Dairy Manure Applications in Irrigated Wheat Production Systems

Summary

This publication provides best management practices for irrigated wheat production systems receiving dairy manure applications. Recommendations are based on field research conducted in southern Idaho.

However, there is a limit to the amount of manure that these systems can handle. Increasing manure application rate and frequency led to issues with lodging, low falling numbers, nitrate leaching, and excess soil phosphorus (P), potassium (K) and salt accumulations.

To optimize grain yield and quality in manured systems with minimal negative environmental impact, consider the following recommendations:

• Conduct soil, manure and flag leaf testing to determine appropriate application rates for manure and supplemental fertilizer applications. Follow established university recommendations for irrigated wheat nutrient management.
• To avoid increasing protein levels above industry standards, select hard red over soft white varieties for fields with a history of manure applications.
• Consider using crop P uptake potential to determine manure application rates. This approach can prevent a wide range of environmental and agronomic issues associated with overapplication of manure.
• On irrigated wheat production fields with silt loam soil texture, prevent yield losses and nitrate leaching by applying stockpiled dairy manure at rates below 16 ton/acre/year (dry weight basis).
• Nitrate leaching losses may be reduced or eliminated by the use of soil tests and university recommendations to determine supplemental N fertilizer application rates.
• Bale wheat straw to draw down excess soil K accumulations.
• Monitor for elevated sodium adsorption ratio (SAR) to avoid potential grain yield losses.

How to use this publication

This publication is a manure nutrient management guide for (1) wheat growers who are interested in fertilizing with stockpiled dairy manure and (2) dairy manure managers who are interested in marketing their product to wheat growers. The recommendations provided are specific to stockpiled dairy manure applications to irrigated wheat production fields with alkaline silt loam soils in the intermountain Pacific Northwest (PNW) region of the United States. This publication is designed to be used in conjunction with soil tests, manure tests and university fertilizer recommendations for wheat. Exercise caution and practice common sense if conditions vary from those described above.

Stockpiled dairy manure is very common in the PNW. The term “stockpiled dairy manure” is defined as a combination of dairy manure and straw bedding that is stored in a static pile for 6 months or longer. In contrast, “dairy compost” is dairy manure that is combined with bedding and turned regularly to stimulate drying, decomposition, pathogen suppression and weed seed degradation. Compared to composted dairy manure, stockpiled dairy manure tends to be richer in ammonium and readily mineralizable organic N compounds, while having a higher moisture content. In contrast, dairy composts tend to be higher in nitrate and stable organic N compounds.

Manure nutrient concentration, moisture content, organic matter content and other chemical parameters specific to the Kimberly study are included in this publication to provide insight on effective manure management practices in wheat production systems. Keep in mind that the manure used on your operation will differ from that used in this study, as manure characteristics can vary by more than tenfold or greater. To avoid over- or underapplication of manure-derived nutrients, the manure characteristics provided in this guide should not be substituted for a manure analysis. Always conduct manure testing before developing a nutrient management plan for fields receiving manure applications.

Manure application rates from the Kimberly study are listed in this guide on a dry weight basis (dwb) and on an annual basis as ton/acre/year (dwb). If the dry matter percentage of a manure is known, either of the following calculations can be used to convert between dry and wet manure applications. To estimate the cumulative amount of manure applied over time, multiply the ton/acre/year rate (dwb) by the number of years of application.

manure rate, wet wt. basis (ton/a) × (dry matter % / 100) = manure rate, dry wt. basis (ton/a)

manure rate, dry wt. basis (ton/a) × (100/ dry matter %) = manure rate, wet wt. basis (ton/a)

Introduction

Irrigated wheat production and large-scale milk production overlap in several areas of the Pacific Northwest, including the Snake River Basin, the Columbia Basin and the Yakima Valley. Dairy operations generate a significant amount of manure, which is applied in irrigated cropping systems that often include wheat in the rotation. Wheat growers often are uncertain about the impacts of manure applications on yield and grain protein, two critical economic parameters.

