Northcentral

Higher nitrogen (N) prices are of concern for farmers who have not already applied their N nor prepaid for this spring's requirements. Whether you're dealing with the higher prices or not, here are a few points to consider about N fertilization.

Account for all N sources
• When appropriate, sample soils to determine nitrate levels. Some universities provide guidance on the timing, depth, and number of cores to take for these samples as well as adjustments for precipitation.
• Figure in the nitrate concentration in irrigation water. Although the amount of irrigation water used varies from year to year, average amounts used over the past few years may serve as a basis for planning.
• Consider taking N credits after a legume. Legumes cause a greater net mineralization of N from soil organic matter, reducing the N rates required for subsequent crops.
• Account for N and other plant available nutrients recoverable from manure.

Consider different times of application
A portion of the N may be applied pre-plant, side-dressed, or interspersed throughout the season. Generally, N applications become more efficient when applied closer to the times when plants have greater N needs.

Watch and evaluate
Look for signs of nutrient deficiencies, not just N but other nutrients as well. An end of season evaluation for N nutrition of corn is available with the stalk nitrate test. This test can help determine if N nutrition was sufficient during the season.

Consider bumping up the intensity of management
More intensive measuring and monitoring better characterize N needs and improve the ability to evaluate current management approaches. Keeping more detailed as well as more frequently updated records increase the chances of managing N in ways that maximize profit in more areas of the field.

RESEARCH RESULTS: Which crops responded to N, phosphorus (P) and potassium (K) fertilizers in 2002? They include corn, soybeans, tomatoes, peppers, wild blueberries, mixed forages, and brown midrib sorghum-sudangrass. Combinations of N and P improved marketable yields of peppers and tomatoes in Ontario, and P improved soluble solids in tomatoes. Check out the interpretive summaries of regional research at www.ppi-ppic.org/northeast

Reports on the land area where manure has been applied are available. The 2001 Census of Agriculture in Canada provides us with information on the area over which livestock producers report spreading manure in 2000. As a percentage of the total land in crop and fallow, manure was applied to 4.8% of this area in Manitoba, 1.4% in Saskatchewan, 4.7% in Alberta and 14.4% in British Columbia. As a percentage of total crop and pasture land, commercial fertilizers were applied to 69% of the land in Manitoba, 59% in Saskatchewan, 56% in Alberta and 41% in British Columbia. Obviously, these Census statistics illustrate that manure plays a small role in meeting the nutrient needs of crops in this region.

While the area where manure is applied is relatively minor, the nutrient application rates are high. In the publication Plant Nutrient Use in North American Agriculture, PPI estimated the recoverable manure nutrients by Canadian province from livestock populations reported in the 2000 and 2001. Using the manure application acreage reported in the 2001 Census of Agriculture, and estimated recoverable manure nutrients, we get a better picture of how nutrients can accumulate in excess of crop requirements. Our estimate is that, on average, manure nutrients were applied at a rate of 37 lb N/A and 63 lb P2O5/A where manure was applied in Manitoba. In Saskatchewan the rates were 34 lb N/A and 53 lb P2O5/A, 57 lb N/A and 87 lb P2O5/A in Alberta, and 69 lb N/A and 81 lb P2O5/A in British Columbia.

Making the most of manure nutrients requires diligent use of nutrient management tools. Soil testing, calculated nutrient inputs and crop removal and careful attention to the sensitivity of adjacent lands and water, all form the basis for an effective manure management plan. Every effort must be made to assist livestock producers in developing and implementing manure management plans that minimize environmental impact, while at the same time building soil productivity with this valuable nutrient resource.

Nitrogen (N) prices have recently taken a turn upward as the result of increases in natural gas prices. Whenever fertilizer prices increase, growers and ag suppliers question whether cutting back is a good idea. Studies across the U.S. have shown that fertilizer price has relatively little effect on optimum rates of application. For example, data taken from a long-term irrigated corn study in western Kansas has shown that an increase in N price of $0.20/lb ($0.15 to 0.35) results in a decrease in optimal N rate of only 12 lb/A when corn is at 2.50/bu. Optimizing N use efficiency is important whatever the price. Practices such as testing for soil nitrate and accounting for legume and manure N are necessary for fine-tuning N rates. Also, making sure available P and K are adequate helps the crop get the most out of every pound of N applied.

For everyone, the economy continues to be the main issue. Tight funds at the farm and retail levels will lead to a lot of tough decisions. It is important to make them with a full complement of information. Reviewing what is known helps to guide the right choices to prepare for the uncertainties that always lie ahead. Dramatic rise in nitrogen (N) prices in the late winter have added further uncertainty and concern. Changes in plans may be necessary, but should be done carefully.

