Progress 10/01/05 to 09/30/11
Outputs
OUTPUTS: Multiple sites in eastern North Carolina were selected based on differences in soil type and water holding capacity to examine the use of remote sensing in the visible, near infrared, and thermal spectra to determine nitrogen requirements for corn. Aerial photographs were used to measure canopy reflectance in the visible and near infrared wavelengths while a thermal imaging system was used to measure reflectance in the far infrared or thermal wavelengths. A split plot design in four blocks was used with two water regimes representing the main plots and five nitrogen rates representing the sub plots. Volumetric soil moisture, tissue nitrogen concentration, nitrogen uptake, leaf chlorophyll, and spectral reflectance were measured at V7 and again at V12. Grain yield was measured to determine the plant response to nitrogen rates within the different water regimes. Strong correlations were found between plant nitrogen uptake and spectral indices of green NDVI and green RVI (R2 > 0.79). Relationships between green NDVI or RVI and optimum nitrogen rates were also strong (R2 > 0.70). Systems tests were conducted at Kinson, NC using three nitrogen management regimes (whole field, current regional recommendation, and site-specific) to determine if the site-specific management of nitrogen based on remote sensing would result in less nitrogen applied, higher corn yield, and an improvement in nitrogen use efficiency. Site-specific systems reduced nitrogen applications by 15%, increased corn yield by 1%, and increased nitrogen use efficiencyA model for predicting nitrogen requirements from a digital image was developed based on the relationship between optimum nitrogen requirements and green NDVI. This model was able to correctly predict nitrogen requirement for wheat in 77% of the cases. Validation testing examining the use of remote sensing systems in comparison to current regional nitrogen recommendation systems found that the remote sensing system developed for corn using aerial images taken at VT reduced the amount of nitrogen applied to corn by 10% with no difference in grain yield between the site-specific remote sensing system and the current nitrogen recommendation system. These results support the observations from the small plot research and indicate that remotely sensed, site-specific nitrogen systems improve nitrogen use efficiency. Data on nitrogen losses to ground water sources shows that there was significantly less nitrogen in the ground water from the sites where the remotely sensed, site-specific nitrogen systems were used. It was noted that groundwater nitrate levels increased in all treatments following corn and decreased during the wheat-soybean cycles of the rotation. PARTICIPANTS: Dr. Dianne Farrar Dr. Ravi Scripada Dr. Jared Williams Dr. Randy Weisz Dr. Jeffrey White Dr. Ronnie Heiniger All of the above individuals either directed graduate studies involving this project or were trained and recieved their Ph.D. as a result of this project. TARGET AUDIENCES: Farmers Agricultural Consultants Extension Agents Environmental Organizations PROJECT MODIFICATIONS: There were no major changes in the approach that we used in this project. The specifications, objectives, materials and methods remained the same as those described in the intial project proposal.
Impacts
A field application system was developed for adjusting N rates based on aerial images and/or canopy temperature. Software for comparing the use of this system for variable-rate application of nutrients was developed and distributed to growers and consultants in North Carolina. Field testing showed that fertilizer use was reduced by 14% by using variable-rate application systems when appropriate. Papers were presented at several national and international meetings and several publications were accepted and printed in scientific journals.
Publications
- Weisz, R., C.R. Crozier, and R.W. Heiniger. 2001. Optimizing nitrogen application timing in no-till soft red winter wheat. Agron. J. 93:435-442.
- Flowers, M., R. Weisz, and R. Heiniger. 2001. Remote sensing of winter wheat tiller density for early nitrogen application decisions. Agron. J. 93:783-789.
- R.P. Sripada, D.C. Farrer, R. Weisz, R.W. Heiniger, and J.G. White. 2007. Aerial color infrared photography to optimize in-season nitrogen fertilizer recommendations in winter wheat. Agron. J. 99:1424-1435.
- R. Weisz, R.P. Sripada, R.W. Heiniger, J.G. White, and D.C. Farrer. 2007. In-season tissue testing to optimize soft red winter wheat nitrogen fertilizer rates: Influence of biomass. Agron. J. 99:511-520.
- Farrer, D.C., R. Weisz, R. Heiniger, J.P. Murphy, and J.G. White. 2006. Minimizing protein variability in soft red winter wheat: Impact of nitrogen application timing and rate. Agron. J. 98:1137-1145.
