{"id":162,"date":"2010-05-07T10:00:52","date_gmt":"2010-05-07T14:00:52","guid":{"rendered":"https:\/\/extension.umaine.edu\/blueberries\/?page_id=162"},"modified":"2023-05-15T14:00:11","modified_gmt":"2023-05-15T18:00:11","slug":"penman-montieth-et-worksheet-with-solar-estimate","status":"publish","type":"page","link":"https:\/\/extension.umaine.edu\/blueberries\/resources\/irrigation\/penman-montieth-et-worksheet-with-solar-estimate\/","title":{"rendered":"Penman-Montieth ET Worksheet with Solar Estimate and Equation Instructions"},"content":{"rendered":"<ul>\n<li>Penman Montieth ET Worksheet <em>(unavailable as of May 2023, updates in<\/em><em> progress<\/em><em>). <\/em><\/li>\n<\/ul>\n<hr \/>\n<p><strong>Instructions:<\/strong><\/p>\n<p>In order to calculate the reference ET using the Penman-Montieth equation<sup>1<\/sup>, the daily values of temperature, relative humidity, and wind speed must be known for your location.\u00a0 These values can usually be obtained online from weather websites.\u00a0 Daily total solar flux values are rarely reported by weather websites but can be either measured directly using a pyranometer ($350-$600) or estimated using a number of different equations. \u00a0In our worksheet, an estimate of daily total solar flux will automatically be calculated and incorporated into the determination of reference ET if the cell for daily total solar flux is left blank.\u00a0 Day of the year values can be obtained from the accompanying chart, and an approximate estimate of the elevation, latitude and distance of your site from the coast are all that are necessary for completing the data input.\u00a0 The resulting daily reference ET value, given in inches of water, can then be multiplied by the crop coefficient for wild blueberry (0.70 for the period May through August) to obtain an estimate of crop water usage for a given day.<\/p>\n<table style=\"width: 80%;border: 1px solid #000000\" border=\"1\" cellspacing=\"0\" cellpadding=\"6\" align=\"center\">\n<thead>\n<tr bgcolor=\"#ffffff\">\n<td valign=\"bottom\" width=\"331\"><strong><span style=\"color: #000000\">Example:<\/span><\/strong><\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\"><strong><span style=\"color: #000000\">Add Values Below<\/span><\/strong><\/td>\n<\/tr>\n<\/thead>\n<tbody>\n<tr bgcolor=\"#eeeeee\">\n<td style=\"text-align: left\" valign=\"bottom\" width=\"331\">Day of the Year (August 3)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">215<\/td>\n<\/tr>\n<tr>\n<td valign=\"bottom\" width=\"331\">Latitude<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">44.6<\/td>\n<\/tr>\n<tr bgcolor=\"#eeeeee\">\n<td valign=\"bottom\" width=\"331\">Approximate distance from coast &gt; 25 miles (yes or no)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">no<\/td>\n<\/tr>\n<tr>\n<td valign=\"bottom\" width=\"331\">Daily Minimum Relative Humidity (%)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">50<\/td>\n<\/tr>\n<tr bgcolor=\"#eeeeee\">\n<td valign=\"bottom\" width=\"331\">Daily Maximum Relative Humidity (%)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">97<\/td>\n<\/tr>\n<tr>\n<td valign=\"bottom\" width=\"331\">Daily Average Relative Humidity (%)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">82<\/td>\n<\/tr>\n<tr bgcolor=\"#eeeeee\">\n<td valign=\"bottom\" width=\"331\">Daily Average Air Temperature (F)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">68<\/td>\n<\/tr>\n<tr>\n<td valign=\"bottom\" width=\"331\">Daily Maximum Air Temp (F)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">86<\/td>\n<\/tr>\n<tr bgcolor=\"#eeeeee\">\n<td valign=\"bottom\" width=\"331\">Daily Minimum Air Temp (F)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">59<\/td>\n<\/tr>\n<tr>\n<td valign=\"bottom\" width=\"331\">Daily Total Solar Flux (MJ\/m^2)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">17.2<\/td>\n<\/tr>\n<tr bgcolor=\"#eeeeee\">\n<td valign=\"bottom\" width=\"331\">Daily Average Wind Speed (mph)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">5.1<\/td>\n<\/tr>\n<tr>\n<td valign=\"bottom\" width=\"331\">Elevation above sea-level (ft)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">165<\/td>\n<\/tr>\n<tr bgcolor=\"#eeeeee\">\n<td valign=\"bottom\" width=\"331\">Penman-Montieth Reference ET (inches\/day)<\/td>\n<td style=\"text-align: center\" valign=\"bottom\" width=\"141\">0.157445863<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><strong>Crop water use: 0.7 x 0.16 inches\/day = 0.11 inches\/day<\/strong><\/p>\n<p style=\"padding-left: 30px\">1) The Penman-Montieth grass reference evapotranspiration values produced by this worksheet were derived using the guidelines established in FAO Irrigation and Drainage paper 56: Crop evapotranspiration &#8211; Guidelines for computing crop water requirements (Allen et al. 1998).<\/p>\n<p><strong>Note<\/strong>:\u00a0 Approximate distance from the coast will only affect the reference ET value if daily total solar flux is estimated.<\/p>\n<hr \/>\n<p class=\"p1\"><span class=\"s1\"><i>Information\u00a0in this publication is provided purely for educational purposes. No responsibility is assumed for any problems associated with the use of\u00a0products\u00a0or services mentioned. No endorsement of products or companies is intended, nor is\u00a0criticism\u00a0of unnamed products or companies implied.<\/i><\/span><\/p>\n<p class=\"p1\"><span class=\"s1\">\u00a9 2009<\/span><\/p>\n<p class=\"p1\"><span class=\"s1\"><b>Call 800.287.0274 (in Maine), or 207.581.3188, for information on publications and program offerings from University of Maine Cooperative Extension, or visit\u00a0<\/b><a href=\"http:\/\/extension.umaine.edu\/\"><span class=\"s2\"><b>extension.umaine.edu<\/b><\/span><\/a><b>.<\/b><\/span><\/p>\n<p class=\"p1\"><i>The University of Maine is an EEO\/AA employer, and does not discriminate on the grounds of race, color, religion, sex, sexual orientation, transgender status, gender expression, national origin, citizenship status, age, disability, genetic information or veteran\u2019s status in employment, education, and all other programs and activities. The following person has been designated to handle inquiries regarding non-discrimination policies: Director of Equal Opportunity, 101 Boudreau Hall, University of Maine, Orono, ME 04469-5754, 207.581.1226, TTY 711 (Maine Relay System).<\/i><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Penman Montieth ET Worksheet (unavailable as of May 2023, updates in progress). Instructions: In order to calculate the reference ET using the Penman-Montieth equation1, the daily values of temperature, relative humidity, and wind speed must be known for your location.\u00a0 These values can usually be obtained online from weather websites.\u00a0 Daily total solar flux values [&hellip;]<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":4551,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"class_list":["post-162","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.2 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Penman-Montieth ET Worksheet with Solar Estimate and Equation Instructions - Cooperative Extension: Maine Wild Blueberries - University of Maine Cooperative Extension<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/extension.umaine.edu\/blueberries\/resources\/irrigation\/penman-montieth-et-worksheet-with-solar-estimate\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Penman-Montieth ET Worksheet with Solar Estimate and Equation Instructions - Cooperative Extension: Maine Wild Blueberries - University of Maine Cooperative Extension\" \/>\n<meta property=\"og:description\" content=\"Penman Montieth ET Worksheet (unavailable as of May 2023, updates in progress). 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