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Crop Roundup: Nitrogen Fixation

04/25/2014 @ 3:04pm

Adequate levels of rhizobia organisms can help to increase nitrogen fixation; satellite imagery and mapping capabilities help growers identify yield-limiting factors; and developments in drought stress tolerance.

Adequate Rhizobia Populations Help Protect Soybean Yields

Maintaining adequate levels of rhizobia organisms in the soil can help increase nitrogen (N) fixation, potentially leading to higher yields, according to DuPont Pioneer agronomy experts. When a field is planted with soybeans in a corn-soy rotation, the rhizobia populations tend to remain adequate. However, when growers change from soybeans to other crops, such as continuous corn, rhizobia populations drop.

“Too little or too much water in a field also may impact rhizobia populations, but the effects are difficult to detect,” says Paul Carter, DuPont Pioneer senior agronomy research manager. “There are some indications drought may curb rhizobia numbers and limit the soybean plant’s ability to fix nitrogen.”
          
There’s no easy way to know a field’s rhizobia levels. If growers are uncertain — especially if they’re targeting yields above 50 bushels per acre — they may want to consider supplying additional rhizobia at planting. It can be a cost-effective way to help boost overall yields. Any field that’s never produced soybeans or that has been producing continuous corn for three years is a candidate for treatment with rhizobia inoculums.     
          
Fortunately, growers have the option of planting soybean seed that’s been treated with rhizobia inoculum. DuPont Pioneer provides a Pioneer Premium Seed Treatment (PPST) offering, PPST 120+, a premium on-seed, inoculant plus extender. PPST 120+ delivers a high concentration of beneficial rhizobia bacteria to the soybean plant.

PPST 120+ is an excellent companion to PPST 2030 FST/IST (fungicide and insecticide seed treatment) and helps prolong on-seed rhizobia life for up to 120 days or more. This provides added flexibility for growers, increasing effectiveness from the time the inoculant is applied until after the seed is planted.
          
“A seed treatment such as PPST 120+ helps provide inexpensive insurance — some peace of mind that nitrogen fixation avoids limiting yields,” Carter says. “As growers push yields to 60 or 70 or 80 bushels per acre, the crop will need more nitrogen. It’s important they exploit the plant’s ability to fix nitrogen as much as possible. This requires adequate rhizobia populations in the field.”
          
Growers may not realize how much N soybeans use during the growing season. Soybeans pull some N from the soil, just as corn does, but they also have a unique way of pulling nitrogen from the atmosphere. The mechanism is a soil bacterium, Bradyrhizobium japonicum, or rhizobia, that turns nitrogen gas in the soil into ammonium, a form the plant can use.

Unless there’s an abundance of N in the soil, the soybean plant will send out a chemical signal that attracts rhizobia bacteria to the roots. The bacteria invade soybean roots and establish colonies in rounded nodules on the roots. The plant supplies carbohydrates and minerals to the rhizobia, which then “fix” the N as ammonium, fueling plant growth and protein development.

 “Rhizobia are living organisms,” says Keith O’Bryan, DuPont Pioneer agronomy research manager. “Any condition that affects the amount of oxygen in the soil can limit their numbers. Stresses such as drought, water saturation, high soil pH or sandy soils can curb rhizobia populations.”  

In-Season Imagery Helps Farmers Grow and Protect Healthy Crops

In the midst of a busy growing season, farmers need immediate information about crop conditions across their fields. Now, the R7Tool by WinField has even greater satellite imagery and mapping capabilities, allowing farmers to swiftly detect in-season issues with nutrient deficiencies, pests, or disease to help protect yield potential.

Powered by GEOSYS technology, the R7 Tool is newly enhanced to provide imagery from three times the number of satellite imagery providers it had in 2013, targeting to deliver approximately 3,000 images (up from approximately 700 last year) and up to 20 cloud-free maps per field from April through August (versus an average of 12 maps per field in 2013.) Cloud-free maps are targeted to be delivered through the R7 Tool within 72 hours of satellite acquisition.

