Back-to-Basics: Regional Updates Archive

Higher fertilizer prices and sometimes limited supplies of fertilizer nutrients are causing many to re-evaluate their current fertilization programs. The International Plant Nutrition Institute has prepared several publications that are valuable resources for these times. The following list provides links to the online information:

Most of the major crops are in better shape this year than last. Rainfalls have been timely in Ontario and through much of the region, though the mid-Atlantic states have experienced some drought. Overall crop condition ratings are higher than they were last year.

Frequent showers in Ontario boosted the growth of corn, soybeans and forages, but made it difficult to make hay. Several records were set for rainfall in July. Many fields of corn look great but are starting to show signs of N deficiency. Moderate but steady temperatures have brought the heat unit accumulation up to normal.

Ontario wheat yielded above average, but with lower than normal quality owing to mildew and sprouts. The Ohio State University’s recommendations for wheat disease management include “Use a well-balanced fertility program and maintain a soil pH from 6.2 to 6.7. Be sure sufficient N, P, and K are available for good seedling growth in the fall. Excessive N may increase losses from foliage diseases.”

With prices for fertilizers and crops in unprecedented territory, managers need to be making careful decisions. The latest issue of Better Crops with Plant Food is focused on economics, and the article Corn Fertilizer Decisions in a High-Priced Market outlines how to ensure the right product is applied at the right rate, time and place.

Soon forage plants will enter the critical fall growth period, during which they store the carbohydrates they need to survive the winter. Adequate potassium (K) is essential for this carbohydrate storage. August is an excellent time to apply K fertilizers. Potassium is particularly likely to run short if previous harvests have been heavy. The amount to apply is an important decision. Make sure it's based on a recent soil test. It’s also helpful to look at the analysis results for K if you’ve sent forage from earlier cuts this year to the lab. Calculating a nutrient budget – nutrients removed by previous harvests minus the amounts supplied in manures and fertilizers – can also help determine the right amount to replace. For harvested cereals underseeded to forage, K should have been supplied at planting, but if it wasn't, applying as soon as possible after cereal harvest will ensure the seedlings develop into winter-hardy plants.

Manure applications following harvests of cereals and silage corn should be guided by soil tests and manure nutrient analysis. Rates should be appropriate to supply the soil's needs for P, K and organic matter. Avoid wasting N by ensuring a cover crop grows to absorb what is released from the manure.

Determining Fertilizer Rates in Times of Changing Crop and Fertilizer Prices
The year 2008 has been a time of great changes in crop production in the world and this has greatly affected farm economics in the Northern Great Plains (NGP) of North America. Grain and oilseed prices were higher in the first quarter of this year than at any time over the past couple of decades. There had been mention over the past 20 years that at some point world grain supplies would be low enough and demand great enough that prices would increase dramatically. That dramatic shift in prices occurred and the market forces of supply and demand were clearly manifested. For example, on December 5, 2005, when wheat supply was quite high and demand low, the wheat price was $2.93 per bushel ($108 per tonne).

Since that time, as wheat supplies decreased, wheat prices gradually began to increase until early 2007 from which time prices rose steeply as a result of increased demand caused by a clearly recognized low supply of world grain stocks. On March 10, 2008, wheat prices reached $11.94 per bushel ($439 per tonne).

The same market forces of supply and demand have affected crop inputs. As farmers world-wide strove to increase production, there was an increased demand for seed, herbicide, and nutrient inputs and prices have increased accordingly. Much of the nutrient inputs for the 2008 crop year were previously purchased in the fall and winter of 2007 and the fertilizer price increases during this calendar year (2008) did not affect fertilizer rate decisions much for this year’s crop. However, as plans are being made for the 2009 crop year many growers are asking if higher fertilizer prices mean that they should trim back the rates of fertilizer applied.