This publication provides insights and recommen-dations for dairy manure application in irrigated wheat production systems, based on local research and related findings in the literature. Specifically, we focus on soil N, P and salt accumulation in response to manure applications and on the influence of these factors on grain protein, grain yield, lodging, falling number and water quality. Recommendations are provided for the use of soil and manure testing to manage manure applications for optimal yield and protein, while minimizing environmental losses of N and P.

Kimberly study background

In 2012, the University of Idaho soil fertility program and United States Department of Agriculture Agricultural Research Service (USDA ARS) station near Kimberly, Idaho, developed a study to evaluate the impact of repeated dairy manure applications on an irrigated cropping system typical for southern Idaho. Findings from this study are designed to help growers and dairy producers improve manure management practices to optimize grain yield and quality while minimizing negative environmental impacts.

Stockpiled dairy manure was fall applied to an irrigated Portneuf silt loam soil in Kimberly, Idaho, from 2012 to 2016 (table 1 and figure 1). The study consisted of two adjacent fields, one with a wheat-potato-barley-sugar beet rotation and the other with a barley-sugar beet-wheat-potato rotation (figure 2). Both fields were irrigated using a solid set sprinkler system.

Dairy manure from local operations was fall applied and incorporated on the same day either every year or every other year preceding the grain crop (barley or wheat). This practice is common among potato and sugar beet growers in the region, as winter nitrate leaching loss is typically minimal due to limited rainfall.

Dairy manure was applied at an average of 16, 31 or 47 ton/acre in a single application on a wet weight basis (equivalent to 8, 16 or 23 ton/acre on a dry weight basis). All manure treatments were supplemented with spring-applied preplant fertilizers, based on agronomic soil tests and University of Idaho fertilizer recommendations for spring wheat production. A fertilizer-only treatment and a control treatment (no nutrients added) were also included. Hard red spring wheat (‘Jefferson’) was planted and harvested in 2013 and 2017 in the “north” field and in 2015 in the “south” field (figure 2).

Grain yield response to dairy manure applications was inconsistent over the years of the study, with some indication of yield loss at rates above 16 ton/acre/year for three years or more (figure 3, top). Grain protein increased consistently from an average of 12.3 percent in the fertilizer-only treatment to an average of 14.5 percent with 23 ton manure/acre/year (dwb) (figure 3, bottom). In the following sections, we discuss how grain yield, grain quality and environmental factors are related to manure, soil and plant nutrient properties.

Soil organic matter

Dairy manure can be an effective source of organic matter (OM) for agricultural soils, as it contains lignin, cellulose and other stable organic components that decompose slowly and can accumulate in the soil over time. Increased OM can improve moisture and nutrient retention, soil structure, aeration, root growth, soil biological diversity and abundance, and water infiltration. The manure in the Kimberly study contained on average 48 percent organic matter and 52 percent mineral components on a dry weight basis (table 1, page 3).

Manure applications can build soil OM quickly on irrigated fields east of the Cascades, where soil OM is limited due to warm summer temperatures, limited winter moisture and a lack of plant residues. Average soil OM for the Kimberly study increased from 1.3 percent for the fertilizer-only treatment to 1.8 percent for the 23 ton/acre (dwb) treatment following the first fall manure application (figure 4). Soil OM increased further from 1.4 percent to 2.5 and 2.7 percent following three and five years of manure applications, respectively (figure 4). These findings illustrate that dairy manure applications can be used to significantly increase soil OM over a relatively short period of time.

These findings suggest that repeated applications of dairy manure at rates above 5 ton/acre/year (dwb) or a one-time application above 16 ton/acre (dwb) may be needed to show significant increases in soil OM. Keep in mind that rates used in this study to achieve soil OM concentration above 2 percent at the 0- to 12-inch soil depth may increase the risk of excess accumulations of N, P and salts (see discussion below).

Nitrogen (N)

Manure N

Manure contains stable organic compounds (lignin and cellulose), readily decomposable organic compounds (proteins and amino acids) and the inorganic N compounds nitrate (NO3-N) and ammonium (NH4-N). Inorganic N and readily decomposable organic N compounds are available for plant uptake, leaching, volatilization and runoff during the first growing season following a manure application. In contrast, stable organic N compounds can take three to five years to be converted to plant-available inorganic forms. During the first year following application, N availability from stockpiled dairy manure is estimated to be only 10–20 percent of manure total N, depending on incorporation timing and ammonium content (Fertilizing with Manure and Other Organic Amendments, PNW 533).

