Agronomic Services — Agrotips
- Test soilless media for annual flowers and vegetable seedling production.
Prior to filling containers and sowing seeds, the analysis of soilless media (substrate) will detect if chemical properties such as pH, electrical conductivity (soluble salts), and nutrient concentrations are ideal for optimum and efficient production of annual flowers and vegetable seedlings. During production, analysis of soilless media is a best management practice that helps to identify if fertilizer has been depleted or if it is excessively high. Also, if a problem occurs during production, this test will help diagnose if the trouble is related to nutrition and suggest appropriate corrective action.
- Scout wheat early and plan to tissue test.
Wheat producers need to count tillers in January and follow up with tissue sampling in late February or March. This approach is the best way to optimize fertilizer purchases and application. At the beginning of green-up in January, 50 to 70 tillers per square foot is optimum. If the count is lower, apply half the spring topdress nitrogen right away. This application will help the crop continue to produce tillers on warm days without excessive growth.
Tissue test in February or March (at Feekes growth stage 5 or Zadoks GS 30) to find out if more nitrogen is needed. Contact your regional agronomist if you need additional guidance on how to count tillers or identify the appropriate growth stage.
- Test source water for tobacco seedling float beds.
Nearly half of the source water samples taken from tobacco float bed operations in North Carolina and about one in five nutrient solution samples have high alkalinity (sometimes known as total carbonates). Alkalinity values greater than or equal to 100 contribute to high pH and soluble-salt problems. When necessary, the solution report provides recommendations for reducing alkalinity by 80%.
- Tobacco transplant producers should doublecheck the nutrient content of their float-bed water by submitting a sample for solution analysis.
Visit www.ncagr.gov/agronomi/pdffiles/2013FloatBed.pdf for details.
- Gear up for spring gardening by checking the quality of your compost.
Everyone knows that the NCDA&CS Agronomic Division analyzes soil samples, but most people are surprised when they find out that it tests compost too. Putting out compost is a good way to improve the physical properties of the soil and increase its moisture-holding capacity. However, compost also contains organic fertilizer nutrients. For this reason, you really ought to know ahead of time how much “fertilizer” you are applying.
To determine the fertilizer value of compost, collect a good, representative sample and send it in for waste analysis. Resultswill tell you the concentrations of nutrients that are available to your plants the first season the compost is applied as well as the compost’s pH and electrical conductivity (a measure of soluble salts). The report also provides the ratio of total carbon to nitrogen, which helps commercial compost producers decide how to best mix feed stocks to optimize decomposition rate.
Visit www.ncagr.gov/agronomi/uyrwaste.htm for instructions on how to collect and submit samples. Additional information is available in our Waste and Compost Analysis Guide.
- Familiarize yourself with wheat tissue sampling guidelines.
Dr. Randy Weisz of N.C. State University has refined wheat fertilization guidelines for North Carolina conditions. Visit www.smallgrains.ncsu.edu/_Pubs/PG/Nitrogen.pdf for details. These guidelines tie recommended fertilizer rates to wheat biomass measurements and tissue test results. Growers who want to use these guidelines must submit both types of samples (biomass and tissue) to the Agronomic Division. For more information, contact your regional agronomist or other agricultural advisor.
Monitor strawberry nutrient status by tissue sampling.
The Agronomic Division recommends monitoring the nutritional status of strawberries and the efficiency of fertilizer programs by submitting a plant tissue sample at least once a month, preferably every two weeks. Sampling should begin with the first flush of growth in the spring and continue throughout the flowering and fruiting season.
Plant tissue samples should be representative of conditions in the field. A good sample includes the most recently mature trifoliate leaves (leaf blades and petioles) from 20 to 25 locations in the field. Detach petioles from the leaves as you collect them but include them in the sample. Information on collecting and submitting strawberry tissue samples is available online at www.ncagr.gov/agronomi/pictorial.htm.
Petiole analysis is a good indicator of the nitrogen currently available for growth and development. Be sure to provide the name of the strawberry cultivar on the Plant Sample Information form.
