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-

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-

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-

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-

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-

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-

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-

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-

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: SILAGE PRODUCTION AND FERTILIZATION.

Winter 2010, No. 7

SILAGE PRODUCTION AND FERTILIZATION

Ensilage or ensiling is a process of preserving forage for later use as animal feed. Silage can be defined as any plant material that has undergone fermentation or “pickling” in a silo. And a silo is any storage structure in which green, moist forage is preserved. Silage production is important in parts of the Great Plains, especially where there are significant numbers of animals in feeding operations such as dairies and feedlots.

There are several advantages of silage compared to hay and other forage conservation systems. These advantages include less field and harvest losses, many crop options, mechanization of harvesting, storage and feeding, less likelihood of weather damage during harvesting, relatively low loss of nutrients with proper ensilage, and silage can be used in many livestock feeding programs. The disadvantages of silage include its bulkiness in handling and storage, it requires additional equipment and structures for harvesting, storing, and feeding, high potential for loss if not stored properly, not readily marketable off-farm, and silage must be fed soon after removal from the silo to minimize spoilage.

The major factors affecting silage quality are the type of crop, stage of maturity, moisture content, and length of chop. Within forage species the stage of maturity has the greatest effect on quality. The optimal moisture content depends on the crop and type of silo used, but is generally around 65 to 70%. Material ensiled below 50% moisture is usually called haylage. Length of chop is a factor since it affects air exclusion in the silo. Fine chopping and packing help ensure proper fermentation.

Many crops, including grasses and legumes, can be preserved through ensilage. The most common and perhaps the best adapted is corn. It is high energy and results in good animal performance. Sorghum (grain and forage) is a popular silage crop in some areas. Alfalfa is also used for silage, but the process of ensilage is somewhat more difficult than with other common crops.

As in hay production, the harvest of a crop for silage results in the export of large quantities of nutrients from a field. For example, a 30-ton harvest of corn silage will remove about 250 lb N, 110 lb P₂O₅, and 250 lb K₂O. This is one of the most important points to keep in mind when designing fertility programs for silage crops.

Nitrogen fertilization can affect fermentation of some crops by decreasing the concentration of soluble carbohydrates required to make high quality silage. This is particularly true with cool season grasses since they tend to be relatively low in available carbohydrates to begin with. On the other hand, corn is relatively high in soluble carbohydrates, so N fertilization is not a concern from this standpoint.

Phosphorus and K fertilization of crops for silage should be based on soil test information and experience. Nutrient removal data should also be considered. Phosphorus and K can be rapidly exported and depleted from soils under silage production if adequate amounts of these nutrients are not applied.

There are many excellent sources of information on the topic of fertilization and ensiling of forages. Among these sources is a practical handbook entitled Southern Forages (available through the International Plant Nutrition Institute, http://www.ipni.net). Other good sources are available through land grant universities and local county extension offices.

- WMS -

For more information, contact Dr. W.M. (Mike) Stewart, Southern and Central Great Plains Director, IPNI, 2423 Rogers Key, San Antonio, TX 78258. Phone: (210) 764-1588. E-mail: mstewart@ipni.net.

Abbreviation: N = nitrogen; K = potassium.

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: TRACKING NITROGEN USE EFFICIENCY ON YOUR FARM: TIPS FOR TRIUMPH.

Winter 2010, No. 6

TRACKING NITROGEN USE EFFICIENCY ON YOUR FARM: TIPS FOR TRIUMPH

If you were asked how good your N management (source, rate, timing, and place of application) was for the crop(s) on each of your fields this past year, how would you answer? Was N managed at the optimum, most economically rewarding rate? Unless on-farm replicated N management comparisons were made, it would probably just be a guessing game for most of us.

The effectiveness of a given N management program, and the efficiency with which the crop utilizes the applied N, will vary greatly with weather conditions, year in and year out. To try to be as efficient as possible, most farmers use local university research results to guide their initial management decisions, but make modifications based on their own field observations and experiences.

Unless we actively monitor the crop’s N status during the growing season, we never really know how well nourished the crop is or was until harvest time. End-of-season crop assessments and documentation of yields on each field, in and of themselves, can provide important feedback on past decisions and help to influence future N management directions. But such measures are merely looks in the rear-view mirror.

