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NC218: Assessing Nitrogen Mineralization And Other Diagnostic Criteria To Refine Nitrogen Rates For Crops And Minimize Losses

Annual/Termination Reports (SAES-422): [04/10/2002] [06/07/2002] [08/18/2003] [05/18/2004] [06/18/2005] [05/09/2006]

Date of Annual Report: 04/10/2002

Report Information:
  • Annual Meeting Dates: 04/12/01 to 04/13/01
  • Period the Report Covers: 04/2000 to 04/2001

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    The activities of the annual meeting primarily concerned committee business, termination of the project activities for FY 1995 - 2001 and protocols for project activities for FY 2001 - 2006.

    Committee Business: The minutes for the 2000 Annual Meeting and the agenda for the 2001 Annual Meeting were reviewed, modified and approved. Committee officers for the coming year were selected and approved (Brouder - Chair, Dick - Secretary, Horwath - Member-at-Large). The location (Kansas City, MO), date (March 27-28, 2002) and time (8:00 AM on 3/27 through noon on 3/28) for the next annual meeting were established.

    Termination of FY ‘95 - ‘01 Activities: The cumulative data sets for the project were reviewed. Preliminary analyses using several different approaches to the data were presented (Walters, time series data; Bundy, identification of the economically optimum N rate and yield responses to this rate) and discussed with the intent of developing strategies for the committee to proceed beyond a simple summary of the database. The committee determined that an overall manuscript was needed that described the justification and objectives of the current project and the extent and depth of the database including a general description of components and ranges in values and conditions and methodologies for field experiments, long-term lab incubation mineralization studies and soil characterization analyses. This overview paper would serve as the primary methodology reference for a minimum of four additional manuscripts detailing in-depth analyses of specific subsets of the database. The subjects of the four additional manuscripts were identified as (1) PMN quick-tests and thermal units, (2) Plant sensing of corn N status, (3) Characterization of soil C pools, and (4) Using testing techniques and N mineralization estimates in making N fertilizer recommendations. Writing teams and lead authors were identified for each paper and timeline for writing (1st drafts to all committee members prior to next year‘s meeting) was established.

    Protocols for Project Activities for FY 2001 - 2006: The committee agreed to establish core experiments that all participating members would conduct in their own states. Protocols are to be defined during the coming year for final approval at next year‘s meeting with the 1st growing season of the new project to be 2002. Three types of core experiments were identified for the new project: 1) sites that have been previously used and have historic records of N management, 2) new sites having uniform crop/soil management where N rate studies would be established, and 3) small-sized plots where N15 would be used to evaluate available N pools in soils taken up by plants. The possibility of using "strip trial" experiments for some of these sites was discussed. A protocol writing committee of Randall*, Bundy, Hoeft, Schmidt and Walters was identified to meet in late July or August to develop the protocols for the core experiments. Horwath will provide an N15 protocol for this effort. Preliminary results for two enzyme assays of arylamidase and glucoseamidase, which provide organic N for mineralization to NH4-N and will be used for soils collect in the current project, were presented and discussed (Tabatabai).


    URL: Copy of minutes

    Accomplishments:
    Committee members completed field research on cropping systems and N management approaches to address the two project objectives (FY ‘95 - ‘01 project). The two objectives were (1) to determine the feasibility of using thermal units coupled with an appropriate measure of potentially mineralizable soil N to predict current season N availability, and (2) to characterize active N and C pools subject to mineralization in cropping systems. Systems examined included continuous corn or corn-soybean rotations with inorgranic and/or organic (crop residues, cover crops, manures, other biosolids) N sources. Laboratory analyses of plant and soil samples including long-term incubations of soil samples to quantify potentially available N were also completed. All field sites data have been compiled into two separate subsets that feature either summary harvest data with soil test data or timed measurements of soil N, temperature, water content and plant N uptake data throughout the season. A final draft of the databases compiling field and laboratory measurements on plant and soil samples collected from 74 experimental sites was made available to committee members for individuals to pursue the statistical analyses required for the manuscripts outlined above (Summary of Annual Meeting Minutes: Termination of FY ‘95 - ‘01 Activities).