- Sripada, R.P., R.W. Heiniger, J.G. White, C.R. Crozier, and A.D. Meijer. 2006. Attempt to validate a remote sensing-based late-season corn nitrogen requirement prediction system. Online. Crop Management doi:10.1094/CM-2006-0405-01-RS.
- Sripada, R.P., R.W. Heiniger, J.G. White, and A.D. Meijer. 2006. Aerial color infrared photography for determining early in-season nitrogen requirements for corn. Agron. J. 98:968-977.
- Sripada, R.P., R.W. Heiniger, J.G. White, and R. Weisz. 2005. Aerial color infrared photography for determining late-season nitrogen requirements for corn. Agron. J. 97:1443-1451.
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: A field application system has been developed for adjusting N rates based on canopy temperature. Software for comparing the use of this system for variable-rate application of nutrients has been developed and is being distributed to growers and consultants in North Carolina. Field testing has shown that fertilizer use can be reduced by 14% by using variable-rate application systems when appropriate. A manuscript has been published detailing this software and its use. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Corn Growers, Crop Consultants, Agricultural Scientists, Agronomists PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Projects in 2010 will continue research into using canopy temperature to measure N requirements for corn. Two field tests will be conducted using different N rates at planting and layby with the purpose of developing relationships between a N stress index (NSI) calculated from canopy temperature and vapor pressure deficit and economic optimum N rates. Analysis of three years of data indicate a strong relationship between NSI and optimum N rates. A field application system featuring a thermal sensor, portable computing systems, and appropriate software has been developed to drive a variable-rate N applicator.
Publications
- Havlin, J. and R.W. Heiniger. 2009. Variable rate decision support tool. Precision Agric. 10:356-369.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: Projects in 2009 continued research into using canopy temperature to measure N requirements for corn. Measurements of canopy temperature and tissue nitrogen concentration revealed a clear relationship between canopy temperature and the nitrogen status of the crop. Two field tests were conducted using different N rates at planting and layby with the purpose of developing relationships between a N stress index (NSI) calculated from canopy temperature and vapor pressure deficit and economic optimum N rates. Analysis of two years of data indicate a strong relationship between NSI and optimum N rates. A field application system featuring a thermal sensor, portable computing systems, and appropriate software are being developed to drive a variable-rate N applicator. PARTICIPANTS: Dr. Ronnie Heiniger is the principal investigator in this project. He directed the field research and provided guidance in experimental design and data analysis. Dr. Randy Weisz provided guidance and expert analysis of the relationships between canopy temperature and N requirement. Timothy Smith was the field technician who did the field work and data collection for the project. TARGET AUDIENCES: Target audiences are farmers and agricultural consultants who supervise fertility practices for growing corn. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
A field application system has been developed for adjusting N rates based on canopy temperature and is in the final stages of testing. Software for comparing the use of this system for variable-rate application of nutrients has been developed and is being distributed to growers and consultants in North Carolina. Field testing has shown that fertilizer use can be reduced by 14% by using variable-rate application systems when appropriate. A manuscript has been published detailing this software and its use.
Publications
- Havlin, J.L. and R.W. Heiniger. 2009. A variable-rate decision support tool. Precision Agriculture, Springer US, 22.04.2009, vol. 10, no. 4, pp. 356-369
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Projects in 2008 focused on using canopy temperature to measure N requirements for corn. Previous measurements of canopy temperature and tissue nitrogen concentration revealed a clear relationship between canopy temperature and the nitrogen status of the crop. Two field tests were conducted using different N rates at planting and layby with the purpose of developing relationships between a N stress index (NSI) calculated from canopy temperature and vapor pressure deficit and economic optimum N rates. Initial analysis of the data indicated a strong relationship between NSI and optimum N rates. A field application system featuring a thermal sensor, portable computing systems, and appropriate software are being developed to drive a variable-rate N applicator. Field tours and demonstrations were conducted at one of the test sites to illustrate to growers the techniques and equipment being developed. A demonstration at the 2008 Kinston Precision Agriculture Field Day showed growers the prototype application equipment being developed. PARTICIPANTS: Key individuals in this project are R.W. Heiniger and P.R. Weisz. In 2008 collaboration from J.A. Havlin and G.R. Roberson was helpful in developing technology or training modules. Training sessions depended on county personnel and supporting organizations such as Southern States Cooperative, Inc. and Helena Chemical Co., Inc. to provide data, funding, advertisement, and technical support. TARGET AUDIENCES: The target audience for this project has been growers of crops such as corn and wheat. The goal is to change their current farming practices resulting in less N applied, less environmental contamination, and increased yield or profit. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
There was an increased interest from growers in adopting site-specific management practices for N applications due to the rising cost of N fertilizer. As a result there was an increase in the number of growers and the number of acres using the practices developed in this project. Currently, it is estimated that over 180,000 acres of corn and wheat were managed using the techniques and practices developed in this research. A new company providing aerial photographs for this process began operations in North Carolina in 2008 to serve this growing need. Field tours and demonstrations increased the awareness of growers to these new techniques. Training sessions were held in two locations, Statesville and Kinston, with the goal of helping growers management N applications through site-specific technologies.
