Key Considerations For Manure Application To Soybeans

During the last decade, the number and size of confined animal feeding operations has continued to increase. In the Midwest, corn is the primary recipient of liquid manure from these facilities. However, while the density of production animals has continued to increase, the corn acreage available for manure application has not. To avoid over-application of manure to corn land, producers are pursuing other crops such as soybeans as alternative crops to receive manure.

Why Consider Applying Manure To Legumes?

The justification often applied for manure use on legumes is their ability to reduce N fixation when a readily available N source such as manure is applied. In addition, crops such as soybeans can utilize the phosphorus and potassium applied with the manure, thus reducing the costs of commercial fertilizer. For example, a 60 bushel/acre soybean crop in Iowa may remove up to 228 lbs. of nitrogen, 48 lbs. of phosphorus (P2O5) and 90 lbs. of potassium (K2O) per acre.

While there may be some economic, practical and environmental reasons to apply manure to both corn and legumes such as soybeans there are also some disadvantages of such practices.

Effects Of Manure Application To Soybeans

One area of concern is related to the environmental consequences of manure application to row crops such as soybeans, and specifically concerns about nitrate losses through subsurface drainage systems. Relative to environmental considerations, it should be noted that application of manure on corn residue prior to soybeans may have some benefit compared to application of the manure prior to corn on soybean residue since sufficient soil residue cover may be maintained with injection into cornstalks. In addition, there are questions on whether there are any negative impacts of manure application on soybean yields.

Yield Impacts

Several studies have been performed in the Midwest region of the U.S. resulting in positive yield increases related to liquid swine manure application on soybeans. However, there is no single conclusion as to why an increase in yield occurs. The studies identify yield increases from manure as the potential result of in-field initial nitrate, P, K, or other nutrient deficiencies. So, manure provided the nutrients that were deficient resulting in a yield increase and offsetting costs for purchased fertilizer. However, not in all cases was the yield increase sufficient to overcome application costs.

In addition to potential environmental concerns some studies have noted rare occurrences of reductions in soybean yield when manure is applied prior to soybeans and higher occurrences of common soybean diseases. A Minnesota study recommended that application of manure be avoided on fields with a history of white mold due to potential yield suppression due to manure application. Others have noted that manure application prior to soybeans can increase certain soybean diseases, specifically Pythium and Phytophthora damping off and Phytophthora root rot.

Another precaution that has been raised relative to liquid swine manure application to soybeans is that soybean seed germination and emergence can be sensitive to salts, so that if manure is applied close to planting time, there is a potential for injury especially if the soybean is planted into the manure or very near the manure.

Environmental Impacts

There have been few studies that have documented the environmental impacts of manure application to soybeans. A Minnesota study in the 1990’s evaluated the impact of liquid swine manure application on nodulating and non-nodulating soybeans. They found that applying manure at greater nitrogen rates than needed for maximum soybean yields did not adversely affect soybean yield. However, they found that application of nitrogen from the liquid swine manure increased post harvest soil nitrate levels. They also found greater increases in soil nitrate levels early in the growing season than post harvest.

Nitrogen

Manure application rates supplying from 0 to 446 lb N/acre in 89 lb N/acre increments were used in the study. Post-harvest soil nitrate levels were on average 37.7 lb N/acre (0-48 in) when no manure was applied and increased to 39.9, 44.4, 51.0, and 60.0 lb N/acre at applied nitrogen application rates of 50, 100, 150, and 200 lb N/acre, respectively. So, at an applied nitrogen application rate of 100 lb N/acre which might be about one-half of crop removal (soybean) the post-harvest soil nitrate was increased by about 15% compared to when no manure was applied.

Two drainage water quality studies in Iowa have evaluated the impact of liquid swine manure application to both corn and soybeans within a corn-soybean rotation. For a four-year study (2001-2004) at the Gilmore City research site in Pocahontas County, applying liquid swine manure at the rate of 150 lb N/acre (total nitrogen) before both corn and soybeans did not increase either corn or soybean yields compared to a rate of 200 lb N/acre of manure applied every other year before corn. In addition, the total of 300 lbs (two years of 150 lb N/acre) versus the 200 lb N/acre two-year-rate resulted in nitrate-N concentrations in tile drainage increasing on average from 17 to 23 mg/L, a 35% increase that was statistically significant.

For a six-year study (2001-2006) at the ISU Northeast Iowa Research Farm, applying liquid swine manure at the rate of 150 lb N/acre (total nitrogen) before corn and 200 lb N/acre (total nitrogen) before soybeans increased corn and/or soybean yields slightly some years (on average 3 and 2 bu/acre for corn and soybeans, respectively) compared to 150 lb N/ac of manure applied every other year before corn. The total of 350 (one year of 150 lb N/acre and one year of 200 lb N/acre) versus the 150 lb N/acre two-year-rate resulted in nitrate-N concentrations in tile drainage increasing on average from 21 to 38 mg/L, an 81% increase.