    Results from several North Central states field studies will be used to help agronomists better predict the amount of N released by mineralization of organic N present in soils during the growing season. This will allow producers to credit this mineralized N against fertilizer N recommendations, so excess N will not be applied and potential for losses of N from agricultural soils to surface and groundwater resources will be minimized. Specific examples of committee activities that can be directly incorporated into commercially-practiced N management strategies include demonstrating that (1) adjusting N applications based on PSNT results or N crediting should greatly reduce the risk of losing excess N to water resources and does not increase economic risk, (2) cover crop-based organic and low-input cropping systems that add C to soil have the potential for storing N and making it available for future crop use, while minimizing the risk of nitrate pollution, and (3) the Greenwood dilution curve provides a universal age-dependent N dilution curve that can be used to calibrate technologies designed to monitor N sufficiency of maize in a real-time fashion.

    Impact Statements:
    Last Modified: unknown

    Date of Annual Report: 06/07/2002

    Report Information:
  • Annual Meeting Dates: 03/27/02 to 03/28/02
  • Period the Report Covers: 04/2001 to 04/2002

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    Activities. The major part of the annual meeting was devoted to the discussion and approval of a set of protocols for experiments that will be conducted across the North Central region during the remainder of this project (i.e. through the 2005 growing season). The main objective in conducting these experiments is to test the relative ability of several new rapid tests to predict N mineralization and availability across soil types, management systems and climatic regimes. By pooling data from all researchers, a more precise and accurate test can be achieved. The ultimate goal will be to produce a guidance document for agricultural professionals focusing on nitrogen best management practices and optimum rate determinations for the region. Briefly, each study will test crop response when various nitrogen fertilizer rates are applied prior to planting. The ability of experimental rapid soil tests to predict crop yield and nitrogen uptake will then be evaluated. Protocols for three different types of experiments will be conducted. These include experiments that will be conducted at new sites using small plots, at new sites using field strip sized plots, and at existing sites using small plots where previous nitrogen response studies had been conducted.

    Committee Business. The minutes of the 2001 Annual meeting were approved. Committee Officers were selected and approved as follows (Chair - Warren Dick; Secretary - William Horwath; John Schmidt - Member-at-Large; and Sylvie Brouder - Past Chair). The next meeting will be held at the Embassy Suites-Airport in Kansas City, MO on March 19-20, 2003.

    It was moved and approved to have Dr. Gary Harmon (Cornell University) join the NC218 group as his research interests and experience matched closely with the goals of the group. Gary Lemme provided his Administrative Advisor‘s report and Ray Knighton presented the CSREES representative‘s report.


    URL: Copy of minutes

    Accomplishments:
    Several potential new methods to predict nitrogen mineralization and availability to crops have been recently developed by committee members. These methods, as well as several other existing procedures, have been the focus of much of the research activities during the past year. The two major tests to be studied by NC218 Committee members include (1) a rapid assessment of the amino sugar content in soils using alkaline hydrolysis and (2) a rapid enzyme assay procedure for beta-glucosaminidase activity in soils.

    Impact Statements:
    1. A study conducted in California indicated that cover crop-based organic and low-input cropping systems that add C to soil have the potential for storing N and making it available for future crop use, while minimizing the risk of nitrate pollution. A study in Nebraska revealed that plant density and nutrient management levels significantly affected yield, harvest index, stover yield, components of yield, and nutrient uptake. Current fertilizer recommendations that are based on a yield goal that i
    2. In Kansas, a study found that reducing nitrogen rates by 50 lb/acre could be practiced without a risk of reducing corn yield. This amount of fertilizer reduction will save corn producers about $10/acre in production costs which translates to $30,000,000 for about 3,000,000 acres of corn planted annually in Kansas. This also translates into fewer nitrates in the groundwater below agricultural fields, providing environmental benefits to the Kansas public. Another study conducted in Kansas revealed
    3. Researchers in Indiana have established a water quality field station where fertilizer nitrogen loss to surface water is measured on a daily basis. Different nitrogen management systems including rotations, fertilizer rates and fertilizer sources (inorganic versus manure) have an impact on surface water quality. Fall nitrogen applications to fields in Wisconsin to promote corn residue decomposition did not improve no-till corn yields and do not appear to be justified. Fall nitrogen did not consi
    4. Some farmers may be unknowingly contributing to nitrogen pollution problems by not taking proper credit for nitrogen additions associated with phosphorus applications. Research in Illinois indicated that if proper credit for nitrogen additions that is added with phosphorus fertilizer is recognized, nitrogen application rates could be reduced by 35 to 45 kg/ha. This not only saves on production costs but will have a significant impact on reducing nitrogen loss from tile lines, thus improving wate
    5. Recently a method was developed for assay of beta-glucosaminidase activity in soils. This enzyme is involved in carbon and nitrogen mineralization in soils. Crop rotations and nitrogen fertilization on the activity of this enzyme and its relationship to nitrogen mineralization in soils of two long-term field experiments in lowa (initiated in 1978 and 1954, respectively) impacted the activity of this enzyme. Understanding the relationship between the beta-glucosaminidase activity in soils and nit
    Last Modified: unknown

