{"id":599,"date":"2026-03-25T13:42:13","date_gmt":"2026-03-25T13:42:13","guid":{"rendered":"https:\/\/extension.colostate.edu\/routt\/?post_type=resource-cpt&p=599"},"modified":"2026-03-25T22:05:32","modified_gmt":"2026-03-25T22:05:32","slug":"understanding-soil-sampling-and-soils","status":"publish","type":"resource-cpt","link":"https:\/\/extension.colostate.edu\/routt\/resource\/understanding-soil-sampling-and-soils\/","title":{"rendered":"Understanding Soils and Soil Sampling"},"content":{"rendered":"\n
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Soils and soil parameters, such as nutrient levels, can vary within a field and from field to field. These variables can affect a wide range of management decisions. Western Colorado soils can include heavy clay to well-drained sandy soils encompassing many characteristics including being shallow or deep, deficient or adequate in organic matter content, or high in salts\u2013to name a few.<\/p>\n\n\n\n

Soils in river valleys and surrounding areas of Western Colorado were formed by sandstone from the Uncompahgre uplift, volcanic rock, and deposits left by the Mancos Sea, a prehistoric inland sea. The Mancos Sea advanced and retreated 29 times, laying down layers of salty soil each time, which compressed into Mancos Shale. When the sea finally withdrew from the area, deposits were as deep as two miles thick. Volcanic flows later capped parts of these salty deposits.<\/p>\n\n\n\n

Mancos Shale decomposes into very productive soil with a high capacity to hold water and plant nutrients. By managing the area\u2019s long growing season (up to 188 days) and utilizing highly-developed irrigation systems, the river valley can be excellent for crop production.<\/p>\n\n\n\n

Soil Testing<\/h2>\n\n\n\n

A soil testing program helps to manage the land and helps to answer the following questions:<\/p>\n\n\n\n

    \n
  1. Are soil nutrients deficient or excessive?<\/li>\n\n\n\n
  2. Which crop fertilizer program is best?<\/li>\n\n\n\n
  3. Does the soil have a salinity problem, and what effect will the salt have on the crop?<\/li>\n\n\n\n
  4. What is the pH and organic matter level, and can it be adjusted?<\/li>\n<\/ol>\n\n\n\n

    Annual field sampling and testing is recommended for accurate crop and nutrient management.  Obtaining a representative soil sample from the planting area is critical for accurate results. To begin, divide the area into sites that are similar in soil type, slope, or other characteristics. <\/p>\n\n\n\n

    For collection, use clean equipment, free of soil particles and rust. Collect 15-20 samples from the top eight to 12 inches of soil in a random or systematic pattern. You can do this in up to 40 acres of land. Mix the samples from a single sample area in a plastic bucket. Collect about two cups of the mixed sample to submit to the laboratory for analysis. Nitrogen recommendations for irrigated crops, should include subsoil samples (12 to 24 inches) as well as surface samples to account for the available nitrogen throughout the root zone.<\/p>\n\n\n\n

    More About Soil Samples<\/h2>\n\n\n\n

    The samples can be air dried prior to sending them or they can be sent in a moist condition. Do not oven dry samples or expose them to extremely hot conditions. Keep samples in the shade or in a cooler with ice to prevent heat buildup if conditions are hot and dry. Western Colorado soils tend to be calcareous, which means that they contain residual or free lime (lime as small particles in the soil). The testing process should use lab procedures designed for these high lime type soils.<\/p>\n\n\n\n

    In Colorado, the analysis of soil samples should use ammonium bicarbonate-DPTA (AB-DTPA) to extract soil for analysis. AB-DTPA is a multi-use extractant for nitrate, phosphorus, potassium, and micronutrients and is used primarily by the Soil, Water, and Plant Testing Laboratory at Colorado State University. Other processes can be used to determine the nutrient levels in soils, however these are appropriate for more acidic pH levels.  The AB-DPTA analysis provides the best results for high pH (alkaline) soils.<\/p>\n\n\n\n

    Western Colorado\u2019s river valley soils typically have a pH of 7.5 to 8.5, a basic alkaline condition.  Although soil pH can sometimes be reduced by using acidifying agents, such as elemental sulfur or sulfuric acid, Western Colorado soils are highly buffered with free lime (calcium carbonate).  If sulfur is added to the soil, it combines with water and oxygen through bacterial activity, producing sulfuric acid.  The sulfuric acid will neutralize calcium carbonate to produce water, carbon dioxide and calcium sulfate and, instead of changing the pH when this reaction occurs, salt levels may increase, due to the increase in concentration of the salt gypsum (calcium sulfate). \u201cAlkaline\u201d is not the same as \u201calkali.\u201d  \u201cAlkali\u201d refers to sodium salts, while \u201calkaline\u201d refers to pH.  Very few areas in Western Colorado have problems with sodium salt; our salts area typically calcium-based.<\/p>\n\n\n\n