Stockpiled dairy manure amendments used in the Kimberly study contained predominantly organic N compounds (83 percent), with a mean C-to-N ratio of 13.6 (table 1, page 3).

Soil N and grain protein

Impacts of dairy manure applications on soil N can often be tracked by testing for total N (organic N, nitrate and ammonium). Across all treatments in the Kimberly study, 97 percent of the soil N was in the form of organic N compounds.

With a one-time manure application, manure rate had minimal effect on soil total N (figure 5). In contrast, following three and five years of repeated dairy manure applications, soil total N increased with increasing manure rates (figure 5). Thus, fields with a history of repeated manure applications may have a lower requirement for N additions in comparison to fields with no previous applications.

Soil N concentration can influence grain protein concentration because N is a basic component of the amino acids used to form proteins. In the Kimberly study, plant-available forms of N (nitrate and ammonium) mineralized from organic N compounds in the soil were evaluated during a wheat rotation year (figure 6). Grain protein concentration was compared to mineralized N near planting in April and near harvest in July (figure 7).

Increasing mineralized N was associated with increasing grain protein. Grain protein was found to be more strongly correlated to mineralized N accumulated from April to July than to soil N concentration in April. This finding suggests that increased grain protein concentration following manure treatments likely results from organic N mineralization from manure N over the summer. See Nitrogen Management for Hard Wheat Protein Enhancement (PNW 578) for more information.

Soil N: Environmental implications

Nitrate leaching potential tends to be lower for dairy manure than for other animal manures (such as hog and poultry), since a large quantity of the N is in organic N compounds that are resistant to mineralization.

Irrigated wheat production systems often have minimal nitrate leaching losses for several reasons: (1) wheat plants remove significant amounts of N from the soil, (2) the majority of the N in the wheat plant is in the harvested grain, (3) water use by wheat plants is relatively efficient and (4) the irrigation season is short, ending in early to mid-July. In the intermountain region of the PNW, cool winter temperatures and low levels of winter precipitation also contribute to minimal nitrate leaching over the winter.

In the Kimberly study, wheat N uptake potential ranged from 259 to 301 lb N/acre following three manure application events over a five-year period (figure 8). Increased N uptake was correlated to increased manure application rates and soil total N concentration.

To determine whether soil nitrate had leached below the root zone, fall soil samples were collected to a 4-foot depth following wheat harvest in late September of 2013 and 2017. Following one application of manure in 2012 (data not shown), manure applications did not significantly increase soil nitrate concentration at the 3- to 4-foot depth in 2013. However, in 2017, after five years of manure application, soil nitrate concentration increased with increasing manure rate and frequency (table 2). At the 3- to 4-foot soil depth, annual manure applications exceeding 16 ton/acre (dwb) or biennial applications exceeding 23 ton/acre (dwb) significantly increased soil nitrate concentration (table 2). Because manured fields were supplemented with N fertilizers based on soil tests, it is uncertain how much of the N originated from manure and how much came from fertilizer.

These findings illustrate that soil nitrate leaching can occur in irrigated wheat production systems receiving stockpiled dairy manure applications on silt loam textured soils, especially if manure is applied annually at rates above 16 ton/acre (dwb). They also underscore the challenge of working with soils that contain appreciable quantities of N that can be mineralized following preplant soil nitrate-N and ammonium-N analyses. To prevent nitrate leaching from these systems, it is important to follow responsible N fertilizer management practices, and it may be necessary to reduce manure application rates and frequency.

Phosphorus (P)

Manure P

Dairy manure used in the Kimberly study contained an average of 1.4 percent P2O5. An estimated 90 percent of the manure P is in the plant-available form of orthophosphate (table 1, page 3). Less than 10 percent is organic P (Carey, et al., 2011). For this reason, P availability of stockpiled dairy manures produced in this region is estimated at 70–90 percent, only slightly lower than the P availability of ammonium-phosphate-based fertilizers.

