Source: IOWA STATE UNIVERSITY submitted to
REAL-TIME SOIL NITRATE ANALYSIS SYSTEM FOR PRECISION NITROGEN APPLICATION
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0186740
Grant No.
2001-35102-09879
Project No.
IOW06531
Proposal No.
2000-01002
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Nov 15, 2000
Project End Date
Nov 14, 2003
Grant Year
2001
Project Director
Birrell, S. J.
Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
AGRI & BIOSYSTEMS ENGINEERING
Non Technical Summary
Over the last half century, agricultural production has increased dramatically due to the introduction of new hybrids, improved agronomic knowledge, mechanization of agriculture, pesticides and chemical fertilizers. Unfortunately, the widespread use of nitrate fertilizers has increased the potential for contamination of water resources leading to human health risks. The goal of this project is to develop a real-time soil nitrate sensor. A real-time nitrate sensor used in conjunction with established soil nitrate test recommendations, such as the pre-sidedress nitrate test (PSNT) could have a significant impact on fertilizer application. There is potential for reduction in fertilizer inputs with negligible reductions in yield, while reducing the potential for environmental degradation due to excess nitrate in the environment.
Animal Health Component
80%
Research Effort Categories
Basic
20%
Applied
80%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1020110200040%
2050110202040%
4020110202020%
Goals / Objectives
The overall goal this research is to develop a real-time soil nutrient analysis system, based on ion-selective field-effect transistors (ISFETs). The work concentrates on the development of nitrogen sensors, due to the economic importance of these fertilizers and the potential environmental effects of excess fertilizer applications. However, the proposed analysis system could be adapted to sense potassium, phosphate, soil pH, soil micro-nutrients and used for the simultaneous analysis of multiple nutrients. The objectives are: 1) Develop a real-time soil sampler and extraction system for soil nutrient analysis. The system must minimize reagent consumption to allow for continuous sampling, and be capable of within-field collection of soil samples at multiple depths. 2) Develop a miniaturized flow injection analysis (FIA) system using ion-selective field effect transistors (ISFETs) to sense nutrient levels in soil extracts. The overall FIA/ISFET system must survive field operation and be capable of self-calibration. 3) Integrate and evaluate the soil sampling and extraction system and the FIA/ISFET system to develop a prototype real-time soil analysis system for testing in a soil bin and in fields.
Project Methods
The time lag between obtaining a soil sample and the result must be minimized (< 10 s). The sampling period should be considerably less, to allow averaging of individual readings to account for extremely short range variability. The consumption of extracting solutions must be minimized to reduce costs and eliminate potential environmental or crop damage from extractants deposited in the soil. Objective 1: The extraction of a consistent percentage of the nutrient in the soil sample must be achieved for a reliable soil nutrient analysis system. The effect of soil type and texture, sample volume, sample preparation, and rate of extraction solution injection on extraction performance is being tested. The soil sampling system will use multiple sensors to analyze the nutrient concentration at specific depths to obtain multiple readings from which the average nutrient levels of the profile can be calculated. Different configurations of the soil sampling mechanism will be tested in a soil bin. The precision of the system will be evaluated in terms of the volume of soil collected, soil to extract ratio, and nitrate concentration of the filtrate obtained. The interaction between travel speed, soil type and texture, soil compaction, soil moisture, mixing and filtration time will be evaluated. Objective 2: Previous work on the ISFET/FIA analysis system used conventional peristaltic pumps and injection valves. A miniaturized system using micro-valves, which are now commercially available, will provide a significant improvement in performance over the previous system. The integrated FIA/ISFET analysis system will include a injection loop to control the sample volume to eliminates the effect of pressure pulsations and inconsistent flow rates of the sample stream. The integrated system will include the necessary configuration for automatic calibration, and will be designed to switch from analyzing unknown samples to standard solutions, which will be used to automatically determine the calibration constants. The deviations between the predicted nitrate concentration for individual ISFETs and the mean predicted concentration for all the sensors provide the opportunity for error checking. During analysis and self-calibration, a large deviation for any single sensor may indicate failure of that particular sensor or an outlier result. Objective 3: The complete system must operate without significant operator intervention, even during a calibration sequence. Control software will be developed to automatically run the system and record the results. The software will track and flag potentially erroneous results, warn the operator when failure of an individual ISFET is detected or if the calibration is not within specifications. The integrated system will be tested in a soil bin and in fields having a range of soil types and conditions. The system will be tested in a soil bin at various soil moisture contents and soil nitrate levels. The results of the tests will be analyzed to determine the precision and accuracy of the sensor and the recovery efficiency of the system.

