September Strawberry Bed Preparation: Build Plasticulture Fertility Before the Plants Arrive

September is an important strawberry month in the Southeast, even when the transplants will not reach the field until October. Commercial plasticulture growers are shaping beds, installing drip irrigation, preparing mulch, reviewing soil tests, and deciding which nutrients belong beneath the plastic before planting begins. Once those beds are formed and covered, correcting a major fertility mistake becomes much harder, which gives the preplant program more importance than another routine fertilizer application later in the season.

Fall-planted strawberry production is also highly regional. In much of the Southeast, strawberries are commonly established in fall as an annual crop and harvested the following spring, while northern production systems often rely more heavily on spring-established matted rows or different protected-culture schedules. North Carolina State University’s Southern Regional Strawberry Plasticulture Production Guide recommends soil testing several months before planting, adjusting pH toward roughly 6.0 to 6.5, and basing preplant phosphorus and potassium on the soil report rather than using one fixed fertilizer blend across every field. Clemson’s updated 2025 strawberry guidance uses the same general pH range and likewise emphasizes soil testing before lime and fertilizer decisions are made.

Georgia provides a good example of how broad the fall planting window can be within the Southeast. UGA describes annual hill strawberries in middle and south Georgia as a fall-planted crop, with planting commonly occurring from about mid-September into early November and early October often providing a useful target under normal conditions. The exact date should still follow local Extension recommendations, cultivar, transplant type, weather, and farm conditions rather than a national calendar, but September remains the month when much of the soil and fertility foundation needs to be finished.

The important point is that strawberries should not be fertilized simply because bed preparation has begun. The preplant fertilizer program needs to reflect what the soil already contains, what the crop will require during establishment, and what can be supplied later through fertigation. A field that needs nitrogen and sulfur may justify ammonium sulfate, while another field with adequate sulfur or an already-low pH may be better served by a different nitrogen source. The product should follow the nutrient need rather than determining the nutrient plan.

Plasticulture Gives Growers Less Room to Correct Preplant Mistakes

Plasticulture is efficient because fertilizer, irrigation, bed shape, and mulch are organized into a controlled production system, but that efficiency also means the grower needs to make several important decisions before the plastic goes down. Once the bed is shaped, drip tape is installed, and mulch is stretched over the surface, incorporating lime or correcting a severe preplant phosphorus or potassium deficiency becomes much less practical.

NC State’s regional production guide recommends taking representative soil samples well ahead of planting so lime and other amendments can be incorporated before bedding. The guide also describes preplant fertilizer as something that should be determined from the soil report, with phosphate, potash, and sulfur decisions made before the final bed is formed. This is very different from treating the planting date as the moment when fertility planning begins.

The plastic itself also changes the way the soil environment behaves. Rainfall no longer falls directly onto most of the bed surface, fertigation becomes a major nutrient-delivery tool during the production season, and roots become concentrated within a managed bed whose moisture depends heavily on drip irrigation. A preplant nutrient excess can therefore remain within a relatively confined root zone instead of being diluted across a larger volume of soil.

That makes precision more valuable. The goal should be to place enough fertility in the bed for establishment without creating a salt concentration or nutrient imbalance that has to be managed for the rest of the season.

Soil pH Needs to Be Correct Before the Crop Is Planted

Strawberries perform best in moderately acidic soil, with several Southeastern Extension programs targeting approximately pH 6.0 to 6.5 for plasticulture and home production. NC State recommends adjusting pH into that range before planting, while Clemson likewise identifies 6.0 to 6.5 as a desirable target for strawberry soil in South Carolina.

A field below the target range may have adequate fertilizer on paper while still providing an unfavorable root environment. Excessive acidity can affect nutrient availability and root development, while an unnecessarily high pH can create problems with micronutrient availability. Correcting the pH before strawberries are planted gives roots a much stronger environment from the beginning than trying to manage around a pH problem with repeated fertilizer applications.