Yet, the importance of those “after-the-fact” looks in the rear-view mirror should not be downplayed. When crop yield is evaluated per unit of N applied (e.g. bushels, hundred weight, tons, or bales per pound of N applied per acre), and those values are tracked for each field each year, over a period of years, a great deal can be learned. There are other ways to measure crop N use efficiency, but these calculated values serve as perhaps the
most practical field-level measure of N use efficiency. An upward trend in the calculated values over time implies that N use efficiency may be improving. If the trend in values of yield per unit of applied N is fl at or declining over time, then closer scrutiny of the N management program, and possibly a detailed assessment of the entire crop management system, is called for.

To begin moving your N management program toward greater effectiveness and efficiency, and to help improve your bottom line while protecting the environment from controllable N losses, start with some simple calculations for each field on your farm. Divide crop yield by the applied N rate, and plot the values for each year, on each field. The results may reveal your prowess as a top-notch N manager … or they could serve as important indicators of the need for a N management tune-up. Either way, tracking N use efficiency for each field can be just as important as monitoring the milking performance of a dairy cow. Without performance records, it is difficult to make critical management decisions that are essential to remaining competitive in the farming business.

- CSS -

For more information, contact Dr. Clifford S. Snyder, Nitrogen Program Director, IPNI, P.O. Drawer 2440, Conway, AR 72033-2440. Phone (501) 336-8110. Fax (501) 329-2318. E-mail: csnyder@ipni.net.

Abbreviation: N = nitrogen.

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: SOCIAL MEDIA IN AGRICULTURE.

Winter 2010, No. 5

SOCIAL MEDIA IN AGRICULTURE

Traditionally, agricultural information exchange has been dominated by industrial media such as newspapers, television, and magazines. In recent years, however, technology awareness and computer literacy are increasing across all demographics and various forms of social media are being used more and more by people looking for news, education, and other information related to agriculture. Social media can be defined as internet-based applications that allow the creation and exchange of user-generated content. It is the blending of technology and social interaction that creates value in these types of media.

Education and outreach efforts by industry and university extension personnel have often been identified as valuable or successful based on the face-to-face interaction with clientele. Dr. John Fulton, a precision agriculture extension specialist at Auburn University, sees social media as a means of enriching his efforts, not a hindrance to them. Dr. Fulton says: “If I restrict dialogue only to a one-on-one conversation, then only that person can take advantage of it.” By sharing the information exchanged during one face-to-face encounter through his social media network, Dr. Fulton has the opportunity to serve potentially millions of other growers asking the same questions or facing similar challenges. Social media also provides growers a quick and easy way to build relationships and to interact with people in agriculture that they might never have connected with otherwise.

There are many different forms of social media, including web, social, and micro blogs (a blend of the term web log), podcasts, video, and other file sharing sites. Some specific applications that the International Plant Nutrition Institute (IPNI) currently uses include YouTube and Twitter. YouTube is a video-sharing website where users can upload and view videos. IPNI has created a “channel” on the YouTube site where all of our posted videos are collected. The web address is http://www.youtube.com/PlantNutritionInst. You do not need an account to view videos, only to post your own. All of the videos are also available through the IPNI website,http://www.ipni.net/video. The value of using YouTube is that viewers with no knowledge of IPNI can find the videos and be directed back to the IPNI website to become familiar with the Institute. For example, only 23% of the viewers of one of our posted videos, “The Right Way to Grow Wheat”, were referred from the IPNI website. The majority of viewers find our videos by using a YouTube search or by viewing related videos. YouTube also facilitates downloads of our videos to mobile devices, such as smart phones and iPads, which have become a more frequent means of viewing our material over the past six months.

Twitter is a microblogging service that allows users to post and read text-based messages of up to 140 characters. The messages or “tweets” are usually visible to the public. However, authors may restrict delivery to only their subscribers or “followers”. Users can send or receive messages via the Twitter website or mobile devices. The IPNI twitter account can be accessed athttp://www.twitter.com/PlantNutrition. A tweet from IPNI will typically be a short statement about a new posting on the website and a link to the full article or news item, such as: Better Crops with Plant Food (2010, No. 3) is loaded with articles that focus on spatial variability. #ag http://info.ipni.net/Y53U6

The value of using Twitter to call attention to these postings is that it draws immediate visibility to an item that might not be seen otherwise by people who don’t frequently visit the website. Another advantage is that a user can “retweet” any message to their list of followers, broadening the distribution beyond IPNI subscribers. An additional way to increase the number of viewers is by appending the message with a “hashtag”. In the case of IPNI tweets, the hashtag is #ag. This link makes the tweets searchable to others within the agriculture community who might be following related users but are not familiar with IPNI.

