Questions on: Fertilizing
Ron Smith, Horticulturist, NDSU Extension Service
Q: You mentioned that a good fertilizer combination for grass is 20-8-3-6. Where do you purchase this combination? I have called green houses and other places, but have not had any luck. (e-mail reference)
A: That was just an example, not a real fertilizer analysis. There are plenty of good winterizer materials out there, such as 22-3-14, 22-4-11 and 15-5-15. Call one of the major outlets to find out if they have anything approaching that ratio.
Q: I recently applied Scotts Turf Builder with Plus 2 Weed Control on my front and back lawn. A day later I noticed brown burned spots all over the place. Before that, my lawn was green but had a lot of "dollar weeds" in front while the back yard had some dandelions. Is there anything I can do to get rid of the burned spots? I looked at the directions after I noticed the burned spots and read that I should have applied the fertilizer in the morning while the grass was still wet or after it has been lightly sprinkled. I think the grass burned because I put the fertilizer on dry grass. (E-mail reference)
A: All you can do is water and wait. Forget the combination products because they donít do as good a job as straight fertilizer or straight herbicide. Next time read the label first; you'll be surprised at what you can learn.
Q: When should we put Weed and Feed on our lawn? Some of our neighbors fertilized in April but we were told once by a county agent that a good rule of the thumb is to do it about Memorial Day, Fourth of July and Labor Day. (Grand Forks, N.D.)
A: Your county agent was right but you should forget the Weed and Feed combo. If you have a weed problem, purchase a herbicide separately to get a more effective and easier control. Then fertilize your lawn -- sometime within the next week or two.
Q: Would this be a good time to fertilize bluegrass with 22-3-14? (Maddock, N.D.)
A: As long as at least half of the nitrogen source was from WIN (water insoluble sources). If it is all water soluble (WSN) or termed "nitrate nitrogen" or "urea nitrogen" then don't use it, for fear of stimulating late growth of the grass. A true winterizing fertilizer has a higher K value than the nitrogen.
A: Good questions! In fact, I just published an article on the very subject, so I guess that makes me an "expert!" The applications are usually of both pre-emergence and post-emergence herbicides combined with fertilizer, which can either be a straight nitrogen or a "complete" fertilizer containing nitrogen, phosphorus and potassium (N, P and K). The pre-emergence herbicide is applied first, early in the season to control any weed seed germination. Subsequent applications are usually of post-emergence herbicides that should be spot applied as weeds become noted in the turfgrass and are usually for broadleafed weeds like dandelion, thistle, plantain, etc. If broadleaf herbicides are applied in a blanket fashion and not selectively, there is a potential for problems with woody ornamentals, depending on what they are using for the herbicide. As far as the fertilizer goes, the applications are usually light enough to not burn or over-stimulate the turf but to keep it growing in a steady, healthy manner. Kind of like eating several small meals throughout the day, rather than pigging out on a Sunday morning brunch. Questions to ask a potential lawn care service provider include: length of time in business; training in handling of pesticides and fertilizers; are their broadleaf herbicide applications selectively applied to only where the weed(s) exist or is a blanket application made over the entire lawn; can they provide an organic service, and a list of reference clientele. A good lawn care service provider will have many lawns to refer you to and will proudly do so. As far as doing good goes, research has shown that homeowners bungle the task way more often than any service company personnel do. They over-apply fertilizer and pesticides, often using "revenge" spraying to "get those #@!&!! weeds" and as a result compromise the quality of their home environment and possibly their community. Lawn care service providers daily make up mixes and calculate square feet for accurate application. The homeowner is on a learning curve every time he tries it, getting it right sometimes, blowing it most of the time. In most cases a lawn care service is a good investment.
A: Those troublesome gnats will probably be gone this spring. First things first. Yes, there will be plenty of weeds, but not nearly as bad if you had tried to plant the grass in the spring. Activate your irrigation system in May, not April. Water only if the grass needs it. When you mow the lawn for the third time this spring (at 3 inches, by the way) then you can apply a broad-leaf herbicide to control your weeds. A week on either side of Memorial Day weekend, apply some fertilizer, the lawn type, such as 28-3-6 or something similar. Right around the same weekend would be a good time to apply some grub control. Several products on the market can be watered in with your irrigation system. Grubs are a reality in everybody's lawn, so don't worry about them, as there are natural predators that often keep them in check. Manage your irrigation system so that you are applying about 1 inch of water per week either through rainfall or irrigation cycling. This should be enough to keep the lawn green and healthy. Since you have an irrigation system, make another application of fertilizer--lightly this time, about 0.75 pounds of actual nitrogen per1000 square feet. Around Labor Day weekend, again apply herbicide as needed in troublesome spots and over-seed as needed. Another application of fertilizer at this time would also be good, at the same rate as your first one. If those pesky bugs return this spring, catch some, preserve them in denatured alcohol, and send them to me for ID. We can then figure out what to do with them.
Q: My hollyhocks seem to have a fungus. Do you use sulfur powder on them? If so, where do I find it? Is this the time of year to use it? Also, should I fertilize the lawn yet? (Gwinner, N.D., e-mail)
A: As the hollyhocks start new growth, spray them with All-Purpose Fungicide (Daconil 2787).
