A Self-powered And Autonomous Fringing Field Capacitive Sensor Integrated Into A Micro Sprinkler Spinner To Measure Soil Water Content

We present here the design and fabrication of a self- powered and autonomous fringing field capacitive sensor to measure soil water content. The sensor is manufactured using a conventional printed circuit board and includes a porous ceramic. To read the sensor, we use a circuit that includes a 10 kHz triangle wave generator, an AC amplifier, a precision rectifier and a microcontroller. In terms of performance, the sensor's capacitance ( measured in a laboratory prototype) increases up to 5% when the volumetric water content of the porous ceramic changed from 3% to 36%, resulting in a sensitivity of S = 15.5 pF per unity change. Repeatability tests for capacitance measurement showed that the theta(v) sensor's root mean square error is 0.13%. The average current consumption of the system ( sensor and signal conditioning circuit) is less than 1.5 mu A, which demonstrates its suitability for being powered by energy harvesting systems. We developed a complete irrigation control system that integrates the sensor, an energy harvesting module composed of a microgenerator installed on the top of a micro sprinkler spinner, and a DC/ DC converter circuit that charges a 1 F supercapacitor. The energy harvesting module operates only when the micro sprinkler spinner is irrigating the soil, and the supercapacitor is fully charged to 5 V in about 3 h during the first irrigation. After the first irrigation, with the supercap fully charged, the system can operate powered only by the supercapacitor for approximately 23 days, without any energy being harvested.17

Chapter 19 - Soil CO2 Emissions in a Long-Term Tillage Treatment Experiment A2 - Muñoz, María Ángeles

Abstract The aim of our study was to investigate the effect of plowing (P) and no-tillage (NT) management on soil CO2 emissions from an arable field (i.e., winter wheat) in a 13- year-old experiment. In 2015, CO2 measurements were taken weekly in P and NT during the growing season and biweekly during the dormant season using the static chamber technique. Measurements were more frequent in a 7-day campaign scheduled right before and immediately after a soil disturbance caused by plowing to detect the short-term effects of soil management on CO2 emissions. We investigated the relationship among soil CO2 emissions, soil temperature, and soil water content. Soil CO2 emissions increased during the vegetation period and were higher in NT than P, although they were only significant from jointing to maturity stages. In contrast, CO2 emissions were higher in P compared to NT at a relatively short but well-monitored measurement interval just after plowing. Long-term systematic plowing resulted in lower CO2 emissions than that in NT during vegetation season, but a sudden pulse in CO2 emissions were detected in P directly after soil disturbance caused by plowing. These observations indicate that plowing can temporarily have a major effect on soil CO2 emissions

Correcting the Temperature Influence on Soil Capacitance Sensors Using Diurnal Temperature and Water Content Cycles

The influence of temperature on the dielectric permittivity of soil is the result of counteracting effect that depends on the soil’s composition and mineralogy. In this paper, laboratory experiments showed that for a given water content, the soil dielectric permittivity was linearly related to the temperature, with a slope (α) that varied between samples taken in the same soil. These variations are difficult to predict and therefore, a simple and straightforward algorithm was designed to estimate α  based on the diurnal patterns of both the measured dielectric permittivity and the soil temperature. The underlying idea is to assume that soil water content variations can be known with a reasonable accuracy over an appropriate time window within a day. This allows determining the contribution of the soil water content to the dielectric permittivity variations and then, the difference with the observed measurements is attributed to the soil temperature. Implementation of the correction methods in a large number of experiments significantly improved the physical meaning of the temporal evolution of the soil water content as the daily cycles for probes located near the surface or the long-term variations for more deeply installed probes

Determination of Gas Emission Characteristics from Animal Wastes Using a Multiplexed Portable FTIR-Surface Chamber System

Livestock production is a growing source of air pollution at regional, national, and global scales. Improved livestock manure management has the potential to reduce environmental impacts; however, there is an urgent need for cost-efficient, reliable, and easy to maintain measurement and monitoring capabilities to precisely quantify emissions from livestock manure. This research describes and evaluates a novel measurement method based on the multiplexed portable Fourier Transform Infrared (FTIR) spectroscopy analyzer - surface chamber techniques for continuous measurements and monitoring gas emissions from manure sources. The multiplexing system was designed and developed to automate the chamber network, controlling the movement of chambers and accurately managing chamber air flow distribution. The measurement accuracy of the developed system was evaluated under controlled laboratory conditions. The result of the statistical hypothesis testing showed that there is no statistically significant differences among the measurement results from each of the twelve chambers. While microbial activity is a key factor for formation of gaseous compounds in manure, the magnitude of gas exchange between manure and the atmosphere largely depends on manure physical characteristics. A series of soil science measurement and modeling techniques were applied to determine a set of fundamental physical, hydraulics, and thermal properties of cattle manure to support advanced modeling of gas emissions from manure sources. The liquid water retention characteristic for cattle manure was found to be close to that of organic peat soils. The results also suggested that Richards equation can describe the hydrodynamics taking place in cattle manure relevant to natural drying processes. However, the uncertainties of the measurement results could be due to the complexity of shrinkage, surface crust formation, and shrinkage cracks. Carbon dioxide (CO2), methane (CH4), and ammonia (NH3) emissions were estimated and characterized in field plots using the developed gas emission measurement system. The measurements included four treatments; beef manure, dairy manure, beef compost, and dairy compost. The estimated CO2, CH4, and NH3 emissions from the surface application with dairy manure were the highest among other treatments, while those from the surface application with beef compost were the lowest. Impacts of temperature and water content on gaseous emissions were found to be correlated significantly. Overall, this dissertation provides a solid foundation upon which future research can build in better understanding and modeling animal waste emission processes that impact the environment

Towards understanding belowground resources acquisition: applying data driven methods for deriving root water uptake profiles in grasslands of different diversity

Although root water uptake is an important component in the plant-soil-water relation for single plants and on ecosystem scale, studies investigating the effect of co-existing plant species on community water use have been conducted without estimating root water uptake profiles. However, knowledge of root water uptake is essential for understanding of intra- and interspecific interactions of plants. For those reasons, minimal-invasive and easy to use methods for estimating root water uptake are inevitable. Within this dissertation, an attempt has been made to identify a simple but sufficient accurate method for estimating evapotranspiration and root water uptake profiles from soil water content measurements without a priori information on root distribution parameters. Subsequently, this method was applied to investigate the effect of co-existing plant species on community root water uptake. First, four different complex water balance methods were evaluated regarding their applicability on the ecohydrological issue. Therefore, a synthetic experiment with numerical simulations for a grassland ecosystem was conducted. In the second part, an additional accuracy assessment considering magnitudes of evapotranspiration, soil texture variability, and sensor uncertainty was carried out on 12 weighable lysimeters. Third, we investigated the effect of co-existing plant species on the community root water uptake. Analysis of estimated root water uptake profiles were combined with measurements of leaf water potentials and stomatal conductance, which constitutes the novelty of this thesis. The results indicate that the investigated communities with higher species richness are able to adjust their root water uptake strategy in a way that the water use of the entire community is optimized