Publications
- R. Weisz, R.P. Sripada, R.W. Heiniger, J.G. White, and D.C. Farrer. 2007 In-season tissue testing to optimize soft red winter wheat nitrogen fertilizer rates: Influence of biomass. Agron. J. 99:511-520.
- Williams, J.D., C.R. Crozier, J.G. White, R.W. Heiniger, R.P. Sripada, and D.A. Crouse. 2007. Illinois soil nitrogen test predicts southeastern U.S. corn economic optimum nitrogen rates. Soil Sci. Soc. Am. J. 71: 735-744.
- R.P. Sripada, D.C. Farrer, R. Weisz, R.W. Heiniger, and J.G. White. 2007 Aerial color infrared photography to optimize in-season nitrogen fertilizer recommendations in winter wheat. Agron. J. 99:1424-1435.
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Progress 10/01/06 to 09/30/07
Outputs
In wheat, a five-year study found that using tiller counts and tissue testing consistently resulted in an increase in wheat yield and grower profit while reducing the amount of nitrogen applied. Our previous research developed a system for using remote sensing to determine tiller counts. Research in 2007 resulted in a system for measuring nitrogen concentrations in wheat leaves using a photograph. This system was tested on farmer fields and resulted in a significant savings in nitrogen applied. These systems for measuring tillers and nitrogen in the leaf were demonstrated at the North Carolina Small Grain Field Day, county meetings, field tours, extension publications and the Precision Farming Field Days. For corn, over three dozen field tests were used to develop a relationship between green reflectance from the corn canopy and optimum nitrogen requirement. An index was identified that was able to accurately predict corn nitrogen requirements (R2 > 0.89). Field tests
found that using this index to determine the amount of nitrogen to apply to corn reduced nitrogen application rates by 50% while increasing corn yield 3 to 5 bushels per acre. Other studies as a part of this project tested new methods of measuring plant available nitrogen in the soil. These studies indicated that certain methods could determine nitrogen available for plant uptake at planting. A complete nitrogen management system based on soil testing and aerial photographs to predict nitrogen needs is being tested. One result of this testing was a clear indication that growers should apply at least 50 pounds of nitrogen at planting. County meetings and field tours were used to show grower how such a system could be implemented on their farm and how they would use it to reduce nitrogen applications.
Impacts
In wheat, growers have increased their use of tiller counts and tissue tests by using aerial images. In 2007, the number of growers using this system increased with over 150,000 acres of wheat was managed this way. Field studies found that growers reduced costs by $2.00 per acre resulting in a savings of $300,000. In Corn, growers readily adopted the recommendations of changing how nitrogen was applied at planting. Surveys at summer field days showed that over 60% of the growers were applying at least half of the nitrogen required by the crop at planting. Based on field comparisons at the Kinston test site and from grower reports, this practice helped increase corn yield by 20 to 25 bushels per acre despite drought conditions. Many growers found that their yields actually increased over those recorded in 2001 when weather conditions were ideal for corn. If we conservatively calculate that only 1/10 of the state corn acres realized a yield increase from this practice,
this amounts to an increase of 120,000 bu of corn grown in North Carolina. At $2.00 per bushel the financial gain to the state economy was $480,000.
Publications
- Sripada, R.P., R.W. Heiniger, J.G. White, C.R. Crozier, and A.D. Meijer. 2006. Attempt to validate a remote sensing-based late-season corn nitrogen requirement prediction system. Online. Crop Management doi:10.1094/CM-2006-0405-01-RS.
