23 pages; includes maps. This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Overdahl, C. J.

Schoper, R. P.

Simkins, C. A.

23 pages; includes maps. This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu.Schoper, R. P.; Overdahl, C. J.; Simkins, C. A.. (1978). Pocket guide to fertilizer recommendations. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/169041

University of Minnesota Digital Conservancy

co ,.... "' E. ~ I N M <t z 1-w _J _J :J CD z g (/) z w 1-X w <{ 1-0 (/) w z z :2 u.. 0 >-1-(/) a: w > z :J • w (.) > a: w (/) z g (/) z w 1-X w _J <{ a: :J 1-_J :J (.) a: (.? <{ Contents Page Introduction . . . . . . . . . . . . . . . . . . . . . 3 General Fertility Guide . . . . . . . . . . . . 5 Fertilizer Recommendations . . . . . . . 5 Alfalfa ......................... 5 Corn .......................... 7 Wheat, Barley, Oats ............. 9 Soybeans ...................... 10 Sugarbeets .................... 11 Sunflowers .................... 12 University Soil Tests .............. 14 Nitrogen ....................... 14 Phosphorus .................... 16 Potassium ..................... 17 Sulfur ......................... 17 Zinc ........................... 19 Organic Matter ................. 20 Soil pH and Lime Recommendations ........... 22 Testing Fees ..................... 23 Pocket Guide to FERTILIZER RECOMMENDATIONS R.P. Schoper, C.J. Overdahl, and C.A. Simkins* Introduction Soil analysis with today's equipment is relatively simple, but University of Minnesota soil scientists have years of experience in background field experi-ments and research in soil chemistry. The costly research is justified be-cause annual fertilizer use in Minneso-ta exceeds 550,000 tons of N, 320,000 tons P20 5 and 360,000 tons of K20. Monetary returns on this investment usually are 2 or 3 fold. This publication provides farmers with information on the use of fertilizer and soil amendments based on the most recent experimental evidence. The authors intend that these recom-mendations predict the nutrient re-quirements of plants for maximum ec-onomical yields. *R.P. Schoper is an assistant extension soils spe-cialist and instructor, C.J. Overdahl and C.A. Simkins are extension soils specialists and pro-fessors, University of Minnesota. 3 Map 1. Average phosphorus (P) and potassium (K) fer-tility status of Minnesota's major soil types Soil area Phosphorus level Potassium level 1 Medium-high Medium 2 Medium Low-medium 3 Medium-high Medium 4 Low-medium Medium 5 Low High 6 Low-medium High 7 Low-medium Low-medium 8-11 High Low 4 General Fertility Guide Soil test Relative level P low 0-10 medium 11-20 high 21-30 very high over 30 (lbs/A) K 0-100 101-200 201-300 over300 Fertilizer Recommendations ALFALFA Fertilization Pointers • Test ·soil to determine lime, phos-phorus, potassium, and sulfur needs. • Apply enough fertilizer to bring soil to a high fertility level at seeding. 5 • Apply enough fertilizer each year to maintain soils at high fertility. • For new seedings, phosphorus, po-tassium, sulfur, and lime should be applied as needed and mixed with the top 6 inches of soil. • On established stands, phosphorus and potassium should be top-dressed in the fall or following the first cutting. • In area 9 and 10 boron applied at the rate of 2-4 pounds per acre will elim-inate boron deficiency. Table 1. Phosphorus and potassium fertilizer rec-ommendations at seeding time Nutrient Phosphorus- P205 Potassium - K20 ------~l.f~rtility lf!~'---­Low Medium High Very high ---------------lbs/A ---------------80 60 20 0 240 160 40 0 Table 2. Phosphorus and potassium fertilizer rec-ommendations for established stands of alfalfa Nutrient Phosphorus- (P2 05) Potassium - (K20) 6 Soil fertility level Low Medium High Very high --------------- I bs/ A ---------------60 40 30 0 180 120 60 0 CORN Fertilization Pointers • Test soils to determine fertility sta-tus. Soils testing very high do not need further P (phosphorus) and K (potassium) broadcast applications. • If soils are slow to warm up, use starter fertilizer to insure P and K supply. • Add nitrogen according to yield goal. "Rule of Thumb"- 1 pound of N (nitrogen) for