Cotton Petiole Analysis: A Useful Diagnostic Tool

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Cotton Petiole Analysis: A Useful Diagnostic Tool.

Spring 1996, No. 8

COTTON PETIOLE ANALYSIS: A USEFUL DIAGNOSTIC TOOL

Petiole analysis is a useful tool in maintaining plant health, evaluating soil fertility programs…and guiding farmers and their advisors in making nutrient management decisions to support profitable crop yields. It is a practice worth using in high yield cotton production.

Petiole analysis allows crop advisors and farmers to monitor nutrient status in a timely manner, important in maintaining nutrient balance. Also, certain nutrients compete with each other while others are synergistic in terms of plant uptake.

• Nitrogen deficiency, for instance, can result in small stalks and bolls or lead to increased boll shedding. Too much nitrogen can trigger excess vegetative growth, increase disease susceptibility, delay maturity, increase the frequency of boll rot and lead to lower lint quality.
• Potassium enhances photosynthesis, late season boll fill, disease resistance and lint quality. Too much potassium antagonizes magnesium utilization from low magnesium testing soils.
• Magnesium, the central element in the chlorophyll molecule, also serves to activate many enzyme systems and promotes seed formation.
• Phosphorus, involved with energy transfer and storage, improves root and seedling establishment and stimulates seed and oil development.

Petiole analyses allow crop advisors to determine the nutrient status at weekly intervals and recommend corrective treatments where needed. It helps to evaluate factors such as:

• the need for late season boron, potassium and/or nitrogen applications;
• the effectiveness of previously applied fertilizer;
• the potential for outbreaks of certain leaf spot diseases;
• the risk of early cut-out;
• potential harvest date.

Effective use of petiole analyses requires close attention to details. For best results several factors must be considered:

• pre-arrangement for laboratory analyses and rapid return of test results, by electronic mail where possible;
• adequate training of cotton scouts in the technique of proper plant and field sampling and handling of petiole samples;
• time of day and time since irrigation affect petiole composition;
• sampling of problem and normal areas for comparative purposes;
• reliable laboratory result interpretation and sound agronomic recommendations for optimum profitability.

Cotton petiole analysis is growing in acceptance as a diagnostic tool that provides good opportunity to monitor the nutritional status of high yield cotton and provides an opportunity for in-season adjustments essential for top profits.

-NRU-

Rice Responds to Phosphorus and Potassium

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Rice Responds to Phosphorus and Potassium.

Spring 1996, No. 7

RICE RESPONDS TO PHOSPHORUS AND POTASSIUM

Many rice growers in the Midsouth have traditionally not applied phosphorus fertilizer to their fields. Under flooded conditions, the phosphorus that is bound with iron and aluminum oxides is changed chemically and becomes more available to the rice plants. However, a recent study in Arkansas has documented a profitable response to phosphorus application on soils testing low in phosphorus and potassium. Phosphorus should be applied to low testing soils, especially where the soil pH is above 7.0. Each bushel of rice removes about 0.3 pounds of P₂O₅. Yields above 150 bushels remove more than 40 pounds of P₂O₅, and after several years, available reserves of soil phosphorus can be decreased if supplemental phosphorus is not supplied.

In fields which fail to green up after midseason nitrogen applications, the problem may be potassium deficiency. Arkansas research has also shown good responses to potassium fertilization on such fields. When a rate of 60 pounds of K₂0 per acre was applied as potassium chloride, the yield in one study was increased 10 bushels, from 172 to 182 bushels per acre. When the needed phosphorus was also applied at a P₂O₅ rate of 40 pounds per acre, yields were increased further to 198 bushels per acre. Phosphorus and potassium worked together to increase the rice yields.

There is some grower concern about the risk of increased “salting out”, or salt-induced stand reduction, with increased potassium fertilization. The Arkansas research has shown that some stand reduction may be possible during early seedling development as soluble salts wick near the soil surface with soil drying. However, even with some mild stand reduction, which did not prevent adequate plant populations, rice yields were increased as potassium deficiency was overcome. When the required phosphorus was applied with the needed potassium, stand loss was reduced and yields were improved.

Field observations and lab diagnoses by agronomists and plant pathologists have documented increased rice diseases and poor yields where phosphorus and potassium needs have been neglected. Adequate phosphorus and potassium nutrition promote:

• the opportunity to flood the field in a timely manner and avoid some of the weed competition;
• improved tillering;
• decreased susceptibility to diseases;
• more efficient utilization of applied nitrogen;
• decreased risks associated with delayed plant maturity and delayed harvest.