    Date of Annual Report: 08/18/2003

    Report Information:
  • Annual Meeting Dates: 03/19/03 to 03/20/03
  • Period the Report Covers: 04/2002 to 04/2003

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    Activities of the annual meeting primarily concerned committee business, a review of contributions of individual states to overall committee objectives, and development of plans for the coming year.

    Committee Business: Complete minutes of the March 19-20, 2003 meeting can be found on the NC-218 home page on the NIMSS (http://www.lgu.umd.edu/project/home.cfm?trackID=1014). Archives of past meeting minutes and annual reports of accomplishments for 2002 and 2003 can also be found at this same web site. Committee officers for the coming year were elected (William Horwath, Chair), John Schmidt (Secretary), Carrie Laboski (Member-at-Large) and Warren Dick (Past Chair). The location (Holiday Inn-Airport, Kansas City, MO), date (March 17-18, 2004) and time (8:00 AM on 3/17 through noon on 3/18) for the next meeting were established.

    Report of Meeting Activities and Plans for Next Year: The administrative report was presented by Gary Lemme. Members of the committee reviewed efforts to write draft manuscripts of data collected from the previous NC218 project. These papers tentatively plan to focus on the following topics:


    1. Methods and characterization of data collected during last project including crop

    response and field histories.

    2. Potential N mineralization quick test and their relationship to thermal units.

    3. Plant sensing of N status.

    4. Relationship of soil mineralizable C to mineralizable N.

    5. Using testing techniques to predict soil N mineralization and develop fertilizer recommendations.


    D. Walters presented a new maize growth model. Initial results of model simulations suggest that planting date is critical to avoid high night temperatures during the latter part of the growing season.

    Discussion of the protocols to be used for the new project ensued. Each state reported on their plans to conduct field experiments according to the protocol developed for NC218 studies in the previous year.


    URL: Copy of minutes

    Accomplishments:
    The use of the Illinois Nitrogen Soil Test (INST), which is based on estimating amino sugar nitrogen (AS-N) content in soil, was tested in several states. The preliminary data from Michigan suggest that the INST may be useful in helping to predict sites where sugar beet will not benefit from additional fertilizer N, and perhaps may be used to fine tune N fertilizer recommendations for individual fields. The strong correlation of AS-N with organic matter suggests that organic matter may be as useful when making field specific nitrogen recommendations.

    Temporal variation of INST values was studied in soils from Illinois and Minnesota. At two Illinois locations, the values decreased from early spring into the summer, but at two other Illinois locations, the values remained constant throughout the sampling period. There was a significant decrease in INST values at two of the Minnesota locations, but the decrease was somewhat later in the season than observed at Illinois. If, in fact, the amino sugar levels, as measured by the INST, reflect the easily mineralizable N source found in the soil, this decrease in values in early to midsummer would be expected. The decrease in Illinois N Soil Test values occurred at the same time and at approximately the same magnitude at the 0-6 inch and 6-12 inch depth. This trend offers promise that a 6 inch soil sample will adequately characterize the available N supply of a field.

    Spatial variability of the INST within a field ranged from a low of 35 ppm in one field to as much as 189 ppm in another. In three of the four fields studied, over 70 percent of the samples were within 10 percent of the mean. However, in the field that varied by 189 ppm from the low to high sample, only 14 percent of the samples were within 10 percent of the mean. In general, the variation tended to follow a pattern within a field, with the high values being grouped together, most likely indicating an effect of past management.