Lime also needs time to react, which is why September should not be the first time a grower thinks about pH for an October planting. Clemson recommends applying required lime several months before strawberry establishment when possible so the neutralizing reaction has time to begin. When September arrives and the beds are nearly ready to be shaped, large lime corrections become less convenient because incorporation opportunities are disappearing.

This is also why an acidifying nitrogen fertilizer should never be treated as a quick pH correction. Ammonium sulfate can gradually contribute to soil acidification as its ammonium nitrogen is nitrified, but that is not the same as a calibrated program for raising or lowering soil pH. On an already acidic strawberry field, repeated use of an acid-forming N source may actually increase the importance of future lime management.

Nitrogen Is Important, but Preplant Nitrogen Should Not Carry the Entire Season

Strawberries need nitrogen for leaf development, crown growth, flowering, and fruit production, but the crop does not require its entire seasonal nitrogen supply before the transplants are set. One of the advantages of plasticulture is the ability to supply nutrients later through fertigation as crop demand increases.

NC State’s Southern Regional Strawberry Plasticulture Production Guide recommends a maximum preplant nitrogen rate of about 60 pounds per acre for cultivars such as Chandler and Camarosa, while noting that lower rates may be sufficient depending on soil type and cultivar. That recommendation should be understood as a regional ceiling and production guideline rather than as a universal U.S. rate, because cultivars, soils, transplant systems, and state fertilizer recommendations differ.

The larger principle is that preplant N should establish the crop without forcing unnecessary vegetative growth. Too little nitrogen can leave weak, pale transplants that develop crowns slowly, but excessive nitrogen can produce overly vigorous foliage, increase disease pressure, and make fertility harder to balance later.

Plasticulture gives growers opportunities to adjust the program after establishment. That flexibility is valuable because the condition of the transplants, winter weather, soil temperature, and spring crop load will all influence how much nitrogen the planting can use efficiently later in the season.

Sulfur Should Have a Reason for Being in the Program

Sulfur receives less attention than nitrogen or potassium, but strawberries require S for proteins, enzymes, and normal plant development. NC State includes sulfur in its strawberry tissue-testing program and identifies sulfur among the nutrient deficiencies that can occur in June-bearing strawberries under Southeastern production conditions.

That does not mean every strawberry acre needs a large preplant sulfur application. Soil texture, organic matter, previous fertilizer sources, irrigation water, manure or compost history, and regional recommendations all influence whether additional sulfur is likely to produce a response. A field that has received sulfate-containing fertilizer repeatedly may already have enough, while a sandy field with limited organic matter may present a stronger deficiency risk.

The form of sulfur also matters. Sulfate sulfur is immediately plant available but relatively mobile in soil, particularly on coarse-textured ground. Applying substantially more sulfate than the young crop can use leaves that nutrient exposed to movement below the most active root zone.

September fertility planning should therefore treat sulfur as a real nutrient requirement without turning it into another automatic ingredient. When nitrogen and sulfur needs overlap, one product can supply both efficiently; when sulfur is already adequate, its presence in a fertilizer should not be used to justify an unnecessary application.

Ammonium Sulfate Fits When Strawberries Need Both Nitrogen and Sulfur

Where the soil and fertility program call for both nitrogen and sulfate sulfur, Supply Solutions Ammonium Sulfate 21-0-0 + 24% Sulfur can fit preplant strawberry fertility. The product contains 21 percent ammoniacal nitrogen and 24 percent sulfur, allowing growers to supply those two nutrients without automatically adding phosphorus or potassium.

NC State specifically lists ammonium sulfate among the nitrogen sources that can be used in plasticulture strawberry fertility programs and identifies sulfate-containing fertilizers as potential sulfur sources where S is required. The reason to use ammonium sulfate is therefore specific: the crop needs nitrogen, sulfur has agronomic value on that field, and the fertilizer source fits the pH and overall nutrient program.

