Soil Fertility Management - Soils and Soil Supplements - Lecture Slides, Slides of Biology

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Unit 9: Soil Fertility Management Docsity.com Objectives • Understand objectives of soil fertility management • Philosophies/techniques of precision farming • Using & obtaining valid soil samples • Considerations in making/following fertilizer recommendations • Knowledge of fertilizer quality • How to calculate fertilizer blends • Fertilizer application methods • Benefits/limitations of manure use Docsity.com Goals & Concerns in Fertility Management • Efficient land managers: spend <20% of production costs on fertilizers, expect >50% increase in yields • Fertilizers may not be profitable if: – Water is the most limiting factor – Other growth hindrances – insects, diseases, acidity, extreme cold – Increased yield has less market value than the cost of buying/app of fertilizer Docsity.com Goals & Concerns in Fertility Management • Fertilizers – generally most profitable farm input • Soil fertility problems usually the easiest to solve • Soil nutrients typically present in finite amounts, don’t replenish themselves • Crops typically contain: (in rank of amount found in the plant) N, K, Ca, P, Mg, S Docsity.com Goals & Concerns in Fertility Management • Utilizing fertilizers may help cut unit cost of production by maximizing yield – Improved fertility = improved yields, improved aesthetic appeal • Environmental concerns abound – Fertilizer laws viewed as lax by some – Farmers may be the primary cause of non-point- source pollution Docsity.com Scale of Land Management • Large- & Medium-Scale Management – Large-Scale • Low levels of operational precision, little reliance on sophisticated technology • May be most feasible/profitable for some • Simple & low-tech • Some shy away from high tech for other reasons Docsity.com Scale of Land Management • Disadvantages – Some parts of field may receive too much/little fertilizer or pesticide – Less than optimal yields – Inefficient use of fertilizers & pesticides – Higher cost of production/unit – Environmental pollution due to over application • Advantages – Minimal technological training & instrumentation needed – Field operations can be performed w/ standard, readily available, cheaper equipment Docsity.com Scale of Land Management – Medium-Scale • Subdivide field into two+ management units – Delineation may be based on: » Soil types » Past management differences » Farmer’s observations • Ex. High, medium, low N application areas in the field • Same equipment/technology needs as for large-scale management farmers Docsity.com Scale of Land Management – Potential to substantially decrease fertilizer/chemical application rates – Potential to substantially decrease input costs – Does require expensive technology, equipment & extensive technical knowledge Docsity.com Soil Sampling Standard method for determining soil fertility Use w/ precision farming to minimize inputs Accuracy of sample is key!!!! Docsity.com Soil Sampling • Depth & Number of Samples – Sampling depth – 7-12” for typical soil analysis • Shallower depth for no-till/sod crops – acid-layer can form at very top of soil structure • For accurate N analysis – 24-36” depth – For composite sampling – fewer # samples decreases accuracy of analysis Docsity.com Soil Sampling • Uniformity of Sampling Areas – Examine field for differences in soil characteristics, past treatments – Consider: • Uniformity of productivity • Topography • Soil texture • Soil structure • Drainage • Depth/color topsoil • Past management Docsity.com Soil Sampling – Sampling area • Each composite sample should represent <12.5 ac – Grid sampling can be as small as you need – 5-10 ac grids are common • Providing Detailed Soil & Cropping Background – Helps to provide w/ soil analysis to increase accuracy of fertilizer recommendations Docsity.com Soil Sampling – Include: • Previous crop • Crop (s)) to be grown • Realistic yield goal • Last liming & fertilization rates • Manure applications • Soil series (if known) • Drainage info • If irrigation used Docsity.com Soil Tests • Soil Test for N – No good tests for soil available N – Most states provide N recommendations based on yrs of field plots trials on various crops, soils, management, fertilizers – N recommendations consider: • Previous crops • Estimates N carryover • N needed to decompose residues • Projected yields • Climate Docsity.com Soil Tests – Lab N tests accurate, but nearly impossible to interpret • Some will discourage N testing – Behavior of carryover N unpredictable – can make analyses invalid • Leaching • Denitrification • Mineralization • Climate Docsity.com Soil Tests – N recommendations based on yield goals rather than soil reserves – Corn Rule – 1.2-1.4#N/bu of yield goal • How much N should be recommended for corn following corn, expected yield 120 bu/ac? • How much N should be recommended for corn following soybeans, expected yield 195 bu/ac? Docsity.com Soil Tests • Soil Test for Ca & Mg – Related to need for lime – Well-limed soils rarely Ca & Mg deficient – Mg deficiency more common than Ca • Coarse-textured or acidic soils • Many yrs using non-Mg containing lime – Mg testing for: • Exchangeable soil Mg • % Mg saturation of soil colloids • Ratio of K:Mg Docsity.com Soil Tests • Soil Test for S & B – S testing inaccurate – acts much like N • Can test – but must take variability into account – Boron level recommendations • <1.0 ppm – deficient for plant growth • 1-5.0 ppm – adequate • >5.0 ppm – excess/toxicity risks Docsity.com Soil Tests • Soil Test for Micronutrient Needs – Difficult to develop accurate tests due to relatively infrequent need for field supplementation – Can be done, if requested for a specific need – Adds expense to soil analysis Docsity.com Analysis of Plants – When is plant analysis most helpful? • Treatment of an easily-corrected deficiency • Long-growing crops: turf, tree fruits, forests, sugar cane • Quick Tests in the Field – Can test for N, K status in plants • Collect ~20 leaves for sample – Must be random from different locations – Don’t select only affected-looking leaves Docsity.com Analysis of Plants • Chop/mix, squeeze sap & test • Most effective for greenhouse/nursery growers – Amendments can easily be made – High possible economic losses • Total Plant Analysis – Done in a lab – Should be tested by stage of development – Random sampling key Docsity.com Analysis of Plants – Indicate part of plant sampled & be consistent – Dry to prevent spoilage (confounds results) – Wrap in paper and mail w/ complete report – complete history, information critical Docsity.com Analysis of Plants • Visual Nutrient Deficiency Symptoms – Chlorosis – yellowish to whitish appearance to foliage, stem – Necrosis – dead tissue – Causes: disease, insect damage, salt accumulation, stress, nutrient deficiencies – Some visual symptoms same for many diseases/deficiencies Docsity.com Analysis of Plants – Nutrients are relocated in the plant by two pathways • Xylem – water-carrying vessels – All nutrients can pass through • Phloem – sugar-carrying vessels – Not all nutrients can relocate – Mobile nutrients – travel freely – Immobile nutrients – can’t be moved from their location in the plant – Mobile nutrient deficiencies tend to occur on older leaves – plant sacrifices old for new tissue Docsity.com Analysis of Plants – Immobile nutrient deficiencies – symptoms on shoot/root tips, fruits • Can’t be treated from the soil w/ fertilizer – plant can’t send Ca (ex) to the ripening fruit – Mobile nutrients: • N, P, K, Cl, Mg, S – Immobile nutrients: • Cu, Mn, Zn, Fe, Mo, S – Very immobile nutrients: • B, Ca Docsity.com Fertilizer Recommendations • Test Reports – Labs usually full-service • Soil, plant, manure, irrigation water testing – See soil test report Docsity.com Fertilizer Quality Fertilizer grade – amounts of N, P, K in a fertilizer required by law to be listed • Also required: – Weight of material, manufacturer • Optional: – Filler composition, acidity in soil potential Calculating fertilizer N, P, K amounts • 10-20-10 • 15-12-18 Docsity.com Fertilizer Quality • Amounts listed as: elemental N, phosphate, potash (not direct indication of elemental P, K supplied) • Acidity & Basicity of Fertilizers – Most affect soil acidity in some regard • Superphosphate, Triplesuperphosphate, Potash – neutral • MAP, DAP, all N fertilizers – acidifiers Docsity.com Fertilizer Calculations • Calculating Fertilizer Mixtures – Mixing 34-0-0 ammonium nitrate & 0-46-0 TSP to get 1 ton mixture of 15-10-0 • How much of each do we need? – How about if we needed a 12-14-6 fertilizer for a customer? • What might we use for each ingredient? • How much of each would we need? Docsity.com Fertilizer Calculations • Weights of Fertilizer to Apply – Planting corn expected to yield 125 bu/ac • How much N do we need? • Soil analysis recommended 88#/ac phosphate • How much ammonium nitrate & TSP do we need? • What is our final application rate? Docsity.com Fertilizer Calculations • Calculations Involving Liquid Fertilizers – Use dry