first number. I.e. if you want a 1.0lb/1000 sq. ft rate of the 26-0-0 product, then spread 3.8 lbs of this product per 1000 sq ft. (100 / 26 = 3.8)

Now, you’ll get varying recommendations based on your grass type, maintenance requirement, but in general you’ll see:
St. Augustine - 2-4lbs of nitrogen per 1000 sq. ft. annually, divided over 3-4 applications. I.e. putting down 0.5lbs/1000 sq. ft 4 times a year, would net you 2lbs annually.
Centipede - 1-2lbs of nitrogen per 1000sq. ft annually.
Zoysia - 2-4lbs of nitrogen per 1000 sq. ft. annually
Bermuda - Bermuda loves nitrogen. University guides will tell you 2-4lbs of nitrogen per 1000sq. Ft. annually. But assuming adequate irrigation and mowing to keep up with growth, you can easily put down 1-1.5lbs of nitrogen per 1000 sq. ft. per month if you need aggressive growth and titrate down accordingly.

Now, most products are a fast-release nitrogen source, meaning it’s in and out pretty quickly. However, there are some products that have a slow-release component, most well known is milorganite. These products breakdown over 8-10 weeks and provide a source of nitrogen. Many St. Aug and Centipede lawn owners prefer this as their nitrogen source to avoid over fertilizing their lawns. There are also some mixed products that contain fast and slow release nitrogen. You’ll need to read the label for breakdown of percentages of each.

When to fertilize: General rule of thumb is April 15/tax day. But really, just when you’re grass is actively growing.


Other Soil amendments and soil testing:
So while nitrogen may be the most talked about additive to the lawn, there are other important nutrients and factors that are important to lawn health. Not only phosphorus and potassium, but also iron, micronutrients, pH of your soil can all have an effect. So this is where soil testing comes into play.

When, How, and Where to soil test:
-- Ideally once a year before you make any amendments to the soil, so fall or spring seems to be when most people will test their lawn.
-- Most kits will provide you suggest how to take a soil sample. In general you want to sample 4-8 spots in your lawn, mix the soil and send the needed amount off. It’s best to zone off what you are testing if you have different areas (i.e. back yard vs front yard vs landscape beds, fruit trees etc.). I personally have a soil sampler, which makes collecting a breeze: Soil Sampler - Amazon link

Where - Most university Ag extension offices offer soil analysis and kits may be found at your local nurseries or garden center. I have linked LSU website here: LSU Ag Soil testing

There are also commercial tests available as well, which may provide some more nuance in the testing. I have used A&L great lakes before: A&L Great Lakes Soil testing

Most soil analysis will provide recommendations for annual N-P-K applications, as well as possible adjustments needed to address pH (such as lime or sulfur applications). Luckily for most of you in LA, you’ll likely have nutrient rich soil. The rest of us will be adding potash(K) and a variety of other amendments to help things along.

pH - Most of us in the south are more likely to have an acidic soil vs a alkaline soil. To raise a pH, you’ll use lime. You’ll have recommendations provided as part of the soil analysis, but to add some nuance: In terms of what to use, most would tell you to get dolomitic lime which is "slow" acting. While it takes longer to get into the soil, it does last longer(3years), you can apply more at one application(50lbs/1000sq ft at one time from what I've read), so can be cheaper.

Fast acting like does get into the soil faster, but can also leach faster and you are limited to around 10lbs/1000sqft per application. So need more frequent applications, so more costly.

Changing pH is usually considered a marathon not a sprint. So most would tell you do the recommended applications and check again in 2-3 years.

Watering/Irrigation:
General recommendations is 1-1.5inch of water per week depending on the time of year and temperatures. Depending on your soil type you may be able to do this once per week(Clay soils) with a long watering session or you may need to break it up over the course of a week/daily or every other day (Sandy soils) with shorter sessions. If you are unsure of your soil type, some soil analysis testing will provide a CEC number which will guide you regarding on how well your soil will hold water and nutrients. You can use a rain gauge or a tuna can to determine how long it takes to delivery the amount of water you need.

Mowing:
Mowing often will always provide some of the best results. You take off less of the leaf blade each time, which minimizes stress on the lawn. Additionally, you don’t need to bag and can instead mulch, and with so little taken off, the clippings will breakdown quickly and provide nutrients back to your grass.
Mowing height in general - St. Aug. 2-4 inches, Centipede 1.5-2 inches, Zoysia 1-3 inches, Bermuda 1-2.5 inches. These can always be taken to the extreme and maintained a lower level (sub 1inch) if you’re trying to achieve that fairway look.
Scalping: beginning of the spring as your lawn is starting to green up. Mow as low as you can go and bag all of the clippings. You can then maintain one notch (or more) above your scalp level. This is particularly useful for bermuda. But can apply to other grass types. Some people do not likely to scalp St. Aug or Zoysia grasses.