- Sripada, R.P., R.W. Heiniger, J.G. White, and A.D. Meijer. 2006. Aerial color infrared photography for determining early in-season nitrogen requirements for corn. Agron. J. 98:968-977.
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Progress 10/01/05 to 09/30/06
Outputs
Research projects were done at several sites in eastern North Carolina to validate the measured relationship between the spectral index developed through four years of research and nitrogen requirements for corn. In addition, these sites were used to determine the impact of thermal properties of the corn canopy on nitrogen requirement. The focus of the work in 2006 was to validate relationships found between a relative green difference vegetative index (RGDVI) and nitrogen requirement at growth stage (V7 and VT). Examination of the nitrogen recommendations derived from improved algorithms based on RGDVI at VT compared to the measured optimum nitrogen rate indicated that the relationship using RGDVI was able to capture 90% of the variability in optimum nitrogen rates. Measurements of canopy temperature and tissue nitrogen concentration revealed a clear relationship between canopy temperature and the nitrogen status of the crop. Systems tests at Kinston, NC testing the
use of remote sensing systems in comparison to current regional nitrogen recommendation systems found that the remote sensing system developed for corn using aerial images taken at VT reduced the amount of nitrogen applied to corn by 10% with no difference in grain yield between the site-specific remote sensing system and the current nitrogen recommendation system. These results support the observations from the small plot research and indicate that remotely sensed, site-specific nitrogen systems improve nitrogen use efficiency.
Impacts
This research indicates that the use of remote sensing can result in accurate predictions of nitrogen rates for corn. Field studies indicate that the improvement in accuracy will reduce the amount of nitrogen applied by 10% and can decrease the cost of nitrogen application on corn. Data from studies using canopy temperature to measure crop nitrogen requirement found strong indications that canopy temperature could also be used to determine nitrogen rates for corn. This would lead to a quicker, less expensive, procedure for determining nitrogen rates.
Publications
- Nelson, J.R., R. Heiniger, and L. Hendrickson. 2005. Determining the value of a site-specific decision support system using aerial photographs to prescribe crop inputs for cotton. pp. 1983-1994. Proc. of the 2005 Beltwide Cotton Conference. New Orleans, LA. 4-7 Jan. 2005. National Cotton Council. Memphis, TN.
- Sripada, R., R. Heiniger, J. White, R. Weisz, and C. Crozier. 2005. Remote sensing based early and late in-season N management decisions in corn. In D.J. Mulla, R.H. Rust, and W.E. Larson (ed.). Proceedings of the 7th International Conference on Precision Agriculture. Minneapolis, MN. 25-28 July 2004. ASA, CSSA, SSSA. Madison,WI.
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Progress 10/01/04 to 09/30/05
Outputs
Research projects were done at two sites in eastern North Carolina to validate the measured relationship between the spectral index developed through four years of research and nitrogen requirements for corn. In addition, these sites were used to determine the impact of thermal properties of the corn canopy on nitrogen requirement. A split-split plot design in five blocks was used at Plymouth and Lewiston to examine the impact of nitrogen treatments both at planting and at layby and water regimes on nitrogen requirements for corn. Aerial photographs were taken twice during the year at V7 and V12 to measure reflectance in the visible and near infrared wavelengths. Volumetric soil moisture, tissue nitrogen concentration, nitrogen uptake, leaf chlorophyll, and canopy temperature were measured at the same time that the aerial photographs were taken. Grain yield was measured to determine the plant response to nitrogen. The focus of the work in 2005 was to validate
relationships found between a relative green difference vegetative index (RGDVI) and nitrogen requirement at growth stage (V7 and VT). Examination of the nitrogen recommendations derived from the algorithms based on RGDVI at VT compared to the measured optimum nitrogen rate indicated that the relationship using RGDVI was able to capture 82% of the variability in optimum nitrogen rates. Although RGDVI tended to over-predict nitrogen requirements, the slope of the relationship between measured and predicted nitrogen rates did not differ from 1. Measurements of canopy temperature and tissue nitrogen concentration revealed a clear relationship between canopy temperature and the nitrogen status of the crop. These data are being analyzed with the data taken in 2003 to develop a relationship between canopy temperature and nitrogen requirement. Systems tests at Kinston, NC testing the use of remote sensing systems in comparison to current regional nitrogen recommendation systems found that
the remote sensing system developed for corn using aerial images taken at VT reduced the amount of nitrogen applied to corn by 10% with no difference in grain yield between the site-specific remote sensing system and the current nitrogen recommendation system. These results support the observations from the small plot research and indicate that remotely sensed, site-specific nitrogen systems improve nitrogen use efficiency.