    Small plot research conducted in 2001 showed that only one site tested in Illinois, that had an INST value >240 mg N/kg soil, had corn that responded to fertilizer inputs. In 2002, there was no response to applied N at any site that had an INST level greater than 240 mg N/kg soil. Over two years of work in Illinois, the INST has done a good job predicting non-responsive sites with only one failure out of 29 experiments. Results collected from the farmer-conducted WATER plots, however, were much less consistent than from the small plot studies. Corn, grown at 12 of the sites (over the two years of the WATER plot studies) that were projected as non-responsive by INST, responded to fertilizer N. Most of these failures occurred in 2002, a year characterized by heavy rains early in the spring and early summer followed by very dry soils through most of the rest of the growing season. These unusual climatic conditions undoubtedly would have had a negative impact on microbial activity necessary to convert the AS-N to plant available inorganic N.

    A total of twelve field (new-small plot) sites were developed in Nebraska in 2002 following the NC-218 protocol. Sites were located across the state in all irrigated maize agroecosystems. In addition, one existing long-term tillage site (1985-2002) was sampled for the NC-218 project. 2002 was an excellent year for maize growth and all twelve sites were N responsive with average fertilized grain yields for nine of the twelve sites, for which data have been processed, being 232 bu/acre (14.5 Mg/ha). Exhaustive surface soil samples were also taken in 2002 from a long-term tillage x rotation study located in Concord, NE. Results showed that crop rotation with soybean nearly always resulted in greater native N supply than is experienced under continuous corn even though there is a net deficit of nitrogen to the soil following soybean harvest. The overall N budget of corn/soybean rotation and the estimates of indigenous N supply to corn following soybean suggest that N is being depleted from soil as a result of this rotation.

    Other soil N test studies were conducted as part of NC218. The activity of the enzyme b-glucosaminidase (EC 3.2.1.30) has also been proposed as a means of rapidly assessing N mineralization and, thus, available N in soil. Results from Iowa, clearly show b-glucosaminidase plays a major role in N mineralization in soils, and is affected by cropping systems and soil management. A preplant soil nitrate test was a good predictor of the economic optimum N rate for continuous corn, second-year corn following alfalfa, and corn following soybean grown in Wisconsin, but not for corn following alfalfa. Soil N tests including the INST, direct alkalization of soil samples, or the soil arylamidase activity test are being evaluated individually and in combination with other diagnostic N tests. The light fraction of organic matter (i.e. relatively undecomposed particulate organic matter) is being tested in California as an assessment tool to help determine soils that are not responsive to fertilizer addition.

    First year studies, at The Ohio State University, revealed N uptake by corn was increased when applied in combination with S. This first year study was conducted under severe drought conditions.

    A File Transfer Protocol (FTP) site has been set up on the University of Nebraska - Lincoln server for sharing data among the NC-218 participating states. Work is also progressing at the University of Nebraska  Lincoln on the development of a crop production model entitled Hybrid-Maize. The model will be used to generate yield potential maps for agroeco-regions within the corn belt for more precise development of fertility recommendations that better match yield potential.

    Impact Statements:
    1. Development of more accurate nitrogen fertility tests is absolutely essential in maintaining high levels of production that is economical and environmentally acceptable.
    2. NC218 has been the leader in proposing, developing and testing new methods to assess N fertility in soils.
    3. These studies make it possible to identify soils that require additional N inputs to improve crop growth and soils that are non-responsive and should not have fertilizer N applied to them.
    Last Modified: unknown

    Date of Annual Report: 05/18/2004

    Report Information:
  • Annual Meeting Dates: 03/17/04 to 03/18/04
  • Period the Report Covers: 04/2003 to 04/2004

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    Activities of the annual meeting primarily concerned committee business, a review of contributions of individual states to overall committee objectives, and development of plans for the coming year.

    Committee Business: A discussion took place regarding changes in status of committee members. J. Schmidt was slated to become Chair in 2004 but was going to resign from the committee. The committee decided that W. Horwath would remain chair to fill the successional void. C. Laboski will be taking a position at the University of Wisconsin. At this time, C. Laboski plans to remain a member of the committee but will be representing Wisconsin instead of Michigan. She will insure that Michigan data and reporting occur until her replacement is determined. D. Olk was nominated for Member-at-Large.