Social media provide a quick and responsive network for people involved in agriculture to gather and exchange information. It allows immediate dissemination of important emerging issues and the sharing of positive information among producers and consumers of agricultural products. IPNI is committed to providing science-based plant nutrition and fertilizer use information to industry, farmers, agricultural and environmental leaders, scientists, and public policy makers. So, follow us on Twitter @PlantNutrition to receive all the latest updates.

-SBP-

For more information, contact Dr. Steve Phillips, Southeast Director, IPNI, 3118 Rocky Meadows Rd., Owens Cross Roads, AL 35763. Phone (256) 529-9932. E-mail: sphillips@ipni.net.

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: STARTER FERTILIZER – WHY IT’S DONE.

Winter 2010, No. 4

STARTER FERTILIZER – WHY IT’S DONE

Starter fertilizer. It’s not the easiest practice to put into place – special attachments, more cost, and logistics of tending tanks or bins to name a few. But many farmers make it a part of their regular planting practices. Why?

First, with starter fertilizer, a little goes a long way. Because it is placed near the seed at planting, it is accessible to a young root system. For some crops, like corn and wheat, roots take up nutrients at the fastest rate early
in the season. A concentrated supply of nutrients within easy reach of a limited root system increases the chances that roots can continue to take up nutrients at a rapid rate without running short. Because they are strategically
placed and timed, starter fertilizers are one of the more efficient applications made.

Starter fertilizers can be used as a strategy for managing within-field nutrient variability. It has been shown time and again that soil fertility varies across the field and so does crop response to applied nutrients. Agriculture is able to measure and document this variability more than in the past. However, site-specific approaches still carry risk that some areas of the field may not be properly characterized and under-fertilized. Applying a small quantity of nutrients across the entire field as starter fertilizer helps manage this risk.

Nutrients in starter fertilizer provide synergistic effects. Nitrogen and P can cause roots to proliferate in the zone where starter fertilizer was applied. Potassium does not proliferate roots, so co-application with N and/or P is needed for roots to more fully explore the K supply in the starter. Nitrogen, in the ammonium form, results in acidification of the zone of soil right around the root. This lower acidity has been shown to increase P uptake by young plants. Phosphorus also supplies needed energy early in the plant for the active uptake of K.

The most commonly observed effect of starter fertilizer is more rapid early season growth. While this response is probably the most visually striking, it does not necessarily mean that a yield response will occur. As a plant continues to develop and its roots explore more soil, starter fertilizer supplies progressively less of the total nutrients taken up, making nutrient supplies elsewhere in the soil profile more important. End of season yield responses depend on how quickly and to what extent a plant root system accesses these other supplies. Under conditions where root exploration is limited or slowed, yield responses are more likely. This holds true as well when soils are less fertile.

Many would argue that when striving to achieve consistently higher yields, a starter fertilization program should be seriously considered. Whether or not it fits a particular farm depends on many things beyond those strictly agronomic. However, starter fertilizer does provide some level of insurance against nutrient variability and adverse growing conditions and is a management practice with a rather extensive body of scientific studies supporting its use.

-TSM-

For more information, contact Dr. T. Scott Murrell, Northcentral Director, IPNI, 1851 Secretariat Dr., West Lafayette, IN 47906. Phone: (765) 413-3343. E-mail: smurrell@ipni.net.

Abbreviations: N = nitrogen; P = phosphorus; K = potassium.

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: WHAT SULFUR SOURCE SHOULD I USE?.

Winter 2010, No. 3

WHAT SULFUR SOURCE SHOULD I USE?

Sulfur has been recognized as restricting crop production in parts of the world. Soil S budgets are negative in many areas, where more S is removed from the field in harvested crops than is supplied by various inputs.
Much of the S in soil is present in organic matter, where it is unavailable for plant uptake until it is converted to sulfate. Plants require adequate S for many reactions, including synthesis of proteins and enzymes.

When additional S is needed to meet crop needs, there are many excellent sources of this nutrient. Elemental S was once mined directly from the earth. It is now more typically obtained from coal, crude oil, and natural
gas during refining or during scrubbing of combustion gases. A number of common earth minerals are also used as S sources for agriculture.

Elemental S is not water soluble and must be oxidized by soil bacteria to sulfate before it can be taken up by plant roots. The speed of this microbial process is governed by environmental factors such as soil temperature and moisture, as well as the physical properties of the S.

Various approaches have been used to enhance the conversion of elemental S to plant-available sulfate. The speed of elemental S oxidation is directly related to the particle size, where smaller particles have a greater surface area for the soil bacteria to act on. Therefore, large particles of S may require months or years of biological action before oxidizing significant amounts of sulfate. Fine, dust-sized particles are oxidized quickly, but are not easy to apply.

