Question of the Week
Answer: The proper soil pH for blueberries is 4.5 to 5.0. If you have a pH of more than 5.5, it is recommended that you amend your soil to lower the pH before planting the blueberries.
If you would like to get your soil pH below 5.0, then the materials would optimally be applied a year before planting to allow time for them to react with the soil. These materials include sulfur and acidic organic matter such as peat moss, cottonseed meal, pine needles, and pine bark. Elemental sulfur and iron sulfate are used for large adjustments in soil pH and are listed as restricted materials in the OMRI (Organic Materials Review Institute) Generic Materials List, which means that they can be used providing that certain requirements are met.
Once your soil is at the optimum pH and you have planted your blueberries, you can maintain your current level by mulching with acidic materials such as peat, cottonseed meal, or pine needles.
If you choose to add the peat moss (or other material mentioned above, excluding elemental sulfur) before planting, replace half of the back fill with the acidic organic matter. Depending on the size of your planting stock, five gallons is feasible. After planting, mulch each row four to six inches deep and three to four feet wide. Compost adds a lot of organic matter, but pine needles would be sufficient as well. Expect to lose about one inch of the mulch per year through decomposition. Replenish it every other year with one to three inches of fresh mulch and avoid allowing the depth to increase.
Since blueberries are a perennial crop, it will be difficult to manage weeds once the berries are planted. Start with as clean a bed as possible. Cover crops are a great way to prevent weeds initially, and they offer the added bonus of increasing organic matter in your beds. In order to prevent the cover crop from re-growing and becoming a weed, it will be important to provide plenty of time for the crop to break down before planting. Once you till it in, allow two to three weeks before planting to allow the cover crop to break down.
Another option for preventing weeds, once your area is tilled, is using a landscape fabric. This effectively prevents weeds while allowing air and water penetration. It is an expensive investment initially but may pay off, depending on your weed pressure. Many people use pine needles to mulch blueberries, but if your pH is low to begin with, this approach is not recommended. By far, the cheapest option would be straw.
For a summer cover crop, sudan grass or buckwheat are good choices. The seed germinates best when soil temperatures are higher. Both of these help with weed management. You can mow your summer cover and incorporate in late summer/early fall (mid-August). At this point, you can plant your blueberries or keep it standing (it will be dead) to hold the soil over the winter for spring planting.
For more information, see the ATTRA publication Blueberries: Organic Production. This guide addresses key aspects of organic blueberry production, including soils and fertility, cultural considerations, pests, and diseases, as well as marketing. It is available at https://attra.ncat.org/attra-pub/summaries/summary.php?pub=14.
Also see the ATTRA publication An Overview of Cover Crops and Green Manures. This publication summarizes the principal uses and benefits of cover crops and green manures. It is available at http://attra.ncat.org/attra-pub/covercrop.html.
The New York State Agriculture Experiment Station has developed an online guide for cover crops. It details planting, maintenance, and incorporation information for many types of cover crops suitable in the Northeast. It is available at
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