The timing can fit preplant incorporation when the bed is being prepared and the N and S are part of the soil-test-based fertility plan. Because the material is soluble, it should be distributed uniformly rather than concentrated in a narrow zone where young strawberry roots could encounter excessive fertilizer salt. Later nitrogen requirements can then be managed through fertigation or another crop-specific program rather than trying to place the entire season’s N under the plastic before transplanting.

The problem ammonium sulfate solves is a combined nitrogen-and-sulfur requirement. It does not correct low phosphorus, low potassium, poor drainage, nematodes, weak transplants, a severe pH problem, or planting mistakes that leave crowns at the wrong depth.

The 21-0-0 Analysis Needs to Be Calculated Before the Spreader Is Loaded

Ammonium sulfate contains 21 percent nitrogen, which means the amount of fertilizer product is considerably larger than the number of pounds of actual N being supplied. A recommendation expressed as pounds of nitrogen therefore needs to be converted into product weight before application.

If a fertility plan calls for 30 pounds of actual nitrogen per acre from ammonium sulfate, approximately 143 pounds of product would supply that amount because 30 divided by 0.21 equals about 143. That same application would also deliver roughly 34 pounds of sulfur because ammonium sulfate contains 24 percent S. If 40 pounds of actual nitrogen were supplied entirely through ammonium sulfate, roughly 190 pounds of product would be required, bringing approximately 46 pounds of sulfur with it.

Those calculations reveal why the sulfur requirement needs to be evaluated along with nitrogen. A grower should not automatically use enough ammonium sulfate to satisfy the entire N requirement if doing so supplies far more sulfur than the field needs. Ammonium sulfate can instead provide part of the nitrogen program, with another N source supplying the remainder when that combination better matches the target nutrient rates.

The fertilizer analysis should be treated as a fixed nutrient ratio, not as permission to let one nutrient rate determine all the others.

Ammonium Sulfate Is Acidifying, Which Can Be Helpful or Harmful Depending on the Field

As ammonium nitrogen is converted to nitrate, acidity is generated in the soil. That gives ammonium sulfate a stronger acidifying effect than many other common nitrogen sources over time. On a field with an undesirably high pH, that characteristic may fit the long-term fertility direction, while on an already-acidic strawberry soil it becomes something the grower needs to manage carefully.

Supply Solutions describes its Ammonium Sulfate 21-0-0 + 24% Sulfur as an acid-forming nitrogen-and-sulfur fertilizer, but that property should not be confused with a predictable short-term pH amendment program. Soil pH changes depend on buffering capacity, fertilizer rate, repeated applications, lime history, and other soil processes.

A strawberry field testing near the lower end of the desired pH range should therefore not receive large amounts of ammonium sulfate simply because the crop needs nitrogen. Another N source may fit better if sulfur is adequate and additional acidification is undesirable.

Good fertilizer selection considers what the product will do over several seasons, not only what it supplies immediately after application.

Phosphorus Should Follow the Soil Test, Not the Fact That Strawberries Are Being Planted

Phosphorus is important during establishment because it supports energy transfer and root development, but soil phosphorus can accumulate after repeated fertilizer, compost, manure, and previous crop applications. A planting does not automatically need additional P simply because young roots are developing.

NC State’s plasticulture guide recommends using the soil report to determine preplant phosphate, while the broader North Carolina fertilizer guidance likewise bases fall strawberry P₂O₅ on soil-test status rather than a fixed rate where testing is available. Clemson’s nutrient recommendations similarly reduce phosphorus rates as soil P rises and can recommend no additional P when the soil already contains enough.

This is one reason ammonium sulfate can be useful on certain fields. The 21-0-0 analysis allows nitrogen and sulfur to be supplied without continuing to add phosphorus where soil-test P is already sufficient.

A balanced fertilizer is only balanced if the soil needs the nutrients in that ratio. Applying equal proportions of N, phosphate, and potash to a high-P field is convenient for the spreader but poorly matched to the crop’s actual nutrient requirement.

