Summer 2001

Northcentral

In many areas of the Northcentral region, Spring has been marked by cool, wet conditions. Many producers have had to plant late and some are still waiting to plant. Those who used starter fertilizer on corn in these areas have a good chance of seeing benefits. Applying fertilizer near the seed row during planting can produce significant yield increases under the conditions we are seeing now.

Many farmers originally planning on planting corn are now considering switching to soybeans or other crops that can be planted later, such as winter wheat. When planting has occurred, it has often been under less than optimum conditions, so soil compaction will likely be a more prevalent problem this year. The need for adequate supplies of K have been well demonstrated for corn under compacted conditions. The restricted rooting volume requires adequate K levels in the upper soil profile where the roots are located.

With so much prolonged wet weather, there is an increased chance of significant losses of N from denitrification. Denitrification is the conversion of soil nitrate to gaseous forms of N. This process results in the movement of N from the soil to the air. Many farmers are wondering how much of the N they applied is still left. Testing soils for nitrate may provide much needed information on how much, if any, additional N to apply. A watchful eye on the crop will also provide information on whether or not N appears to be sufficient.

With so many unknowns this season, it will be important to carefully monitor the crop as it develops. Visual deficiency symptoms may emerge, but plants can also be deficient in nutrients without exhibiting many signs. Tissue testing is a valuable tool that helps evaluate a crop's nutritional status, especially unseen nutritional needs, or "hidden hunger".

Owing to water quality concerns and a low corn:nitrogen price ratio, much attention is being given to reducing nitrogen (N) rates using the pre-sidedress soil nitrate test (PSNT). The PSNT, usually sampled in June, can be helpful in last-minute rate decisions. But it shouldn't replace the careful consideration of other important factors, such as expected yield, in-field variability, past crop history, and knowledge of the N cycle. The N rate decision is very much a risk management decision: balancing the risk of deficiency with the risk of unutilized nitrate in the soil following harvest. Factors that boost the crop's utilization of applied N include: selecting the best hybrid and population for high yield, early planting, and adequate supply of other nutrients including phosphorus (P) and potassium (K).

Cool weather in May should result in some excellent yields of hay and haylage. Replacing the nutrients removed is important, particularly following the first and second cuts. Producers can gain valuable information on the nutrient status of their forages, by examining the forage quality analysis for P and K concentrations. 2000 growing season reminded many producers of the importance of soil conservation. Heavy rains eroded many soils. As the 2001 planting season approaches, growers using conservation tillage practices will need to pay particular attention to starter fertilizer programs. The heavy snow cover persisting into March in many areas may result in cool soils at planting.

Flax has received considerable attention by the research staff at the Brandon Research Centre of Agriculture and Agri-Food Canada. A project recently initiated by Dr. Cynthia Grant is evaluating fertilizer P management on flax. Results to date from this project indicate that applying twice the P requirements to the crop before the flax may be the best way to fertilize flax in rotation. IMC is providing financial support to this project through its membership in the Potash and Phosphate Institute and Foundation for Agronomic Research. Results from this project will go a long way in helping to clarify those factors that are leading to the lack of response when P fertilizer is applied when seeding flax.

Planting of some crops continues but will soon be winding down. The majority of spring planted crops in the region are rated in the "fair" to "excellent" range by the state ag statistic services. With the generally good soil moisture and yield potential this season, growers should make sure that row crops receive adequate in-season N, and where appropriate P and K, for the production of optimum yield. Summer pasture and hay production potential is also good this year. Remember that where hay is harvested large amounts of nutrients are exported from the field. For example, each ton of alfalfa removes about 15 lb P2O5 and 60 lb K2O, hybrid bermudagrass about 46 lb N, 12 lb P2O5, and 50 lb K2O, and sorghum-sudan about 40 lb N, 15 lb P2O5, and 58 lb K2O. For growers to optimize forage quantity and quality and avoid depleting soils of needed nutrients an adequate and balanced fertility program must be employed. Consider topdressing established forage stands this summer with blends that include appropriated levels of P, K and other needed nutrients.

While this diversity in conditions is perhaps more typical than we have experienced in recent years, it has created challenges in crop and pest management. Slow growth seemed to enhance herbicide injuries where moisture and temperature was limiting. Populations of insect pests, such as army worms, were unusually high in some of these same areas. Each stress makes the crop more susceptible to the impact of other stresses later in the season.