Impacts
This research indicates that the use of remote sensing can result in accurate predictions of nitrogen rates for corn. Field studies indicate that the improvement in accuracy will reduce the amount of nitrogen applied by 10% and can decrease the cost of nitrogen application on corn. Data from studies using canopy temperature to measure crop nitrogen requirement found strong indications that canopy temperature could also be used to determine nitrogen rates for corn. This would lead to a quicker, less expensive, procedure for determining nitrogen rates.
Publications
- Hong, H., C. Crozier, J.White, R. Weisz, R. Heiniger, and R. Sripada. 2005. Remote sensing for precision N management in a corn-wheat-soybean rotation. pp. 1351-1365. In D.J. Mulla (ed.). Proceedings of the 7th International Conference on Precision Agriculture and Other Precision Resources Management. Minneapolis, MN. 25-28 July 2004. University of Minnesota, St. Paul, MN.
- Sripada, R.P., R.W. Heiniger, J.G. White, and R. Wiesz. 2005. Aerial color infrared photography for determining late-season nitrogen requirements for corn. Agron. J. 97:1443-1451.
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Progress 10/01/03 to 09/30/04
Outputs
Research projects were done at three sites in eastern North Carolina to examine the use of visible, near infrared, and thermal spectra to determine nitrogen requirements for corn. A split-split plot design in five blocks was used at Plymouth and Lewiston to examine the impact of nitrogen treatments both at planting and at layby and water regimes on nitrogen requirements for corn. Aerial photographs were taken twice during the year at V7 and V12 to measure reflectance in the visible and near infrared wavelengths. Volumetric soil moisture, tissue nitrogen concentration, nitrogen uptake, leaf chlorophyll, and canopy temperature were measured at the same time that the aerial photographs were taken. Grain yield was measured to determine the plant response to nitrogen rates within the different water regimes. The focus of the work in 2004 was to quantify relationships found between green RVI and nitrogen requirement at growth stage (V7). Unfortunately, the examination of
this relationship at V7 found that green RVI could only account for 43% of the differences in nitrogen requirements at that early growth stage. Current work is focused on using thermal imaging or other plant measurements to help improve the prediction of nitrogen rates. Systems tests at Kinston, NC testing the use of remote sensing systems in comparison to current regional nitrogen recommendation systems found that the remote sensing system developed for corn using aerial images taken at VT reduced the amount of nitrogen applied to corn by 10% with no difference in grain yield between the site-specific remote sensing system and the current nitrogen recommendation system. These results support the observations from the small plot research and indicate that remotely sensed, site-specific nitrogen systems improve nitrogen use efficiency. Data on nitrogen losses to ground water sources shows that there was significantly less nitrogen in the ground water from the sites where the remotely
sensed, site-specific nitrogen systems were used. It was noted that groundwater nitrate levels increased in all treatments following corn and decreased during the wheat-soybean cycles of the rotation.
Impacts
Using the relationships developed through this research, growers are using aerial images to determine tiller density and nitrogen requirements in wheat and adjusting nitrogen applications in corn. Field data indicate that, on average, nitrogen applications have been reduced by 8 to 10% and that yields of corn and wheat have increased slightly (2 to 4%). These results have increased the number of growers using remote sensing and increased the demand for in-season aerial photography. Initial ground water data shows that using in-season remote sensing to adjust nitrogen rates reduces ground water nitrogen concentrations during periods of greater rainfall and reduced potential evapotranspiration.
Publications
- Weisz, R., J.G. White, R. Heiniger, B. Knox, and L. Reed. 2003. Long-term variable rate lime and phosphorus application for piedmont no-till field crops. Precision Agriculture. 4:311-330.
- Flowers, M., R. Weisz, and R. Heiniger. 2003. Quantitative approaches for using color infrared photography for assessing in-season nitrogen status in winter wheat. Agron. J. 95: 1189-1200.
- H. Li, J.G. White, R. Weisz, C. Crozier, R. Heiniger, and D.A. Crouse. 2003. Spatial association of soil chemical and physical properties with soil map units in a coastal plain soil. p.p. 167-180. In P.C. Robert, R.H. Rust, and W.E. Larson (ed.). Proceedings of the 6th International Conference on Precision Agriculture and Other Precision Resources Management. Bloomington, MN. 14-17 July 2002. ASA, CSSA, SSSA. Madison,WI.