If tissue analysis reveals plant nutrient deficiencies, consider the following factors before taking corrective action:
- soil pH and nutrient levels,
- environmental conditions such as rainfall and temperature,
- disease and insect pressure, and
- plant appearance and stage of development.
- Check source water used in greenhouse and nursery operations and correct any SAR (sodium adsorption ratio) problems.
Water used in plant production, including greenhouse-grown tobacco transplants, should have an SAR value of 4 or less. For ornamental plants in a nursery setting, SAR values of 10 or greater are cause for concern. High SAR values are most common for water samples from coastal areas.
A high SAR value on a solution report indicates an imbalance among sodium (Na), calcium (Ca) and magnesium (Mg) cations. This imbalance can cause leaf burn due to foliar uptake of Na. In mineral soils, this imbalance can also lead to poor soil structure, which hinders infiltration of water. In soilless container media, however, this effect is negligible.
The best way to reduce SAR to the desired level is to add calcium from a source such as gypsum. To calculate the amount of gypsum needed to reduce SAR to 4, follow these steps.
- Calculate the amount of calcium required in parts per million (ppm).
Ca needed = 0.004725 Na² – 1.64 Mg – Ca,
where Na, Mg and Ca are the ppm concentrations listed on the solution report.
- Calculate the appropriate rate of gypsum (22% Ca) to apply by inserting the Ca needed value from step 1 into the following equation.
Ca needed × 0.0607 = ounces gypsum per 100 gallons of water
- Test for nematodes before planting vegetables.
Nematodes pose a major threat to nearly all vegetable crops in all soils. Unless you intend to apply a preplant fumigant, it is a good idea to collect soil samples for nematode assay before seedlings are planted and mulched. Any steps to prevent nematode problems must be taken long before the crop is established. For information on collecting and submitting samples for nematode assay, visit www.ncagr.gov/agronomi/uyrnem.htm.
In home gardens, no chemicals are available for nematode management. However, there are some plant cultivars with resistance to root-knot nematodes. See NemaNote 12 for details.
- Now is the time to collect tissue samples from wheat.
Depending on where you live, you may need to sample now (eastern counties) or wait until late March (western counties). The best time to take tissue samples is when the wheat is at Zadoks Growth Stage 30 or Feekes Stage 4–5. At these growth stages, stems are upright and tillering has stopped. To collect a sample, break wheat plants off about 1/2 inch above the ground. Each sample should consist of about two handfuls of wheat—a composite gathered from 10 to 20 areas throughout the field. A pictorial guide to tissue sampling is available online at www.ncagr.gov/agronomi/pictorial.htm. Be sure to read the new wheat sampling and fertilization guidelines from NCSU.
- When growing peanuts, use agronomic tests to monitor zinc levels in the soil.
Growers who value the prime farmland where peanuts are produced should consider using alternate sites for waste application. Peanuts are very sensitive to certain metals found in waste, particularly zinc. Soils with NCDA&CS zinc index (Zn-I) values as low as 300 can be toxic to peanuts, even though other crops can tolerate levels up to Zn-I=2000.
In some areas, soil test data for peanut land already appear to show increases in zinc levels, indicating that waste is being applied to these fields. An important aspect of managing sites where waste is applied is to maintain a pH of 6.0–6.5. Low soil pH increases the availability and toxicity of metals.
- Apply lime now if recommended by your soil report.
By now, you should have already submitted soil samples and received your report. If lime is recommended, go ahead and apply it as soon as possible. For lawns, you may want to aerate the ground before application to maximize the ability of the lime to move into the soil profile. Liming soils to the target pH of the intended crop increases availability of plant nutrients already in the soil and supplies additional calcium and/or magnesium. Since liming can take up to 6 months to adjust pH, it is important to apply lime as far in advance of planting as possible.
Check your crop's sulfur needs.