Both of these studies applied a relatively high nitrogen rate to the soybeans, but at these rates when liquid swine manure was applied every year in a corn-soybean rotation there was an increase in nitrate-nitrogen concentrations in the subsurface drainage water. However, it is unknown what direct water quality risk there would be with lower application rates specifically at rates ranging from 100-125 lb N/acre to soybeans. While the results discussed above were for studies on tile drained soils it is expected that there would be similar risks on non-tile drained soils relative to nitrate concentrations moving below the crop root zone.

Phosphorus

The application of manure to both corn and soybean, as noted above, could increase the risk of nitrate loss. Additionally the annual application of manure could increase the buildup phosphorus which could be of concern mainly from a surface runoff perspective. Considering a 60 bu/acre soybean crop the phosphorus removal (P2O5) might be 48 lb/acre and the potassium removal (K2O) might be 90 lb/acre, and a 200 bu/acre corn crop might remove 75 lb/acre of phosphorus (P2O5) and 60 lb/acre of potassium (K2O). This might result in a two-year removal of 123 lb/acre of phosphorus (P2O5) and 150 lb/acre of potassium (K2O).

Applying liquid swine manure at a nitrogen application rate of 150 lb N/acre to corn and 100 lb N/acre to soybeans (250 lb N/acre in two year rotation) might result in an overall phosphorus application of 172 lb/acre and an overall potassium application of 194 lb/acre (using values for liquid swine manure from a grow-finish operation (wet/dry). These application rates could be a long-term concern relative to phosphorus build up since crop removal might be 123 lb/acre for phosphorus with a phosphorus application of 172 lb/acre. A phosphorus buildup could have implications relative to the phosphorus index.

Pros, Cons, And Recommendations For Manure Application To Soybeans

Pros

  • Manure can supply phosphorus (P), potassium (K) and other nutrients;
  • Manure application on cornstalks can provide greater crop residue cover and lower erosion potential when injected or incorporated into cornstalks instead of soybean stubble on erosive land;
  • Manure application to soybeans can provide flexibility in application plans; and
  • Manure application to soybeans may improve soybean yields in some case.

Cons

  • Manure application to soybeans has the risk to increase nitrate in the soil profile which may increase the risk of nitrate loss;
  • Manure application to both corn and soybeans at an N rate for both crops could lead to a buildup of phosphorus; and
  • Manure application to soybeans under certain conditions may increase the risk of soybean diseases which could negatively impact yield.

Recommendations

  • Limit manure application to soybeans to a rate that compensates for N that would not be fixed by the soybean – this may be in the range of 100 lb N /acre;
  • Possibly limit manure application to soybeans to rates that fulfill the P and/or K requirements of the soybean crop or two-year corn-soybean rotation; and
  • Avoid manure applications when there is low crop utilization (i.e., fall applications).