    Committee leadership for the 2005 meeting is: William Horwath Chair Carrie Laboski Secretary Dan Olk Member-at-Large Warren Dick Past Chair

    Report of Meeting Activities and Plans for Next Year: Gary Lemme presented the administrative report. Members of the committee reviewed efforts to write draft manuscripts of data collected from the previous NC218 project. These papers tentatively plan to focus on the following topics:

    1. Methods and characterization of data collected during last project including crop response and field histories. 2. Potential N mineralization quick test and their relationship to thermal units. 3. Plant sensing of N status. 4. Relationship of soil mineralizable C to mineralizable N. 5. Using testing techniques to predict soil N mineralization and develop fertilizer recommendations.

    D. Walters presented a new maize growth model. Initial results of model simulations suggest that planting date is critical to avoid high night temperatures during the latter part of the growing season.

    Discussion of the protocols to be used for the new project ensued. Each state reported on their plans to conduct field experiments according to the protocol developed for NC218 studies in the previous year.

    Accomplishments:
    The use of the Illinois Soil Nitrogen Test (ISNT), which is based on estimating amino sugar nitrogen (AS-N) content in soil continued to be tested in several states. The results from these studies are beginning to question to value of the Illinois N test as a predictor of in season N availability. The test did show a strong correlation with organic matter suggesting that total organic matter may be as useful when making field specific nitrogen recommendations.

    Temporal variations of ISNT values were shown not to be consistent from site to site in Illinois. At three locations, ISNT values decreased from April through late May and then commenced to increase back to the initial spring value by early November. At the other two locations, levels fluctuated over time, but showed no consistent trend. Based upon this work, it appears that the best time for soil sampling will be early spring. These results indicate the amino sugar pool may fluctuate as a result of such factors as climate, crop phenology or management, and therefore a more ridgid soil sampling protocols may need to be developed to standardize results of the ISNT.

    The ability of the INST to predict economic response of corn to N fertilizer was a major issue discussed. If the INST is to be predictive, there should be higher responses at low INST values and low responses at high INST values. Additionally, an INST threshold should exist above which the response is zero. At this time, the data being accumulated by NC218 researchers do not behave in this manner. It must be noted that many of the locations had an INSTcritical value of greater than 250 mg kg-1, which is the threshold set by the University of Illinois. It appears that two populations may exist in the data set. Additional analysis needs to be done to determine if there are certain characteristics of a population or if the variation is random.

    The activity of the enzyme B-glucosaminidase (NAGase) was shown to be related to N mineralization in soils. Studies on the effect of three tillage systems (no-till, chisel plow, and moldboard plow) and four residue placements) bare, normal, mulch, and double mulch) in soils showed that the activity values of NAGase were significantly affected by tillage and residue management practices, being the greatest in soils with no-till/double mulch and least with no-till/bare and moldboard/normal. NAGase activity was greatest under no-till/double mulch-treated soils. Linear regression analyses showed that the NAGase activity was significantly correlated with organic C in surface soils (r = 0.89***) and with organic C content at different depths (r = 0.97***).

    Analysis of the NC-218 mineralization test data set continued on a 72 site-year database evaluating the effectiveness of a suite of mineralization quick tests in estimating potentially mineralizable N (PMN) as determined by long-term aerobic incubation. Variation in extractable N and PMN was analyzed in relation to previous crop and site manure history. Preliminary analyses indicate that previous manure management was the primary determinant contributing to variability in quick test relationship to PMN.

    Small plot research conducted in 2001 showed that only one site tested in Illinois, that had an ISNT value >240 mg N/kg soil, had corn that responded to fertilizer inputs. In 2002, there was no response to applied N at any site that had an ISNT level greater than 240 mg N/kg soil. Over two years of work in Illinois, the ISNT has done a good job predicting non-responsive sites with only one failure out of 29 experiments. Results collected from the farmer-conducted WATER plots, however, were much less consistent than from the small plot studies. Corn, grown at 12 of the sites (over the two years of the WATER plot studies) that were projected as non-responsive by ISNT, responded to fertilizer N. Most of these failures occurred in 2002, a year characterized by heavy rains early in the spring and early summer followed by very dry soils through most of the rest of the growing season. These unusual climatic conditions undoubtedly would have had a negative impact on microbial activity necessary to convert the AS-N to plant available inorganic N.

    Second year studies, at The Ohio State University, revealed that sulfur significantly (Pd0.05) increased the yield of corn. The average yield across all N application rates for the no-S plots was 9.41 Mg/ha, which was significantly (P = 0.05) less than when S was applied. The average yield when S was applied was 9.97 Mg/ha -- a 6.0% increase.