Before planting, study your soil report carefully. Throughout North Carolina, soil levels of sulfur can be critically low. This plant nutrient moves easily out of the root zone in sandy coastal plain soils or sandy bottom lands in the western part of the state. In the piedmont, heavy clay soils may restrict root growth and limit access to sulfur reserves. Your NCDA&CS soil report indicates whether application of additional sulfur is necessary. If heavy rains occur early in the season, it is advisable to check sulfur levels again.
- Use plant tissue and solution analyses to manage fertility of greenhouse tomatoes.
Tomatoes and other greenhouse crops benefit from intensive management. Have source water samples tested before nutrient solutions are mixed so you can identify and correct any potential problems. After mixing nutrient solutions, submit samples to make sure injectors are working properly and target concentrations are being achieved. Finally, collect plant tissue samples weekly to monitor the crop's nutrient status and adjust fertilizer rates accordingly.
- Fertilize Christmas trees.
Each spring, apply 1/2 ounce of nitrogen uniformly over a 5×5-ft area around each tree. If trees were transplanted the previous fall and the potassium recommendation was 100 lb/acre or more, apply the remainder of the recommended potassium.
- For effective bermudagrass sprayfield maintenance, remove winter annuals.
Harvest on time, even if weather is less than ideal. Remove the overseed at the "boot" stage of growth-prior to emergence of seed heads from the sheath. For rye, this is usually early April but varies with species and weather. In some years, follow-up harvests of the winter annual may be needed.
Early April is seldom a good time to dry hay in the field, so plan to remove the winter annual as chopped or baled silage. Timely harvest of the winter annual permits bermuda to emerge from dormancy and develop leaf area before summer annual grasses and weeds germinate. If annual ryegrass was sown, plan on multiple harvests. A herbicide may be warranted for heavy regrowth.
- Submit soil samples for lawns and gardens (and some crops) now.
Now is a good time for horticulturists and homeowners to prepare for their spring gardening and landscape projects by taking soil samples. Warm-season grasses and many landscape plants will benefit from lime and fertilizer applied in the coming months. If you haven't already done so, there is still time to take samples from fields where you intend to plant late spring crops like burley tobacco, cotton, and bermudagrass pastures. In April, the lab can normally process samples within two weeks. When you receive your report, pay particular attention to lime recommendations and make application as soon as possible for maximum effectiveness.
Sidestep the high cost of fertilizer by using animal waste as a plant nutrient source.
Farm-generated wastes are a widely available and inexpensive alternative to commercial fertilizers. Animal wastes provide essential plant nutrients and also improve soil physical properties, such as water infiltration, aeration and nutrient-holding capacity. Before applying waste material as fertilizer, send a sample to the NCDA&CS Plant/Waste/Solution/Media Section. This laboratory tests for levels of plant nutrients and, when necessary, can measure pH, lime value and soluble salts. Based on analytical results, the waste report provides estimated rates of nutrient availability for the first growing season. With this information, you can figure out how much waste it will take to meet the specific nutritional needs of a crop. Supplemental applications of commercial fertilizer may be necessary, depending on rate of nutrient availability, cropping system, environmental guidelines and other factors.
- Use tissue test results to improve crop production.
For high-value crops, in particular, plant tissue analysis is a valuable tool for optimizing monetary inputs and yield. It is a way to monitor the effectiveness of an ongoing fertilization program. It is a way to identify existing or potential nutrient problems. It can also be a way to gauge plant readiness for harvest.
The part of the plant to be sampled and the time of sampling vary by crop. Visit www.ncagr.gov/agronomi/pictorial.htm for specific sampling instructions for several major crops. Samples can be dropped off at the NCDA&CS Plant/Waste/Solution/Media lab in Raleigh, mailed through the U.S. Postal Service, or shipped via UPS or Fed Ex. Basic tissue testing costs $5 per sample, and results are typically posted on the NCDA&CS Agronomic Division website [www.ncagr.gov/agronomi] two business days after samples arrive at the lab. Special tests to measure chloride, molybdenum or petiole nitrates cost an extra $2 per test per sample.
- Spring and summer are the best times to take soil samples from established lawns and gardens.