Potassium Deserves Close Attention in Strawberry Production

Strawberries require substantial potassium for water relations, carbohydrate movement, plant growth, and fruit development. NC State’s plasticulture recommendations make potassium a soil-test-based component of the preplant program, with potassium sulfate, potassium nitrate, and potassium chloride among the possible fertilizer sources.

The source should follow the production system. Potassium sulfate can be particularly useful where potassium and sulfur are both needed, while potassium nitrate contributes N and K. Potassium chloride may provide an economical K source where chloride and salinity considerations allow it.

What should not happen is choosing the K source solely because a product is marketed for fruiting plants. Soil-test potassium, the amount of K already supplied by other fertilizers, salinity, chloride exposure, sulfur status, and fertigation plans all influence which source fits best.

A field receiving ammonium sulfate for N and S may still require potassium from a separate product, while another field may obtain sulfur through potassium sulfate and therefore have less reason to use ammonium sulfate for all of its N.

One Fertilizer Does Not Need to Supply the Entire Preplant Program

Strawberry fertility becomes easier to manage when growers stop expecting one fertilizer grade to satisfy every nutrient requirement. A field may need nitrogen and sulfur from ammonium sulfate, potassium from potassium sulfate or another K source, phosphorus only if the soil test justifies it, and lime only where pH needs correction.

NC State lists several separate fertilizer sources within its plasticulture system, including ammonium sulfate, potassium sulfate, potassium nitrate, potassium chloride, and phosphate fertilizers. That range reflects the fact that nutrient recommendations rarely align perfectly with one standard bag analysis.

Using multiple targeted sources can appear more complicated than applying one complete blend, but it allows growers to match actual nutrient rates more closely. A field testing high in phosphorus should not continue receiving phosphate merely to obtain nitrogen. A low-K field should not be forced into the nitrogen rate contained in whatever N-P-K blend happens to supply the required potash.

Precision is especially important in a high-value crop where fertilizer cost is small compared with the cost of transplants, plastic, labor, irrigation, pest management, and harvest.

Soil Salt Levels Matter in the Concentrated Root Zone

Strawberry roots occupy a relatively shallow zone, especially during early establishment. Under plastic mulch, irrigation and fertilizer can create concentrated wetting and nutrient patterns that expose young roots to soluble salts if preplant rates are excessive or fertilizer is poorly distributed.

This risk is another reason not to place concentrated fertilizer directly beneath or against the transplant. The preplant material should be broadcast and incorporated according to regional recommendations so salts are distributed through the bed volume rather than creating a narrow high-concentration zone.

Ammonium sulfate is a soluble fertilizer, and potassium fertilizers are also salts. Combining several high-rate soluble sources without calculating the total nutrient program can create a harsher establishment environment even when each individual fertilizer contains nutrients the crop requires.

The correct question is therefore not simply whether strawberries need N, K, or S. It is whether those nutrients are being supplied at an appropriate total rate and distributed through enough soil to support young roots safely.

Water Management Begins Before the Transplants Arrive

The bed should contain adequate moisture when strawberries are planted because transplant roots need immediate contact with moist soil. UGA’s annual hill guidance emphasizes forming a firm, moist bed with drip irrigation installed under the plastic before planting.

Freshly dug bare-root plants require particularly careful water management because roots may have been exposed during handling and transplanting. UGA notes that fresh-dug plants can require intensive irrigation during the first establishment period, while potted plants generally establish with less stress.

Fertilizer cannot compensate for poor transplant hydration. A strawberry plant with dry roots or poor soil contact will not suddenly establish because additional nitrogen was added nearby. Water, crown placement, and root-to-soil contact need to be correct before the fertility program can deliver its intended response.

This is especially important in warm fall weather because September and October temperatures can still produce substantial evaporative demand in the Southeast.