    Impact Statements:
    1. Development of more accurate nitrogen fertility tests is absolutely essential in maintaining high levels of production that is economical and environmentally acceptable. NC218 has been the leader in proposing, developing and testing new methods to assess N fertility in soils.
    2. These studies make it possible to identify soils that require additional N inputs to improve crop growth and soils that are non-responsive and should not have fertilizer N applied to them.
    Last Modified: unknown

    Date of Annual Report: 06/18/2005

    Report Information:
  • Annual Meeting Dates: 03/09/05 to 03/10/05
  • Period the Report Covers: 03/2004 to 03/2005

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    Activities of the annual meeting primarily concerned committee business, a review of contributions of individual states to overall committee objectives, and development of publication meant for practitioners and cooperative extension for the dissemination of best management practices to increase fertilizer nitrogen use efficiency, brainstorming ideas for the next project and plans for the coming year.

    Committee Business: P. Scharf was elected member-at-large. Committee leadership for 2005-2006 is C. Laboski  chair, D. Olk  secretary, and W. Horwath  past chair. L. Bundy announced that C. Laboski would become Wisconsins official representative to the committee. The next annual meeting will be March 8 and 9, 2006 in Kansas City. The date is subject to change depending on when the NC ASA meeting is next March. W. Horwath will arrange a meeting at the SSSA annual meeting in Salt Lake City for the committee to finalize its proposal for the next project.

    Committee leadership for the 2006 meeting is: Carrie Laboski Chair Dan Olk Secretary Peter Scharf Member-at-Large William Horwath Past Chair

    Report of Meeting Activities and Plans for Next Year: Gary Lemme presented the administrative report. Members of the committee reviewed efforts to write draft manuscripts of data collected from the previous NC218 project and current projects. These papers tentatively plan to focus on the following topics:

    1. Methods and characterization of data collected during last project including crop response and field histories. 2. Potential N mineralization quick test and their relationship to thermal units. 3. Plant sensing of N status. 4. Relationship of soil mineralizable C to mineralizable N. 5. Using testing techniques to predict soil N mineralization and develop fertilizer recommendations.

    D. Walters presented a new maize growth model. Initial results of model simulations suggest that planting date is critical to avoid high night temperatures during the latter part of the growing season.

    Discussion of the protocols to be used for the new project ensued. Each state reported on their plans to conduct field experiments according to the protocol developed for NC218 studies in the previous year. There was general agreement to study the basic N mechanisms/chemistry along with looking at growing season-long dynamics. W. Horwath stated there was a need to combine techniques to show functional components such that results from an incubation type study would not be dependent on substrate/environment of the study. A tentative objective was defined as: Characterize the chemical composition of the mineralizable fraction of soil N. Sub-objectives include: 1) characterizing inter-annual variability of N mineralization as impacted by soil and crop management; and 2) estimate the turnover time of N and C in the mineralizable (or gross) pools. A potential title might be: Defining soil N fractions that contribute to N availability. Potential outputs from the project could be: 1) expand current projects outreach publication to a national scope. It was discussed to write a base proposal of research activities and then propose additional activities pending funding from a NRI/NSF grant.


    URL: Copy of minutes

    Accomplishments:
    Results on the Illinois Soil Nitrogen Test (ISNT), based on estimating amino sugar nitrogen (AS-N) content was presented for the third year from ongoing NC-218 research projects. As from the previous years results, this years result continue to question the value of the ISNT as a predictor of in season N availability. In a positive note, the ISNT continues to show a strong correlation with total soil organic matter (SOM) suggesting that total SOM or some fraction of SOM may be useful in developing a modified INST or new method to estimate specific field fertilizer nitrogen recommendations.

    Temporal variation in ISNT values continued to be inconsistent and show nonsignificant relationships to fertilizer nitrogen applications at both nonresponsive and responsive sites at all sites being examined by NC-218 investigators. The ability of the INST to predict economic response of corn to N fertilizer continued to be a major issue discussed. The NC-218 members are of the opinion that the test in its current state will not be useful as a predictive tool to address issues over application of fertilizer nitrogen.

    Results showing the relationship of the enzyme B-glucosaminidase (NAGase) activity to N mineralization continued to show a strong relationship. Studies on the effect of tillage systems and residue management continued to show the strong relationship between NAGase and N mineralization. The results prompted discussion by the group to hypothesize that the determination of specific fractions of soil organic matter may be useful to predict N mineralization.