Soil P: Agronomic implications

Phosphorus applications are recommended for wheat when Olsen soil test P concentration is below 20 ppm (Southern Idaho Fertilizer Guides, CIS 373 and CIS 828). Dairy manure is considered an excellent source of P and is often applied to wheat and other crops as a way to supply P to plants, while also supplying organic matter and other nutrients.

The average P loading rate in the Kimberly study ranged from 190 to 670 lb P2O5/acre for each manure application event, depending on the treatment rate. This is more than enough P to support optimal growth in wheat. Supplemental P fertilizer applications were needed only when manure applications were at or below 8 ton/acre/year (dwb).

It is important to note that the impact of manure application rates will vary, depending on the P concentration of the dairy manure, lime content of the soil and other factors. Practices such as annual soil testing, manure testing prior to application and use of university nutrient recommendations can help to prevent under- or overapplication of P.

Applying dairy manure based on crop P removal potential supplies adequate quantities of many secondary nutrients and micronutrients (table 3). However, as expected, manure N alone did not supply enough N to support optimal wheat production in the Kimberly study, which is why supplemental fertilizer N was needed for manure treatments. Results will vary depending on manure nutrient composition and history of manure application.

Soil P: Environmental implications

When P accumulates at the soil surface, runoff can transport P to nearby waterways, leading to biological disruptions and outbreaks of algal blooms that can negatively impact humans and wildlife. Thus, dairy producers often face regulatory limits on manure application rates.

In the Kimberly study, wheat P uptake potential was approximately 112 lb P2O5/acre regardless of manure application history (figure 9). After five years of manure applications at a rate of 23 ton/acre (dwb), soil Olsen P reached an average of 170 ppm, greatly exceeding crop uptake potential (figure 10). This finding suggests that wheat will not remove more P just because it is available (luxury consumption). The resulting accumulation of P creates a risk of P runoff losses.

Most of the P in a wheat plant resides in the grain, which is removed during harvest (figure 9, page 8). By basing manure application rates on crop P removal potential, P accumulation at the soil surface can be prevented.

Potassium (K)

Manure K

Potassium is typically the most abundant plant nutrient in dairy manure, and stockpiled manure is considered a rich source of K for wheat and other plants (table 1, page 3). Manure K is predominantly in the soluble ion form of K+, which is readily available to plants. Potassium availability for most stockpiled dairy manures produced in this region is 80–100 percent.

Average K loading rate in the Kimberly study ranged from 585 to 1,750 lb K2O/acre for each manure application event, depending on the treatment rate. Wheat plants generally need only 300 lb K2O/acre to support growth.

Soil K concentration

Potassium applications are recommended for wheat when Olsen soil test K concentration is less than 75 ppm (Brown, et al., 2001). In the Kimberly study, soil test K levels were never below 75 ppm, even for control treatments where no K sources were applied during the course of the study (figure 11). However, it is not advisable to allow soil test K values to decrease to 75 ppm. In general, soil K levels should be maintained to meet the needs of the most K-demanding crop in the rotation.

Manure applications can be a cost-effective way to increase soil test K when dairy manure sources are readily available. Practices such as annual soil testing, manure testing prior to application and use of university nutrient recommendations can help growers meet a crop’s K needs with manure applications.

In contrast to other nutrients, wheat and other crops often accumulate more K than is needed to support optimal growth. In wheat, increased K uptake is reflected in increasing K concentration in the straw. Among manure treatments in the Kimberly study, shoot K uptake ranged from 339 to 404 lb K2O/acre in 2017, compared to 317 lb K2O/acre for the fertilizer-only treatment (figure 12). Grain K uptake ranged from 82 to 90 lb K2O/acre and was not affected by manure treatments (figure 12).

Increased lodging incidence was observed in the Kimberly study with increasing manure rate and frequency. In addition to other factors, K uptake in the straw seems to be linked to lodging incidence, as discussed in Appendix B.

Despite the potential for luxury uptake of K, intensive dairy manure applications can increase soil K concentration, especially in fields receiving repeated applications. In the Kimberly study, soil K was greater than 1,000 ppm following six years of annual manure applications at a rate of 23 ton/acre/year (dwb) (figure 11, page 9). Residue removal practices such as baling straw after grain harvest may help to lower soil K concentration over time.

Soil K typically is not regulated by environmental agencies due to its lack of harmful properties for water or air.