Once soil test levels drop to the point that rice will respond to phosphorus and potassium, wheat and soybean yield losses have probably also occurred. If soybeans or wheat are rotated with rice on fields with low phosphorus and potassium tests, they can also benefit from fertilization. Some growers in the past may not have fertilized soybeans which were rotated with rice because of low soybean prices. With improved soybean prices this year, it may be time to reevaluate your soybean fertilization program…to benefit the soybeans and the rice grown in rotation.

High yielding rice varieties, which respond to higher nitrogen rates, require balanced phosphorus and potassium nutrition. Can you afford to apply the nitrogen necessary for high rice yields and risk poor returns on your nitrogen investment…because you short-changed the crop’s phosphorus and potassium needs? Plan now to get your crop off to a fast and efficient start and optimize your rice yields and profits with improved phosphorus and potassium management.

-CSS-

It’s Not too Late to Apply Phosphorus for Soft Red Winter Wheat on Poorly-Drained Soils

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: It\’s Not too Late to Apply Phosphorus for Soft Red Winter Wheat on Poorly-Drained Soils.

Spring 1996, No. 6

IT’S NOT TOO LATE TO APPLY PHOSPHORUS FOR SOFT RED WINTER WHEAT ON POORLY-DRAINED SOILS

Farmers frequently say, “I know fertility doesn’t limit my yields because for years I’ve been soil testing and following the resulting recommendations.” However, intensive soil sampling on many fields in the last few years reveals that this frequently is untrue. It’s common to see low testing areas completely masked by very high testing areas in the same field when conventional soil sampling procedures are used. In addition to plant nutrients, soil pH can vary widely. In the western Corn Belt, fields averaging near-neutral in pH often have acid areas testing below 5.5 surrounded by soil zones testing greater that 7.5. You would never realize a problem existed without intensive soil sampling.

The general pattern of soil areas within fields with untapped yield potential varies with cropping system, soil types and field history. The hidden potential in fields with good manuring or fertilizing histories often is found in the field areas currently producing the highest yields. Intensive sampling of fields with limited nutrient applications in the past often shows that the low yielding areas have the greatest hidden potential.

For example, recent landscape position sampling in North Dakota has shown that low yielding hill tops frequently test substantially lower in several nutrients than the bottom areas in the same field. The hilltops were lower in organic matter and higher in pH due to a combination of less soil development and soil erosion. Compared to the bottom areas, test values averaged 56 percent for nitrate, 38 percent for phosphorus, 13 percent for chloride, 35 percent for sulfate, and 53 percent for zinc. In many cases fertilizer application rates based on field averages would leave several nutrients limiting for the hilltop positions. Removing these nutritional limitations will not likely make these hilltops yield as well as other areas of the field, but soil test data indicate yields could be increased substantially. In this case, the major hidden yield potential exists in the soil areas that are currently the lowest yielding.

High residue management that allows more water to soak into hilltop portions of the landscape rather than run off, combined with more intensive nutrient management approaches could produce excellent returns. Landscape position sampling of fields that haven’t been manured or fertilized extensively in the past could help develop more profitable fertilization programs even if variable rate application equipment isn’t being used. More intensive sampling allows for more accurate determination of the type and rate of nutrients to apply uniformly across the field. Variable rate equipment brings additional precision by matching crop needs and application rates.

In contrast, fields with histories of extensive fertilizer or manure use often show that areas testing low in nutrient availability coincide with high yielding areas.Decades of greater nutrient removal from these areas have resulted in soil fertility depletion when nutrients have been applied uniformly across the field based on the average yield of the field. Such fields become more variable the longer they are farmed using conventional methods. The hidden yield potential is found in the areas that are already the highest yielding but that could be even higher yielding if nutrient limitations were removed.

Intensive soil sampling is a practice that can help growers find yield robbing nutrient deficiencies. The elevated crop prices of 1996 further increase financial rewards for identifying and correcting these deficiencies.

-CSS-

Intensive Soil Sampling: A Critical Step in Tapping Your Field’s Hidden Yield Potential

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Intensive Soil Sampling: A Critical Step in Tapping Your Field\’s Hidden Yield Potential.