Crown Depth Is One of the Most Important Planting Details

Strawberry transplants are unusually sensitive to planting depth because the crown needs to sit at approximately the soil surface. Planting too deeply can bury the crown and encourage rot, while planting too shallowly can leave roots exposed and allow the plant to dry out.

UGA’s transplant-establishment guidance stresses checking crown position and ensuring that roots or plug media make direct soil contact rather than sitting above the bed or being separated from soil by plastic mulch. These physical details can have more influence on stand establishment than another fertilizer application.

Bare-root plants also need roots positioned downward instead of bent upward into a “J” shape. Poorly positioned roots can stunt plants for the entire production cycle, which means a field can show uneven growth later even when soil fertility is uniform.

When a September fertility plan is correct but October establishment is poor, the problem may have nothing to do with nutrients.

Drainage Still Matters Under Plastic

Plastic mulch prevents direct rainfall from entering most of the bed surface, but it does not make drainage problems disappear. Water can move into beds from row middles, accumulate after heavy storms, or remain trapped where bed formation and field grading are poor.

Clemson describes strawberries as best suited to well-drained sandy loam soils and cautions against poorly drained sites because strawberry roots are sensitive to saturated conditions. UGA likewise recommends fertile, well-drained soil with adequate moisture-holding capacity rather than heavy wet soil or excessively drought-prone sand.

Raised plasticulture beds improve drainage around the root zone, but they cannot fully correct a field with severe underlying drainage problems. Saturated roots lose access to oxygen, disease pressure increases, and nutrient uptake declines even when fertilizer rates are otherwise correct.

A pale, weak strawberry transplant in a wet section of the field should therefore not receive extra nitrogen until the drainage problem has been considered.

Nematode and Disease History Belong in the Preplant Plan

Strawberry establishment is expensive enough that growers should avoid planting into a field with a known biological problem and hoping fertilizer will compensate. UGA recommends evaluating nematode risk before planting and selecting fields carefully because soilborne pathogens and nematodes can reduce root performance and crop vigor.

Crop history matters as well. Certain previous crops can increase disease concerns, while repeated strawberry production on the same ground can allow pathogen populations to build. Regional commercial strawberry systems may use fumigation, crop rotation, resistant cultivars, or other integrated practices to manage these risks.

A diseased root system absorbs fertilizer poorly. Increasing nitrogen in response to weak plants may create a more expensive field without correcting the organism damaging the roots.

September is therefore the time to review field history alongside the soil test rather than treating fertility as an isolated decision.

Sandy Strawberry Ground Benefits From Split Fertility Later in the Season

Coarse-textured soils can lose soluble nutrients more readily because water moves through the profile quickly and nutrient-holding capacity is lower. That is one reason strawberry fertility after establishment is often supplied gradually through fertigation rather than as one large preplant application.

UGA strawberry guidance recommends spoon-feeding fertilizer more frequently on sandy soils so nutrients remain within the effective root zone rather than being exposed to greater leaching loss. The specific spring rates in that guidance apply to Georgia production rather than all U.S. strawberry systems, but the principle is widely useful.

That same reasoning supports restraint in September. Preplant fertilizer should provide a foundation, while later applications can respond to tissue testing, crop development, soil type, and irrigation.

Putting the entire seasonal nutrient budget under plastic before planting removes much of the flexibility that makes plasticulture fertigation valuable.

Tissue Testing Should Eventually Confirm Whether the Program Is Working

The soil test tells growers what is present before the season begins, while plant tissue testing shows what the strawberries are actually taking up. NC State recommends regular tissue analysis during the flowering and fruiting season so nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and several micronutrients can be monitored as crop demand changes.

That distinction matters because two fields with similar soil tests may produce different tissue results when irrigation, root health, cultivar, temperature, or fertilizer placement differs. A nutrient present in the bed is not useful if the plant cannot access it.