Secondary macronutrients (Mg, Ca and S) and micronutrients (Zn, B, Cu, Mn and Fe)

Dairy manure also contains secondary macronutrients (magnesium [Mg], calcium [Ca] and sulfur [S]) and micronutrients (zinc [Zn], boron [B], copper [Cu], manganese [Mn] and iron [Fe]). Average Mg, Ca, S, Zn, B, Cu, Mn, Na and Fe concentrations for dairy manures used in the Kimberly study are illustrated in table 4.

When manure is applied on the basis of P uptake, it typically supplies these nutrients at levels sufficient to meet requirements for wheat. In the Kimberly study, application of manure on a P removal basis matched or exceeded wheat nutrient needs for K, Mg, S, Cl, Fe, B, Zn, Cu and Mn. Nutrient supply exceeded wheat nutrient demand by 1.5 to 63 times when manure was applied based on P crop removal potential (table 3, page 8).

The calcareous soils of southern Idaho contain sufficient Ca and Mg to support optimal growth in wheat and other plants. However, Ca and Mg from manure may be of benefit on soils that have a known history of Ca or Mg deficiency.

Supplementing manure applications with micronutrients is unlikely to improve yield or protein unless manure rates are very low (below 5 dry ton/acre), manure micronutrient concentrations are low or free lime (calcium carbonate) concentration in the soil is above 6–8 percent. Micronutrient deficiencies or toxicities induced by excessive accumulations of other soil nutrients were not apparent in the Kimberly study.

It should be noted that excessive soil Cu accumulations can occur on fields receiving dairy manure, lagoon water, lagoon sludge or composts that contain copper sulfate wastewater from hoof baths. The impact of high levels of Cu on wheat was not evaluated.

As with N, P and K, practices such as annual soil testing, manure testing prior to application and use of university nutrient recommendations are useful tools for avoiding micronutrient deficiency or toxicity issues.

Sodic and saline conditions

Salt issues, including reduced water availability, salt toxicities and soil crusting, are a concern on soils receiving dairy manure applications, as manure contains significant amounts of K, Mg, Ca, Cl and Na (table 3, page 8). This issue can be amplified in semiarid regions such as southern Idaho, eastern Oregon and central Washington, where minimal winter precipitation prevents salts from being leached through the soil profile.

Sodicity

Sodicity occurs when excessive quantities of soluble Na are present in the soil compared to other salt cations (Ca and Mg). This can cause soil crusting, sodium toxicity, reduced soil aeration and degradation of soil structure.

The sodium adsorption ratio (SAR) is the amount of Na relative to Ca and Mg, as measured in a water extract formed from a saturated soil paste. The risk of sodium problems is moderate for SARs between 5 and 13 and high for SARs over 13 (Managing Salt-Affected Soils for Crop Production, PNW 601-E).

Dairy manure contains significant amounts of Na. In the Kimberly study, manure contained an average of 1.1 percent Na (table 4, page 10). One manure application at a rate of 23 ton/acre (dwb) increased SAR from 0.7 to 1.4, but SAR increased significantly, to 4.3 and 3.4, following three and five repeated annual applications, respectively (table 5).

In the Kimberly study, grain yield was negatively correlated with SAR at the 0- to 12-inch soil depth, up to a SAR of 4.3 (figure 13). Grain yield was more highly correlated to SAR than to any other soil OM parameter evaluated, including EC; total N; Olsen P; extractable and soluble forms of Ca, Mg, K and Na; and OM content.

Controlled research studies are needed to further explore the potential for wheat yield losses associated with high SAR. In the meantime, wheat growers are advised to monitor SAR on fields with a history of manure applications. For more information on how to identify and remediate sodic soil conditions, see Managing Salt-Affected Soils for Crop Production (PNW 601-E).

Salinity

Saline soil conditions are caused by accumulations of soluble Ca and Mg salts. Soil electrical conductivity (EC) is commonly used to identify soils with salt issues, as salts serve as a natural conductor for electricity.