    Related Resources<\/h2>\n\n\n\n
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    \n\t\t\tGarden Notes\t\t<\/h2>\n\n\t\t
    \n\n\t\t\t\t\t\t\t

    \n\t\t\t\t\tSoil\t\t\t\t<\/h3>\n\t\t\t\n\t\t\t

    \n\t\t\t\tSoil pH\t\t\t<\/p>\n\n\t\t<\/div>\n\n\t<\/a>\n\n<\/article>\n\n

    \n\n\t\n\n\t\t

    \n\t\t\tFeature\t\t<\/h2>\n\n\t\t
    \n\n\t\t\t\t\t\t\t

    \n\t\t\t\t\tSoil\t\t\t\t<\/h3>\n\t\t\t\n\t\t\t

    \n\t\t\t\tFrom Dirt to Soil\t\t\t<\/p>\n\n\t\t<\/div>\n\n\t<\/a>\n\n<\/article>\n\n

    \n\n\t\n\n\t\t

    \n\t\t\tResearch\t\t<\/h2>\n\n\t\t
    \n\n\t\t\t\t\t\t\t

    \n\t\t\t\t\tEmergency Disaster Recovery\t\t\t\t<\/h3>\n\t\t\t\n\t\t\t

    \n\t\t\t\tSoil Erosion Control After Wildfire\t\t\t<\/p>\n\n\t\t<\/div>\n\n\t<\/a>\n\n<\/article>\n\n

    \n\n\t\n\n\t\t

    \n\t\t\tResearch\t\t<\/h2>\n\n\t\t
    \n\n\t\t\t\t\t\t\t

    \n\t\t\t\t\tSoil\t\t\t\t<\/h3>\n\t\t\t\n\t\t\t

    \n\t\t\t\tChoosing a Soil Amendment\u00a0\t\t\t<\/p>\n\n\t\t<\/div>\n\n\t<\/a>\n\n<\/article>\n\n

    \n\n\t\n\n\t\t

    \n\t\t\tResearch\t\t<\/h2>\n\n\t\t
    \n\n\t\t\t\t\t\t\t

    \n\t\t\t\t\tSoil\t\t\t\t<\/h3>\n\t\t\t\n\t\t\t

    \n\t\t\t\tDiagnosing Saline and Sodic Soil Problems\t\t\t<\/p>\n\n\t\t<\/div>\n\n\t<\/a>\n\n<\/article>\n\n

    \n\n\t\n\n\t\t

    \n\t\t\tResearch\t\t<\/h2>\n\n\t\t
    \n\n\t\t\t\t\t\t\t

    \n\t\t\t\t\tSoil\t\t\t\t<\/h3>\n\t\t\t\n\t\t\t

    \n\t\t\t\tControlling Soil Erosion from Wind\t\t\t<\/p>\n\n\t\t<\/div>\n\n\t<\/a>\n\n<\/article>\n\n<\/div>\n\n<\/div>\n","protected":false},"excerpt":{"rendered":"

    Soils and soil parameters, such as nutrient levels, can vary within a field and from field to field. These variables can affect a wide range of management…<\/p>\n","protected":false},"author":45,"featured_media":0,"parent":0,"menu_order":0,"template":"","meta":{"_acf_changed":false,"footnotes":""},"area_tax":[],"county_tax":[],"global-category_tax":[],"global-offering_tax":[],"global-sub-category_tax":[],"global-topic_tax":[307],"region_tax":[],"resource-type_tax":[],"class_list":["post-599","resource-cpt","type-resource-cpt","status-publish","hentry"],"pp_statuses_selecting_workflow":false,"pp_workflow_action":"current","pp_status_selection":"publish","pp_post_mime_type":"","acf":[],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/resource-cpt\/599","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/resource-cpt"}],"about":[{"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/types\/resource-cpt"}],"author":[{"embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/users\/45"}],"version-history":[{"count":0,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/resource-cpt\/599\/revisions"}],"wp:attachment":[{"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/media?parent=599"}],"wp:term":[{"taxonomy":"area_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/area_tax?post=599"},{"taxonomy":"county_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/county_tax?post=599"},{"taxonomy":"global-category_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/global-category_tax?post=599"},{"taxonomy":"global-offering_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/global-offering_tax?post=599"},{"taxonomy":"global-sub-category_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/global-sub-category_tax?post=599"},{"taxonomy":"global-topic_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/global-topic_tax?post=599"},{"taxonomy":"region_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/region_tax?post=599"},{"taxonomy":"resource-type_tax","embeddable":true,"href":"https:\/\/extension.colostate.edu\/routt\/wp-json\/wp\/v2\/resource-type_tax?post=599"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}