Northcentral

In many areas of the Northcentral region, winter is not leaving quietly. March snow storms may mean a late start to spring tasks. Before the rush begins, it is important to have several plans in mind, so that things run as smoothly as possible when the window of opportunity opens. Fertility is an important part of the planning process. If late planting shortens the growing season, starter fertilizers may provide some needed maturity advancements to help the crop "catch up". If cool, wet conditions exist at planting, there is an increased chance that starters will provide economic benefits, particularly in reduced tillage systems. Concern over prices have many growers thinking primarily about N. However, it is important to take a balanced approach to nutrient management.

Too much of one nutrient and not enough of another limits yields and leads to inefficient use of nutrients and the money spent on them. For instance, N is used more efficiently by corn when K and P supplies in the soil are adequate. Several crops also respond to S, such as canola or corn grown in sandy soils. Potatoes respond well to P, and responses have been observed even at high soil test P levels. Sugar beets have recently been shown to respond to starter fertilizer containing both N and P. All of these crops require N, but the impact of the N applied depends heavily on the supply of other nutrients. The key is to think about all nutrients needed by a crop and to become familiar with the scientific research guiding their application. Only then will nutrient dollars be spent wisely.

Recent research has confirmed a higher frequency of response to starters in corn grown with conservation tillage systems. Specific nutrients to include in the starter depend on soil test levels, but in many situations all three of the primary nutrients N, P and K will help boost the vigor of seedlings after they emerge, and push yields to higher levels.

Specific conditions that improve chances of response to starters include:
• Cool, wet soils in the spring
• Warm soils at planting followed by an extended cool period
• Full-season corn hybrids planted late
• Soils testing medium or low in P&K
• Spatial variability in soil fertility

Even on fields testing high in P&K, crops may still respond to small amounts of banded or seed-placed fertilizers. Last year, for example, applying 140 lb/A of a 10-20-20 starter boosted corn yield by 17 bu/A, averaged over six hybrids, in a replicated no-till experiment near Hershey, Pennsylvania. The field's bulk soil test was high in P and optimum (medium) in K, but later grid sampling showed high levels of spatial variability within the field.

In response to the increased acreage of annual crops seeded with no-till, western Canada PPI director Dr. Adrian Johnston has worked with research scientists to evaluate the role of balanced fertilizer management in this new production system. IMC is providing financial support through its membership in the Potash and Phosphate Institute and Foundation for Agronomic Research. In the absence of tillage, there is a concern that immobile nutrients like P and K may stratify near the surface of no-till fields. Working on fields with high soil test K levels, addition of starter K to side banded N and P fertilizer blends has resulted in grain yield increases with spring wheat and flax. Continued research will determine if the response is due to an improper soil test determination of soil K levels, or a reflection of the minimal soil disturbance associated with no-till.

Nitrogen prices will be higher this spring than in the past. Many are asking how to best manage fertility under these conditions. Quantifying soil nitrate-N through soil testing and adjusting N fertilization rates accordingly is a good idea considering the high value of N. Some are questioning whether cutting N, and for that matter P and K, rates in response to higher N price is wise. Research across the U.S. has shown that fertilizer price has relatively little effect on optimum rates of application. For example, a long-term irrigated corn study in western Kansas has shown that a $0.10/lb increase in N price at $2.30/bu corn results in a decrease in optimum N rate of only 7 lb/A. The same study showed that where P fertilization was omitted net revenue declined by an average of $116/A/year ($2.30/bu corn and $0.25/lb N). Therefore, overreaction to N prices by significantly cutting rates should be avoided. Additionally, caution is advised in cutting needed P and K since this may result in substantial profit losses.

Farmers should be encouraged to get their plans finalized as soon as possible and be sure their orders are in. Their fertilizer application, tillage and planting equipment should be carefully checked over to be sure it is field-ready. Preventative maintenance and repairs done now will save costly delays when fieldwork begins. Replacing worn parts now will help avoid downtime and lost days in the field.

Recheck all soil tests and plans for fertilizer rates. By maintaining high P and K levels, maximum efficiency of N can be obtained. The optimum N rate for maximizing yield is often lower when P and K levels are high (Figure 1.) Higher yields can be obtained with less N when the K soil test level is high. Higher yields are obtained with the high K soil test scenario, regardless of the N rate.

Figure 1. Optimum N rate may actually be lower when
soil test K is at optimum level.

Matching N rates to realistic yield goals will ensure maximum efficiency of fertilizer dollars invested, and leave less of the N to potentially get into tile and surface drains where it can lead to water quality problems. A well-balanced N-P-K plan can ensure the nutrients are used by the crop and can help minimize environmental risks.

If the season gets tight and planting delays become a problem, it may be wise to consider side-dress N applications. Before making that decision, be sure equipment will be available to do the job. Starter fertilizer may also be a good idea this year. It will get the crop off to a faster start and help improve stand establishment. Under reduced tillage, early planting dates, and any condition that could cause early-season stress, starter can provide a critical boost to the crop.