For wheat, grain yield reductions are not expected for EC levels up to 6.0 dS/m (Managing Salt-Affected Soils for Crop Production, PNW 601-E). The highest average EC level in our manure study was 3.0 dS/m (table 5, page 11). We were unable to directly link EC to grain yield differences (figure 13, page 11). However, salt-sensitive crops such as beans, alfalfa, potatoes and corn that are produced in rotation with wheat may suffer yield losses if EC levels remain high. For more information on how to identify and remediate saline soil conditions, see Managing Salt-Affected Soils for Crop Production (PNW 601-E).

Soil testing

As in non-manured systems, traditional soil testing and university agronomic recommendations are very effective tools for maximizing plants’ efficiency at using manure nutrients while preventing excessive applications of specific nutrients.

Soil testing recommendations specific to irrigated conditions in the Pacific Northwest can be found in Southern Idaho Fertilizer Guide: Irrigated Winter Wheat (CIS 373), Southern Idaho Fertilizer Guide: Irrigated Spring Wheat (CIS 828) and Nutrient Management Guide: Irrigated Soft White Wheat (Eastern Oregon) (EM 9015). For guidance on how to interpret upper soil test thresholds for crop production fields receiving intensive dairy manure applications, see CIS 1156, Dairy Manure Field Applications: How Much Is Too Much?

When having soils analyzed from fields with a history of dairy manure applications, we recommend including the following analyses in your standard agronomic soil testing package:

• pH
• NO3-N and NH4-N
• Olsen P (alkaline conditions) or Bray P (acidic conditions)
• Olsen K or acetate K
• Electrical conductivity (EC)
• Sodium adsorption ratio (SAR)
• Plant-available copper (DTPA Cu)

Soil and plant testing to estimate N release from manure N

Estimating mineralizable soil N is of great interest for wheat production, as these plant-available N compounds are a key factor in determining final grain protein levels (see page 5). Several preplant soil test methods for N mineralization are under evaluation, but none has yet been shown to accurately predict N availability for wheat produced east of the Cascades (Nitrogen Management for Hard Wheat Protein Enhancement, PNW 578).

Flag leaf testing for total N is an established plant testing method used to evaluate in-season N status in wheat crops. It can provide an indication of late-season mineralized N release from manure N and other organic N sources. While flag leaf testing was not evaluated in the Kimberly study, this method can be an effective tool for managing grain protein with late-season N management (PNW 578).

Manure testing

Nutrient concentration in manure sources can vary more than tenfold due to variations in cattle type, manure management method, plant residue characteristics, manure age, composting method, nutrient content of feed rations, climate and other variables. Thus, you should always analyze dairy manure amendments for nutrient content prior to application. Doing so will increase your ability to complement applications with fertilizer nutrients without over- or underfertilizing.

Information on sampling method; manure nutrient analysis methods; and expected N, P and K availability specific to stockpiled manures can be found in Sampling Dairy Manure and Compost for Nutrient Analysis (PNW 673). Information on estimating plant-available forms of N, P and K based on manure test values for various animal species and manure types can be found in Estimating Plant-Available Nitrogen from Manure (EM 8954-E).

For more information

Extension publications

Bary, A., C. Cogger, and D. Sullivan. 2016. Fertilizing with Manure and Other Organic Amendments. PNW 533, http://cru.cahe.wsu.edu
/CEPublications/PNW533/PNW533.pdf, Pullman, WA: Washington State University Extension.

Brown, B. 2001. Southern Idaho Fertilizer Guide: Irrigated Winter Wheat. CIS 373, http://www.extension
.uidaho.edu/publishing/pdf/CIS/CIS0373.pdf, Moscow, ID: University of Idaho Extension.

Brown, B., J. Stark, and D. Westermann. 2001. Southern Idaho Fertilizer Guide: Irrigated Spring Wheat. CIS 828, http://www.extension.uidaho.edu
/publishing/pdf/CIS/CIS0828.pdf, Moscow, ID: University of Idaho Extension.

Brown, B., M. Westcott, N. Christensen, B. Pan, and J. Stark. 2005. Nitrogen Management for Hard Wheat Protein Enhancement. PNW 578,
https://www.extension.uidaho.edu/publishing
/pdf/PNW/PNW0578.pdf, Moscow, ID: University of Idaho Extension.