It is always a good idea to take soil samples several weeks before planting a garden or renovating a lawn; then if lime is needed, you have time to apply it properly and let it begin to work before planting. For established plantings, spring and summer are good times to submit samples because there is no peak-season fee. Reports are usually posted online within 10 days.
The soil lab urges clients to enter and submit soil sample information online via the PALS website instead of filling out a paper sample information form. The online option sends sample information to the lab electronically and helps prevent data entry errors and duplications. A printed copy of the electronic Soil Sample Information form must be submitted with the samples. Links on the Agronomic Division homepage — www.ncagr.gov/agronomi — provide detailed instructions.
Samples must be submitted in NCDA&CS soil boxes, which are available from all county Cooperative Extension offices and from the Agronomic Division office in Raleigh. Reports are posted online in PALS.
- Collect petiole samples from vinifera vineyards during full bloom.
To monitor the nutrient status of vinifera grapes, collect a tissue sample during full bloom. The sample should consist of at least 50 petioles collected from leaves opposite the first or second bloom cluster from the bottom of the shoot. Collect petioles randomly from throughout the entire vineyard. Do not collect more than two petioles per vine. Place the sample in a paper bag or envelope. The plant tissue report—available in a few days—will let you know if your fertilization program is meeting your crop's needs.
If you want to use tissue analysis to diagnose a suspected nutrient problem, collect a petiole sample as soon as you see symptoms. Don't delay—time is critical when correcting nutrient problems. To troubleshoot a problem, you should collect four different samples: 1) a petiole sample from symptomatic leaves, 2) a similar petiole sample from healthy plants, 3) a soil sample from the problem area and a soil sample from the healthy area. Send all samples along with a completed Plant Sample Information form and Diagnostic Soil Sample Information form to NCDA&CS Plant/Waste/Solution/Media Section. There is a $7.00 processing fee for each grape petiole sample.
Prepare for a fall vegetable garden by soil testing.
If you are thinking about planting a fall vegetable garden in July or August, then you need to take the first step in June. Soil test! The test is free at this time of year, and sampling instructions are available at www.ncagr.gov/agronomi/pdffiles/samhome.pdf. Sample boxes can be picked up at all county Cooperative Extension offices. The Agronomic Division prefers that you visit the PALS website to fill out your sample information form and submit it electronically. You will still need to print a copy of the form and send it in with your samples. Within two weeks, your report will be posted online with lime and fertilizer recommendations for a productive garden.
- Test source water for irrigation systems.
Before you turn on that drip or overhead irrigation system, it is a good idea to collect samples of your source water and have it tested by the NCDA&CS Agronomic Division. Chemical problems with source water can affect plant growth and quality. By testing water now, you can correct any problems before you start irrigating your crops.
Solution analysis is a service that measures the chemical properties of water that affect plants. In eastern North Carolina, high alkalinity is a potential water problem. Irrigating with highly alkaline water can lead to an increase in soil pH that can limit availability of some essential plant nutrients, especially micronutrients.
The solution report indicates whether alkalinity is a potential problem and, if so, provides helpful advice to correct it. Some other potential source water problems include high soluble salts, iron, boron, sodium or chloride. Once identified, these problems can either be corrected or effectively managed to prevent plant growth problems.
- If crop plants are stunted and/or discolored, check for nematodes.
The best way to find out if nematodes are responsible for an area of poor crop growth is to collect and submit two sets of soil samples: one for nematode assay and one for fertility analysis. An accurate diagnosis of nematode populations during the growing season provides a sound basis for effective management in the future. Knowing the species and numbers present facilitates informed selection of resistant varieties and crop rotation strategies.
- Fertilize centipedegrass lawns in June.
The nitrogen fertilization rate and schedule for centipedegrass are different from those of other warm-season grasses. Centipede requires only 0.5 pound of nitrogen per 1000 square feet per year, and all of this amount should be applied in June. The majority of centipede growth problems that are fertility related result from applying too much lime and phosphorus or inadequately maintaining soil potassium levels. These problems can be prevented by soil sampling and following recommendations. If you have not taken a soil sample in the last two or three years, you may want to do so to find out your lawn's fertility needs. When filling out the Soil Sample Information form, use the crop code (022) specifically assigned to centipedegrass.
