Calibration of a common shortwave multispectral camera system for quantitative agricultural applications

Unmanned aerial systems (UAS) for collecting multispectral imagery of agricultural fields are becoming more affordable and accessible. However, there is need to validate calibration of sensors on these systems when using them for quantitative analyses such as evapotranspiration, and other modeling for agricultural applications. The results of laboratory testing of a MicaSense (Seattle, WA, USA) RedEdge™ 3 multispectral camera and MicaSense Downwelling Light Sensor (irradiance sensor) system using a calibrated integrating sphere were presented. Responses of the camera and irradiance sensor were linear over many light levels and became non-linear at light levels below expected real-world, field conditions. Simple linear corrections should suffice for most light conditions encountered during the growing season. Using an irradiance sensor or similar system may not properly account for light variability in cloudy or partly cloudy conditions as also identified by others. A simple stand for aiding in reference panel imagining was also described, which may facilitate repetitive, consistent reference panel imaging

2019 Nebraska Water Productivity Report

Nebraska’s agricultural production is diverse and vast, ranking the state fourth in total value of agricultural products in the U.S. The state is a national leader in terms of agricultural production: it is the third largest producer of corn and second largest in cattle production. Nebraska is also the second largest producer of ethanol and distillers’ grains. The production and use of these three commodities are highly interlinked. Corn is a major input in livestock feed and the ethanol industry. Ethanol plants then produce distillers’ grains as a co-product that is also used as livestock feed, thus forming what the Nebraska Corn Board refers to as “Nebraska’s Golden Triangle.” The main objective of the current report is to assess the water productivity of crops and livestock products, and the water, energy and carbon footprint of ethanol produced from corn. The findings show that: • The observed shift to more efficient irrigation systems (eg. changing from gravity to center pivot systems) and setting regulatory limits on pumping for irrigation has helped to reduce the field level irrigation application depth in three Natural Resources Districts (NRDs): Central Platte, Lower Niobrara, and Tri-Basin. The irrigation application rate in the three NRDs studied has dropped on average 20% for cornfields and 8% for soybean fields between 2004 and 2013. • The yield and modeled water productivity (WP) of both irrigated and rainfed corn decreases from eastern to western Nebraska. The drop in irrigated corn yield in western Nebraska is due to a shorter growth season in the west compared to eastern part of the state due to altitude • The modeled water productivity of the two major crops, corn and soybeans, has increased over the years. Between 1990 and 2014, the average WP of corn and soybeans has increased 1.7 and 1.8 times, respectively. These increases closely follow the increase in the crop yields in Nebraska. • There are WP gaps for corn and soybeans that, if targeted investments and improvements are feasible, will help reduce pressure on water resources. • Livestock production (swine and cattle, and eggs) has increased considerably between 1960 and 2016. The increase in livestock production has been accompanied by an increase in animal feed demand. The rate of feed demand has risen more slowly than the rate of increased production, due to increases in livestock productivity. • From 1960 to 2016, the WP of livestock products (beef, pork, chicken meat, turkey meat, milk, and eggs) increased considerably, from 1.8 times for beef to 5.1 times for milk. • Setting benchmarks, estimating the WP gaps, and identifying the critical factors affecting WP are potential future areas of research and investment to enhance the WP of livestock products. • Bioethanol from Nebraska’s corn produces roughly two times more energy output for every unit of fossil fuel input and reduces greenhouse gas (GHG) emission by 53% relative to gasoline

Evapotranspiration mapping of commercial corn fields in Brazil using SAFER algorithm

SAFER (Simple Algorithm for Evapotranspiration Retrieving) is a relatively new algorithm applied successfully to estimate actual crop evapotranspiration (ET) at different spatial scales of different crops in Brazil. However, its use for monitoring irrigated crops is scarce and needs further investigation. This study assessed the performance of SAFER to estimate ET of irrigated corn in a Brazilian semiarid region. The study was conducted in São Desidério, Bahia State, Brazil, in corn-cropped areas in no-tillage systems and irrigated by central pivots. SAFER algorithm with original regression coefficients (a = 1.8 and b = –0.008) was initially tested during the growing seasons of 2014, 2015, and 2016. SAFER performed very poorly for estimating corn ET, with RMSD values greater than 1.18 mm d–1 for 12 fields analyzed and NSE values < 0 in most fields. To improve estimates, SAFER regression coefficients were calibrated (using 2014 and 2015 data) and validated with 2016 data, with the resulting coefficients a and b equal to 0.32 and –0.0013, respectively. SAFER performed well for ET estimation after calibration, with r2 and NSE values equal to 0.91 and RMSD = 0.469 mm d–1. SAFER also showed good performance (r2 = 0.86) after validation, with the lowest RMSD (0.58 mm d–1) values for the set of 14 center pivots in this growing season. The results support the use of calibrated SAFER algorithm as a tool for estimating water consumption in irrigated corn fields in semiarid conditions