Reviewing latest soil tests is a good place to start. While testing for N still has questionable value in many situations, it may help to have that information on the table. At least as important to N management is a good soil test for phosphorus (P) and potassium (K). Potassium, especially, has a major impact on efficiency or N use by crops. It is not uncommon to see 20 to 30% improvement in N use efficiency just from building K soil tests to the optimum levels. If K tests are low, even in parts of the field, it may be wise to spend the fertilizer dollars on K first, even though the most common approach would be to rob K dollars to pay for the N.

If you don't have a recent soil test, there may be time to get one done before planting. Use caution in interpreting spring tests. On many soils, considerable K is released over the winter and spring tests tend to give elevated values. Recommendations may need to be adjusted for this effect to be sure enough K is available.

Some farmers are considering switching crops as a reaction to higher N costs. Some may be growing soybeans on more acres instead of corn. Changing crop rotation plans should not be done lightly. Review the reasons behind the current plan and thoroughly analyze options before upsetting a well-designed cropping system. Soybeans following soybeans can cause some serious yield reductions that will easily overshadow savings on N. If changes are made, don't forget to go ahead with the P and K that would normally be applied for the corn, especially if the normal practice is to fertilize only for the corn year. The nutrient plan should not be interrupted.

Changing to other crops not normally grown is a big risk. Lack of experience with a new crop is an immediate caution. The uncertainty of market is another major concern. Proceed carefully. Major adjustments can greatly increase exposure to uncertainties. The best approach is to proceed with a well-developed plan. Review all available information to fine-tune nutrient management plans. Take extra effort to do all field operations in a timely fashion and use the best practices available. Then 2003 can still be a good year if the right steps are taken for good management.

Many fields that were rutted during a wet harvest last fall and winter have been smoothed and are ready to receive any fertilizers that were not applied last fall. If wet weather continues, farmers will be facing a conflict of time for planting and fertilization operations.

No firm planting intentions by farmers are known at this time. Last year's acreage of major crops is expected to be maintained, largely due to the absence of information to the contrary.

Forest management and forest fertilization does not look as attractive this year as a result of poor pulpwood prices, which detract from thinning operations in pine plantations that should precede fertilization operations. Some southern public tree nurseries are reporting a surplus of pine seedlings because of reduced pulpwood and timber harvests, which result in a lower replanting demand.

In the east, winter grain crops are rated as fair to good, with as much as 20 to 25% rated in poor condition. Wheat fertilization has begun in much of the region. Aerial application is being relied on in much of the midsouth area because fields are too wet to travel with ground applicators. Many of these midsouth fields may be receiving diammonium phosphate (18-46-0) with the first nitrogen (N) application to help offset the potential for phosphorus (P) deficiency on cool, wet soils that have marginally sufficient soil test P levels.

Nitrogen price and N fertilizer availability is a concern among farmers and many fertilizer dealers. Cotton, corn, rice, sugarcane, and forage producers are deliberating over their N purchases this spring. Since cotton is a major crop common to the majority of the Southeastern states, PPI developed N rate response graphs, based on university research across the Cotton Belt. These graphs and a comparison of economic optimum N rates for cotton, across a range in N prices and cotton prices, have been posted to the PPI-PPIC website and will be made available to farm press editors and others. (website: www.ppi-ppic.org.) The cotton N response data indicate that the economic optimum N rate is affected little by considerable ranges in fertilizer N price or a range in cotton prices. This information will help to guide farmers and their crop advisers in making N rate decisions this spring, and remind them that significant reduction in N rates could negatively impact farm profit potential.

In the Western U.S., two major factors always must be considered when gearing up for a new season. Much of the region is perpetually short of water during critical times. Where plentiful irrigation water is available, high production levels are common. However, many areas rely on rainfall and snowmelt for water. After several years of back-to-back below-average rainfall, the moisture condition is growing desperately critical in many areas.

In addition to adequate water, crop growth is frequently limited by an inadequate supply of nutrients. The reason we fertilize is simple: it's a good return on an investment! The old adage "better late than never" may work in some circumstances, but it is not true for plant nutrition. If the plants go without adequate nutrients during periods of peak demand, yield potential is lost forever - it will not ever reach back in time and catch up! It's kind of like a raincoat - it is always better to put it on before the rain starts.

It should be obvious that high yields put a serious drain on the soil nutrient supply. With the recent rise in fertilizer prices, everyone is trying to maximize crop production while being as efficient as possible with all inputs. However, trying to conserve on nutrient applications due to rising fertilizer prices and limited water is frequently a poor economic decision. It has been known for many years that when adequate amounts of phosphorus and potassium are present in the soil, crops use nitrogen (N) fertilizer more efficiently. This efficiency factor is always important, but becomes even a greater concern when N fertilizer prices increase.

Similarly, plants supplied with an adequate nutrient supply have a larger and healthier root system - resulting in greater water use efficiency. Whether water is scarce again this growing season - or if late season storms ease the drought, balanced nutrition is one of the best investments you can make in yourself and in your crop.