One of the most important management tasks of a good farmer is taking a good soil sample. The recommendations based on these samples will help determine yield and profitability. A number of factors have an effect on the soil test results

Murdock, Lloyd W.

English

University of Kentucky

University of KentuckyUKnowledgeSoil Science News and Views Plant and Soil Sciences7-1982Seasonal and Yearly Fluctuations of Soil TestsLloyd W. MurdockUniversity of Kentucky, lmurdock@uky.eduRight click to open a feedback form in a new tab to let us know how this document benefits you.Follow this and additional works at: https://uknowledge.uky.edu/pss_viewsPart of the Soil Science CommonsThis Report is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in Soil ScienceNews and Views by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu.Repository CitationMurdock, Lloyd W., "Seasonal and Yearly Fluctuations of Soil Tests" (1982). Soil Science News and Views. 157.https://uknowledge.uky.edu/pss_views/157COOPERATIVE EXTENSION SERVICE University of Kentucky, College of Agriculture Lex i 40546 . Department of Agronomy . Soil Science News&Views Vol. 3, No. 6, July 1982 One sample. bility . Seasonal and Yearly Fluctuations of Soil Tests Lloyd Murdock of the most important management tasks of a good farmer is taking a good The recommendations based on these samples will help determine yield and A number of factors have an effect on the soil test results. soil prof ita-• Seasonal Fluctuations Seasonal fluctuations change the results of some of the soil test factors. During the summer and the fall as soils dry, the soil water moves to the surface and brings with it dissolved salts from deeper in the soil. This concentrates some nutrients near the surface and increases their apparent availability as shown by soil tests. The more mobile the element the greater the effect. The most mobile element in abundant supply in a well fertilized soil at this time is (NO)) nitrogen. As the nitrate moves with the water and concentrates in the upper 6 inches, it brings with it cations. At the same time nutrients are being taken from the soil by plant uptake. The overall effect is small and will cause little change in the fertility recommendations. These increased salts at the soil surface also lower the pH. The increased cations at the surface display ~ from the soil into the soil solution. This causes the pH to decrease as the soil dries. The pH is also lowered during this same time by nitrifi-cat-ion of ammonium nitrogen released from soil organic matter or added as fertilizer. At high rates of fertilization these effects are quite significant. Large additions of fertilizer can cause the soil pH at midseason to be 0.6 to 1.0 pH units below that prior to fertilization. If the soil becomes moist some of this effect is alleviated and the pH will increase to some extent. When sampling in the summer it should be realized that the pH is abnormally low at time of sampling. Wh~n sampling in the winter and spring one should keep in mind that the crop will grow in a soil with a pH lower than that shown by the soil test result. It helps to take the soil samples the same time each year so that the seasonal .fluctuations will be removed when comparing soil tests of different years. The College of Agricultu re is an Equal Opportunity Organization wtlh respect to education and employment and Is authorized to provide research. educational Information and other services only to Individuals and instituti ons that function without regard to race. color. natJonaJ ortgtn. sex. religion. age and handlcap.lnqulrles regarding compliance with Title VI and Title VII oftheCtvll Rights Act of 1964. Title[)( oft he Educallonal Amendments. Section 504 oft he Rehabilitation Act and other related matters should be directed to Equal Opportunity Office. Kentucky Coopera tive Extension Servtce. University of Kentucky. Room S-105. Agricultural Science Building-North. Lextng10n. Kentucky. 40546. UNIVERSITY OF KENTUCKY, KENTUCKY STATE UNIVERSITY, U.S. DEPARTMENT OF AGRICULTURE, AND KENTUCKY COUNTIES, COOPERATING -2-Yearly Fluctuations How accurate is the . soil sample? Soil test results often will vary greatly from one year to the next, causing farmers to question the validity of soil testing. The primary cause of this, in most cases, is in the soil sampling. Many soils are highly heterogenous. In addition to this, uneven soil erosion, type of tillage, depth of tillage, time of sampling, contaminants, uneven soil fertility application patterns, and lack of an adequate number of cores can also cause variation in soil test results. Because of this, a soil sampling history should be established. This would mean testing the soil and recording the results. In future years when test results appear to be unrepresentative, the history can be used to make a decision on the validity of the results. The soil test history is also useful in a number of other ways. The table below shows this variability in a series of samples taken from the same field by a farmer over a number of years. The field was in a corn and soybean rotat~on for grain production only. It is easy to see that the 1978 results are out of line and should be discarded and recommendations based on another sample or past history. Yearly Variability of Soil Test Results from Soil Samples Taken By a Farmer from a Sloping Upland Field in Caldwell County Year ~ ~ ~ ---~-lb/ac-----1972 6.5 11 236 1973 6.5 29 255 1978 6.6 7 182 1979 6.6 20 352 1980 6.2 27 285 • The best way to m1n1m1ze the variability which such fluctuations can have on soil test values is to (l) do a good job of sampling the field each time it is sampled and (2) sample at about the same time each year and keep a good field record system to include date at which samples were taken and lime and fertilizer application was made. • • 

Seasonal and Yearly Fluctuations of Soil Tests

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1157&amp;context=pss_views

Seasonal and Yearly Fluctuations of Soil Tests

Abstract

Similar works

Full text

Available Versions

University of Kentucky