Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Illinois research zeroing in on optimum soil nitrogen rates

02.09.2005


A new study to evaluate the Illinois Soil N Test (ISNT) calls into question traditional soil fertility recommendations and promises a radical new soil-based approach that will benefit crop yields, the environment, and the bottom line for farmers.

In a forthcoming issue of the Soil Science Society of America Journal, scientists at the University of Illinois at Urbana-Champaign will outline how current nitrogen recommendations are faulty, the soybean credit is invalid, and balanced fertility makes for optimum nitrogen uptake. As well, the article highlights the importance of plant populations and crop residue management for proper usage of nitrogen fertilizers.

"Our work involved 102 on-farm nitrogen-response studies conducted throughout Illinois in six growing seasons from 1990 to 2003. A site-by site evaluation of the proven-yield method showed that current fertilizer recommendations are not only wrong, they are scientifically indefensible," said Richard Mulvaney, a professor of soil fertility.



"We’re on the edge of a revolution in nitrogen fertilizer recommendations," said Saeed Khan, a research specialist in agriculture and co-developer of the ISNT that estimates the soil’s nitrogen-supplying capacity. "We’re going away from yield-based management to a system that quantifies the main source, which is the soil,"

"The traditional ’proven-yield’ approach says higher yielding areas need more fertilizer nitrogen, whereas crop nitrogen response is typically lowest in these areas. We have found that what matters most is how much nitrogen comes from the soil. Rich soils need less nitrogen from fertilizer, while poorer soils need more," Mulvaney said.

Balanced Fertility

Mulvaney and his colleagues looked at several sites where a high ISNT value was incorrect in predicting negligible response to applied nitrogen and concluded that balanced fertility is key to efficient crop use of fertilizer nitrogen.

"Two of these sites had a soil pH down around 5. It has been known for a hundred years that acidity inhibits the mineralization of nitrogen," Mulvaney said. "So although these soils tested high by the ISNT, the nitrogen wasn’t available to the crop because of reduced mineralization."

Low levels of potassium and/or phosphorous were noted for other high-testing sites that were unresponsive to nitrogen.

"Low potash levels in the soil can limit the utilization of nitrogen," Khan said. "For example, potassium is involved in numerous enzymatic reactions in the plant, so even though nitrogen may be taken up when potassium is deficient it won’t be utilized efficiently in making amino acids, proteins, and many other essential plant components."

Plant Populations

A decade ago, the normal plant population for corn was 18,000 to 24,000 plants per acre. Today, it’s more like 30,000 to 35,000 plants per acre.

"We noticed that several of the sites where the ISNT failed in recent years had much higher plant populations. And this makes perfect sense, as a larger soil reserve would be required to feed more plants per acre. So we’ve realized that it would be necessary to adjust the critical test level according to plant density," Mulvaney said.

"This fact has far-reaching consequences. It means that we now have a basis for both variable-rate planting and nitrogen fertilization," said Khan. "So, if a farmer has a high ISNT value in part of a field, not an unusual occurrence, he can boost his planting rate somewhat to take advantage of a greater soil nitrogen reserve. Or vice versa, if an area has a low ISNT value, the farmer could plant lower populations or add more fertilizer."

Crop Residues

Increased plant populations lead to more crop residues after harvest, below as well as on the soil surface. The extra residues have an effect on soil nitrogen cycling and availability, and can increase the critical level for the ISNT.

"Crop residues are about 40 percent organic carbon," Mulvaney said. "There is an inherent link between microbial cycling of carbon and nitrogen that has long been overlooked in managing nitrogen fertilizers. With higher planting rates, more nitrogen will initially be tied up or immobilized, but some of this will subsequently be released or mineralized as the microbes die and decay."

The Soybean Credit

Higher planting rates have also impacted the proven-yield practice of reducing nitrogen recommendations by 40 pounds per acre when corn follows soybean.

"We have seen ISNT levels that are higher in corn-after-corn than corn-after-soybeans, which is consistent with the greater nitrogen requirements we observed for a corn-soybean rotation," Khan said. "So in many cases, the proven-yield method is overfertilizing continuous corn and underfertilizing corn after soybeans."

The soybean credit originated several decades ago, when planting and nitrogen rates were considerably lower than at present. Soybeans are legumes. They nodulate and therefore fix atmospheric nitrogen, but are more apt to use soil resources when available. Mulvaney maintains that with today’s production systems, soybeans vary widely in their net effect on soil nitrogen availability, which was found to be negative when the ISNT value was high.

Need for Improved Soil Sampling

Although corn roots grow to a depth of seven feet, nutrient needs are often assessed by sampling only the upper seven inches of soil. "And fertilizer is seldom applied below this depth," Mulvaney said. "So I worry that we are depleting the subsoil, where the crop really needs the fertility, while we concentrate fertilizer where the crop doesn’t benefit from it as much -- especially in a dry year. I suspect we have to recalibrate soil tests to the most effective sampling depth -- whatever that is."

Gary Beaumont | EurekAlert!
Further information:
http://www.uiuc.edu
http://www.aminosugarntest.com

More articles from Agricultural and Forestry Science:

nachricht Alkaline soil, sensible sensor
03.08.2017 | American Society of Agronomy

nachricht New 3-D model predicts best planting practices for farmers
26.06.2017 | Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>