Farm Talk

Crops

November 26, 2013

Not all fertilizer bands play the same song

Parsons, Kansas — The often used expression, “Same song, different verse,” refers to something that is practically the same as something else. So often, P and K are used in the same sentence when people talk about banded fertilizer applications, as if both were different verses of the same song. Actually, P and K fertilizer bands play different “songs” because they behave differently in soil.

One of the primary reasons fertilizer is banded is to increase short-term efficiency of use by the plant. Bands of P are known to cause an increase in root proliferation, as are bands of N. Bands of K, however, do not have this effect. This means that bands of P will be explored more thoroughly by root systems than bands of K. The implication, of course, is that applying P and K together in a band will help make better use of the concentrated K supply, due to the increased root growth caused by P.

Bands of K may not remain as concentrated in soils over time as bands of P. There are a couple of reasons for this. First, crops like corn and soybean take up more K than P during the season. Corn takes up about two-and-a-half times as much K as P while soybeans take up about twice as much (expressed as K2O and P2O5). Secondly, K moves more in soils than does P, causing bands of K to become more diffuse over time relative to P. So, greater uptake combined with greater mobility limits the longevity of concentrated bands of K.

In the short-term, corn and soybean plants themselves redistribute K in soils to a greater extent than P. This occurs for a couple of reasons. First, K leaches from plant residue and unlike P, does not require microbial decomposition to be released. This means that K in the plant is returned to the soil more quickly than P. Secondly, a greater proportion of the K taken up by the above-ground plant biomass exists in the plant residues returned to the field. For corn, about 80 percent of the total K taken up is in the stover, compared to only about 30 percent for P. For soybean, the percentages are 45 percent for K and 20 percent for P. A lot of the K leached from plants occurs during senescence, before crop harvest, meaning that most of the K is redistributed into the crop row. Consequently, plants become effective redistributors of K in the soil, moving it from throughout the root zone and concentrating it to the row, particularly at the soil surface. While P is also redistributed in this manner, it is not done so to the degree that K is.

Just how long P and K bands will last in soil depends upon many factors. Soil mineral composition, rooting depth, environmental conditions, and soil wetting and drying cycles are but some of the many factors at play. To gain an idea of how long bands will last under a specific set of conditions, on-farm monitoring through soil testing is suggested. Select areas can be monitored frequently to gain a sense for band longevity, remembering that if bands are placed near crop rows, concentration of K by the plant may overwhelm detection of lower rates of banded K.

So the next time P and K bands are assumed to be the same, remember that they really have very different characteristics, both in the soil and in the way they interact with plants. Bands of P and K really do play different songs. £

1
Text Only
Crops
  • cornplantlatemay2.jpg WASDE report eases low crop price fears

    USDA’s April 9 World Agricultural Supply and Demand Estimates continued a series of recent reports that have offered corn and soybean producers a more optimistic grain-price outlook than what was expected for most of the winter, Purdue Extension agricultural economist Chris Hurt says.

    April 15, 2014 1 Photo

  • USDA: Corn acres expected to drop 4%

    The amount of American cropland devoted to corn is expected to shrink about 4 percent this year as farmers devote more acres to soybeans, the U.S. Department of Agriculture said last week.

    April 8, 2014

  • Bt-resistant rootworms ID’d in five states

    Researchers say bugs are developing resistance to the widely popular genetically engineered corn plants that make their own insecticide, so farmers may have to make changes.

    April 1, 2014

  • MU economist: Corn, bean price volatility next 5 years

    Expect volatility in the soybean and corn markets over the next five years, said Pat Westhoff, director of the University of Missouri Food and Agricultural Policy Research Institute (MU FAPRI).
    Look for corn prices to drop to $4 per bushel and soybean to $10 per bushel on average for the next five years, he said.

    March 25, 2014

  • marestail.jpg Plan now to control marestail in soybeans

    Controlling marestail in soybeans has been a big challenge for Kansas no-till producers in recent years.
    Because soybeans are generally planted later in the season, and marestail generally germinates in the fall or early spring, application timing and weed size are critical factors to successful control.

    March 18, 2014 1 Photo

  • Checking alfalfa for winter injury

    In the last couple of weeks, I’ve heard many concerns about alfalfa production for this spring.
    Cold temperatures and lack of snow cover are the two main issues producers are worried about for next season’s crop production, as certainly the alfalfa plant could die if exposed to extremely cold temperatures. In general, alfalfa plants can tolerate up to three weeks of winter injury before the plants are killed.

    March 11, 2014

  • soypods.jpg USDA reports on status of GE crops

    Genetically engineered (GE) varieties with pest management traits became commercially available for major crops in 1996.
    More than 15 years later, adoption of these varieties by U.S. farmers is widespread and U.S. consumers eat many products derived from GE crops — including corn-meal, oils, and sugars — largely unaware that these products were derived from GE crops.

    March 4, 2014 1 Photo

  • wheat-head.jpg Everest still leads Kan. wheat acres

    For the second year in a row, a variety of wheat developed by Kansas State University, is the leading variety in Kansas.

    February 25, 2014 1 Photo

  • RickReimer.jpg Innovation, exports fuel soybean demand

    Brent Hayek is revved up about potential new uses for soybeans, and he is piling up the miles to share his enthusiasm.

    February 18, 2014 2 Photos

  • red_clover.jpg Seed legumes on snowy fields

    Winter seeding clover over grass pastures works best in February. Frozen fields are ideal and a snow cover makes seeding easier.

    February 11, 2014 1 Photo

Hyperlocal Search
Premier Guide
Find a business

Walking Fingers
Maps, Menus, Store hours, Coupons, and more...
Premier Guide
Seasonal Content