Farmers and dealers who delayed anhydrous ammonia application last fall due to persistent warm temperatures were generally able to make up for it this spring. This practice helped reduce N losses and "bought" a lot of public awareness that farmers and the fertilizer industry were taking risks in taking positive steps to protect the environment through adjusting management practices.

Crop growth has accelerated as moisture and temperature improved in early June, except for smaller areas where corn and soybeans have not yet been planted. While the 2000 growing season seemed to favor the northern and southern areas more than the central Corn/Soybean Belt, the opposite seems to be happening in 2001. Timely rains will be critical to development of the crop in most of the southern and eastern Midwest. Delayed planting in some fields will increase the risk of drought later in the season.

Fertilizer rates were generally maintained for fields that were planted to corn. Where substantial acreage was shifted to soybeans, P and K applications suffered and N use decreased. The logistics of transportation and warehousing this year were more challenging than usual as a result of a combination of uncertainties of weather and of crop and fertilizer prices.

Looking ahead to summer months, we can expect the contrasts to continue and weather to be a dominant concern. Stresses from drought, high insect pressures and weed control problems will likely be above normal. Such stresses could also set the stage for increased disease incidence. Fields that have been "shorted" on potash applications in the past couple of years will be especially susceptible to stalk rot and lodging similar to the case in 2000. Watch for late-season K deficiencies in crops. The first visual effect is yellowing along the leaf margins. This eventually proceeds to necrosis (dying) of these leaf margins, and progression to the center of the leaf and to other leaves on the plant.

In soybeans the older (lower) leaves usually show the symptoms first, but in recent years the deficiency has been common in upper leaves of soybeans as well, especially after full bloom. This may be due to the roots drawing water and nutrients from lower in the profile in soils with low K levels in the subsoil. The rapidly growing upper leaves compete with the developing pods on the lower part of the plant…and lose the fight for limited nutrient supplies. This condition seems more common in reduced tillage and ridge-plant situations.

In corn, K deficiency also causes necrosis of leaf margins, but another symptom is increased stalk disease and decreased lodging resistance. Lodging is the result of the combined effect of several factors, but low K level in the plant is commonly one of them. Where K soil test is high, the plant is better able to withstand the effects of injury due to insects, nematodes, disease, and even low water supply. High K in the plant maintains efficiency in use of water and other nutrients, making physiological systems function more efficiently.

Early planting in the central Corn/Soybean Belt areas will likely mean earlier maturity, depending on growing degree day accumulation during June. Early pollination of corn should lead to early maturity. Farmers should be ready to harvest earlier than normal to avoid losses. Early harvest in turn means soil sampling and fertilizer application for the 2002 crop could start early as well. Dependence on day length to trigger maturity means soybean maturity is less likely to be advanced due to early planting. But the dynamics of weather/crop interaction will still impact pod filling, disease pressures and overall yield potential. 2000 season closed out with mixed signals for planning for 2001.

The fall was generally open for field activity, although many areas of the central Midwest suffered severe lodging in corn, slowing the harvest process. Late season disease problems, presumably triggered by drought stress, led to lower than expected corn and soybean yields in the central Corn Belt. Test weight and other grain quality components were reduced by in many cases. Farmers who have maintained strong fertility levels were better able to survive these stresses and realize better yields.

Peripheral areas had excellent yields and contributed to record or near-record yields for many farmers. Farmers followed the advice of university and industry specialists and held back on N application until the soil temperatures cooled to levels where losses are minimized. Unfortunately, rainfall came along with the cooler conditions and ended the season before all of the N could be applied. P and K applications were delayed somewhat by harvest problems, but movement was generally good.

If adjustments are needed for 2001, consider strip or starter placement as alternatives to help increase nutrient efficiency, especially in reduced tillage systems. If soil tests are high, placement is less of a concern and any method of application is acceptable.
What does this all mean for 2001 plans? We cannot predict what the coming growing season will be for any specific area, so the best approach is to plan for a good year.

Moisture shortages have been relieved in many areas. Where yields were higher than normal, adjustments may be needed to replace higher levels of P and K removed in the harvested crops. Where disease and lodging were a problem in 2000, pay special attention to soil test levels. Low soil P and K can contribute to late-season stress, premature dying of plants and reduced yields and grain quality.