Spring 1996, No. 5

INTENSIVE SOIL SAMPLING: A CRITICAL STEP IN TAPPING YOUR FIELD’S HIDDEN YIELD POTENTIAL

Farmers frequently say, “I know fertility doesn’t limit my yields because for years I’ve been soil testing and following the resulting recommendations.” However, intensive soil sampling on many fields in the last few years reveals that this frequently is untrue. It’s common to see low testing areas completely masked by very high testing areas in the same field when conventional soil sampling procedures are used. In addition to plant nutrients, soil pH can vary widely. In the western Corn Belt, fields averaging near-neutral in pH often have acid areas testing below 5.5 surrounded by soil zones testing greater that 7.5. You would never realize a problem existed without intensive soil sampling.

The general pattern of soil areas within fields with untapped yield potential varies with cropping system, soil types and field history. The hidden potential in fields with good manuring or fertilizing histories often is found in the field areas currently producing the highest yields. Intensive sampling of fields with limited nutrient applications in the past often shows that the low yielding areas have the greatest hidden potential.

For example, recent landscape position sampling in North Dakota has shown that low yielding hill tops frequently test substantially lower in several nutrients than the bottom areas in the same field. The hilltops were lower in organic matter and higher in pH due to a combination of less soil development and soil erosion. Compared to the bottom areas, test values averaged 56 percent for nitrate, 38 percent for phosphorus, 13 percent for chloride, 35 percent for sulfate, and 53 percent for zinc. In many cases fertilizer application rates based on field averages would leave several nutrients limiting for the hilltop positions. Removing these nutritional limitations will not likely make these hilltops yield as well as other areas of the field, but soil test data indicate yields could be increased substantially. In this case, the major hidden yield potential exists in the soil areas that are currently the lowest yielding.

High residue management that allows more water to soak into hilltop portions of the landscape rather than run off, combined with more intensive nutrient management approaches could produce excellent returns. Landscape position sampling of fields that haven’t been manured or fertilized extensively in the past could help develop more profitable fertilization programs even if variable rate application equipment isn’t being used. More intensive sampling allows for more accurate determination of the type and rate of nutrients to apply uniformly across the field. Variable rate equipment brings additional precision by matching crop needs and application rates.

In contrast, fields with histories of extensive fertilizer or manure use often show that areas testing low in nutrient availability coincide with high yielding areas.Decades of greater nutrient removal from these areas have resulted in soil fertility depletion when nutrients have been applied uniformly across the field based on the average yield of the field. Such fields become more variable the longer they are farmed using conventional methods. The hidden yield potential is found in the areas that are already the highest yielding but that could be even higher yielding if nutrient limitations were removed.

Intensive soil sampling is a practice that can help growers find yield robbing nutrient deficiencies. The elevated crop prices of 1996 further increase financial rewards for identifying and correcting these deficiencies.

-PEF-

Review Your Nutrient Management Plans Now

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Review Your Nutrient Management Plans Now.

Spring 1996, No. 4

REVIEW YOUR NUTRIENT MANAGEMENT PLANS NOW

Now is a good time to review your nutrient management plans for the coming crop season. Changes in weather, crop rotation plans or yield goals may have shifted nutrient needs. Analyze yield data from last year’s crop. Does your maintenance fertilizer plan match the nutrients removed in the harvested crop? Did you adjust for expected nitrogen carryover from legume crops grown last year? Do planned fertilizer applications support the yield goals for the next season?

Consider manure applications made in the fall and winter. Be sure to make adjustments for nutrients applied in manure. If applications were less than anticipated, you may need to adjust fertilizer application upward. What about soil moisture? Your plans last fall may have been based on expected moisture and weather patterns. Are those projections still accurate? If fall and winter fertilizer applications were not made as planned, you may need to make adjustments to be sure adequate nutrients are supplied to the crop.

Market prices for crops may have increased since plans were made last fall. Don’t limit potential profits by being too conservative on fertilizer application. If you have used a marketing plan and forward contracted grain at a higher price, you may want to take a little extra risk and push yield goals a bit higher. Optimum fertilizer rates don’t change much over a wide range of crop prices and fertilizer prices, but it may be worthwhile to re-check crop budgets to be sure the optimums still fit the plan.