Medidas do balanço de energia sobre pomar de bananeira na região Semiárida do Nordeste do Brasil

The objective of this work was to evaluate the reliability of eddy covariance measurements, analyzing the energy balance components, evapotranspiration and energy balance closure in dry and wet growing seasons, in a banana orchard. The experiment was carried out at a farm located within the irrigation district of Quixeré, in the Lower Jaguaribe basin, in Ceará state, Brazil. An eddy covariance system was used to measure the turbulent flux. An automatic weather station was installed in a grass field to obtain the reference evapotranspiration (ET0) from the combined FAO-Penman-Monteith method. Wind speed and vapor pressure deficit are the most important variables on the evaporative process in both growing seasons. In the dry season, the heat fluxes have a similar order of magnitude, and during the wet season the latent heat flux is the largest. The eddy covariance system had acceptable reliability in measuring heat flux, with actual evapotranspiration results comparing well with those obtained by using the water balance method. The energy balance closure had good results for the study area, with mean values of 0.93 and 0.86 for the dry and wet growing seasons respectively

Energy balance measurements over a banana orchard in the Semiarid region in the Northeast of Brazil

O objetivo deste trabalho foi avaliar a confiabilidade da técnica das correlações turbulentas, analisando as componentes do balanço de energia, a evapotranspiração e o fechamento do balanço de energia nas estações de crescimento seca e úmida, na cultura da banana. O experimento foi realizado em uma fazenda localizada no distrito irrigado de Quixeré, na Bacia do Baixo Jaguaribe, Ceará. Foi utilizado um sistema de correlações turbulentas na obtenção das medidas dos fluxos turbulentos. Uma estação meteorológica automática foi instalada em um gramado para a obtenção da evapotranspiração de referência (ET0) pelo método FAO-Penman-Monteith. A velocidade do vento e o deficit de pressão do vapor são as variáveis mais importantes no processo evaporativo em ambas as estações. Na estação seca, os fluxos de calor têm ordens de magnitude similares, enquanto na estação úmida o calor latente é superior. O sistema de correlações turbulentas apresentou confiança aceitável na obtenção dos fluxos de calor, com a evapotranspiração real mostrando valores similares aos obtidos pelo método do balanço hídrico. O fechamento do balanço de energia apresentou bons resultados para a área de estudo, com valores médios de 0,93 e 0,86 para as estações seca e chuvosa, respectivamente.The objective of this work was to evaluate the reliability of eddy covariance measurements, analyzing the energy balance components, evapotranspiration and energy balance closure in dry and wet growing seasons, in a banana orchard. The experiment was carried out at a farm located within the irrigation district of Quixeré, in the Lower Jaguaribe basin, in Ceará state, Brazil. An eddy covariance system was used to measure the turbulent flux. An automatic weather station was installed in a grass field to obtain the reference evapotranspiration (ET0) from the combined FAO-Penman-Monteith method. Wind speed and vapor pressure deficit are the most important variables on the evaporative process in both growing seasons. In the dry season, the heat fluxes have a similar order of magnitude, and during the wet season the latent heat flux is the largest. The eddy covariance system had acceptable reliability in measuring heat flux, with actual evapotranspiration results comparing well with those obtained by using the water balance method. The energy balance closure had good results for the study area, with mean values of 0.93 and 0.86 for the dry and wet growing seasons respectively

Water productivity benchmarks: The case of maize and soybean in Nebraska

Water productivity benchmarks for irrigated and rainfed agriculture will provide relevant information to manage scarce water resources and control groundwater level decline. We analyze the temporal and spatial variation of the water productivity (WP) of maize and soybean in Nebraska, with WP defined as harvested crop weight per total evapotranspiration. The results show that WP of both maize and soybean increase from west to east within Nebraska and have increased over the last 25 years, mainly due to the increase in crop yields (land productivity). We derive WP benchmarks for each crop per climate zone. Increasing actual WPs in the state to benchmark levels will increase yields by 21% for maize and by 19% for soybean. The WP benchmark levels for the two crops presented here will help formulating targets for closing water productivity gaps and improving the sustainability of water use in the state. Appendix A attached belo