- Flowers, M.D., R. Weisz, and R. Heiniger. 2003. In-season nitrogen based site-specific management in winter wheat. p.p. 206-221. In P.C. Robert, R.H. Rust, and W.E. Larson (ed.). Proceedings of the 6th International Conference on Precision Agriculture and Other Precision Resources Management. Bloomington, MN. 14-17 July 2002. ASA, CSSA, SSSA. Madison,WI.
- Shripada, R.P., R.W. Heiniger, J.G. White, J.M. Burleson, C.R. Crozier, and R. Weisz. 2003. Aerial color infrared photography for determining in-season nitrogen requirements for corn. 2003. p.p. 1508-1520. In P.C. Robert, R.H. Rust, and W.E. Larson (ed.). Proceedings of the 6th International Conference on Precision Agriculture and Other Precision Resources Management. Bloomington, MN. 14-17 July 2002. ASA, CSSA, SSSA. Madison,WI.
- Flowers, M. R. Wiesz, and R. Heiniger. 2004. In-season optimization and site-specific management in for soft red winter wheat. Agron. J. 96:124-134.
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Progress 10/01/02 to 09/30/03
Outputs
Two sites in eastern North Carolina were selected based on differences in soil type and the availability of irrigation. Studies were conducted at these sites to examine the use of remote sensing using visible, near infrared, and thermal spectra to determine nitrogen requirements for corn. A split-split plot design in five blocks was used to examine the impact of nitrogen treatments both at planting and at layby and water regimes on nitrogen requirements for corn. Aerial photographs were taken twice during the year at V7 and V12 and a thermal scanner was used at V12 to measure reflectance in the near infrared and thermal wavelengths. Volumetric soil moisture, tissue nitrogen concentration, nitrogen uptake, leaf chlorophyll, and canopy temperature were measured at the same time that the aerial photographs or thermal scans were taken. Grain yield was measured to determine the plant response to nitrogen rates within the different water regimes. The focus of the work in
2003 was to validate the strong relationships found between green RVI and nitrogen requirements in 2002 and to determine if a similar relationship could be used at an earlier growth stage (V7). Results from the field trials where nitrogen was applied at V12 showed that the green RVI could predict nitrogen requirements accounting for 91% of the variability between predicted and observed data. However, the examination of similar relationships at V7 found that green RVI could only account for 43% of the differences in nitrogen requirements at that early growth stage. Current work is focused on using thermal imaging to help improve the prediction of nitrogen rates. Systems tests at Kinston, NC testing the use of remote sensing systems in comparison to current regional nitrogen recommendation systems found that the remote sensing system described by Flowers et al., 2001 reduced the amount of nitrogen applied to wheat by 12% with no difference in grain yield between the site-specific remote
sensing system and the current nitrogen recommendation system. These results support the observations made in the corn phase of the rotation and indicate that remotely sensed, site-specific nitrogen systems improve nitrogen use efficiency. Data on nitrogen losses to ground water sources is still being assessed, but two years data from ground water samples shows that during critical periods of the year such as spring or late fall there was significantly less nitrogen in the ground water from the sites where the remotely sensed, site-specific nitrogen systems were used.
Impacts
Using the relationships developed through this research, growers are using aerial images to determine tiller density and nitrogen requirements in wheat and adjusting nitrogen applications in corn. Field data indicate that, on average, nitrogen applications have been reduced by 8 to 10% and that yields of corn and wheat have increased slightly (2 to 4%). These results have increased the number of growers using remote sensing and increased the demand for in-season aerial photography. Initial ground water data shows that using in-season remote sensing to adjust nitrogen rates reduces ground water nitrogen concentrations during periods of greater rainfall and reduced potential evapotranspiration.
Publications
- Flowers, M., R. Weisz, R. Heiniger, B. Tarleton, and A. Meijer. 2003. Field validation of a remote sensing technique for early nitrogen application decisions in wheat. Agron. J. 95:167-176.
- Heiniger, R.W., R.G. McBride, and D.E. Clay. 2003. Using Soil Electrical Conductivity to Improve Nutrient Management. Agron. J. 95:508-519.