each bushel ex-pected. Table 3. Phosphorus and potassium fertilizer rec-ommendations for corn with a yield po-tential greater than 100 bushels per acre Nutrient Soil fertility'-'1"-'ev'-"-ei'-----Low Medium High Very high --------------- lbs/ A ---------------Phosphorus - P 205 ~- 100 80 60 30 Potassium - K2o~· 160 130 100 30 *30 pounds P205 and 30 pounds K20 should be applied as starter if the soil tends to warm up late in the spring, if only small amounts are required, or when the yield goal is less than 100 bushels per acre. 7 Table 4. Nitrogen recommendations* Amount of nitrogen (Nl to apply when the ~revious cro~ was: Poor alfalfa Good Corn, Soybeans, or clover, alfalfa Yield sugar· potatoes, black or goal beets small grain fallow clover ------------------- lbs/ A -------------------161-200 bu/A, over 210 180 150 100 24 T/A 130-160 bu/A 180 160 130 80 20-24 T/A 101-129 bu/A 130 110 80 30 or 16-20T/A 70-100 bu/A 80 60 40 15 10-15 T/A Less than 70 bu/A or 50 50 15 15 lOT/A *Although some nitrogen is desirable when row fertilizer is used, high rates of starter nitrogen are not essential. 8 WHEAT, BARLEY, OATS Fertilization Pointers • In low rainfall areas or seeding dur-ing very dry conditions, .do not ex-ceed 40 pounds N+K20 per·acre in the row. • If small grain is a companion crop for a legume hay, do not exceed 30 pounds N per acre. If the recom-mended fertilizer for alfalfa estab-lishment is broadcast (table 1) the P20 5 and K20 recommendation for small grain may be omitted. • Caution: Urea forms of nitrogen should not exceed 10 pounds nitro-gen per acre in the row. • Retest soils for P and K once every 3 years. In western Minnesota, a 0-24 inch sample for nitrates each year will improve the accuracy of nitro-gen recommendations (map 2). Table 5. Phosphorus and potassium recommen-dations for small grain Nutrient Phosphorus- P205 Potassium - K20 Soil fertility level Low Medium High Very high ---------------lbs/A ---------------60 40 30 20 60 30 15 0 9 Table 6. Nitrogen recommendations for small grain Previous crop Corn, sugarbeets Small grain, soybeans Black fallow, alfalfa, organic soil Amount of nitrogen to ap· ply on current crop (lbs/A) Barley and oats Wheat 60 90 40 70 20 20 SOYBEANS Fertilization Pointers • Omit nitrogen unless small amounts such as 10 or 15 pounds per acre are used with P and K in the row. • Fertilize soils when levels of P and K are low to medium. • Inoculate soybeans where they have not been grown recently. • Consider liming if the soil pH is be-low6.0. Table 7. Phosphorus and potassium recommen-dations for soybeans Nutrient Phosphorus- P20s Potassium - K20 10 Soil fertility level Low Medium High Very high --------------- lbs/ A ---------------90 60 30 0 100 75 25 0 SUGARBEETS Fertilization Pointers • Sugarbeet seeds and seedlings are sensitive to fertilizer salts and ger-mination damage may occur if N and K fertilizer materials contact the seed. • Due to the effect of nitrogen on sug-ar percentage and quality, avoid ex-cess use of nitrogen fertilizer. The accuracy of nitrogen recommenda-tions can be greatly improved by measuring the nitrate-nitrogen level in the 0-24 inch soil layer (map 2). • On low or medium testing soils phosphorus or potassium should be applied before the deepest tillage operation. Table 8. Phosphorus and potassium recommen-dations for sugarbeets Nutrient Phosphorus- P205 Potassium - K20 Soil fertility'-'1"-'ev=el __ Low Medium High Very high --------------- lbs/ A ---------------150 100 50 20 150 100 50 0 11 Table 9. Nitrogen recommendations for sugar-beets Previous crop Amount of nitrogen to apply -------------- lbs/ A --------------Corn, sugarbeets Small grain, soybeans Alfalfa, clover, black fallow SUNFLOWERS Fertilization Pointers 100 80 20 • Test soils to determine fertility sta-tus. Soils testing very high do not need broadcast application of P and K. • Sunflower seeds are sensitive to salts; use no more than 10 pounds of N + K20 per acre in contact with the seed. • Accuracy of nitrogen recommenda-tions for sunflowers in western Min-nesota is improved by a test of the 0-24 inch soil zone for nitrate-nitrogen content. 