Focus on These Two Things, Cut Costs Elsewhere

Chad Lee, Extension Agronomist, University of Kentucky

Farmers are looking where to cut production budgets for 2015. Three of my colleagues and I were honored to speak at the National Commodity Classic this year. During our presentation, one of my colleagues closed out our session by saying that the two things farmers need to do is: 1) use appropriate soil-applied fertilizers based on soil tests; and 2) use highly effective weed control, which probably includes a soil residual herbicide. All of us in the room agreed that these are probably the two things many farmers will cut in 2015.

Yield Goals Could Cost You This Year

Chad Lee, Extension Professor, Grain Crops, University of Kentucky

Recently, I worked with a small group of farmers who were interested in trimming costs, but not yield, in 2015. They provided their soil test values, historical yields, crop history, and intended production practices for 2015. Those producers reported that were applying $124 per acre more for fertilizer than what was recommended by the University of Kentucky. Even if we factored in enough fertilizer for the following soybean crop, they were spending about $100 per acre more. They were using yield goals to make their fertilizer decisions.

Producers enjoy farming based on yield goals. Yield goals are positive thinking. They are a challenge to the producer to try to reach higher yields. Annual budgets have yield goals. Loans require an estimate of income which requires a projected yield. Yield goals are easy to market and easy to understand. Yield goals also could cost you a lot of money in 2015.

The Dangers of Applying Fertilizers and Manures to Frozen Ground

Edwin Ritchey, Extension Soils Specialist, University of Kentucky

Some producers are taking advantage of frozen ground conditions to apply nitrogen to wheat fields or manure to corn fields. While this practice reduces the risk of compaction or rutting of fields, there are other factors to consider. Applications to frozen ground are at higher risk for runoff and loss of those nutrients.  When the soil is frozen or saturated, water is not able to infiltrate into the soil profile and the water and nutrients can runoff to adjoining properties or waterways. NRCS Code 590 prohibits the application of manure to frozen ground for this reason.

Which Fertilizer Recommendation is Best?

Lloyd Murdock, Extension Soil Scientist, University of Kentucky

There are two concepts for making fertilizer recommendations. Both take the same soil test but they usually result in two very different fertilizer recommendations. One is the Sufficiency concept and the other is the Cation Saturation Ratio (CSR).

The Sufficiency concept is based on local or regional research on similar soil types that find a level of each plant nutrient resulting in maximum yield. When a soil test is below this Sufficiency level, crops respond to the addition of the nutrients.

The CSR was developed in the 1940’s to create an ideal balance of calcium (Ca), magnesium (Mg) and potassium (K) that would result in maximum crop yields.

Fertilizer Use in Argentina

Note: The following is an update on fertilizer practices in Argentina over the past 20 years. The changes in fertilizer practices over time in Argentina are impacting fertilizer demands in a global fertilizer economy.

Martin Navarro, Graduate Student, Plant and Soil Sciences
John Grove, Agronomic Soil Science, Plant and Soil Sciences

It will soon be spring in Argentina, and fertilizer purchase decisions are being made. Unlike the U.S., where fertilizer use has been a common practice for many years, Argentina’s linear growth in fertilizer use began only 20 years ago (Figure 1). This increased use of fertilizers has been associated with a continued increase in crop yield (Figure 2). It should be noted that the severe drop in fertilizer use in 2008 and 2009 was due to a reduction in the area of corn and wheat,with a corresponding increase in the area of soybean.

Figure 1: Fertilizer consumption in Argentina, from 1990 to 2009.

 
Figure 2: Annual grain (corn, soybean and wheat, averaged together) yield in Argentina, from 1990 to 2009.
 
