Critical Area Treatment Guide


Many times after the construction of a pond, home, road, or on other construction sites, the soil has been disturbed and there is no topsoil remaining. This is a very droughty, inhospitable condition for plant growth. Adding top soil to the site is an option; however it is quite expensive and many times can be more of a problem than a solution as it contains an abundance of weed seeds. These weeds can cause problems in the planting at a later date and potentially out-compete the native plants.

Since the topsoil has been removed from these areas, much of the soil's water holding capacity has also been lost. As a result, choose plants or mixes that love dry sites.

The best method for breaking dormancy is to plant the seed between December and February 15th (this may vary slightly depending on you latitude). A benefit of winter planting is that the freezing and thawing and rain works the seeds into the soil, establishing seed to soil contact. This causes the seeds to imbibe water and germinate when the temperature is warm enough.

Once construction is completed, lime and fertilizer should be applied uniformly and, if possible, worked into the area to be seeded, in amounts according to soil test or as a minimum, the amounts listed below:

Limestone: 1500 lbs ENM/acre
Nitrogen: 30 lbs/acre
Phosphate: 90 lbs/acre
Potash: 90 lbs/acre

The soil is in its best condition for seeding immediately after construction, however this not always the best time to plant native seeds. The following is a rough guide to establishing native grasses and wildflowers on sites where construction is completed during the various times of the year.

A. November 1 through February 1 - Plant native seeds as soon as possible. B. February 1 through May 15 - Purchase and cold moist stratify wildflower seeds for 4 to 6 weeks in refrigerator, mix with native grasses and plant by May 15. See guide on cold moist stratification to understand this process. The earlier one plants, the better. If water is available for irrigation, one may plant as late as June 15.

C. May 15 through August 31 - Plant cover crop. Maxi gain sorghum sudan is a great choice. However, other summer annuals, such as millet, may be used, but caution should be taken to ensure that it does not produce seed. It is best to disk or till cover crop before planting your desired mix between Jan 1 and Feb 15. If disking is difficult to do, one can evaluate the cover crop, keeping in mind the importance of seed to soil contact, to decide if broadcasting the seed on top of it is an option. Either way, broadcast seeds on top of ground by Jan 15 and let the weather put seeds in contact with soil to aid in germination. It is advisable to increase seeding rates for an inferior seed bed.

D. August 31 through October 31 - Plant cover crop, of oats and or wheat. It is best to lightly disk or till cover crop before planting your desired mix between Jan. 1 an Feb. 1. If disking is difficult to do one can evaluate cover crop, keeping in mind the importance of seed to soil contact. Broadcast seeds on top of ground by Jan 1, let the weather put seeds in contact with soil to aid in germination, and then spray with an herbicide by March 1. It is advisable to increase seeding rates for the inferior seed bed.

If only Warm Season Native Grasses are desired one can do a dormant seeding November through March or plant April through June 15. If a cover crop is present, and disking is difficult to do one can evaluate cover crop, keeping in mind the importance of seed to soil contact planting should be done by May 1. It is advisable to increase seeding rates for the inferior seed bed. If wheat or oats has been used for cover crop spraying as explained in step D may be needed.

Mulching with a weed free straw is advisable on these critical areas. A layer of straw mulch (50% of ground is visible) will allow seedlings to germinate but conserve water at the soil surface. On steep sites mulch heavier (20% of ground is visible). It is advisable to increase seeding rates on erosive slopes because it is difficult to keep seed in place. Mulching may not be required if a cover crop has been used and not disked before planting.

On erosive sites with long or steep slopes and /or where there is a concentrated flow ofwater it is possible that seeds can be carried away in the flow of water. In this case, one can cold moist stratify seeds and plant around May 1; mulching the site with weed free mulch can help reduce the risk as well. If irrigation water is available, light weekly waterings for a month is advisable so that the seedlings get a good start.

If cover crop has been used broadcast another 30 lb. of nitrogen per acre with the wildflowers at seeding time as nitrogen will be used in the breakdown of the cover crop.






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