12 Table 10. Phosphorus and potassium recommen-dations for sunflowers Nutrient Soil fertility level Low Medium High Very high --------------- I bs/ A ---------------Phosphorus- P205 Potassium - K20 60 40 10 0 60 40 10 0 Table 11. Nitrogen recommendations for sun-flowers Amount of nitrogen Previous crop to apply ·---·-·-------lbs/A --------------Corn, sugarbeets, 80 Small grain, soybeans 60 Alfalfa, clover, 20 black fallow 13 University Soil Tests NITROGEN (N) The ability of a soil to supply nitro-gen is influenced by a variety of factors including total organic matter, soil moisture, soil temperature, cropping history, and residual fertilizer nitrogen. Since most soils do not have sufficient nitrogen supplying potential for satis-factory yields of nonleguminous crops, the nitrogen requirement of each crop must be carefully weighed against the calculated soil nitrogen supplied. In western Minnesota the accuracy of nitrogen recommendations for small grain crops and sugarbeets can be improved by analyzing the soils for nitrate-nitrogen (N03-N) in the upper 2 feet ofthe soil profile. Because ofthis, a soil nitrate test is available for those desiring it (map 2). In other areas and for other crops, nitrogen recommen-dations are based on soil organic mat-ter, cropping history, yield potential, and soil type. Nitrogen recommendations based on a soil nitrate-nitrogen test apply only in western Minnesota (shaded area of mao). 14 Map 2. Reference for nitrate test (shaded areal Nitrogen recommendations based on nitrate-nitrogen in soil, if nitrogen test run. Nitrogen recommendations not based on nitrate-nitro-gen test. To calculate how much nitrogen fertilizer to apply, subtract the soil test nitrate-nitrogen value from the appropriate crop given below and the difference is what should be applied per acre. 15 Crop Total nitrogen needed lbs/A Wheat (yield goal more than 60 bu/acre) ..... 140 Wheat (yield goal 51 to 60 bu/acre) ......... 120 Wheat (yield goal41 to 50 bu/acre) ......... 1 00 Wheat (yield goal under 40 bu/acre) ......... 80 Oats, barley, millet, rye, and annual canaryseed ......................... 100 Sugarbeets ............................ 170 Sunflowers ............................ 100 PHOSPHORUS (P) Various soil factors including or-ganic matter level, soil temperature, pH, and previous applications of ma-nure or commercial fertilizers affect the availability of phosphorus. Map 1 illus-trates the average phosphorus fertility status of Minnesota's soils based on soil test summaries. In a situation where a soil test is unavailable, the general fertility of soils in an area can be a guide. The need for phosphorus is critical for most crops early in the growing season when plant demands in rela-tion to root growth is high. These early season demands are often accentu-ated by wet or cold soil conditions which further restrict root develop-ment. 16 POTASSIUM (K) Quantities and uptake of potassium in soils varies with soil texture, crop species, soil temperature, and relative quantities of soil calcium and magne-sium. Map 1 is a guide to the general potassium fertility of various soil types in Minnesota. Crop demands for potassium are generally greatest midway through the growing season; however, crops growing on soils with low potassium levels respond to starter applications. SULFUR (S) Studies in Minnesota show that soils vary greatly in sulfur supplying capaci-ties. Deficiencies most frequently oc-cur on sandy, or low organic matter soils. Deficient areas are usually out-side principal industrial sites. Most soils low in sulfur-supplying power are in north central Minnesota (map 3). Not all soils in the nonshaded area are sulfur sufficient. However, exten-sive research indicates that a response to applied sulfur is extremely rare. Fre-quently, high subsoil sulfur levels are responsible for this lack of response; therefore, sulfur is recommended only on a trial basis if low sulfur tests are obtained in the nonshaded area. 17 Map 3. Approximate area (shaded) of highest probable sulfur-deficient soils 18 If extractable sulfur is less than 7 ppm (yield increase highly possiblel: For alfalfa and clovers: At t1me of establishment, broadcast 50 pounds per acre of sulfur. Th1s applica-tion would requ1re 50 pounds of elemental sulfur or 300 pounds of gypsum (18 percent sulfurl/acre. Re-peat application every 3 years For corn and small grain: Broadcast 20 pounds per acre of sulfur or apply 10 pounds per acre of sulfur as starter. Repeat application every year. If extractable sulfur is between 7 and 12 ppm (yield increase possiblel: For alfalfa and clovers: Apply sulfur on a tnal basis only If a response is noted, use recommendation here For corn and small grain: no sulfur recommended. If extractable sulfur is greater than 12 ppm (yield in-crease unlikelyl: For alfalfa and clovers: no sulfur recommended. For corn and small grain: no sulfur recommended. ZINC(ZN) Research indicates that deficiencies of zinc are almost always associated with a number of conditions including. • soil pH -deficiencies are generally found on soils with a pH greater than 7.0. • soil phosphorus content- zinc availability is greatly reduced by ex-cess use of phosphorus fertilizers. • preceding crop- if sugarbeets, the possibility of zinc deficiency in-creases. 19 • crop to be grown -field corn is the crop most likely to be zinc deficient in Minnesota. Map 4 shows the areas of Minnesota where zinc deficiencies occur most fre-quently. Deficiencies are easily con-trolled by applying 10 pounds of zinc per acre as zinc sulfate. One applica-tion should be sufficient for 2 to 4 years and is most effective when broadcast and plowed down. Zinc chelate and other zinc sources may be effective also, but may be more expensive. Yield mcrease Zinc soil test Relative expected from (ppm) level zinc applications Less than 0.5 Low H1ghly poss1ble 0.5 to 1.0 Medium Possible More than 1.0 High Unlikely ORGANIC MATTER Research in Minnesota shows that organic matter levels are not consist-ently correlated with crop responses to fertilizer. However, knowing the per-centage of organic matter in soils is useful in determining the proper rate of many herbicides. The percent organic matter will be determined by the Uni-versity Soil Testing Laboratory on re-quest. 20 Map 4. Zinc deficiency in Minnesota 0 Probable zinc-deficient area II Possible zinc-deficient area 0 Zinc deficiency unlikely 21 SOIL pH AND LIME RECOMMENDATIONS Lime improves crops by promoting desirable biological activity and in-creased nutrient availability. Such ben-efits are realized through higher yields and better quality. If alfalfa is part of the cropping rota-tion, pH levels of 6.5 or higher are de-sirable. If alfalfa is not in the rotation or if adequate lime is in the subsoil, pH levels of 6.0 or more are adequate. Claims are sometimes made that an imbalance between calcium and mag-nesium is present in Minnesota soils. This leads to recommendations for cal-citic limestone. No research data or sound theoretical concepts support this idea. Soils with a favorable pH, 6.0 or more will always contain adequate calcium and the use of calcitic rather than dolomitic limestone will not be beneficial. 22 Testing Fees $3 regular series (pH, lime, P, K, O.M., texture) used for standard fertilizer and lime recommendations. $2 nit rate test $2 zinc test $2 sulfur test $1 soluble salt test $1 pH and lime test only $2 organic matter test For further information or for submit-ting soil samples, contact the local county extension office or Soil Testing Laboratory 1529 Gertner Ave. University of Minnesota St. Paul, MN 55108 Issued in furtherance of cooperative extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Roland H. Abra-ham, Director of Agricultural Extension Service, University of Minnesota, St. Paul, Minnesota 55108. The University of Minnesota, including the Agricultural Extension Service, is committed to the policy that all persons shall have equal access to its programs, facilities, and employ-ment without regard to race, creed, color, sex, national origin, or handicap. (P-193A) 23 

Pocket guide to fertilizer recommendations

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Pocket guide to fertilizer recommendations

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