An interactive, web-based platform that performs detailed field-by-field analysis, the R7 Tool is the industry’s only provider of on-demand, in-season satellite imagery. This bird’s-eye view helps farmers identify emerging crop nutrition and agronomic problems, giving them and their local agronomists opportunities to find potential solutions that could help optimize return on investment.

“By working with a specially trained agronomy expert, farmers can use the R7 Tool to get the information they need to detect crop nutrition, disease and pest issues, which allows them to correct factors that could limit crop performance and compromise yield potential,” said Dave Gebhardt, director of agronomic data and technology, WinField.

Farmers who are interested in using the R7 Tool by WinField for their in-season crop management practices should visit with the R7 specialist at their local cooperative. These in-season images work in conjunction with the NutriSolutions analysis, which uses tissue sampling to provide customized plant nutrient recommendations. Additional information on the R7Tool and NutriSolutions tissue sampling and analysis can also be found at winfield.com.

DuPont Pioneer Announces New Innovation to Help Corn Plants Better Withstand Drought Stress

DuPont Pioneer announced its scientists have made a significant advancement in developing corn plants that successfully withstand drought stress.  In an upcoming edition of the scientific publication, Plant Biotechnology Journal, Pioneer scientists reveal a new finding that higher yielding corn plants succeed under drought conditions when naturally occurring ethylene stress hormone levels in the plant are reduced through a transgene. The study, “Transgenic Alteration of Ethylene Biosynthesis Increases Grain Yield in Maize under Field Drought-Stress Conditions” by Jeff Habben and colleagues is the most in-depth research effort of its kind reported to date in peer-reviewed scientific literature.

 “This advancement is particularly crucial at a time when the U.S. is experiencing a historic drought in places like California, and much of the world is worried about the continued availability of water to grow food crops, ” says Jerry Flint, vice president for Biotech Affairs and Regulatory at DuPont Pioneer. “The new advances in drought tolerant corn reflect the DuPont Pioneer commitment to identifying sustainable solutions to increase food availability to meet the needs of the people today, without compromising the ability of future generations to do the same.”

Drought advancements like these are critically important as drought remains the leading cause of crop yield loss and the effects of drought reverberate far beyond agriculture communities, causing global food prices to increase.  Already, the California Farm Water Coalition estimates that the drought in California has cost $5 billion as of February.  Estimated crop losses from a widespread drought in 2012 reached $40 billion in lost crops and livestock and U.S. crop prices hit historic highs due to the drought according to the National Climatic Data Center.
 
Study findings
The Pioneer research spanned testing in multiple locations in numerous genetic backgrounds over two years. Jeff Habben, scientist and lead author of the article explains that corn breeders at Pioneer have been developing hybrids that are productive under drought stress conditions for more than 80 years, starting its first drought-specific breeding program in York, Neb. in the mid-1950s.  This effort has been very successful in generating germplasm with improved drought tolerance and scientists are now achieving a better understanding of the underlying mechanisms that contribute to this productivity.

Importantly, the identified transgenic approach has the additional benefit of enhanced nitrogen use efficiency, resulting in another potential management tool for farmers. Renee Lafitte, a fellow author, who has evaluated tropical corn states, “It’s not just about improving productivity for farmers, we also need to maintain and improve sustainability of our land and water resources.  We believe that transgenes, in combination with superior hybrids and agronomic management, are the tools that can help farms be more sustainable and productive.”

Habben further discusses the study’s findings by noting that ethylene is a stress hormone prevalent in almost all plants, but in highly variable levels depending on plant type, plant tissue, and stress conditions. “We’ve always believed that corn plants are too conservative in their response to drought and readily terminate kernels or only partially fill the ear when drought hits,” states Habben, “so we are working to help the crop get through critical developmental stages by modulating ethylene levels to maintain improved yield stability.”

Pioneer leads the industry in on-farm testing using year-round managed stress environments. The advancements made in understanding ethylene biology have potential applications for other crops and could enhance the already strong Pioneer brand Optimum AQUAmax hybrid line-up developed through a native trait approach. Optimum AQUAmax hybrids are expected to be planted on more than 10 million acres in 2014.

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