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The Illinois Soil Nitrogen Test: Should It Be Used In Iowa?, John E. Sawyer, Mohammod Ali Tabatabai 2016 Iowa State University

The Illinois Soil Nitrogen Test: Should It Be Used In Iowa?, John E. Sawyer, Mohammod Ali Tabatabai

John E. Sawyer

The test was developed several years ago at the University of Illinois by researchers in the Department of Natural Resources and Environmental Sciences. It is a laboratory procedure designed to measure N liberated from soil heated for 5 hours with dilute alkali solution (sodium hydroxide). The test does not measure nitrate, but does measure exchangeable ammonium and a fraction of soil organic N.


Postemergence Application Of Herbicides In Corn, Michael D. Owen, John E. Sawyer, Robert G. Hartzler 2016 Iowa State University

Postemergence Application Of Herbicides In Corn, Michael D. Owen, John E. Sawyer, Robert G. Hartzler

John E. Sawyer

The Iowa 2006 corn crop is mostly in the ground and much of it will be emerged by the end of the week. Planting progressed rapidly in late April prior to the current wet conditions, and this prolonged wet period will impact weed management plans for those fields planted prior to the rain but not treated with preemergence herbicides or nitrogen (N) fertilizer. This article is revised from a 2003 discussion and will describe two important issues.


Potassium Deficiency Symptoms In Corn, John E. Sawyer 2016 Iowa State University

Potassium Deficiency Symptoms In Corn, John E. Sawyer

John E. Sawyer

The dry conditions this spring have resulted in corn plants expressing potassium (K) deficiency symptoms the past 2 weeks. This phenomenon has appeared in previous dry spring seasons and is back again this year, especially in southern Iowa. Areas of the state that received adequate rainfall are generally not showing K deficiency symptoms. Symptoms can appear even though soil K is adequate for crop production. How can this occur? Uptake of K by plants requires an active root system, especially in the soil zone where plant-available K is located.


Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Historically, sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. Soil supply or combination from sources such as manure or precipitation has met crop S needs. However, soil S levels or supply may become depleted with prolonged crop removal, sulfate leaching, low precipitation deposition, and declining soil organic matter. The objective of this study was to determine if corn and soybean yields would respond to S fertilizer rate and material at multiple sites across Iowa soils and climatic conditions.


Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Historically sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. The soil supply or combination from sources such as manure or precipitation has met crop S needs. However, soil S levels or supply will become depleted with prolonged crop removal, sulfate leaching, low precipitation deposition, and declining soil organic matter. The objective of this study was to determine the responsiveness of corn and soybean to S application (first year and residual second year) and S fertilizer material at multiple sites across Iowa soils and climatic conditions.


Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Historically, sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. Soil supply or combination from sources such as manure or precipitation has met crop S needs. However, soil S levels or supply may become depleted with prolonged crop removal, sulfate leaching, low precipitation deposition, and declining soil organic matter. The objective of this study was to determine if corn and soybean yields would respond to S fertilizer rate and material at multiple sites across Iowa soils and climatic conditions.


Surface Waters: Ammonium Is Not Ammonia – Part 1, John E. Sawyer 2016 Iowa State University

Surface Waters: Ammonium Is Not Ammonia – Part 1, John E. Sawyer

John E. Sawyer

A recent article in The Des Moines Register newspaper has caused considerable controversy regarding nitrogen in Iowa streams and rivers. The article (High ammonia levels threaten D.M.’s water, April 6, 2008) featured information about “ammonia” levels in certain Iowa surface water systems during the recent winter time period. The implications were that manure and fertilizer application to cropland, and subsequent snowmelt and runoff, had resulted in higher than normal “ammonia” levels in surface waters. In the article there was a comparison of the reported levels to an ammonia reading of 0.10 parts per million considered harmful to ...


Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Historically, sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. Soil supply or combination from sources such as manure or precipitation has met crop S needs. However, soil S levels or supply may become depleted with prolonged crop removal, sulfate leaching, low precipitation deposition, and declining soil organic matter. The objective of this study was to determine if corn and soybean yields would respond to S fertilizer rate and material at multiple sites across Iowa soils and climatic conditions.


Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

Sulfur Fertilizer Application To Corn And Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Historically sulfur (S) application has not been recommended on Iowa soils for corn and soybean production. The soil supply or combination from sources such as manure or precipitation has met crop S needs. However, soil S levels or supply will become depleted with prolonged crop removal, sulfate leaching, low precipitation deposition, and declining soil organic matter. The objective of this study was to determine the responsiveness of corn and soybean to S application (first year and residual second year) and S fertilizer material at multiple sites across Iowa soils and climatic conditions.


How Do Uncertain Prices Influence Phosphorus And Potassium Fertilization This Fall?, Antonio P. Mallarino, John E. Sawyer 2016 Iowa State University

How Do Uncertain Prices Influence Phosphorus And Potassium Fertilization This Fall?, Antonio P. Mallarino, John E. Sawyer

John E. Sawyer

Crop prices and phosphorus (P) and potassium (K) fertilizer prices have changed significantly in the last two years, and there is considerable uncertainty about future prices. Profitable crop production requires appropriate soil P and K levels, so careful fertilization planning is required. Iowa State University (ISU) soil-test interpretations and fertilization guidelines in extension publication PM 1688, A General Guide for Crop Nutrient and Limestone Recommendations in Iowa (available to order or to download from www.extension.iastate.edu/pubs), were last updated in November 2002. Some important changes were to recommend higher soil-test K (STK) levels for all crops and ...


In-Season Nitrogen Fertilization Of Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

In-Season Nitrogen Fertilization Of Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Nitrogen (N) fertilization is not a traditional nutrient management practice for soybean production in Iowa. Soybean is a legume plant and is assumed to adequately obtain needed N through symbiotic fixation. However, there is interest in using N fertilization to increase yield and grain protein due to the recognition of the large N requirement associated with high yields. Despite the fact that soybean is a legume, it readily utilizes soil inorganic N and will do so preferentially to symbiotic N2 fixation. Depending on the residual inorganic N level and soil N mineralization characteristics, approximately 40 to 75% of the N ...


In-Season Nitrogen Fertilization Of Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

In-Season Nitrogen Fertilization Of Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Nitrogen (N) fertilization is not a traditional nutrient management practice for soybean production in Iowa. Soybean is a legume plant and is assumed to adequately obtain needed N through symbiotic fixation. However, there is interest in using N fertilization to increase yield and grain protein due to the recognition of the large N requirement associated with high yields. Despite the fact that soybean is a legume, it readily utilizes soil inorganic N and will do so preferentially to symbiotic N2 fixation. Depending on the residual inorganic N level and soil N mineralization characteristics, approximately 40 to 75% of the N ...


In-Season Nitrogen Fertilization Of Soybean, John E. Sawyer, Daniel W. Barker 2016 Iowa State University

In-Season Nitrogen Fertilization Of Soybean, John E. Sawyer, Daniel W. Barker

John E. Sawyer

Nitrogen (N) fertilization is not a traditional nutrient management practice for soybean production in Iowa. Soybean is a legume plant and is assumed to adequately obtain needed N through symbiotic fixation. However, there is interest in using N fertilization to increase yield and grain protein due to the recognition of the large N requirement associated with high yields. Despite the fact that soybean is a legume, it readily utilizes soil inorganic N and will do so preferentially to symbiotic N2 fixation. Depending on the residual inorganic N level and soil N mineralization characteristics, approximately 40 to 75% of the N ...