Re-check N plans. Even with the higher prices, it is dangerous to reduce rates. Split application and side-dressing can help improve efficiency of N use and reduce losses. It also provides an opportunity to make late adjustments for expected changes in potential yield. But remember, if the crop runs out of N before maturity, potential yields and profits suffer. Tight profit margins make fine-tuning of management details especially important for 2001. Review records, soil test, and yield goals. Remember, cutting back on basic inputs like fertility is not likely to improve yields and profits. Maintain best management practices to hedge against growing season stresses.

Rainfall has been more abundant this spring and crops have emerged with good stands and prospects for good yields. Some drought stress can be expected each year as a result of the sandy nature and low water holding capacity of coastal plain soils. Strong "back to the basics" educational programs must be continued to remind growers of the value of a balanced nutrition program as a component of their overall production system of best management practices.

Educational meetings and conferences are abundant in the Southeast and the program content is focused upon site-specific management adjustments that improve crop yield and profitability. The value of a balanced nutrition program is essential for plants to best cope with stress conditions, to efficiently utilize available moisture and other inputs and to harvest the greatest part of a crop's yield and profit potential.

The Potash & Phosphate Institute is actively involved with the development of these meetings and is emphasizing the need to understand the basic functions of nutrients such as P and K in plant growth and how they contribute to improving productivity and profitability. The PPI is also working more closely with forestry and forage crops scientists to identify the need for improvements in nutrient management and to document for farmers the agronomic and economic value of fertilizing these millions of "cropland" acres for not only higher yields but also higher quality and value of the harvested crop.

Many farmers delayed any application of N on corn and cotton until the crops emerged to a good stand. Many have decided to increase the N applied at side-dressing because of the favorable moisture. Unfortunately, many elected to reduce or eliminate P and K applications on these same fields, which could limit crop N use-efficiency. Some fertilizer dealers and crop advisers are encouraging farmers to collect tissue samples for plant nutrient analyses before crop reproductive growth, to detect any potential nutrient imbalances in time to take corrective action.

Because of the recent relatively cool, moist weather, some cotton acreage is showing significant seedling disease injury, including black root rot. These weather conditions may have also favored the potential for Verticillium wilt in cotton. The early stages of Verticillium wilt can be easily confused with midseason or late season K deficiency. Farmers should consult their Certified Crop Adviser, fertilizer dealer, or county Extension agent to properly diagnose any foliage symptoms that resemble K deficiency, Verticillium wilt, or Fusarium wilt. If disease is not identified, and soil tests tissue (leaf blades or petioles) analysis confirm K deficiency, soil and/or foliar applications of K can help limit yield loss. The decision to apply any midseason K, should be based on: 1) knowledge of the soil moisture status, 2) the potential for rainfall or the ability to irrigate in a timely manner, 3) the fruiting maturity and boll load, 4) adequate insect control, and 5) an adequate amount of time (i.e. growing degrees) to allow bolls to mature after fertilization.

Adequate K nutrition may hinder the development of Verticillium wilt symptoms or reduce the severity of the disease in cotton, although the mechanism by which this occurs is not well understood. Potassium has been reported both to increase and to decrease disease severity caused by Rhizoctonia solani, to decrease the severity of leaf blights caused by Alternaria and Cercospora species, and to decrease the severity of Phymatotrichum root rot. Elevated K fertilization levels may help plants compensate for impaired nutrient uptake or translocation due to disease or nematode damage. Where available soil K is marginal, fertilization with N and P increases the requirement for K leading to increased incidence of Fusarium wilt because K requirements are not being met.

Forage crop fertilization needs should also not be overlooked. Good soil moisture has raised forage yields and the potential for increased hay harvests. Potassium should be applied in balance with N and other nutrients, especially in hay meadows, to at least replace harvest removal of plant nutrients.

Crop health and development should be monitored at least weekly…..in all crops. If problems are detected, …… or if there is a concern that the developing yield potential may exceed the pre-plant nutrient supply, plant tissue tests can be quite helpful in diagnosing nutrient imbalances. Farmers and Certified Crop Advisers should consult their plant analysis laboratory now to get instructions on proper tissue sampling methods, sample shipment, and the time required to receive the analytical results. This could expedite accurate diagnoses and corrective action to salvage crop yield potential.

Fertilizer management issues of current concern include efficiently managing 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 P (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 likely be completed for California during 2001. 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 are anticipated to be implemented before the end of 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.