Drought Planning

Drought. We know how it’s affected the crops, and we’re beginning to see how it’s affecting supplies and prices. But how will it impact our nutrient management for the next crop? Here are some issues to consider.

Residual Soil Nitrate

Soil nitrate can be higher after a drought. Decreased downward movement of soil water and reduced nitrogen (N) uptake by stressed plants are key causes. Whether or not residual N will be available for next season’s crop depends greatly upon the precipitation that occurs after the harvest of the present one. For instance, research in Minnesota has shown that precipitation occurring in early spring to early summer is associated with higher losses of nitrate in tile drainage.

Pulses of nitrogen can also occur any time dry soils are rewetted. As soils dry, organic matter releases N (mineralizes) more slowly, approaching zero under very dry conditions. In addition, some soil microbes are killed. When dry soils are rewetted, a sudden pulse of inorganic N may occur, termed a “flush” or a “hot moment.” This pulse can last for days to weeks. A significant portion of this flush is thought to come from the decomposition of the microbes recently killed during the dry spell. Another contributor to the flush is the release of organic compounds from the reactive sites at clay mineral surfaces.

Because the fate of unused N is so uncertain and relies so heavily on environmental conditions, it is advisable to incorporate soil N tests as part of the decision-making process for the next crop. Soil N tests are the best early-season diagnostic tool for assessing the quantity of residual soil N that could potentially be available. States vary considerably in their suggestions for use of soil N tests, so consulting local guidance is required.

A strategy that can help keep N from leaving the rooting zone is planting cover crops. Local expertise is needed to manage these successfully, because there are many considerations beyond just nitrate recovery.

Among these are choice of cultivar, soil moisture depletion, pathogen carryover, and how well the release of N from the cover crop is synchronized with the following crop’s nutritional needs. Cover crops have been shown to scavenge significant amounts of residual soil nitrate, reducing how much leaches into tile lines; however, they must be managed properly to benefit the entire cropping system.

N Credits From Soybeans

The soybean N credit is a reduction in the N recommended for corn following soybean compared to corn following corn. While the exact causes of this reduction are still under investigation, several contributing factors have been identified.

The most commonly cited factor in the N credit is biological N fixation. In an Illinois study comparing nodulated to non-nodulated soybean isolines, soil N supplies were higher after nodulated soybeans than after non-nodulated soybeans. However, both types of soybeans produced higher N supplies than where corn was grown. Consequently, additional factors beyond just biological N fixation are important for determining the N credit.

Soybean also appears to produce a pool of readily mineralizable N in the soil. This pool is thought to come from the soybean roots and the organic compounds they release. Decomposing soybean residue therefore releases N quicker than corn residue — soon enough to be used by the succeeding corn crop, which reduces the amount of fertilizer N needed.

During a drought, N mineralization slows, and biological N fixation in soybean nodules lessens. Drought can reduce both the number of nodules on soybean roots as well as the quantity of N fixation in the nodules themselves. All of these changes can result in a decrease in soil N supply for the following corn crop.  It is not clear just how much the N credit is affected. Sparse data indicate that the credit may range between half to the full rate normally used.

Nutrient Budgets

After harvest, nutrient budgets will need to be reassessed. Here are a few things to consider.

First, crops planted for grain were, in many areas, harvested for forage instead. Any time there is a change in how much of the plant gets harvested, there is a corresponding change in how much of each nutrient is removed from the field. For instance, about 20% of a corn plant’s above-ground potassium (K) is in the grain. If corn gets cut for silage instead, the entire quantity of K in the above-ground plant parts gets removed, rather than just the 20% that was originally planned for. If these changes go unrecognized, unwanted depletion of soil resources can occur.

Second, some growers who have planted cover crops to guard against soil erosion, reduce runoff and capture soil nitrate, are planning to harvest those cover crops because forage supplies are so short. Deciding to harvest, rather than leave, these crops increases nutrient removal beyond what was originally planned.

Third, tissue testing is a best practice this harvest season. Drought may or may not cause an increase in nutrient concentration, depending on which plant parts were harvested and analyzed, what crop was grown, and when the drought occurred. A classic example is high nitrates in drought-stressed corn cut for silage. Measuring nutrient contents in harvested crop portions takes the guesswork out of how the drought affected nutrient removal.

Soil Testing

No article on the drought would be complete without at least mentioning the need to test soils this season. In many areas of the Corn Belt, K tests will be particularly prone to some large variability from previous years’ tests, so it is good to be prepared for the possibility that some results may take some additional time to interpret.

Soil testing remains the best and most scientifically sound approach available for determining rates of nutrients needed.

Drought created a lot of unforeseen changes in nutrient cycles that could impact future management. Reassessments are critical. Measure the nutrients in the crops removed this year, whether it was grain or forage.

Compare that removal to what was planned and reexamine nutrient budgets. Measure what’s left in the soil to make informed adjustments to future applications of nutrients.

The cropping system connects source, rate, time and place decisions of 4R Nutrient Stewardship to nutrient performance. The cropping systems throughout much of the U.S. underwent a real shock in 2012 causing a need to reevaluate what “right” means for 2013.