Work with your fertilizer dealer and crop consultant to make any revisions in plans.Letting your dealer know of any changes in plans will help in planning for supplies needed and scheduling of application equipment. Your dealer will appreciate knowing your plans early and will be better able to meet your needs and schedule.

Planning ahead is always a good management practice. It is easier to review and revise plans than to wait until the last minute. Early planning is a good way to be sure all of the details are considered. Keep on file the rationale behind your plans, including calculations of application rates needed and any economic analysis. Then review those plans as more information becomes available on weather, prices and yields. Review new research results that may have come out since the plans were made. Take advantage of the latest information and incorporate it into your plan.

Most important, plan for a good year. You cannot predict all of the factors that will affect next season’s production, but planning for a bad year is one of the best ways to ensure you will have one.

-HFR-

Corn Responds to Seed-Placed Phosphorus

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Corn Responds to Seed-Placed Phosphorus.

Spring 1996, No. 3

CORN RESPONDS TO SEED-PLACED PHOSPHORUS

The use of fertilizers placed with the seed is a practice frequently used by corn growers. The effectiveness of seed placement is particularly high for supplying phosphorus to corn in cold soils or soils testing low in phosphorus. Recent research at the University of Guelph in Ontario, Canada, has confirmed the benefit of seed-placed fertilizer, and has shown that these benefits extend to soils testing high in phosphorus as well.

Experiments conducted at Elora, Ontario, in 1993 and 1994 utilized a liquid ammonium polyphosphate fertilizer (10-34-0). The fertilizer was placed with the seed at a rate of 13 pounds of P₂O₅ per acre. A comparison treatment was placement in a band 2 inches to the side and 2 inches below the seed. The effect of seed placed phosphorus was evaluated at soil phosphorus levels ranging from low to very high (6 to 70 pounds per acre by the Olsen soil test).

Averaged over two years, placement of phosphorus with the seed boosted yields by an average of 9 bushels per acre. The response to seed placement was independent of soil test level. Plant tissue concentrations of phosphorus, at a growth stage when the fourth to fifth leaf tips were emerged from the whorl, were much higher with seed placed fertilizer than without. The increased phosphorus supply at this growth stage was the primary factor that increased yields.

Studies in 1995 compared other fertilizer materials for seed placement at a wider range of locations. Again yield responses of 6 to 11 bushels per acre were attained. No differences were found among the liquid fertilizers 10-34-0, 6-24-6, 8-19-3 and granular monoammonium phosphate (13-52-0). One site with a soil test rating of very high (104 pounds per acre) showed no response to seed placed phosphorus, indicating there was an upper limit at which the soil alone would supply adequate phosphorus for seedling growth.

Essentially all of the yield response was attained at fertilizer rates as low as 5 pounds of P₂O₅ per acre. Rates two to four times higher were shown to delay emergence, even though the yield response was still positive. When soil tests were low or medium, optimum yields were attained only when seed placed phosphorus was applied in addition to that broadcast or banded. The low optimum rates indicate that seed placed phosphorus should be viewed as a supplement to rather than a replacement of typically recommended phosphorus applications. The amount that can safely be placed in contact with the seed is far less than the amounts required to maintain soil phosphorus levels when crop removal is considered.

These results emphasize the importance of phosphorus availability during early seedling growth. Even though the planting dates in these experiments were not early, the growth of seedlings depended strongly on phosphorus. While colder soils respond the most to phosphorus supply, warm air temperatures can often increase shoot/root ratios, leading to increased demand for nutrients from each unit of root. If nutrient supply is good, the crop canopy can be established faster and more efficiently.

Take advantage of high shoot/root ratios. Supply phosphorus with care and your crops will take care of you!

-TWB-

Knowledge is Never a Burden

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Knowledge is Never a Burden.

Spring 1996, No. 2

KNOWLEDGE IS NEVER A BURDEN

We are in the age of information…a real communication revolution. But do you sometimes feel there is so much information constantly being thrown at us that it is impossible to understand…much less utilize…any of it? Perhaps you feel more like an accident victim on the “Information Superhighway” rather than a beneficiary. Don’t be discouraged, but rather be selective. In crop production, ask yourself what information is important for efficient, high yield production and focus on that information and the tools to best utilize it.

