Non Technical Summary
Fertilizer application rates that do not match crop usage pose an economic loss for farmers, and excess applications can result in environmental degradation of water and atmosphere. A significant portion of the nitrogen applied to U.S. fields is not needed, due to the availability of nitrogen from the soil. Soil nutrients, especially nitrogen, vary spatially and temporally, within the field and soil profile. In order to deal with the significant variability challenges, a large number of soil measurements must be taken on each field. Using conventional lab analysis, this is not cost-effective. In-field measurements represent an appealing alternative, yet these must be accurate and affordable. This project will develop the field-deployable test equipment required to evaluate several sensor technologies in a side-by-side comparison. Soil sensing technology used for this application will be electrical, optical, and electro-chemical. The sensors to be used in this project
represent the most viable candidates from those categories, and have shown initial feasibility to meet the criteria. However, most have not been widely tested under in-field conditions, nor has a thorough side-by-side comparison been conducted. In order to perform this feasibility comparison test, equipment will be devised to collect and process the soil cores, and bring them into contact with the sensors. Results from in-field sensors will be compared with laboratory-analyzed soil tests.
Animal Health Component
Research Effort Categories
Goals / Objectives
Soil-supplied nitrogen is not accounted for in many regions due to the difficulty in measuring it accurately. Soil nutrients, especially nitrogen, vary spatially and temporally, within the field and soil profile. Using conventional lab analysis, it is not cost-effective to accurately characterize the nitrogen variability on most fields. In-field measurements represent an appealing alternative, yet these must be accurate and affordable. As it is unlikely that a single measurement will be able to account for the complex biological and chemical factors affecting optimal crop nutrient rates, this project will evaluate several sensor technologies in a side-by-side comparison. Soil sensing technology that may ultimately be deployed in-field can be categorized as electrical, optical, and electro-chemical. The sensors planned for this proposal represent the most viable candidates from those categories, and have shown initial feasibility to meet the criteria. However, most have
not been widely tested under in-field conditions, nor has a thorough side-by-side comparison been conducted. In order to perform this feasibility comparison test, equipment will be devised to collect and process the soil cores, and bring them into contact with the sensors. Objectives for this project are: Objective #1: Develop equipment that will being soil into contact with the soil sensors, and determine feasibility of producing and using this equipment in various soil and field conditions. Objective #2: Conduct field trials with the sensor devices. Objective #3: Compare results from each sensor with lab-analyzed soil samples. Objective #4: From the results of this Phase I project, establish a clear direction for the development of an in-field sensing system during a Phase II. The thorough investigation of sensor candidates during the Phase I portion will insure that the system is optimized for accuracy, affordability, and timeliness.
The three main areas that offer an opportunity for improved fertilizer efficiency are: 1) measuring profile soil nitrate and nitrogen mineralization potential with adequate spatial resolution, in a cost-effective and timely manner, 2) accompany those measurements with improved measurements of other soil factors such as pH, soil moisture, and compaction that affect mineralization and nitrogen use and loss, and 3) simultaneously measure other soil nutrients such as potassium with increased spatial resolution. In order to optimize a system, a side-by-side comparison of the best candidates will be conducted. While the sensors that will be used in this research have all been the subjects of various research initiatives, and results have been published, much of the work was done in a lab setting with very few sensor comparisons. Obstacles to such a test include the lack of suitable field equipment needed to prepare the samples, and to accommodate the sensors in order measure
the samples. The project will address those research gaps in several ways. First, by developing equipment that will collect sensor measurements of the soil profile. This will consist of NIR and Mid-IR spectroscopy, ion-selective electrodes, and soil electrical property measurements. Second, by calibrating sensors to lab measurements. Sensor measurements will be calibrated to laboratory measurements of nitrate N, amino N, total nitrogen, total carbon, P, K, pH, magnesium (Mg), calcium (Ca) and cation exchange capacity (CEC). Calibration methods will include single and multi-variate regression for electrical and electrochemical measurements, chemometric techniques such as partial least squares regression for NIR and Mid-IR, along with wavelet analysis and regression techniques for Mid-IR. Third, by comparing results from all sensors. Validation of results will be accomplished using leave-one-out cross-validation (i.e., predicted R-sq. values), splitting the data set into calibration and
validations sets, and/or use of independent data sets.