Progress 11/15/00 to 11/14/03

Outputs
A critical component to successful development of a real-time soil sensing system is the ability to automatically sample a known mass (or volume) of soil for extraction and analysis. A Real-Time Electro Pneumatic Soil Sampling System (REPS) method based on pressurized air for real time soil sampling was developed and tested both in the laboratory and preliminary field tests. Laboratory tests have been conducted to evaluate the effect of soil type, soil density (soil compaction) and soil moisture levels on obtaining a known sample mass. The tests proved that the laboratory system was relatively successful in obtaining a constant mass of soil. The coefficient of variation in samples mass was less than 20% when all three soils, moisture contents and soil compaction levels were included. The effect of soil type and compaction level was not very large. The moisture content was found to significantly affect the actual mass of soil collected. However, it was found the effects of moisture contents, soil density and soil type could be compensated for and used to estimate the actual soil mass, provided the moisture content was known (R2=0.9, regression slope=0.91). A prototype field sampling system was been designed, and preliminary field tests conducted to optimize operational parameters. The performance of the REPS system under dynamic conditions was evaluated in a soil bin. The REPS was capable of obtaining a relatively consistent soil sample in a short time (< 70 ms) with a coefficient of variation of less than 27%. The effects of speed, moisture content, pulse duration and pressure level on the sample mass were investigated and all were found to be highly significant effect on sample mass. However, sample mass could be predicted with a relatively high degree of confidence (R2 = 0.86), if the travel speed and moisture content are known. The soil mixing, extraction system and filtration system were been designed and the relevant software control developed. Further tests of the REPS in broad range of soil types and conditions are recommended. The very short sampling period and relatively consistent sample mass make the REPS a good candidate for real-time soil nutrient sampling system. The final goal of this work is development of a real-time soil sensing system capable of determining all soil macro-nutrient levels. Therefore, the solutions used in the system must extract a sample containing all the soil macro-nutrient ions (N,P,K), and be compatible with different ISFET membranes. A laboratory test stand has been developed to evaluate the response of different ion selective membranes and their performance for different universal extracting solutions. These tests have shown that the use of a universal extractant is possible, for nitrate and potassium membranes. Although, the universal extractants have a significant effect on the sensor detection limits, the low concentration response was still satisfactory for soil nutrient testing. The development and testing of phosphate membrane will begin shortly.

Impacts
Soil macro-nutrients, especially nitrate nitrogen, can vary both spatially and temporally. A real-time sensor that automatically collects and analyzes soil samples could provide data to optimize variable-rate fertilizer application. This project has made good progress on the development of components of a real-time soil macro-nutrient sensor, based on ion-selective field effect transistor technology. The technology dictates that a sample of soil be collected so that an extracting solution can be used to obtain a liquid sample containing the soil macro-nutrient ions. An electro-pneumatic device for rapid soil sample collection has been developed and tested across a range of soil types. Laboratory investigations of membranes and extracting solutions have demonstrated the potential of using a single extraction to support real-time analysis of soil nitrate, plant-available phosphorus, and potassium. The successful development of multi-nutrient real time soil sensors would have a major impact on the potential to optimize fertilizer utilization to increase agricultural production while reducing the environmental impacts.