Plants have much more genetic potential than we have management skill. What we actually do in managing a crop is minimize yield loss from that genetic maximum. So each decision…each detail… is important in squeezing the most out of that genetic potential. An uninformed decision based on habit or expediency can be very costly. Let’s consider some decisions:

• Variety—Crop varieties are constantly being improved. Today’s best choice may be tomorrow’s loser. It’s important to be informed of the latest university and industry releases. And very importantly, how each new variety should be managed to maximize its potential.
• Planting date and population—Know the ideal date to plant and how seasonal soil temperature might affect this date. Plant population and uniformity of planting also influence final yield.
• Pest control—Pests…insects, weeds, and diseases…must be controlled early before they rob yield potential. Preventative controls ensure no yield potential is lost. One aspect of preventative pest control that we seldom appreciate is the benefit from fertilizers. Plants that are well-fed and growing vigorously tend to be more resistant to a broad spectrum of pests. Potassium is especially noted in this regard. And in more recent years chloride has become recognized as effective in reducing a number of root and leaf diseases of small grains and other crops.
• Fertilizer management—Do you know which nutrients are most frequently deficient in your area? When was the last time you had your fields tested? Nitrogen must be managed on a crop by crop basis because it can be leached below the crop root zone by water. On the other hand, phosphorus and potassium nutrition can be built up in the soil and handled on a long-term basis since they are immobile in most soils. Starter fertilizer encourages rapid early growth, especially important in cool, wet springs or short growing seasons. In-season nutrient applications by side dressing or application through irrigation systems is an effective tool in high yielding production systems striving for even higher yields.

Information is the basis of all our decisions. Regardless of the source…county Extension agent, local fertilizer dealer, or the Internet…the key is knowing what questions to ask.

You may have heard about Variable Rate Technology. In this case the same information that we have always used is simply being utilized more intensely. Rather than look at the average value across a field, for a certain factor, we can now map its variation in detail. Monitors can be hooked up to grain combines to map yields on the go. We can superimpose on these yield maps information on soil tests, weeds, soil topography and other characteristics. We can now adjust our inputs to account for variation within individual fields. It is not so much using new information as it is better utilizing present information with new tools.

Don’t be intimidated by the volume of information available, but rather learn to be selective and learn to use that information better. We have the tools, and after all, knowledge is never a burden.

-AEL-

Role of Potassium in Crop Establishment

Source : Agri-Brief. International Plant Nutrition Institute.

ผ่านทางAgri-Brief: Role of Potassium in Crop Establishment.

Spring 1996, No. 1

ROLE OF POTASSIUM IN CROP ESTABLISHMENT

Planting high quality seed in a well prepared seedbed with enough moisture to assure a rapid, uniform stand is the first step in achieving acceptable yields. Seedbed fertility is also important, especially for immobile nutrients such as potassium.

Potassium plays many key roles in plants. It activates enzymes, maintains cell turgor, enhances photosynthesis, reduces respiration, helps transport sugars and starch, aids in nitrogen uptake and is essential for protein synthesis. In addition to plant metabolism, potassium improves crop quality because it extends the grain-filling period, increases kernel weight, strengthens stems, increases disease resistance and helps the plant better withstand stress.

Potassium is critical to get the crop off to a good start and good finish. Deficient plants have poorly developed root systems, grow slowly, lodge easily, produce smaller seeds and have lower yields. They also use water inefficiently, are less winter hardy and are more susceptible to disease.

Phosphorus is well known to promote early root formation and growth, but potassium may have an even greater effect on root development. Cereal plants have two root systems ¾ seminal roots which develop from the seed at planting and nodal roots which develop at the crown level later in plant development. Potassium deficiency affects both of these root systems.

An Australian study, where wheat was grown with and without nitrogen, phosphorus and potassium, has shown root growth is most severely affected by potassium.Lower root numbers were evident in the potassium-deficient plants within four days after seeding. Three weeks later, the plants grown without potassium had half the seminal roots of the plants grown without nitrogen or phosphorus. And, 30 days after seeding, the potassium deficient plants had not initiated any nodal roots, although the nitrogen and phosphorus deficient plants had.

Potassium shortage influenced root length in the same way. Length of seminal roots for plants grown without potassium 16 days after seeding was only 15 percent of plants supplied with normal potassium. This compares to 70 percent for phosphorus and 98 percent for nitrogen.

Because potassium plays such an important role in early root development, and because it moves very little in the soil ¾ starter fertilizers should be an important part of your nutrient management plans.

Remember, plants need as much potassium as nitrogen…some plants need even more.

-TLR-