- Flowers, M., R. Weisz, and R. Heiniger, and P.R. Weisz. 2001. Remote Sensing of Winter Wheat Tiller Density for Early Nitrogen Application Decisions. Agron. J. 93:783-789.
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Progress 10/01/01 to 09/30/02
Outputs
Two sites in eastern North Carolina were selected based on differences in soil type and water holding capacity to examine the use of remote sensing in the visible, near infrared, and thermal spectra to determine nitrogen requirements for corn. Aerial photographs were used to measure canopy reflectance in the visible and near infrared wavelengths while a thermal imaging system was used to measure reflectance in the far infrared or thermal wavelengths. A split plot design in four blocks was used with two water regimes representing the main plots and five nitrogen rates representing the sub plots. Volumetric soil moisture, tissue nitrogen concentration, nitrogen uptake, leaf chlorophyll, and spectral reflectance were measured at V7 and again at V12. Grain yield was measured to determine the plant response to nitrogen rates within the different water regimes. The results supported the work done in 2001. Strong correlations were found between plant nitrogen uptake and
spectral indices of green NDVI and green RVI (R2 > 0.79). Relationships between green NDVI or RVI and optimum nitrogen rates were also strong (R2 > 0.70). Systems tests were conducted at Kinson, NC using three nitrogen management regimes (whole field, current regional recommendation, and site-specific) to determine if the site-specific management of nitrogen based on remote sensing would result in less nitrogen applied, higher corn yield, and an improvement in nitrogen use efficiency. Site-specific systems reduced nitrogen applications by 15%, increased corn yield by 1%, and increased nitrogen use efficiency. Data on nitrogen loss to ground water sources is still being assessed. In wheat, four sites were used to validate the use of remote sensing to determine tiller number and nitrogen requirements. A model for predicting nitrogen requirements from a digital image was developed based on the relationship between optimum nitrogen requirements and green NDVI. This model was able to
correctly predict nitrogen requirement for wheat in 77% of the cases.
Impacts
Based on the results of this research into relationships between nitrogen requirements and crop nitrogen status and spectral properties, growers have increased the amount of nitrogen applied at planting, reduced the total amount of nitrogen applied by 10%, and started using in-season tissue testing to determine nitrogen requirements for wheat. Results from county demonstration tests indicate that corn yields have been increased by 5% while the amount of nitrogen applied has been reduced. This has increased grower profit in wheat-soybean-corn cropping systems. Data on the impact of these nitrogen management practices on nitrogen losses to surface and ground waters are expected to show reductions in nitrogen loading.
Publications
- No publications reported this period
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Progress 10/01/00 to 09/30/01
Outputs
Three sites in eastern North Carolina were selected based on differences in soil type and water holding capacity to examine the use of remote sensing in the visible, near infrared, and thermal spectra to determine nitrogen requirements for corn. Aerial photographs were used to measure canopy reflectance in the visible and near infrared wavelengths while a thermal imaging system was used to measure reflectance in the far infrared or thermal wavelengths. A split plot design in four blocks was used with three water regimes representing the main plots and four nitrogen rates representing the sub plots. Volumetric soil moisture, tissue nitrogen concentration, nitrogen uptake, and leaf chlorophyll were measured at V12 at the same time that the remote sensing measurements were taken. Grain yield was measured to determine the plant response to nitrogen rates within the different water regimes. Strong correlations were found between plant nitrogen uptake and spectral indices
of green NDVI and green RVI (R2 > 0.83) and between tissue nitrogen concentration and reflectance in the thermal wavelengths (R2 = 0.91) when measured within water regimes. Relationships between green NDVI or RVI and optimum nitrogen rates were also strong (R2 > 0.80). In wheat, four sites were used to validate the use of remote sensing to determine tiller number and nitrogen requirements. Validation of the algorithm used to determine tiller numbers found that it accurately predicted tiller counts (R2 = 0.87). A model for predicting nitrogen requirements from a digital image was developed based on the relationship between optimum nitrogen requirements and green NDVI. This model will be tested and validated in 2002. The first year of systems testing using three nitrogen management regimes (whole field, current regional recommendation, and site-specific) showed that all three resulted in similar yield but that the site-specific management system used less nitrogen and resulted in lower
costs.
Impacts
Results of the nitrogen management systems test were used in educating growers on the benefits of site-specific nitrogen management. This resulted in improved production practices and better nitrogen use efficiency as documented by farm visits and producer records. Use of aerial images to determine tiller counts increased in 2001 and a continuing improvement in wheat yield has been noted.