One approach to enhance the rate of S oxidation is to add a small amount of clay to the molten S prior to cooling and forming small pellets (“pastilles”). When added to soil, the clay swells with water and the pastille disintegrates into fine particles that are rapidly oxidized.

Very thin layers of elemental S can be incorporated during fertilizer granule manufacturing. This S is quick to oxidize and become available for plant uptake. This reaction can have a positive impact on the plant availability of some micronutrients, such as zinc and iron, which become more soluble as the pH declines. Finely ground elemental S is sometimes added to fertilizer suspensions. Elemental S is also used as a fungicide for crop protection. Elemental S and sulfuric acid are commonly used in the reclamation of calcareous soils that contain elevated sodium and in the treatment of irrigation water containing excessive bicarbonate.

A number of excellent soluble sulfate fertilizers are available to provide a rapid supply of nutrients. The selection of a particular soluble material depends on price, availability, form, and the other nutrients that accompany the sulfate. A few examples of commonly used S fertilizers include:

Non-Soluble – Elemental S
Semi-Soluble – Gypsum (15 to 17% S)
Soluble – Ammonium sulfate (24% S); Epsom salt (13%); Kieserite (23% S);
Langbeinite (22% S); Potassium sulfate (18% S); Thiosulfate (10 to 26% S)

- RLM -

For more information, contact Dr. Robert Mikkelsen, Western North America Director, IPNI, 4125 Sattui Court, Merced, CA 95348. Phone: (209) 725-0382. E-mail: rmikkelsen@ipni.net.

Abbreviation: S = sulfur.

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: THE ROLE OF POTASSIUM IN REDUCING THE INCIDENCE OF CROP DISEASES.

Winter 2010, No. 2

THE ROLE OF POTASSIUM IN REDUCING THE INCIDENCE OF CROP DISEASES

Potassium is essential for all plants. It is considered one of the macronutrients, along with N and P, because it is used in relatively large amounts compared to other nutrients. For example, an 80 bu/A barley crop will take up about 106 lb N, 43 lb P₂O₅ and 93 lb K₂O. Barley grain contains the majority of the N and P, with 74% and 79%, respectively. The majority of K, about 74%, is in the straw or residue of the crop. Although K is important to many vital plant functions such as plant enzyme activation, water regulation, energy capture from photosynthesis, N uptake and protein synthesis, starch synthesis, and root growth, K is not part of plant manufactured components such as proteins and oils. However, it also contributes to grain or fruit quality, helps prevent lodging, and increases crop disease resistance.

The simple explanation for increasing crop resistance to plant diseases is that by providing balanced plant nutrition, including adequate K, crop plants are healthier. A healthy plant is more able to resist invasion by disease organisms, and recover from a disease episode. However, besides just being healthier, there are other ways that K specifically helps plants resist disease.

Potassium helps crop plants resist disease organism invasion or penetration by strengthening cell wall structure. Plants having adequate K will have thicker cell walls compared to plants deficient in K. This makes it harder for disease organisms to penetrate plant cells and establish an infection. This applies to fungal, bacterial, nematode, insect, and viral disease organisms. Another indirect benefit from stronger cell walls is that plants are less prone to lodging, and stem and leaf architecture is more upright and spread out, thus improving airflow through the crop canopy. This can help slow down the spread of any disease organism through the crop canopy, and result in lower humidity levels that can reduce the growth of pests and diseases that prefer moist environments.

Potassium is also vital for water regulation in plant cells. There are two mechanisms of water regulation that help plants better resist disease establishment. Potassium is important for stomate cell regulation for pore openings on plant leaves. Adequate K nutrition will allow the plant to maintain smaller stomatal openings compared to a K-deficient plant, and also pores are opened and closed more easily and timely, which helps limit the successful invasion of disease organisms into plant leaves. The second water regulation mechanism that can help reduce disease organism penetration into plant cells is that adequate K nutrition helps the plant to maintain increased turgor, or water pressure in cells. A cell with optimum turgor pressure will tend to push organisms away from the cell membrane when the invading organism attempts to push through the cell membrane.

Adequate K in plant cells improves utilization of the building components required for synthesis of starches and proteins. This results in a lower concentration of low molecular weight carbohydrates such as sugars in plant cells. Many disease organism growth rates are increased if there is an ample supply of simple sugars or carbohydrates compared to larger structures such as starches. In a similar way, complex protein structures are more slowly utilized by many disease organisms, whereas higher concentrations of mineral N in the form of ammonium and nitrate, or N contained in basic amino acids, can facilitate more rapid disease organism growth.