High Nitrogen Fertilizer Prices -- Again, John E. Sawyer 2016 Iowa State University

High Nitrogen Fertilizer Prices -- Again, John E. Sawyer

John E. Sawyer

I am often asked what N rate should be applied for corn production. I hesitate to give too simple of an answer, but actually a straightforward rate of 125 lb N/acre for corn following soybean (SC) and 175 lb N/acre for corn following corn (CC) (continuous, second-, or third-year) with good N management works well. If you have followed Iowa State University Extension publications regarding N management over the years, these rates are in the middle of suggested rate ranges provided since at least 1979 (100--150 lb N/acre for SC and 150--200 lb N/acre for CC).


Getting Ready For Fall Fertilization, John E. Sawyer 2016 Iowa State University

Getting Ready For Fall Fertilization, John E. Sawyer

John E. Sawyer

The fall season is a common time for making crop nutrient applications. Soil sampling, and applications of phosphorus and potassium, nitrogen, and manure are a few things to consider as you plan fall fertilization activities.


Getting The Most From Nitrogen Fertilizer Dollars, John E. Sawyer 2016 Iowa State University

Getting The Most From Nitrogen Fertilizer Dollars, John E. Sawyer

John E. Sawyer

For some producers, high fertilizer nitrogen (N) prices will add significant costs to corn production this year. What management options can producers take to get the most return from added N? Where to apply N and at what rate? Allocate more N to where it is needed most. If your N costs are high, or products are in short supply, then allocate more N to the situations with greatest potential response to applied N. This allocation would be to the most responsive crops and rotations.


Farm Energy: Energy Consumption For Row Crop Production, H. Mark Hanna, John E. Sawyer, Dana Petersen 2016 Iowa State University

Farm Energy: Energy Consumption For Row Crop Production, H. Mark Hanna, John E. Sawyer, Dana Petersen

John E. Sawyer

This publication provides an overview of farm energy use related to corn and soybean production in Iowa. Three areas of row crop production--field operations, fertilizer and pesticide application, and artificial drying--are used to illustrate on-farm energy consumption.


Evaluation Of Fertilizer Additives For Enhanced Nitrogen Efficiency In Corn, Daniel W. Barker, John E. Sawyer, Michael J. Castellano 2016 Iowa State University

Evaluation Of Fertilizer Additives For Enhanced Nitrogen Efficiency In Corn, Daniel W. Barker, John E. Sawyer, Michael J. Castellano

John E. Sawyer

The use of N additives and slow release materials with ammoniacal fertilizer varies throughout the U.S. Corn Belt due to differing N loss potentials across climate, soils, and production systems. In Iowa, recent years of high rainfall events and prolonged wet soil conditions has renewed interest to protect fertilizer N loss from denitrification, leaching, and greenhouse gas emission with use of nitrification inhibitors. These loss processes can be significant in Iowa soils that are poorly drained and have high organic matter, high pH, and high populations of denitrifying bacteria. Subsurface tile drainage is also prevalent in farmer fields throughout ...


Farm Energy: Energy Conservation In Corn Nitrogen Fertilization, John E. Sawyer, H. Mark Hanna, Dana Petersen 2016 Iowa State University

Farm Energy: Energy Conservation In Corn Nitrogen Fertilization, John E. Sawyer, H. Mark Hanna, Dana Petersen

John E. Sawyer

Optimum corn yields require nitrogen fertilization in most crop rotations, but the energy consumed during the production of nitrogen fertilizer is considerable. Learn more about maximizing economic, environmental, and energy returns for nitrogen and other fertilizers.


Foliar Fertilization Of Corn And Soybean, John E. Sawyer 2016 Iowa State University

Foliar Fertilization Of Corn And Soybean, John E. Sawyer

John E. Sawyer

Research has been conducted on foliar fertilization of corn over the years, but not overly extensive in Iowa. One reason has been the lack of positive results when studies were conducted. Looking at data from the early 1970s to recent years I don’t find cases where foliar fertilization produced positive yield responses. An example is a study we conducted in 1999 with foliar application of low-biuret urea and mono-potassium phosphate at four growth stages from V6 to VT. There was no yield response with urea application, but a statistically significant yield decrease of 5 to 6 bu/acre with ...


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