Before drastically reducing fertilizer rates it is important to consider the net revenue from producing a crop. Yes, fertilizer prices have increased, but grain prices have also increased. In most cases, the greater potential total revenue from crops more than covers the increased cost of the fertilizer. Most growers want to make sure they apply sufficient fertilizer to achieve target crop yields, but want to avoid over-fertilization. Over-fertilization not only can result in lower profit per acre, but also can affect the environment negatively. For example, excess N and P applications may result in increased potential greenhouse gas emissions of N2O to the atmosphere, and excess P loading to surface waters, respectively.

There are ways to assess the nutrient supply in a field, and then determine and apply the appropriate rate of fertilizer to apply for a specific crop. These time-proven practices are just as important when crop and fertilizer prices are relatively low or high. It is just that there is a tendency to emphasize them more when fertilizer prices are higher.

The first is to estimate the yield and nutrients required for the crop to be grown. Secondly, assess how much nutrients the soil in a field will supply to a crop, and lastly, if the crop demand is greater than the supply from the soil, the nutrient deficit is satisfied by supplying the required nutrients through a fertilizer application.

Row crop conditions across the region are for the most part in the good to fair range. Conditions tend to be somewhat better northward into Kansas and Nebraska. This is supported by the most recent crop and drought index reports. Crop and moisture conditions in the southern areas, particularly Texas, are more variable. It has been a particularly interesting year for cotton, an important crop in the region, with Texas being the biggest cotton producing state in the U.S. Hurricane Dolly essentially wiped-out the cotton crop in the Lower Rio Grande Valley of Texas with estimates of over 91,000 acres destroyed. Also, the High Plains of Texas has lost an additional one million acres of cotton to weather extremes.

Cool season grass production is an important component of many agricultural systems in the Great Plains. Cool season grass species can provide high quality forage and pasture for the fall and spring months. The yield and quality of these grasses can be significantly affected by nutrient inputs, hence it is a good idea to carefully evaluate fertility programs for these systems going into the fall. This is especially true in today’s environment, where we need to do everything possible to assure application of the appropriate balance and rates of nutrients. Following are a few basic fertility pointers to consider for cool season grass pastures and fields.

It is well known that N fertilizer can dramatically affect forage grass yield. For example, when averaged over 31 site years, N alone (120 lb N/A) increased bromegrass forage yield by about 1,400 lb/A in a long-term Kansas study. Nitrogen nutrition also influences forage quality. The primary effect of N on forage quality is usually that of increased crude protein. Up to a point, N application increases protein where other nutrients are not limiting. A good example of this was seen in an irrigated ryegrass study in Texas, where N fertilizer increased crude protein from 12 to 23%.

Higher N fertilizer prices make mixing legumes in cool season grass pasture an increasingly attractive option. Legumes are not a cure-all, but with proper management they can certainly enhance forage production systems and provide additional N. Local extension and seed industry professionals can help in identifying suitable species and establishment practices for specific environments.

Phosphorus can also significantly impact cool season grass yield. Phosphorus is most often associated with early root development, but it also affects winter hardiness, disease resistance, drought tolerance, early growth, and seedling vigor. It also impacts N and water use efficiency. Winter forages usually have higher P content than summer forages. Phosphorus application can increase P tissue levels, thereby impacting forage mineral quality.

The K level in cool season forage tissue is about the same as N. Where soil levels are low, K can dramatically improve pasture and forage crop performance. Other nutrients may also be needed for optimal cool season grass nutrition. Deficiency of S is not uncommon in cool season production. Yields may be increased and forage digestibility may be enhanced by application of S where deficient.

Finally, remember that nutrient release from organic matter in soils tends to be reduced during cool season production because of lower soil temperatures, thus increasing the probability of need for input from external sources. A soil test is usually a good foundation upon which to make nutrient input decisions. Complete and balanced fertility is key to producing optimal yielding and high quality winter pasture and forages.

Despite challenging conditions in several areas of the region this summer, crop conditions heading into the fall are fair to good across most states in the southeast. Kentucky and Arkansas are enjoying the best looking corn with 33 and 23% of the crop rated as excellent, respectively. South Carolina has dealt with some of the worst weather in the region and the corn crop suffered. Harvest is underway in South Carolina, with 48% of the crop rated poor and early yields are low as was expected.