Publications
- Weisz, R., C.R. Crozier, and R.W. Heiniger. 2001. Optimizing nitrogen application timing in no-till soft red winter wheat. Agron. J. 93:435-442.
- Flowers, M., R. Weisz, and R. Heiniger. 2001. Remote sensing of winter wheat tiller density for early nitrogen application decisions. Agron. J. 93:783-789.
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Progress 10/01/00 to 12/31/00
Outputs
Six sites across North Carolina were used to examine the use of color and near-infrared photographs to determine crop nitrogen status at two growth stages in corn, V7 and V12. A significant correlation was found between the normalized difference vegetative index (NDVI) measured at V12 and relative corn yield across all sites(R2=0.88). This and other spectral indices were correlated with plant nitrogen uptake, percent tissue nitrogen, and leaf chlorophyl content. Current analysis is being done to determine if there is a relationship between optimum nitrogen fertilizer rates and any of the spectral indices developed in this project. In wheat, three sites were chosen to examine tiller development and nitrogen status at GS25 and GS30. There was a very strong relationship between tiller number and near-infrared reflectance at GS25 (R2=.92). This confirmed earlier research that found that an infrared photograph could be used to predict tiller number. Validation of this
relationship across wheat varieties and tillage conditions indicates that a single equation can be used. There was also a good relationship between NDVI and plant nitrogen uptake in wheat. However, plant nitrogen uptake is not a good indicator of plant fertilizer requirements. Further investigations are being conducted to find other methods of using spectral information to predict fertilizer requirements.
Impacts
The validation of the relationship between infrared reflectance and tiller number has resulted in the use of aerial photographs to examine fields to determine if they need early nitrogen applications. This has increased the use of tiller density in determining nitrogen rates and timing resulting in a 10% increase in wheat yield and an improvement in nitrogen use efficiency.
Publications
- No publications reported this period
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Progress 10/01/98 to 09/30/99
Outputs
Using the data collected over the past two years a soybean seed growth model was developed which had components describing source and sink contributions to seed weight. This years studies focused on determining how accurately this seed growth model predicted final seed weight under a variety on conditions. Adverse weather in eastern North Carolina in 1999 severely reduced soybean seed weight and final crop yield. Despite the unusual weather conditions, the soybean seed growth model accurately predicted seed weight, R2=0.94, at all five locations across a range of planting dates, seeding rates, and soybean cultivars. Furthermore, the model demonstrated the role that limited photosynthetic flux had on soybean yields. The model accurately predicted which cultivars had the capacity to adjust to low-light, wet conditions and those that did not have such a capacity. This soybean seed growth model improved the accuracy of yield predictions by 21% in the SOYGRO soybean growth
model. Future work on examining differences in soybean seed growth within a field should help identify whether this model would have the ability to determine the causes of site-specific differences in soybean seed weight. This will be the focus of research trials in 2000.
Impacts
Development of a soybean seed growth model with features describing source and sink contributions to seed weight has improved our ability to predict soybean seed weight and to identify the factors which cause reductions in seed weight and soybean yield. This research is leading to improved cultivar selection and identification of best management practices for growing soybeans in the southeast. Current research should help identify site-specific cultivars that would improve soybean yields.
Publications
- No publications reported this period
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Progress 01/01/98 to 12/31/98
Outputs
Field studies were designed to further define the influence of genetics on seed fill in soybean. Results from these studies show that there are variety differences that influence the rate of seed fill based on the accumulation of biomass by the soybean plant. Over 30 different soybean varieties were tested including many of the newer Roundup Ready varieties. Twelve varieties indicated an ability to translocate carbon to the seed during periods of environmental stress. The remaining varieties did not exhibit this trait. To demonstrate the potential value that carbon translocation would have in different environments, two varieties, Holladay and Delta Pine 3588,were compared across a range of different environments using precision technologies. This comparison showed that when grown under stress Holladay had higher yields and less variability in yield. However, in good growing conditions, 3588 had higher yields. This data indicates that varieties could be selected for
particular growing conditions based on their ability to translocate carbon to the seed during periods of stress. Proper variety selection could increase overall soybean yields from 0.4 to 0.8 Mg per ha.
Impacts
(N/A)
Publications
- No publications reported this period
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