fertilizer calculation if sold by weight – If sold by volume, usually applied by volume – See example pg. 336 Docsity.com Techniques of Fertilizer Application – Reasons to broadcast: • Only practical method of application – pastures, turf, etc. • Low-fertility soils needing high fertilizer rates • Easy, cheap, personal preference • Flexible – split applications, ability to add after crop is growing Docsity.com Techniques of Fertilizer Application • Deep Banding – Application of strips into the soil – Either between/side of row, where the seed may be planted – Typically 4-12” depth – Knifing in anhydrous most common • Gas able to dissolve in soil water before it escapes • Losses can be high if dry, sandy Docsity.com Techniques of Fertilizer Application – Disadvantages: • Strong equipment needed • High fuel costs • Danger of dealing w/ anhydrous – Advantages: • High yield response potential • Puts fertilizer where most roots are, very efficient use Docsity.com Techniques of Fertilizer Application • Side-Dressing or Topdressing – Side-dressing – surface or shallow band application put on after crop is growing • Broadcast, surface stripped, sprayed, knifed – Principles to consider: • Decreases potential N losses • Added in the furrow to allow water to help w/ infiltration • Not effective for P, K Docsity.com Techniques of Fertilizer Application • Point Injector Application – place P, K into soil in the root zone w/out significant root damage – Used more in small plots, gardens – Push stick, rod into soil, fill w/ fertilizer, cover – Effective for: fruit trees, grapes, shrubs, etc. – Not common in field use Docsity.com Techniques of Fertilizer Application • Fertigation – application of fertilizer w/ irrigation water – Can apply large quantities of nutrients – Very effective for N • Some see 30-50% more efficient use of N • Cut of 50% in N rates w/ same/better yield – Must be careful of potential problem w/ salts Docsity.com Techniques of Fertilizer Application • Need wetting agent to help the spray to distribute evenly across surface • Helpful when root conditions restrict nutrient uptake • Quick response/remedy to deficiency (also short residual) • Wind must be calm, humidity >70%, temp <85° F Docsity.com Techniques of Fertilizer Application • Fertilizing in Paddy & Other Waterlogged Soils – Paddy rice – production on water covered soils • Water 2-6” deep • One of very few crops that tolerate anaerobic conditions – Difficult to fertilize due to high nutrient loss risks Docsity.com Fertilizer Efficiency Great focus on increasing efficiency of fertilizer use • Research • Real-time sensors in soils that immediately detect nutrient deficiency • Transgenic plants Fertilizer Efficiency – fraction/percentage of added fertilizer that is actually used by the plant Docsity.com Fertilizer Efficiency • Weeds – Response to fertilizer much like crops – N fertilization may increase weed growth > crop growth – Application method can also affect weed growth • Ex – broadcast fertilizer can tend to help weeds get good start Docsity.com Fertilizer Efficiency • Fertilizer-Water Interactions – Availability of nutrients directed impacted by soil water content – Drip fertigation may be most efficient use of water & fertilizer • Common in greenhouses • Can be effective in field use – Israeli farming uses drip irrigation Docsity.com Fertilizer Efficiency • Fertilizing for High Efficiency – Guides to optimal fertilization: • Avoid large additions of N or K (50#/ac +) on sandy soils – use split application • Avoid broadcast applications of urea & ammonia on warm/moist soils – volatilizes easily – incorporate • Avoid N losses on poorly drained soils by using ammonium • Band P • Use starter fertilizer Docsity.com Livestock Manure as Fertilizer • Not as convenient as commercial fertilizer • Pollution anxiety • Nutrient Production & Recovery – Production rates predictable & measurable – Ration has heavy influence on nutrients in manure Docsity.com Livestock Manure as Fertilizer • Manure & Nutrient Budgets – Generous applications of manure no longer norm • Some states require & enforce strict manure management guidelines – Restricted application due to soil P levels instead of N – Manure still can’t meet plant needs alone • Crops remove much higher levels of nutrients/ac Docsity.com Livestock Manure as Fertilizer • Using Manure – Most recognize advantages of using manure – Manure production unevenly distributed in farmland – Expensive to transport very far – Too abundant in areas, not enough land for application Docsity.com