Important Reminder: Do not fertilize cool-season lawn grasses—fescue, ryegrass and bluegrass—during the summer. Wait until September.
- Summer is a good time to submit soil samples from lawns & gardens.
Summer is when the NCDA&CS soil testing lab can process samples most quickly —usually ten days or less. Homeowners and landscapers are urged to submit samples at this time and avoid the peak-season fee (late November through March). Farmers who are maintaining cool-season pastures can also submit soil samples now so they will be ready to apply phosphorus and potassium in late summer or fall.
- Mulch to prevent blossom-end rot of tomatoes.
If garden soils have adequate moisture and a pH in the range of 6.3 to 6.5, tomatoes are not likely to have blossom-end rot. Although this common problem is largely due to calcium deficiency, fertilization is not usually the answer. Any soil with a pH of 6.3 to 6.5 will contain enough calcium. However, during dry periods, plants cannot take up the calcium that is there. If your soil pH is good, you can optimize calcium availability by managing soil moisture. Make sure your plants get an inch of water each week, but be careful not to overwater! Apply 2 to 4 inches of mulch (pine bark, straw, leaf compost or other organic material) to help the soil retain moisture.
- Collect cotton tissue samples.
Collect tissue samples (MRMLs + detached petioles) weekly beginning at early growth (at least by matchhead square or one week before first bloom) and continuing for three to four weeks after first bloom. Follow the sampling protocol that NCDA&CS recommends: www.ncagr.gov/agronomi/pdffiles/11cotton.pdf.
- Collect other agronomic samples as needed.
Note: Forage samples for animal feed analysis should be sent to the NCDA&CS Food & Drug Protection Division. The plant tissue analysis service offered through the NCDA&CS Agronomic Division provides nutrient information relevant to crop fertilization not animal nutrition.
- Home & Garden
Take soil samples now to prepare for fall planting projects such as vegetable gardens, tree and shrub installation and renovation/maintenance of cool-season lawns. Do not wait until fall to submit soil samples for home landscape projects.
- Nursery Crops
Collect pour-thru leachate solution samples to monitor pH, electrical conductivity (EC) and nutrient levels.
Collect tissue samples five to ten days before each anticipated leaf harvest to determine ripeness. An appropriate sample consists of 10 to 12 leaves from the appropriate stalk position.
- Turnaround time is optimal for soil samples submitted in August.
The Agronomic Division’s soil testing lab is processing samples quickly now but will be increasingly busy toward the end of the year. Homeowners, landscapers, golf course superintendents and others with flexible schedules are urged to submit samples before the lab's fall busy season. If cool-season lawn grasses and pastures need to be reseeded, sampling now will make it possible to apply lime well in advance of September or October planting.
- Get rapid identification of plant-parasitic nematode species with new test.
The Agronomic Division's Nematode Assay Section offers a new test that identifies plant-parasitic nematodes based on analysis of molecular DNA. The test costs $10 per sample (instead of $3), but results are available within a couple of days (instead of weeks), and reports can identify nematodes accurately to species. This is particularly useful information for growers who depend on resistant cultivars and/or crop rotation to suppress nematode populations. For more information on this test and how to sample, contact Dr. Weimin Ye at 919-733-2655 or via e-mail at email@example.com.
- Tissue test now to plan for blackberry fertilization next season.
Collect a plant tissue sample about 10–14 days after harvest. Each sample should include 25–30 most recent mature leaves from the primocane. Sampling the floricane is not recommended unless it is specifically to diagnose a problem. If you have different varieties, submit separate samples for each one. Now is also an appropriate time to submit a corresponding soil sample.
Focus on strawberry fertility.
Take soil samples and apply any recommended lime as soon as possible. Generally, strawberries need 100–120 lb of nitrogen per acre per season. Prior to building the beds and laying plastic, apply 30–60 lb of nitrogen along with any phosphorus or potassium recommended on the soil report. Even when soils are high in phosphorus, an additional application of 30 lb can be beneficial for root growth in the fall. Other nutrients that may have a beneficial effect at this time are sulfur and boron (1 lb/acre).