Incidence of crop diseases can be reduced if attention is given to supplying crops with adequate supplies of K. There are two ways to assess whether or not a crop will have, or does have, adequate K. Soil testing for plant available K can show whether or not more K should be applied as fertilizer prior to planting. Plant sampling and tissue testing of crop plants during the growing season might show less than optimum levels of K in plant tissues, and increased K fertilizer rates should be considered for future short-season annual crops. In the case of long-season or perennial crops, there may be a benefit to topdressing K. Advice can be obtained from your local consulting agronomist or certified crop adviser, or from a soil and plant testing laboratory agronomist, to know whether or not K fertilizer might be beneficial.

-TLJ-

For more information, contact Dr. Thomas L. Jensen, Northern Great Plains Director, IPNI, 102-411 Downey Road, Saskatoon, SK S7N 4L8. Phone: (306) 652-3535. E-mail: tjensen@ipni.net.

Abbreviations: N = nitrogen; P = phosphorus; K = potassium.

Source : Plant Nutrition Today. International Plant Nutrition Institute.

ผ่านทางPNT: SOIL FERTILITY SHIFTS IN RESPONSE TO CROP NUTRIENT BALANCE.

Winter 2010, No. 1

SOIL FERTILITY SHIFTS IN RESPONSE TO CROP NUTRIENT BALANCE

Soil fertility rises and falls in response to crop nutrient balances. Nutrient surpluses raise soil test levels; deficits draw them down. It’s not always easy to predict how much, or what the consequences will be, so it’s important
for the crop manager to monitor both as closely as possible. Recent surveys of soil tests and nutrient balances on the state and province scale point to the need to pay close attention to the same on the farm and field scale.

A new soil test summary is out. The International Plant Nutrition Institute recently completed a survey of the public and private soil test laboratories of North America, similar to surveys done every 4 to 5 years for the past several decades by the Potash & Phosphate Institute. There are numerous challenges to conducting such surveys, since soil test methods and interpretations vary among states and provinces, and change over time as well. Nevertheless,
important and consequential trends are showing up.

The 2010 survey included more samples than any previous survey. An estimated 4.4 million soil samples were submitted across North America for this survey compared to about 3.4 million for 2005. The increase likely reflects more widespread and intensive soil sampling by producers, arising from higher and more rapidly fluctuating prices for fertilizers and crop commodities seen in recent years.

In Eastern Canada and the northeastern United States, the soil fertility shifts varied. In many areas, soil test levels for K have moved downward since 2005. For example, in the province of Ontario the proportion of soils testing 80 ppm or less in K grew from 15% in 2005 to 20% in 2010. Soils testing in this range are likely to produce K deficiencies in almost any crop in the absence of fertilization. This trend is not surprising, considering that the amount of K applied to Ontario cropland in the form of fertilizer and manure was only about half that removed by crops in 2009.

However, elsewhere the shifts varied in size and direction. In Pennsylvania, the distribution of soil test K hardly changed at all, while in New York and Virginia, it appears to have shifted upwards.

Soil test P levels often fall into a bimodal distribution. A substantial proportion are in the responsive range, but another large proportion are at levels far above the critical level for crop response. The very high levels result from many years of historical nutrient surpluses. Such soils need to be managed in ways that eliminate the surplus, maximize utilization of the P fertility for the benefit of crop production, and minimize surface runoff and erosion to protect water quality. The frequency of very high soil P tests continued to decline in Ontario, but increased in New York, New England, and Pennsylvania.

The soils of the region remain quite variable in fertility. Even in states and provinces with overall nutrient surpluses, many soils needing nutrient additions can be found. On the other hand, many soils have built up fertility to the point where inputs of P and K amounting to less than crop removal of the nutrient can continue for years. Of course, in such situations it would be important to monitor the decline with regular soil testing.

So, nutrient decisions need to be supported not only by crop nutrient balances, and not only by soil tests, but by both. Using the two tools, you can manage nutrients sustainably.

More detailed information on these changing nutrient balances and soil test levels can be found at this site: http://nane.ipni.net.

-TWB-

For more information, contact Dr. Tom Bruulsema, Northeast Director, IPNI, 18 Maplewood Drive, Guelph, Ontario N1G 1L8, Canada. Phone: (519) 821-5519. E-mail: Tom.Bruulsema@ipni.net.

Abbreviations: K = potassium; P = phosphorus; ppm = parts per million.