Carey, A., A. Moore, and A. Leytem. Phosphorus in the Calcareous Soils of Southern Idaho. 2011. BUL 877, https://www.extension.uidaho.edu
/publishing/pdf/BUL/BUL0877.pdf, Moscow, ID: University of Idaho Extension.

Horneck, D., J. Ellsworth, B. Hopkins, D. Sullivan, and R. Stevens. 2007. Managing Salt-Affected Soils for Crop Production. PNW 601-E, https://extension.oregonstate.edu/catalog/pub/pnw-601-managing-salt-affected-soils-crop-production, Corvallis, OR: Oregon State University Extension Service.

Horneck, D., J. Hart, M. Flowers, L. Lutcher, D. Wysocki, M. Corp, and M. Bohle. 2010. Nutrient Management Guide: Irrigated Soft White Wheat (Eastern Oregon). EM 9015, https://extension.oregonstate.edu/catalog/pub/em-9015-irrigated-soft-white-wheat-eastern-oregon-nutrient-management-guide, Corvallis, OR: Oregon State University Extension Service.

Moore, A., M. de Haro Marti, and L. Chen. 2015. Sampling Dairy Manure and Compost for Nutrient Analysis. PNW 673, http://www
.extension.uidaho.edu/publishing/pdf/PNW
/PNW673.pdf, Moscow, ID: University of Idaho Extension.

Moore, A., and J. Ippolito. 2009. Dairy Manure Field Applications: How Much Is Too Much? CIS 1156, http://www.extension.uidaho.edu/publishing
/pdf/CIS/CIS1156.pdf, Moscow, ID: University of Idaho Extension.

Sheffield, R., B. Brown, M. Chahine, M. de Haro Marti, and C. Falen. 2008. Mitigating High-Phosphorus Soils. BUL 851, http://www.extension.uidaho
.edu/publishing/pdf/BUL/BUL0851.pdf, Moscow, ID: University of Idaho Extension.

Sullivan, D. 2008. Estimating Plant-Available Nitrogen from Manure. EM 8954-E, https://extension.oregonstate.edu/catalog/pub/em-8954-estimating-plant-available-nitrogen-manure, Corvallis, OR: Oregon State University Extension Service.

References

Arnold, G., and S. Custer. 2017. Application of manure to newly planted wheat fields. C.O.R.N. Newsletter. Agronomic Crops Network, Ohio State University. https://agcrops.osu
.edu/newsletter/corn-newsletter/2017-33
/application-manure-newly-planted-wheat
-fields.

Arnold, G., and A. Douridas. 2016. Wheat yield results from topdressing with liquid swine manure. Journal of the National Association of County Agricultural Agents 9. https://www.nacaa.com
/journal/index.php?jid=601.

Gagnon, B., R. Simard, R. Robitalle, M. Goulet, and R. Rioux. 1997. Effects of compost and inorganic fertilizers on spring wheat growth and N uptake. Canadian Journal of Science 77:487–495.

Leytem, A., A. Moore, and R. Dungan. 2019. Greenhouse gas emissions from an irrigated crop rotation utilizing dairy manure. Soil Science Society of America Journal 83:137–152.

Rogers, C., K. Schroeder, A. Rashed, and T. Roberts. 2018. Evaluation of soil tests for measuring potentially mineralizable soil N in southern Idaho soils. Soil Science Society of America Journal 82(5): 1279.

Ross, A., M. Flowers, R. Zemetra, and T. Kongraksawech. 2012. Effect of grain protein concentration on falling number of ungerminated soft white winter wheat. Cereal Chemistry 89(6):307–310. https://doi.org/10.1094/CCHEM-07-12-0085
-RC.

Acknowledgments

We would like to acknowledge the Idaho Wheat Commission, the Idaho Dairymen’s Association, USDA ARS and the University of Idaho for providing financial support for the research used as the basis for recommendations in this publication. We would also like to thank Megan Satterwhite, Katherine O’Brien, Olga Walsh, Myles Miller and Simon Prestigiacomo for their hard work on the Kimberly study project.

Trade-name products and services are mentioned as illustrations only. This does not mean that the Oregon State University Extension Service either endorses these products and services or intends to discriminate against products and services not mentioned.

© 2019 Oregon State University.

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