- Continue to use tissue analysis to optimize timing of flue-cured tobacco harvest.
Collect tissue samples five to ten days before each anticipated leaf harvest to determine ripeness. An appropriate sample consists of 10 to 12 leaves from the appropriate stalk position.
- Test your bulk soilless potting media before planting greenhouse crops.
Before planting greenhouse crops, propagating woody plants or beginning seasonal flower production, commercial producers should sample and test the bulk soilless media they plan to grow their plants in. The procedure, known as saturated media extract (SME), measures nutrient concentration, electrical conductivity and pH. The cost is $5 per sample for North Carolina residents and $25 for out-of-state residents, and test results are available online two working days after samples are checked in to the laboratory. Sampling instructions and sample information forms can be found online at www.ncagr.gov/agronomi/uyrmedia.
- Prepare gardens for fall/winter.
First, if you haven’t had your soil tested in the last three years, do it now! Instructions for collecting samples are online at www.ncagr.gov/agronomi/uyrst.htm#sampling. Act now because after October the lab will begin receiving end-of-season samples from farmers, and the wait for reports will be longer.
If your report indicates that lime should be applied to raise soil pH, don’t delay. Winter soil is usually moist and helps lime neutralize soil acidity before spring planting. However, don’t add lime unless the soil report recommends it! Excess lime can make some nutrients unavailable to plants.
Second, consider protecting garden soils by planting a cover crop or putting out mulch. Legumes—such as crimson clover, hairy vetch, Austrian winter pea—add nitrogen to the soil as well as organic matter when they decompose in the spring. In addition, crimson clover is a beautiful sight when it blooms! Another option is to plant greens such as mustard or kale and enjoy eating the small leaves as they grow.
If you don’t plant a cover crop, you should apply a 2-inch layer of mulch, such as composted leaf material, shredded or chipped pine bark, or pine needles. Straw can also be used if it is good quality without weed seeds. The mulch should be thick enough to reduce weed seed germination and retain soil moisture without impeding adequate water and air movement.
Once you have made these preparations, do not apply fertilizer until spring unless you are planting a fall vegetable garden. In that case, you can still follow these suggestions (even sowing a cover crop around the vegetable beds!), but you will also need to apply fertilizer as recommended on your soil report.
- Ensure that adequate nutrients will be available for a newly planted wheat crop.
If soil pH needs adjusting and you have not done so, go ahead and apply lime before planting. Next, give wheat a good start by fertilizing according to soil test recommendations, especially with regard to phosphorus, potassium and sulfur. When the crop is planted on time, 15 to 30 pounds of preplant nitrogen per acre should be sufficient to promote maximum growth and tillering.
Nutrition will be especially important if wheat is planted after grain sorghum on sandy soils with low CEC because soil nutrient reserves may have been significantly depleted. In that situation, be particularly attentive to crop development. Yellowing, poor stand establishment and lack of tillering could signal a need for additional nitrogen as the season progresses.
- Remember to check for nematode problems during crop harvest.
Plant-parasitic nematodes are common in all field crop soils and often lower yields without being very apparent. Fall is an excellent time to find out if nematode populations are high and, if so, to develop a plan to manage them. When the weather is good for harvest, it is also good for collecting soil samples for nematode assay.
Nematode populations peak at the end of the growing season so samples assayed at this time provide an accurate description of potential hazards. If you submit samples in the fall, you will have time to plan a management strategy.
If you noticed localized areas of poor growth during the growing season, it is a good idea to collect separate soil samples from good and poor areas. Submit two samples from each of these areas-one for nematode assay and one for soil fertility. Comparison of results from good and poor areas and from nematode assays and soil tests is helpful in pinpointing a problem.
- Before planting legume cover or forage crops, be sure to submit soil samples, or get revised recommendations based on recent soil report data.