Topics: , ,

Leave a Reply

One comment on “Drought Planning

Fertilizer Stories
FertilizerFall Fertility 2014: Forecasting Fertilizer Use
September 7, 2014
Great crops this year have tapped the soil, and fall work is definitely called for, but how challenging will that get? Read More
Aerial view of the West Fertilizer explosion site
FertilizerFertilizer Companies Blame City For West, TX, Explosion
August 6, 2014
El Dorado Chemical Co. and CF Industries contend the city failed to properly train the first responders and had insufficient protocols in place to battle the April 17, 2013, blaze at West Fertilizer Co. that triggered the explosion. Read More
FertilizerThe Fertilizer Institute: New President, Renewed Energy
February 3, 2014
Chris Jahn relishes the opportunity to lead the organization through the challenging times ahead. Read More
FertilizerA New Cycle For Fertilizer Demand
January 2, 2014
Changes in the corn market could have a major impact on the crop nutrients sector in 2014, say experts. Read More
Top 100 Articles
Milan Kucerak, president/CEO, West Central
CropLife 100West Central Cooperative And Its New President Are A Match Made In Deviation
June 29, 2015
To appreciate just how unique West Central Cooperative is in the world of ag retail, an observer need only consider Read More
Winter Wheat
CropLife 100South Dakota Co-op Member Owners Vote No On Unification
June 26, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have announced that member-owners have voted Read More
CropLife 100The Andersons Acquires South Dakota Plant Nutrient Manufacturer Kay-Flo
May 20, 2015
The Andersons, Inc., ranked No. 22 on the CropLife 100, has purchased Kay Flo Industries of North Sioux City, SD. “This Read More
CropLife 100North Central Farmers Elevator, Wheat Growers Unification Approved By Board, Still Awaits Member Approval
May 13, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have voted to approve the Unification Read More
CropLife 100AgGateway’s Barcoding Initiative Progressing Nicely
May 8, 2015
According to legend (or Wikipedia), the first step towards modern bar codes came back in 1948, when Bernard Silver, a Read More
CropLife 100Pinnacle Agriculture Acquires Minnesota Retailer
April 14, 2015
Pinnacle Agriculture Holdings, LLC, ranked No. 6 on the CropLife 100,  has successfully acquired Liebl Ag, LLC in Ada, MN.  Read More
Latest News
Crop InputsLand O’Lakes, United Suppliers To Merge Crop Inpu…
June 29, 2015
Land O’Lakes, Inc. and United Suppliers, Inc. of Ames, IA, today announced their intent to merge their crop inputs businesses. Read More
FungicidesHelena To Distribute Unique Summit Agro Fungicide
June 29, 2015
RANMAN 400 SC fungicide, the only fungicide with a FRAC group 21 designation, is now part of the innovative Summit Read More
Eric SfiligojIARC Targets 2,4-D In Latest Report
June 29, 2015
The International Agency for Research on Cancer (IARC) has struck again. Earlier this year in March, this agency of the Read More
Milan Kucerak, president/CEO, West Central
CropLife 100West Central Cooperative And Its New President Are A Ma…
June 29, 2015
To appreciate just how unique West Central Cooperative is in the world of ag retail, an observer need only consider Read More
EquipmentCase IH Launches New Precision Air 5 Series Carts
June 29, 2015
Case IH recently introduced its new Precision Air 5 series air carts, developed to get the most from every plant’s Read More
InsecticidesVestaron Biopesticide Approved In California
June 29, 2015
Vestaron Corporation, a developer of insect control products derived from naturally occurring peptides, today announced that its VST-006330-EP biopesticide has received Read More
InsecticidesValent’s Zeal SC Miticide Receives EPA Approval
June 29, 2015
Valent U.S.A. Corporation announced today that Zeal SC Miticide has been registered by EPA with a new liquid formulation that Read More
Retail FacilitiesUnited Prairie Increased Plant Productivity With Junge …
June 29, 2015
Since 1979, Junge Control continues to provide ag retailers with highly accurate fluid and dry ingredient measuring, mixing and tracking Read More
Winter Wheat
CropLife 100South Dakota Co-op Member Owners Vote No On Unification
June 26, 2015
The Boards of Directors for North Central Farmers Elevator (NCFE) and Wheat Growers (WG) have announced that member-owners have voted Read More
ManagementAsmark Training Center Visit & A Merger No Go
June 25, 2015
CropLife Editor Eric Sfiligoj talks about a visit to the Ford B. West Training Center and the failure of the Read More
Crop InputsWinField: Here’s What We’re Seeing So Far T…
June 25, 2015
One of the most important things you can do throughout the season to help increase yield potential is to ensure Read More
Valent, Commodity Classic 2015
Industry NewsValent Garners FFA Honor
June 23, 2015
Valent U.S.A. Corporation today announced it has been named a 5-star member of the National FFA Foundation. This includes an Read More
Nester Ag intern Brad Nester
Crop InputsOhio NRCS’ New Conservation Practice Standard For Gypsu…
June 22, 2015
Ohio farmers wishing to use gypsum to improve soil quality now have access to technical information and possible financial assistance Read More
Industry NewsWest Central Creates New Executive Team
June 22, 2015
West Central Distribution, LLC officially announced the development of an executive team comprised of Dale Engan, chief executive officer; Michael Read More
MicronutrientsVerdesian Life Sciences Invests In People, Agricultural…
June 22, 2015
In mid-February, the USDA released its new 10-year agriculture projections. While the numbers are new, the theme was consistent. The Read More
Young corn plants
Crop InputsStudy: Crop Rotation Has Positive Impact On Soil Microb…
June 22, 2015
A study authored by Michigan State University (MSU) Department of Plant, Soil and Microbial Sciences assistant professor Lisa Tiemann is Read More
Crop InputsIndiana NRCS Unveils Interim Gypsum Practice Standard
June 22, 2015
Indiana farmers wishing to use gypsum to improve soil quality as part of on-farm conservation programs now have access to Read More
ManagementInside Monsanto’s Bid for Syngenta
June 18, 2015
Monsanto’s possible buyout of Syngenta could send ripples through the retail chain. Learn the latest developments with Retail Week guest Read More