Publications

  • Price R.R., J.W. Hummel, S.J. Birrell, and I.S Ahmad. 2003. Rapid nitrate analysis of soil cores using ISFETs. Transactions of the ASAE. Vol. 46(3):601-610.
  • Yildirim, S., S.J. Birrell, and J.W. Hummel. 2003. Development of a real-time electro-pneumatic soil sampler. In: Proc. itafe'03 - International Congress on Information Technology in Agriculture, Food and Environment, Oct 7-10, Izmir, Turkey. (In press)
  • Kim, Hak-Jin, J.W. Hummel, and S.J. Birrell. 2003. Evaluation of ion-selective membranes for real-time soil nutrient sensing. ASAE Paper No. 03-1075, Am. Soc. of Agric. Engineers, St. Joseph, MI.
  • Yildirim, S., S.J. Birrell, and J.W. Hummel. 2003. Development of a real-time electro-pneumatic soil sampler. ASAE Paper No. 03-1076, Am. Soc. of Agric. Engineers, St. Joseph, MI.
  • Patent Title: A real time electro pneumatic soil sampler Inventors: Saddettin Yildirim, Stuart Birrell, John Hummel Patent Status: Provisional Application Serial No. 60/486,039, July 10, 2003. Joint submission Iowa State University Research Foundation and USDA.


Progress 01/01/02 to 12/31/02

Outputs
A critical component to successful completion of this project is the ability to automatically sample a known mass (or volume) of soil for extraction and analysis. During 2001, laboratory tests were conducted to evaluate the effect of soil type (3 types), soil density (2 compaction) and soil moisture (3 Moisture Contents) on obtaining a known sample mass. The tests proved that the laboratory system was relatively successful in obtaining a constant mass of soil with coefficient of variation of less than 20% for all conditions. In the past year a prototype field sampling system has been designed, and limited field tests conducted in different conditions. The results are encouraging under drier soil conditions. However, as expected high moisture conditions cause operational problems. Further tests will be conducted in the upcoming spring. The soil mixing, extraction system and filtration system has been designed and the relevant software control is being developed. The extraction and filtration system will be tested in a soil bin during the winter, and the initial field testing is planned for the upcoming spring.

Impacts
Precision is a management strategy that seeks to address within-field variability and to optimize inputs such as pesticides and fertilizers on a point-by-point basis within a field and not according to the field average. The full benefit of precision ag. will only be realized if the spatial variation across the field is accurately determined. This often requires data collection on a finer spatial resolution than is feasible with manual and/or laboratory methods, due to prohibitive cost. Sensors will allow the collection of data on a much finer spatial resolution, to more accurately characterize within-field variability. Sensor technology currently lags behind the other enabling technologies necessary for precision agriculture. The successful development of real time soil nutrient sensors would have a major impact on reducing the cost of implementing precision agriculture and significantly affect the adoption rate of the technology in commercial agriculture.

Publications

  • No publications reported this period


Progress 01/01/01 to 12/31/01

Outputs
A critical component to successful completion of this project is the ability to automatically sample a known mass (or volume) of soil for extraction and analysis. Laboratory tests have been conducted to evaluate the effect of soil type, soil density (soil compaction) and soil moisture levels on obtaining a known sample mass. These test included three different soil types, with three different moisture contents and three levels of compaction for each soil. The tests proved that the laboratory system was relatively successful in obtaining a constant mass of soil. The coefficient of variation in samples mass was less than 20% when all three soils, moisture contents and soil compaction levels were included. The effect of soil type and compaction level was not very large. The moisture content was found to significantly affect the actual mass of soil collected. However, it was found the effects of moisture contents, soil density and soil type could be compensated for and used to estimate the actual soil mass, provided the moisture content was known (r2 = 0.9, regression slope = 0.91). The next step to is the design of a prototype field sampling system based on these results.

Impacts
Precision is a management strategy which seeks to address within-field variability and to optimize inputs such as pesticides and fertilizers on a point-by-point basis within a field and not according to the field average. The full benefit of precision ag will only be realized if the spatial variation across the field is accurately determined. This often requires data collection on a finer spatial resolution than is feasible with manual and/or laboratory methods, due to prohibitive cost. Sensors will allow the collection of data on a much finer spatial resolution, to more accurately characterize within-field variability. Sensor technology currently lags behind the other enabling technologies necessary for precision agriculture. The successful development of real time soil nutrient sensors would have a major impact on reducing the cost of implementing precision agriculture and significantly affect the adoption rate of the technology in commercial agriculture.

Publications

  • No publications reported this period