It is WAY too early to fertilize the lawn. Wait until some new growth is showing and you have mowed it at least a couple of times. Then apply a fertilizer that is high in nitrogen (N), with a major part of the N coming from sater insoluble nitrogen (WIN) sources, which should be listed on the bag.
Q: When is the best time of year to aerate a lawn? We mow the grass with a mulcher mower, but it seems like there is a lot of old grass starting to kill the grass in places. (Carrington, N.D.)
A: Core aeration can be carried out anytime the lawn is in active growth, as long as sub-freezing weather is not around the corner. Generally, it is done in late May or around Labor Day, but if you have an irrigation system, you can do it now. I just completed aerating my field just three weeks ago.
You are smart to recycle your grass clippings back to the turf. It is an environmentally sound practice that saves time and benefits the grass plants.
Q. How often should mulch be replenished?
A. Whatever it takes to maintain a 2- to 3-inch layer of mulch, with fall being an ideal time to check and replenish as needed. Be sure to be consistent in the use of the mulch material to avoid a layering effect--if you start out with bark, stay with it--don't change to compost, unless your are up to removing the bark first. Be sure to rake the existing layer of mulch before adding the new material. And be sure the mulch is kept away from the trunk of trees so that it does not encourage disease or rodent activity to develop.
Q. I fertilize my lawn two or three times a season and try to spread the fertilizer as evenly as I can with a hand-held spreader, yet I have spots in the lawn that are a much lighter green than the rest, which is a nice dark green.
Could I help these lighter green spots by applying a fertilizer that has more nitrogen? (Fargo, N.D.)
A. I suggest two fertilizations a year with a quality product such as Scott's Turf Builder. Rent a drop or cyclone spreader and apply according to directions, being sure to overlap the application.
Top quality products like the one I mentioned have a homogenous blend of their fertilizer nutrients, allowing for a uniform application and growth response.
Q: I planted a large area of new lawn last fall, including an area where a new shelter belt is planted. The grass is coming up but so are the weeds. In some areas there is shepherd's purse growing so thick that I am sure it is competing too much with the grass. What can I do about the weeds? There are too many to pull out by hand. At what point can I apply a broadleaf weed killer? Do I need to fertilize the new lawn this spring? Every year I put down pre-emergent crabgrass herbicide, and every year I have tons of crabgrass. I will try again this year, but would like to know when I should put it down. Can you give me an approximate date? Is it OK to cut potentillas way down, maybe a foot above the ground? I have some that seem so overgrown. I am planting dahlias in my garden for the first time this year. Can I plant them now or do I need to wait until the frost free date? Sorry I have so many questions, but it seems like every time I go outside, I think of something else! (Fargo, N.D.,e-mail)
A: You can apply the broadleaf weed herbicide to your new lawn when the weeds are actively growing. It is best to get them in the juvenile stage, as control is much more effective. It would do the lawn good to receive some fertilizer this spring about mid-May. Are you sure you are fighting crabgrass and not quackgrass? Many people get the two turned around. In many weed-and-feed products on the market, the concentration of the herbicide is usually lower than it is when purchased straight without any fertilizer included. The active ingredient (AI) in crabgrass control products is usually pendimethalin or oxadiazon, and in some cases, siduron. All of these are pre-emergence materials that have to be applied BEFORE germination takes place. Another point of confusion for consumers is the fact that some weed-and-feed combinations go after the broadleaf weeds, such as dandelion and broadleaf plantain, and are post-emergence materials that are effective only AFTER the weeds have emerged. Neither of these has any effect on quackgrass, which is a cool-season, rhizomateous, perennial grass. There is no selective product on the market for controlling this weed. Crabgrass starts germination about the time the lilacs are beginning to bloom. Any pre-emergence herbicide needs to be applied just prior to that time, or about when the forsythia stop blooming in your area. Yes, cut the potentilla back as far as possible. We did it to ours this year, as they have just become a tangle of unattractive branches. Better to have attractive fresh-looking foliage and growth rather than something that looks like it was used for mortar practice! With the arrival of May, I would say you can put your dahlias out anytime now. Just keep an eye to the weather, in case a cold snap hits and the tubers have begun to emerge succulent growth. Just toss a sheet or newspaper over the new growth.
Q: Would you please let me know how I can measure the suitability of compost ("the maturity") and what kind of plants can I use in a screening test of the phytotoxic substances in the compost. Best regards. (E-mail reference, New Zealand)
A: The basic rule for compost maturity is the inability to recognize any of the plant parts that make it up, along with a clean, "earthy" smell, not something that smells septic. Toxic substances are very unlikely in a well-digested compost, but salts are sometimes a reality to contend with. A basic test would be to grow a tomato plant and corn plant (a sensitive broadleaf and "grass") to see if they proceed normally. If they both bite the dust, then I'd suspect soluble salts being high, and would recommend cutting it 50 percent (at least) with mineral soil, and repeating the same test. Keep diluting it until you have hit the point where no toxicity symptoms appear.
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