Source: Extension.org, Matt Helmers, Iowa State University

Leave a Reply

Crop Inputs Stories

Monsanto Sign
Crop InputsWhat’s Next For Monsanto, Syngenta?
August 28, 2015
After dropping its $47 billion bid to take over Swiss agribusiness firm Syngenta, Monsanto may be turning its focus to Read More
Golden Harvest Corn stalks
Crop InputsMonsanto: Syngenta Not The Only Horse In Crop Protection Acquisition Race
August 28, 2015
Monsanto Co, having ditched an audacious $46 billion (£30 billion) offer for Syngenta AG, may downshift to a humbler strategy Read More
Corn Field
MicronutrientsHuma Gro Introduces New Boron Liquid Nutrient Formulation For Crops
August 28, 2015
BORO-MAX, a new boron (B) 10% liquid nutrient formulation, has been added to the Huma Gro product line. This new Read More
Crop InputsNFU: Monsanto Decision To Withdraw Syngenta Bid ‘Good For Family Farmers’
August 26, 2015
National Farmers Union (NFU) President Roger Johnson said the organization was very pleased by the news that Monsanto has withdrawn Read More
Top 100 Articles
Crop InputsLand ‘O Lakes, United Suppliers Finalize Merger
August 24, 2015
According to a press release on August 24, owners of United Suppliers, Inc. and members of Land O’Lakes, Inc. “have Read More
West Central Cooperative, Jefferson, IA
CropLife 100Iowa Cooperatives To Explore Unification
August 19, 2015
The boards of directors at two of Iowa’s leading farmer-owned cooperatives yesterday signed a letter of intent to study the Read More
CropLife 100Southern States Coop Hosting Drone Flight This Friday
August 3, 2015
Southern States Cooperative — No. 9 on the CropLife 100 — is hosting an FAA-approved drone demonstration at Grandview Farms Read More
CropLife 100Aligned Ag Distributors Adds Four New Owners
July 30, 2015
Aligned Ag Distributors LLC has announced the addition of four new customer/owners to Franklin Holding Co. LLC. They are: The Read More
CropLife 100Pinnacle Purchases California-Based Specialty Crops Retailer
July 20, 2015
Pinnacle Agriculture Holdings has successfully acquired California-based NH3 Service Co.  Operating as part of Pinnacle’s Performance Agriculture brand, the new locations Read More
Asmus Farm Supply liquid fertilizer facility features 20,000 square feet
CropLife 100Slideshow: Asmus Farm Supply Shows Off Its New Liquid Fertilizer Facility
July 15, 2015
Asmus Farm Supply, Rake, IA, recently added a new liquid fertilizer facility to its company operations. The new liquid fertilizer Read More
Latest News
Monsanto Sign
Crop InputsWhat’s Next For Monsanto, Syngenta?
August 28, 2015
After dropping its $47 billion bid to take over Swiss agribusiness firm Syngenta, Monsanto may be turning its focus to Read More
Golden Harvest Corn stalks
Crop InputsMonsanto: Syngenta Not The Only Horse In Crop Protectio…
August 28, 2015
Monsanto Co, having ditched an audacious $46 billion (£30 billion) offer for Syngenta AG, may downshift to a humbler strategy Read More
ManagementConsolidation hits and a miss; And a look at China’s ch…
August 28, 2015
As Monsanto suspends its pursuit of Syngenta, consolidation news at the retail and distribution level heats up. CropLife magazine’s Executive Read More
Corn Field
MicronutrientsHuma Gro Introduces New Boron Liquid Nutrient Formulati…
August 28, 2015
BORO-MAX, a new boron (B) 10% liquid nutrient formulation, has been added to the Huma Gro product line. This new Read More
Crop InputsNFU: Monsanto Decision To Withdraw Syngenta Bid ‘…
August 26, 2015
National Farmers Union (NFU) President Roger Johnson said the organization was very pleased by the news that Monsanto has withdrawn Read More
Crop InputsMonsanto Withdraws Bid For Syngenta
August 26, 2015
Monsanto Co. abandoned its latest effort to acquire Syngenta AG, the world’s top maker of pesticides, after a sweetened bid Read More
Syngenta Sign
Crop InputsSyngenta Comments On Monsanto Announcement
August 26, 2015
The Board of Syngenta confirms that it received a verbal proposal from Monsanto to acquire the company at a price Read More
Case IH Patriot 2250 Sprayer
EquipmentHigh-powered Case IH Patriot 2250 Sprayer Pushes Throug…
August 26, 2015
Engineered with more muscle, the new 660-gallon-capacity Patriot 2250 sprayer features best-in-class horsepower, along with the fuel efficiency that comes Read More
Crop InputsLand ‘O Lakes, United Suppliers Finalize Merger
August 24, 2015
According to a press release on August 24, owners of United Suppliers, Inc. and members of Land O’Lakes, Inc. “have Read More
TMX-2050 In-Cab Display Launch Run Screen
Eric SfiligojPrecision Ag Could Shine In Increased Spotlight On Agri…
August 24, 2015
By any measure, 2015 is turning into one of the most challenging years agriculture has ever experienced. All throughout good Read More
ManagementCrop Conditions In Minnesota and Traveling Time
August 21, 2015
Editors Paul Schrimpf and Eric Sfiilgoj discuss the crop outlook from a field trip to Minnesota and upcoming travel plans. Read More
HerbicidesREUTERS: Anti-GMO ‘Scientist’ Calls For New…
August 20, 2015
EDITORS NOTE: We feel that it is important to note that there are those that believe one of the lead Read More
Rendering of Syngenta Seedcare Institute expansion
Seed/BiotechSyngenta Announces Seedcare Application And Resource Ce…
August 19, 2015
Syngenta recently announced the Seedcare Application and Resource Center, a collaborative new website designed exclusively for Syngenta Seedcare customers to Read More
Winter Wheat
Industry NewsArysta LifeScience Announces Two New Regional Sales Man…
August 19, 2015
Arysta LifeScience North America recently announced Steve Vining and Phil Reding have each accepted new positions as Regional Sales Managers. Read More
West Central Cooperative, Jefferson, IA
CropLife 100Iowa Cooperatives To Explore Unification
August 19, 2015
The boards of directors at two of Iowa’s leading farmer-owned cooperatives yesterday signed a letter of intent to study the Read More
Golden Harvest Corn healthy leaves
Industry NewsAligned Ag Distributors Names Vice President, Crop Prot…
August 18, 2015
Aligned Ag Distributors LLC have appointed Warren Hragyil to VP Crop Protection. Hragyil comes to Aligned Ag Distributors LLC with Read More
Industry NewsH.J. Baker Hires Manager For Crop Performance Division
August 18, 2015
H.J. Baker has announced Donald Sutton has joined the company’s Crop Performance Division as a part of the U.S. sales Read More
Radish cover crop taproot
Crop InputsSoil Health Field Days Promote Agricultural Evolution
August 18, 2015
Brent Bible practiced no-till farming and the use of cover crops on his farm in Lafayette, Indiana, but until recently, Read More