Similar to corn, most states in the region are reporting fair to good conditions for the cotton and soybean crops. U.S. cotton acreage is down approximately 28% from last year; however, yields in the southeast and most of the mid-south are projected to be higher this year. Kentucky and Tennessee are projected to have the largest increase in average soybean yield over last year, up 13 and 12 bushels, respectively.

Regional Research Activities
IPNI continues to support research projects conducted by university specialists in the region. Several of those projects were highlighted this summer at various events. Dr. Brenda Tubana and Dr. Dustin Harrell, of Louisiana State University (LSU), and Dr. Tim Walker, of Mississippi State University (MSU), discussed their project “Precise midseason N rate determination for use efficiency and yield optimization in rice” at the Rice Research Station Field Day in Crowley, Louisiana. Their work focuses on developing an optical sensor-based strategy for determining midseason N requirements for rice using the crop as an indicator of N fertilizer need. Dr. Tubana is also conducting similar trials in cotton, corn, and sugarcane.

Dr. Brenda Tubana (left) and Dr. Dustin Harrell, LSU, discuss developing
an optical sensor-based N fertilization strategy for rice production.

Dr. Walker also discussed his work on starter N fertilizer for delayed-flood rice production. Results from his work indicate that starter N applications when applied to semi-dwarf cultivars planted on clay soils in the Mississippi River Alluvial Flood Plain can increase seedling plant height and moderately increase rice grain yield. For more information please see Dr. Walker’s article in Better Crops/Vol. 92 (2008, No. 2).

Dr. Peter Scharf, University of Missouri, is also working in the area of variable-rate N applications. At the Nitrogen Use Efficiency conference recently held in Manhattan, Kansas, Dr. Scharf reported results from field-scale studies using crop sensors to make in-season N rate determinations in corn. The figure below demonstrates the variability and range of N requirement often found in agricultural fields throughout the Southeast Region.

Finally, a reminder that the 2008 Southern Plant Nutrient Management Conference will be held in Olive Branch, Mississippi, on November 4-5, 2008. This year, we will feature an update on nutrient management for cellulosic biofuel crops, alternative N management systems, and new methods for determining liming requirements. Certified Crop Advisers are encouraged to attend all of the sessions on Tuesday afternoon and Wednesday morning for extra (CEUs) in soil fertility and plant nutrition. The site of the conference will again be The Whispering Woods Hotel and Conference Center which is just south of Memphis. The hotel room rate will be $99.00 per night for single or double bed accommodations. Please call 662-890-2886 for reservations prior to October 20, 2008. A block of hotel rooms has been arranged at the hotel, under the name “Southern Plant Nutrient Management Conference”. Conference registration will remain the same at last year, $50, and is payable upon arrival. This charge includes the use of facilities, breaks, and the banquet on Tuesday evening.

As the growing season winds down, make sure you keep good harvest records to help guide your decisions for next year. Keep track of the production from each field to identify areas that are trailing in yield or quality. A number of factors can be responsible for disappointing production, but identifying problem spots is the first step to correcting them. First look at primary growth factors such as adequate water and nutrients. Then consider insects, disease, and nematode problems that might be present.

The best way to troubleshoot nutrient problems is to submit matching samples for diagnostic analysis. Take samples from an area where plants thrived and also from an area where plant growth was poor. Submitting samples from both good and poor areas makes it possible to compare them and identify potential deficiencies or toxicities. Using both soil and tissue samples from problem areas is even more effective than either one alone.

The higher prices for fertilizer now have people asking if they can still afford to fertilize. However, it may be more appropriate to ask yourself: “Can I afford not to fertilize with current high crop prices?” So make a careful field-by-field determination of your profitability and determine how your nutrient inputs can support high profits and yield.

We need to continually reexamine how to use crop-growth inputs as efficiently as possible. Applying too little fertilizer will result in poor yields, while over application can result in waste of a valuable resource and cause potential environmental impacts. Don’t postpone careful examination of these important factors until planting season rolls around again. Use the winter to learn all you can about fine-tuning your operation.