High fertilizer costs may have you considering the use of legumes as a cover crop or as part of a forage program. If so, be sure to refer to recent soil report data for your fields as you plan. Legumes have different fertility than many traditional crops.
It is usually not necessary to collect new soil samples from fields that have been sampled within the last two (sandy soils) or three (clay soils) years. To get revised/updated recommendations for your current situation, consult your regional agronomist. If you need to collect new samples, send them to the Agronomic Division soil testing lab now to avoid the processing delays that are common during the fall/winter. The sooner you get your results, the sooner you'll be able to finalize lime and fertilizer purchases or make plans to plant legume cover or forage crops to supply additional nitrogen.
- Fall is an ideal time to apply lime.
Fall liming is an excellent way to prepare for the spring growing season. Whether you are renovating your yard, preparing a new landscape planting or readying your fields for the next crop, fall is the best time to apply lime. However, lime should only be applied according to the recommendations from a recent soil report.
Take advantage of dry fall weather to apply lime as soon as possible. If you delay, wet weather may prevent the application even longer. The earlier you put out lime, the sooner soil pH will be adjusted to meet your planting needs.
- Remember the new fee structure for soil testing and waste analysis.
New agronomic testing fees approved by the State Legislature and the Board of Agriculture this past summer go into effect this fall. All soil samples received during the lab’s peak season (from 6 p.m. November 27, 2013, through March 31, 2014) will incur a $4-per-sample fee. This fee should be paid online via credit card or escrow account before sample shipment. Beginning December 3, 2013, fees for analysis of in-state waste samples increase from $5 to $8.
- Give appropriate care to plants you bring indoors for the winter.
By November, most houseplants should be brought inside to protect them from cold temperatures. Indoors during the winter, plants need less fertilizer and may get too much or too little water. Fertilizing once every four to six weeks with a soluble or time-release fertilizer should provide plenty of nutrients. Fertilizing too often can stress plants as excess fertilizer salts build up in the media.
Check plants frequently to see if they need water instead of watering on a schedule. Overwatering can be a problem in winter months when light is low and growth is slow. Underwatering can also occur as increased use of the home furnace tends to dry both the air and potting media at the same time.
- Check source water used for agricultural purposes.
Water used for agricultural purposes-such as irrigation or fertigation, livestock and poultry watering, aquaculture and fish production-should be analyzed every year. Testing is especially important after an extended wet or dry period. For a fee of only $5 per sample, solution analysis measures concentrations of 13 minerals plus pH, electrical conductivity, alkalinity and hardness. The solution report indicates whether any of these parameters could lead to production problems (such as clogged nozzles or reduced medication efficiency) and provides recommendations to correct any apparent problems.
Use agronomic testing to optimize fertilization of greenhouse crops.
Several laboratory tests are available from the NCDA&CS Plant/Waste/Solution/Media Section to help growers of greenhouse crops keep abreast of potential nutritional problems.
- Soilless media—Sample media prior to filling pots or bags to verify that pH and soluble salts are within the desired ranges.
- Solution analysis—
- Submit samples of source water to determine if there are any problems that need to be corrected, such as high alkalinity or high mineral concentrations.
- Submit samples of nutrient solutions to verify that the injector is working properly and that plants are receiving the targeted nutrient concentrations.
- Plant tissue analysis—Submit samples every couple of weeks to monitor nutrient concentrations in the crop. This test predicts nutrient deficiencies or excesses before symptoms appear so growers can correct the problem quickly with as little reduction in yield as possible.
- Set up an escrow account to avoid delay in processing of agronomic samples.
The Agronomic Division charges a fee for laboratory analysis of plant tissue, waste, source water, nutrient solutions, soilless media and soil (heavy metals analysis and nematode assay only). When these samples arrive without payment, they cannot be processed. The client must be contacted and invoiced. The samples are set aside until payment is received.
Clients can help prevent these delays by calling the division, setting up an escrow account and keeping an adequate balance on hand. This is the most convenient form of payment for clients and for the division. Clients who choose not to establish an escrow account are urged to pay by check. The use of cash is not advisable since sample shipments may be left unattended on the Agronomic Division’s loading dock during nonbusiness hours.