The nutrients most commonly purchased in Argentina are, in declining importance, nitrogen (N),phosphorus (P), sulfur (S), and potassium (K). Most soils found in the more productive region of Argentina (the Pampas) have high levels of bioavailable P because the soil parent material is rich in this nutrient. The use of S is increasingly common, as deficiencies of this nutrient are being increasingly detected. The soils of the Pampas are richer in bioavailable P, in comparison with soils found in other agricultural regions in Argentina. However, Darwich (1999) has reported significant declines in bioavailable P in these soils, relative to original levels, relative even to levels existing in the early 1980’s.
Despite the large increase in fertilizer use in the past 20 years, nutrient replenishment (replacement of nutrients removed in grain) is still very low and a topic of long-term concern.The fraction of total nutrient uptake that is recycled back to the soil averages about 34%, and replenishment of nutrient stocks with fertilizer averages about 41% for N, 61% for P, 6% for K,and 35% for S. This suggests that these soils will be progressively poorer in their fertility. This problem was also evaluated by Ciampitti and Garcia (2008), for soils of the Pampas region, and they concluded that only 31, 53, 1 and 27 % of the N, P, K and S, respectively, exported by crop harvest was replaced by fertilizer addition.

The situation has been improving with time, though only slightly (Figure 3). Phosphorus and sulfur replacement have made slow but steady progress, in part because fertilizers containing these nutrients are now being more routinely applied to soybean, the crop with the largest production area in Argentina. The Argentine fertilizer industry, as well as various Argentine governmental institutions, expects increased fertilizer consumption and greater nutrient replenishment, especially for nitrogen. This expectation is based on anticipated increases in the production areas of both wheat and maize. In Argentina, these cereal crops are generally better fertilized than soybean. Current wheat and maize production areas are now at their lowest levels in 30 years.

In conclusion, Argentine nutrient management is generally characterized by a negative soil nutrient balance, due to rates of replacement/fertilization that are lower than rates of removal. This has resulted in declines in bioavailable N, P, K, and S levels in Argentine soils. Given this context, appropriate fertilizer rates and sources are important to crop production in Argentina, slowing/preventing nutrient export and depletion of soil fertility. Diagnosis of the fertility needs for a field is based in knowledge of the field’s soil and soil testing is important to that knowledge base. Soil chemical analysis and good nutrient management practices are tools indispensable to sustainable Argentine agriculture.

Figure 3: Nutrient application/removal ratios in Argentina from 1993 to 2007.

References:

Darwich N. 1999. Niveles de P disponible en suelos pampeanos. (Levels of bioavailable P in soils of the Pampas). IDIA 409-412: 1-5. INTA. Buenos Aires, Argentina.

Ciampitti I., F. Garcia. 2008. Fosforo en rotaciones agrícolas de la región pampeana central: II. Balance de P. (Phosphorus in agricultural rotations in the central Pampas region: II. P balance). Actas CD XXI Congreso Argentino de la Ciencia del Suelo. AACS. Potrero de los Funes, San Luis.

Avoiding Anhydrous Ammonia Seedling Injury

Greg Schwab, Extension Soil Specialist
Plant and Soil Sciences, University of Kentucky

The extremely wet spring experienced over much of Kentucky has delayed anhydrous ammonia applications. When the soil finally is dry enough for field work to begin, corn producers likely will not be willing to further delay planting to allow anhydrous ammonia applications to become safe. The standard recommendation is to wait 7 to10 days after injection before planting corn, but delayed planting may also reduce grain yield. A second option is to plant corn and then sidedress anhydrous after corn emergence. If anhydrous ammonia is applied before planting, then care must be taken to avoid seedling injury.

The Problem
Free ammonia (NH3) in the soil is extremely to toxic emerging seedlings and their roots. When anhydrous is injected into the soil, it immediately begins to convert into ammonium (NH4+) by associating with hydrogen ions. Hydrogen ions can come from soil cation exchange sites, but most come as a result of splitting water molecules, leaving behind hydroxyl ions (OH-). This reaction dramatically increases the soil pH at the injection site, which allows some free ammonia to exist in the soil for some time. Several soil factors, including moisture content, texture and temperature, affect the length of time that ammonia persists in the soil. Low soil moisture causes the ammonia to persist longer in the soil, as does cooler soil temperatures. However, shot-term ammonia concentrations are higher in warm soils. Excessive soil moisture increases chances of ammonia loss.


For more on this issue, go the Corn and Soybean Newsletter.


Many anhydrous ammonia applications were delayed because of the wet weather.


A handheld pH meter can help you quickly determine the soil pH, and thus, the risk of ammonia injury to germinating and seedling corn.