    Analysis of the NC-218 mineralization test data set continued on a 72 site-year database evaluating the effectiveness of a suite of mineralization quick tests in estimating potentially mineralizable N (PMN) as determined by long-term aerobic incubation. Variation in extractable N and PMN was analyzed in relation to previous crop and site manure history. C mineralization showed a strong influence on N mineralization. These results confirm the notion that a specific fraction of SOM is controlling N mineralization.

    Results from three N response experiments showed that the PSNT had greater potential for predicting optimum N rates for corn than the ISNT. Results with archived samples from numerous N response experiments showed that the INST is not capable of predicting corn N requirements. The INST appears to measure a constant fraction of the N in soil organic matter rather than reflecting the amounts of readily mineralizable N in soils.

    Impact Statements:
    1. Development of more accurate nitrogen fertility tests is critical to addressing the need to maintain high levels of production that is economical and environmentally acceptable. NC218 has provided strong leadership in proposing, developing and testing new methods to assess N fertility in soils.
    2. Each member through there individual state efforts have contributed a great deal of information to outreach efforts to address efficient fertilizer nitrogen application to maintain crop yield and prevent environmental degradation.
    3. We continue in our efforts to develop soil tests that make it possible to identify soils that require additional N inputs to improve crop growth and soils that are non-responsive and should not have recommended levels fertilizer N applied.
    Last Modified: unknown

    Date of Annual Report: 05/09/2006

    Report Information:
  • Annual Meeting Dates: 03/08/06 to 03/09/06
  • Period the Report Covers: 04/2005 to 03/2006

    • Participants:
    Brief Summary of Minutes of Annual Meeting:
    2005 MINUTES: It was agreed to strike from the minutes of the 2005 meeting the phrase "that labs can be certified to perform" found in the second paragraph of the section, "Popular Press Article". Subsequently the minutes were approved as amended.

    STATE REPORTS: State reports were presented by AK, CA, IA, MN, MO, NE, OH, SD, and WI. Little committee-related work was done this year, primarily because the data for this 5-year research phase have already been collected. Discussion topics included recent negative findings with the Illinois Soil N Test, the current status of soil N testing in states, administrative changes in the agricultural colleges at North Central universities, and the need to target educational efforts at the proper sector(s) of the agricultural community--landowner versus farm manager versus crop consultant.

    PROGRESS OF PUBLICATIONS FROM PREVIOUS PROJECT: L. Bundy will soon finish writing a manuscript that characterizes the indigenous soil N supply and N use efficiency in the North Central region. This manuscript will also touch on the topic of a second proposed manuscript regarding the use of soil testing techniques for predicting soil N mineralization and developing fertilizer recommendations. D. Walters presented statistical analysis of the relationship of rapid mineralization quick tests to long-term aerobic incubation. P. Scharf will soon receive galley proofs for a manuscript on plant sensing of N status. No progress has been made with a manuscript on the relationship of soil mineralizable C to mineralizable N. It was decided to not revisit these manuscripts at future annual meetings.

    PROGRESS OF PUBLICATIONS FROM CURRENT PROJECT: G. Randall discussed progress in coordinating a joint outreach publication on best management practices (BMPs) for nitrogen use in the North Central region. Committee members have finished writing half of the sections. He has received state-specific BMPs for many of the North Central states. The committee discussed options for obtaining BMPs from states with inactive or no committee representation.

    C. Laboski discussed progress in compiling data from the committee's evaluation of the Illinois Soil N Test. The majority of states have submitted their data. The sites represent a mix of corn-based rotations, manure application, irrigation, drainage, and duration of experimental treatments. It was decided to publish the results in one joint journal paper and to simultaneously issue press releases in each of the states. The press releases would preferably cite Powerpoint presentations or extension-like publications that would be posted on web sites of each state university.