- Select fertilizer grade based on soil test results.
The three numbers in a fertilizer grade designation refer to percent content of nitrogen (N), phosphate (P2O5), and potash (K2O) on a weight basis. For example, the fertilizer 15-0-14 contains 15% N, 0% P2O5, and 14% K2O, so 100 pounds of it contains 15 pounds N, no P2O5, and 14 pounds K2O.
If your report recommends using a 15-0-14 grade, you don't necessarily have to use that exact grade, but you should look for a fertilizer with a similar ratio—that is, little or no phosphate and roughly equal amounts of nitrogen and potash. Once you find a fertilizer with a similar ratio, then recalculate the rate based on the amount of nitrogen and potash recommended for your crop or landscape area.
- If you apply animal waste to receiver crops, don’t forget to collect the annual soil samples mandated by law.
Many swine and poultry growers throughout the state are permitted through the N.C. Department of Environment and Natural Resources due to legislation addressing animal waste issues. These permits require annual soil testing of all fields that receive application of animal waste. Failure to have a yearly soil report for a given field upon annual inspection may result in a notice of violation. Growers are encouraged to remember this fact and make plans to submit the required samples.
- Use bar-code labels to track arrival of agronomic sample shipments.
Clients who want to know when their soil (and/or other agronomic) samples arrive at the laboratory should use bar-coded address labels available from the Division’s website www.ncagr.gov/agronomi/. Just follow the links to print the desired number of labels, and tape one to the outside of each package of samples. When packages arrive at the lab, they will be scanned and the client will receive an e-mail notification of their arrival.
- Tips on understanding cation exchange capacity (CEC)
Many growers ask questions about the meaning of cation exchange capacity values on NCDA&CS soil reports. In essence, CEC values indicate the ability of a soil to hold nutrients: for example, the higher the CEC value, the greater the capacity of the soil to supply calcium, magnesium and potassium for plant growth. Sandy soils tend to have low CEC values (typically 1-3 milliequivalents per 100 cubic centimeters) and low levels of nutrients. Organic and clay soils tend to have higher CEC values (up to 25 milliequivalents per 100 cubic centimeters) and more nutrients.
Note: Soil reports from other laboratories may report CEC values in units of milliequivalents per 100 grams. These values have to be interpreted on a different scale than NCDA&CS values.
- If crops look stunted or discolored, collect soil and tissue samples for nutrient problem diagnosis.
Soil samples are normally collected before a crop is planted to assess the lime and fertilizer needs for the upcoming season. However, soil samples and matching plant tissue samples collected during the cropping season are excellent for diagnosing a wide range of nutrient problems. The best approach is to collect both soil and tissues samples from "bad" areas, and then to collect both types of samples from "good" areas. Label the samples so you know which are the "good" ones and which are the "bad" ones. Do not collect tissue samples from dead plants.
Use these tips when submitting soil samples.
Processing of soil samples at the NCDA&CS lab goes more efficiently when growers take care to: 1) place sample information forms in plastic, zip-lock bags to prevent moisture problems; 2) use the soil lab's specially designed shipping carton when sending large numbers of samples; and 3) address and label shipping cartons completely and correctly. Visit this Web page for specific information.
- Use waste analysis to manage land application of farm by-products (crop residues, manure, lagoon liquid and sludge, poultry litter, and composts).
Organic wastes provide essential plant nutrients and improve soil physical properties, such as water infiltration, aeration and nutrient-holding capacity. Before application, samples of the waste should be submitted to the NCDA&CS Agronomic Division for testing. Analysis of a standard, in-state waste samplecosts $8 and measures concentrations of essential plant nutrients. Additional specialized tests are available for an extra $10 per test per sample.
The waste report estimates the rates at which nutrients will be available during the first growing season. With this information, you can apply wastes to meet the specific nutritional needs of a crop. Supplemental applications of commercial fertilizer may be necessary, depending on rate of nutrient availability or other factors.
April 8, 2014