Calibration of a common shortwave multispectral camera system for quantitative agricultural applications

Unmanned aerial systems (UAS) for collecting multispectral imagery of agricultural fields are becoming more affordable and accessible. However, there is need to validate calibration of sensors on these systems when using them for quantitative analyses such as evapotranspiration, and other modeling for agricultural applications. The results of laboratory testing of a MicaSense (Seattle, WA, USA) RedEdge™ 3 multispectral camera and MicaSense Downwelling Light Sensor (irradiance sensor) system using a calibrated integrating sphere were presented. Responses of the camera and irradiance sensor were linear over many light levels and became non-linear at light levels below expected real-world, field conditions. Simple linear corrections should suffice for most light conditions encountered during the growing season. Using an irradiance sensor or similar system may not properly account for light variability in cloudy or partly cloudy conditions as also identified by others. A simple stand for aiding in reference panel imagining was also described, which may facilitate repetitive, consistent reference panel imaging

2019 Nebraska Water Productivity Report

Nebraska’s agricultural production is diverse and vast, ranking the state fourth in total value of agricultural products in the U.S. The state is a national leader in terms of agricultural production: it is the third largest producer of corn and second largest in cattle production. Nebraska is also the second largest producer of ethanol and distillers’ grains. The production and use of these three commodities are highly interlinked. Corn is a major input in livestock feed and the ethanol industry. Ethanol plants then produce distillers’ grains as a co-product that is also used as livestock feed, thus forming what the Nebraska Corn Board refers to as “Nebraska’s Golden Triangle.” The main objective of the current report is to assess the water productivity of crops and livestock products, and the water, energy and carbon footprint of ethanol produced from corn. The findings show that: • The observed shift to more efficient irrigation systems (eg. changing from gravity to center pivot systems) and setting regulatory limits on pumping for irrigation has helped to reduce the field level irrigation application depth in three Natural Resources Districts (NRDs): Central Platte, Lower Niobrara, and Tri-Basin. The irrigation application rate in the three NRDs studied has dropped on average 20% for cornfields and 8% for soybean fields between 2004 and 2013. • The yield and modeled water productivity (WP) of both irrigated and rainfed corn decreases from eastern to western Nebraska. The drop in irrigated corn yield in western Nebraska is due to a shorter growth season in the west compared to eastern part of the state due to altitude • The modeled water productivity of the two major crops, corn and soybeans, has increased over the years. Between 1990 and 2014, the average WP of corn and soybeans has increased 1.7 and 1.8 times, respectively. These increases closely follow the increase in the crop yields in Nebraska. • There are WP gaps for corn and soybeans that, if targeted investments and improvements are feasible, will help reduce pressure on water resources. • Livestock production (swine and cattle, and eggs) has increased considerably between 1960 and 2016. The increase in livestock production has been accompanied by an increase in animal feed demand. The rate of feed demand has risen more slowly than the rate of increased production, due to increases in livestock productivity. • From 1960 to 2016, the WP of livestock products (beef, pork, chicken meat, turkey meat, milk, and eggs) increased considerably, from 1.8 times for beef to 5.1 times for milk. • Setting benchmarks, estimating the WP gaps, and identifying the critical factors affecting WP are potential future areas of research and investment to enhance the WP of livestock products. • Bioethanol from Nebraska’s corn produces roughly two times more energy output for every unit of fossil fuel input and reduces greenhouse gas (GHG) emission by 53% relative to gasoline

Evapotranspiration of tamarisk through micrometeorological and remote sensing techniques

The main objective of this study was to determine the daily actual evapotranspiration (ETa) of the tamarisk vegetation utilizing micrometeorological data and remote sensing algorithms. The Bowen ratio method, and the Surface Energy Balance Algorithm for Land (SEBAL) and Simplified Surface Energy Balance Index (S-SEBI) algorithms were used to obtain the ETa of the tamarisk vegetation, located in the preserved area of the Cibola (Blythe, CA/USA). In general, the estimated values of ETa by the SEBAL and S-SEBI algorithms present results close to the measured values in the flux towers. The RMSE between the measured values and the estimated values by SEBAL was 0.4 mmday-1, and for the measured values and the estimated values by S-SEBI was 0.5 mmday-1, resulting in a percentual mean error of 9.5% between the measurements and the SEBAL and 10.6% between the measurements and the S-SEBI, evidencing the applicability of both the algorithms in obtain the daily actual evapotranspiration.Pages: 6260-626