    NEW PROJECT PLANNING: D. Walters, W. Horwath, and D. Olk presented some analytical components of the new project plan, which intends to develop a deeper process-level understanding of soil N cycling in corn-based rotations. D. Walters stressed the need to continue the committee's traditions of a common experimental protocol at all sites and centralized laboratory analyses. He discussed the respective goals of research in long-term plots at research stations versus on-farm plots. W. Horwath discussed the soil N cycle and the application of the A value and 15N studies to understanding soil N cycling. D. Olk discussed the extraction of active fractions of soil organic matter and analyses for their quantities and biochemical nature of N and C. D. Walters discussed application of the hybrid maize model toward understanding the relative effects on crop yield of N availability and other factors. It was emphasized that this phase of research is predicated upon obtaining external funding, given the declining amounts of CSREES funds that are designated for committee research. A grant proposal will be written and submitted to the National Research Initiative (NRI) later in 2006. The degree of participation by each state in the proposal remains to be determined.

    The committee decided to pursue these process-level investigations of N cycling within the context of field trials that will evaluate corn crop response to lowered application rates of N fertilizer. The escalating cost of N fertilizer has prompted calls for lowering the recommended N fertilizer rates. There is, however, concern that reduced fertilizer input would over the long-term deplete the reserves of native soil N. Hence the committee will measure crop growth parameters (yield, N uptake) and the quantity and quality (i.e. chemical nature) of active pools of native soil N at these lower fertilizer rates. D. Walters discussed various programs within the NRI to which the grant proposal could be submitted. He will visit Washington, D.C. in April to further discuss the committee's proposal with NRI program leaders.

    CSREES REPORT: None. CSREES advisor was not present.

    ADMINISTRATIVE ADVISOR'S REPORT: None. Administrative advisor was not present.

    BUSINESS: The committee thanked L. Bundy for 20 years of service to the committee; this was his final committee meeting. J. Sawyer was elected member-at-large. Committee leadership for 2006-2007 is D. Olk, chairman, P. Scharf, secretary, and C. Laboski, past chair. The next annual meeting will be March 7-8, 2007 in Kansas City. To continue the planning for the next 5-year research phase, a subcommittee will meet during June or July in Ames, IA to develop specific protocols for all proposed research activities. A second subcommittee meeting will be held in the autumn to organize the writing of the grant proposal so that it can be submitted to the NRI by the potential December deadline. A conference call will shortly be arranged to gauge the level of interest in the new project plan by new committee members who did not attend this annual meeting. A termination report will be written for the current 5-year phase, which finishes September 30, 2006.

    Accomplishments:
    In 2005-2006 research continued on assessing the Illinois soil nitrogen test (ISNT) for its use predict nitrogen (N) mineralization and fertilizer N requirement for corn. Results showed that ISNT values were not related to observed economic optimum N rates (EONR) in field corn N response experiments and that the ISNT had no ability to separate N responsive from non-responsive sites. ISNT values were strongly correlated with the soil organic matter content of the experimental sites suggesting that the ISNT is measuring a constant fraction of the soil organic N rather than the readily mineralizable N component. Soil organic N fractions were not related to corn N response (percent yield increase due to added N fertilizer relative to control plot yield) although these experiments included cropping systems ranging from first year corn following alfalfa to continuous corn and showed marked differences in yield response to N fertilizer additions. Specifically, results showed that the soil amino sugar-N fraction was not related to observed corn N fertilizer response. Likewise, relationships between corn N fertilizer response and other hydrolyzable N fractions including hydrolyzable ammonium-N, (amino sugar + ammonium)-N, amino acid-N, and total hydrolyzable-N were also poor. A strong correlation was found between ISNT results and amino sugar-N, but ISNT was also strongly related to soil organic matter, soil total N, and soil total C. These results confirm the conclusion that the ISNT is measuring a constant fraction of the soil organic N instead of the readily mineralizable fraction of soil N. Results from this work indicate that the ISNT or the soil organic N fractions studied are not reliable predictors of corn N response. Compilation of data from 2001-2005 across the multiple states was begun. This data will be placed into a database and further analysis of the ISNT and glucosaminidase tests as a means to predict N mineralization and corn response to N fertilizer on a regional basis will be performed.

    Impact Statements:
    1. In 2005-2006 the ISNT has received much popular press as a new tool to refine N rates. However, results show that the ISNT is not a useful tool for predicting soil N mineralization, corn N response, or N fertilizer recommendations.
    2. Results of this work have demonstrated that in many situations farmers can use application rates lower than currently recommended and still attain optimum yield.
    3. Results of this project have been communicated to farmers and consultants across the region through Extension newsletter articles (internet and mail) and local/state/regional Extension meetings/conferences. It is estimated that more than 2,000 people across the country with responsibilities for making N rate decisions have been educated.
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