Using ammoniated phosphates, MAP and DAP, can provide significant savings on overall fertilizer investment if there is a need for buildup and/or maintenance P application. The N that is included may be much less expensive than N from other sources. Where higher P soil tests would improve yields, now may be an excellent time to make those applications.

Farmers and dealers should prepare to improve record keeping, so that they can better track what is done, when operations are completed and what rates of all inputs are used. This will be important information for diagnosing field problems and for evaluating plans for future years. As markets for special genotypes or quality traits expand, and identity preserved crops attract a premium, good records may be a deciding factor in whether a farmer is able to participate in those opportunities.

Finally, it is important this season, as in any season, to plan for a good year. Any attempts to second-guess weather problems are a gamble. Best practices for a good year are usually the best tactic for reducing risks in a bad year.

The agronomic benefits resulting from proper fertilizer use are often overlooked by farmers and their advisers during periods of economic stress in agriculture. The recent surge in the cost of natural gas will not likely justify a retreat in N use below the crop's need for top-profit yield levels. Remember, N is the engine driving plant growth. Plants like cotton, corn or bermudagrass respond, not to fertilizer use economics, but to a physiological need for N for growth. Nitrogen often accounts for fifteen to twenty percent of yield for a crop like corn. Phosphorus and K add another fifteen percent or more to crop yield. Insufficient P and K might lower further the crops ability to efficiently utilize the N provided.

In the Southeast, it is time to plant corn, fertilize forages and get ready for planting other major crops such as cotton, peanuts as well as the assortment of ornamentals, fruits and vegetables. As the 2001 season unfolds, it is important to set attainable crop yield goals and then to provide the crop with the plant food needed to transform those goals into harvested yields. Knowledge has always been the basis for good decisions. Experience has always confirmed that fertile soils are not always the most productive but that productive soils are always fertile.

Some farmers are faced with difficult decisions with restricted budgets. Many will need to consider liming as a priority where soil pH levels have dropped below 5.2 to 5.5. Such acid pH levels reduce the ability of roots to explore the soil and to absorb many essential plant nutrients. Landowners need to help their tenant farmers in cost-sharing liming and fertilization expenses in 2001, to help the 2001 crop and to sustain soil fertility and productivity.

Cotton and soybean acres are expected to increase in 2001, at the expense of some corn and rice acres. Questions about drought avoidance with dryland production of cotton and soybeans presented opportunities to expose the benefits of a strong K fertilization component in the balanced fertilization program. Potassium enhances the water use-efficiency, and enables plants to transpire more effectively and cool themselves. Potassium deficient plants succumb to heat and drought more quickly and yield losses are greater than where adequate potassium has been applied. No-till and reduced-till plantings of both these crops may increase in 2001. Farmers need to pay close attention to providing adequate K fertilizer rates to compensate for any positional unavailability as the K stratifies (accumulates) in the upper few inches of soil. Recent K research with no-till cotton on high CEC soil (clay) in Mississippi, and no-till research on silt loam soils in Tennessee, suggest higher soil test K levels in no-till cotton are needed, compared to conventional tillage, to achieve optimum yields.

Much of the cotton and corn acreage may be planted before any N fertilizer is applied in 2001. Farmers want to maximize the N use-efficiency by more closely matching N application timing with plant growth and nutrient uptake demand. Attention to ample P and K nutrition will help ensure that plants will develop a vigorous root system, that soil moisture will be used efficiently, and that N uptake will lead to high yields and limited risk for environmental N loss.

Fertilizer management issues of current concern include:
• Efficiently managing nitrogen (N) inputs, both inorganic and organic, to avoid nitrate accumulation below the rooting zone. Improved soil test procedures and in-season application techniques are continuing to be evaluated and promoted by the research community. The Salinas Valley has been a focal point of such studies in California.

• Related to the dairy and other animal industries, there is increasing concern about manure management related to excessive accumulation of phosphorus (P loading) in the soil as well as N. The NRCS has developed P management guidelines for large CAFOs (confined animal feeding operations) in Washington, Oregon and Utah utilizing the P-Index concept and in Idaho utilizing the P threshold approach. Guidelines will be developed for California during 2001…and likely other states.

• Increasing acreage is moving to low pressure irrigation systems (drip or micro-sprinkler) for trees, vines and vegetables which meter water and fertilizer very efficiently. This is in response to water cost, likelihood of limited future supplies, and environmental (leaching) issues. Continued research is needed to determine how to maximize the positive interactions between nutrients and different irrigation systems.

• Regulations are being prepared in California to govern content of metal contaminants in P and micronutrient fertilizers. The proposed regulations have had several public hearings and apparently will be implemented in early 2001. The State of Washington has metal regulations in effect similar to the Canadian standards.

• Site-specific fertilizer management programs have been instituted by some dealers. However, these programs are still in their infancy. Progress is slowed by the diversity of crops in the west and the tight economy. Grain, potato, and tomato harvesters utilizing yield monitors are currently in commercial use.