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
Wheat Growers, North Central Farmers Elevator Pursue Merger
CropLife 100Wheat Growers, North Central Farmers Elevator Pursue Merger
March 3, 2015
Two CropLife 100 retailers — South Dakota Wheat Growers (ranked No. 11) and North Central Farmers Elevator (No. 19) — have entered into a Letter of Intent to unify the two companies into a newly named cooperative. Read More
Growmark Group
CropLife 100GROWMARK In 2015: Back, To The Future
March 2, 2015
The nation’s third largest ag retail organization is simultaneously moving forward while remembering its past. Read More
CropLife 100Pinnacle Expands Sanders Brand In The South
February 27, 2015
Pinnacle has acquired Hopkins Seed and Chemical in Qulin, MO, which expands the company's Sanders brand to nine Southern states. Read More
CropLife 100Pinnacle Launches New Providence Agriculture Location In Indiana
February 27, 2015
Pinnacle Agriculture Holdings — ranked No. 6 on the CropLife 100 — has established a new retail location in New Castle, IN, which will operate as part of Pinnacle's Providence Agriculture brand. Read More
CropLife 100Cooperative CHS Returns $518 Million To Owners
February 23, 2015
The 2015 cash return to owners is based on CHS net income of $1.1 billion, the company's second highest on record. Read More
corn field
CropLife 100The Andersons’ Humic DG Now Available In Canada
February 13, 2015
The Andersons, Inc. Turf & Specialty Group has announced its Humic DG product is now available to customers in the Canadian turf, agriculture and horticulture markets. Read More
Latest News
Crop InputsCommodity Classic 2015 Sets Attendance High Mark
March 4, 2015
With nearly 8,000 total attendees, the 2015 Commodity Classic convention and trade show, which took place last week in Phoenix, AZ, shattered previous records for the landmark event, Read More
Young corn plants
FertilizerNew Nitrogen Stabilizer From Simplot Protects Fertilize…
March 4, 2015
By using OmniPierce Technology, Eclipse-N from Simplot Grower Solutions coats and protects more nitrogen, increasing nitrogen efficiency and decreasing loss due to volatilization. Read More
Industry NewsOhio Corn And Wheat Growers Association, Ohio Soybean A…
March 4, 2015
The associations truly appreciate the comprehensive approach and diligent work that the Ohio House of Representatives has dedicated to addressing water quality and House Bill 61. Read More
Mahindra Implement
Industry NewsMahindra USA Aligns With Paladin Attachment For Impleme…
March 4, 2015
Mahindra USA will begin utilizing Paladin Attachments as its implement supplier in April 2015. Read More
Crop InputsValent BioSciences Acquires Mycorrhizal Applications
March 4, 2015
The acquisition adds another strategic platform to VBC’s rapidly expanding global biorational business, providing additional tools for the Biorational Window platform being developed with its parent, Sumitomo Chemical Co., Ltd. Read More
Nutrients for Life Foundation - Plant Nutrient on the Farm Station
Industry NewsNutrients For Life Foundation Launches New Station Prog…
March 4, 2015
This ready-to-implement station provides an interactive opportunity for farms to showcase crop nutrients’ important role in growing healthy crops. Read More
Adjuvants loading
AdjuvantsAdjuvants Continue Upward Trend
March 4, 2015
A dizzying array of developments in crop protection technologies promise to make specialty adjuvants a crucial piece of the puzzle going forward. Read More
Wheat Growers, North Central Farmers Elevator Pursue Merger
CropLife 100Wheat Growers, North Central Farmers Elevator Pursue Me…
March 3, 2015
Two CropLife 100 retailers — South Dakota Wheat Growers (ranked No. 11) and North Central Farmers Elevator (No. 19) — have entered into a Letter of Intent to unify the two companies into a newly named cooperative. Read More
10 Tips for Spring Planter Preparation
Equipment10 Tips For Spring Planter Preparation
March 3, 2015
Kinze Manufacturing offers advice on how to ensure your planter is ready before you hit the field. Read More
Industry NewsOABA 2015 LAUNCH Program Recognizes 20 New Graduates
March 3, 2015
Twenty Ohio agribusiness leaders are being recognized as the latest graduates of Ohio AgriBusiness Association’s LAUNCH program. Read More
EquipmentNew AGCO Website Helps Customers Shop For Certified Pre…
March 3, 2015
RoGator sprayers are among the wide range of CPO equipment available through AGCO's site. Read More
Enlist spray Demo
HerbicidesGuiding New Herbicide Systems’ Launches
March 3, 2015
Under careful watch, the new 2,4-D- and dicamba-tolerant crops hit more acres this season. Read More
Eric SfiligojCommodity Classic 2015: Playing The Waiting Game
March 2, 2015
There was plenty of future-talk at this year’s event as companies (and growers) are largely in a holding pattern of sorts. Read More
Industry NewsHighway Equipment Appoints New Director Of Business Dev…
March 2, 2015
Cory Venable, who joined Highway Equipment Company (HECO) in 2013 as OEM Account Manager, has been promoted to Director of Business Development. Read More
Prairieland FS employees
Eric SfiligojWorkforce Worries
March 2, 2015
Finding good employees almost always ranks as the No. 1 or No. 2 problem for ag retailers in our annual CropLife 100 survey. Read More
Growmark Group
CropLife 100GROWMARK In 2015: Back, To The Future
March 2, 2015
The nation’s third largest ag retail organization is simultaneously moving forward while remembering its past. Read More
CropLife 100Pinnacle Expands Sanders Brand In The South
February 27, 2015
Pinnacle has acquired Hopkins Seed and Chemical in Qulin, MO, which expands the company's Sanders brand to nine Southern states. Read More
CropLife 100Pinnacle Launches New Providence Agriculture Location I…
February 27, 2015
Pinnacle Agriculture Holdings — ranked No. 6 on the CropLife 100 — has established a new retail location in New Castle, IN, which will operate as part of Pinnacle's Providence Agriculture brand. Read More