September fertility should therefore be viewed as the first version of the nutrient plan rather than the final one. The grower establishes the crop using soil-test-based preplant fertility and then uses plant response and tissue analysis to refine the program later.

This prevents the common mistake of trying to predict every nutrient requirement before the first transplant is planted.

Compost and Manure Still Need to Be Counted

Organic amendments can improve soil structure and contribute nutrients, but they also complicate fertility calculations when growers treat them as soil conditioners rather than fertilizer sources. Compost and manure can contribute nitrogen, phosphorus, potassium, sulfur, calcium, and micronutrients in amounts that vary widely with source and maturity.

A field that has received repeated compost applications may already contain high soil phosphorus even though the grower is planning another complete fertilizer before strawberry planting. In that situation, continuing to add P simply because it comes packaged with nitrogen increases the imbalance.

The same issue can occur with potassium. Some manure sources contain substantial K, and failing to credit that contribution can result in unnecessary commercial potash.

A September soil test is particularly valuable on fields with a long amendment history because it shows the cumulative result of those previous applications rather than treating each year as though the nutrient budget starts at zero.

Preplant Fertility Should Support Establishment Without Removing Spring Flexibility

Plasticulture strawberries have a long production season. The crop planted in fall has to establish crowns and roots, survive winter weather, resume growth, flower, set fruit, and carry harvest well into spring. A fertilizer program designed entirely around September cannot anticipate every condition that will occur during that cycle.

The preplant program should therefore correct soil pH, provide needed phosphorus and potassium, establish an appropriate nitrogen base, and address sulfur or other nutrients where evidence supports them. It should not attempt to satisfy every pound of nutrient the crop may use before harvest.

Later fertigation and tissue testing allow growers to respond to the crop that actually develops. A mild winter, cold-damaged stand, unusually heavy fruit load, or aggressive cultivar can change nutrient demand from what was expected during bed preparation.

Leaving room to adjust is part of precision management rather than a sign that the September fertility plan was incomplete.

Build the Strawberry Bed From the Soil Test Outward

Successful fall strawberry establishment depends on getting several pieces right before the transplant crew reaches the field. The soil needs to drain well, pH should be corrected toward the regional strawberry target, preplant phosphorus and potassium should reflect soil testing, drip irrigation needs to deliver water uniformly, and beds should be moist and firm enough to provide immediate root contact. Once plastic is installed, correcting those foundational problems becomes much more difficult.

Nitrogen and sulfur deserve the same discipline. Strawberries need both nutrients, but the field should provide a reason for the source being chosen. Where the crop needs preplant nitrogen, sulfate sulfur has value, and additional acidification will not worsen an already-low soil pH, Supply Solutions Ammonium Sulfate 21-0-0 + 24% Sulfur can provide those nutrients without automatically adding phosphorus or potassium. That makes it especially useful where P and K are being managed separately from the soil-test recommendation.

The product should not be used simply because strawberries respond to nitrogen or because sulfur appears on the guaranteed analysis. The 21-to-24 nutrient ratio needs to fit the actual N and S requirement, the acidifying effect needs to fit the soil pH direction, and the rate should account for every other nitrogen and sulfur source being used. Where those pieces do not align, another nitrogen source may be the better agronomic choice.

September strawberry preparation is ultimately about building a root zone that will support the crop for the entire fall-to-spring production cycle. Growers who test before bedding, correct pH early, separate phosphorus and potassium needs, calculate actual nitrogen rather than pounds of product, manage sulfur deliberately, and preserve flexibility for later fertigation are far better positioned than growers who simply broadcast a familiar complete fertilizer before laying plastic.

Supply Solutions can help growers determine whether Ammonium Sulfate 21-0-0 + 24% Sulfur fits a preplant strawberry program, but the fertilizer should follow the field diagnosis. When nitrogen and sulfur are both needed, the product has a clear job. When they are not, the stronger decision is to leave it out and direct the fertility budget toward the limitations that will actually influence establishment and next spring’s crop.