Managing Fertilizer Inputs Prepared for 2006 Extension Agent Update, Conrad

1. Managing Fertilizer Inputs Prepared for 2006 Extension Agent Update, Conrad by Clain Jones, Extension Soil Fertility Specialistclainj@montana.edu; 406 994-6076http://landresources.montana.edu/soilfertility

2. Questions • How many of you know what N fertilizer sources are available in your county? • Of those, how many have ammonium nitrate available? • Why am I asking?

3. Objectives • Determine if it’s worth fertilizing • Discuss prevalence and causes of yellow winter wheat • Introduce concept of Nitrogen Use Efficiency • Cover common myths and facts about fertilizers: Tissue testing, Monty’s, Liquids, Volatilization

4. Should I fertilize? • What does answer depend on? - Nutrient levels in soil - Fertilizer price, crop price - Yield response curve - Yield potential (and optimism!)

5. Yield Response Curve, Golden Triangle Data from G. Jackson Graph from D. Griffith If had 50 lb N/ac in soil, and yield potential was 53 bu, would you fertilize? How much? (Duane G. will show you later) Why does shape of curve matter?

6. Spring wheat yield as affected by water and N, Havre MEY; Maximum economic yield or return from N assuming a 20:1 wheat price ($/bu) to N cost ($/lb) ratio. Engel et al. (Fertilizer Fact #25).

7. Who has received calls asking about yellow winter wheat this year, or knows they have yellow winter wheat in their county?

8. HIGH N LOW N Post Farm: May 11, 2006

9. Winter Wheat, Moccasin, Crop Rotation Study(2005: spring pea, winter pea, fallow, spring wheat)May 10 2006 Previous crop: pea spring wheat pea Why? Photo: Chen, C. Crop effect: Any guesses on previous crop of yellow winter wheat?

10. Should I topdress? • If wheat is still yellow after this warm spell, and/or yield potential has increased substantially from when fertilizer decision made, then yes. (again will come down to economics) • Caution: if using color to determine if wheat is deficient, verify that it is not disease (generally more spotty in appearance), cold stress (more brown and not uniform) or a sulfur deficiency (yellowing in new leaves first).

11. What should I topdress with? • If temperatures are warm, use ammonium nitrate (AN) if available. • If temperatures are cool and irrigation water is turned on, or ½ inch of rain is in the forecast, use urea (UR) or urea ammonium nitrate (UAN). • If want an immediate green-up response, and AN is not available, use ammonium sulfate (AS). Blend AS and UR for the best compromise between green-up and cost. Ex: AS:UR=1/3:2/3 as N. One caution: Ammonium sulfate can volatilize on calcareous soils.

12. Questions/Discussion?

13. Nitrogen Use Efficiency (NUE) • Calculated by dividing grain yield (lbs) by N input (lbs) • Ex: NUE = yield/(Soil N + Fertilizer N) • NUE sometimes is also expressed as % of N applied (or available) that is removed. (check units)

14. What factors increase NUE? • Fertilizing less. Spring Wheat, Joplin (G. Jackson, unpub. data)

15. What other factors increase NUE? • Preventing losses -Minimizing volatilization (will cover later)-Minimizing leaching (ex: Avoiding over watering) • Using reasonable yield goals, and topdressing if needed • Banding near seed? Malhi and Nyborg, 1992.

16. Winter wheat nitrogen use efficiency Other strategies to increase NUE? • Optimize fertility of other nutrients

17. Winter wheat response to P fertilization (N rate = 110 lb/ac)

18. Questions on Nitrogen Use Efficiency?

19. Fertilizer Myths and Facts • Myth: Tissue testing and soil testing give you similar information. • Fact: Yield response curves have been developed mostly for soil tests, yet not tissue tests; therefore, fertilizer rates should be based on soil tests. • Fact: Tissue tests are better at determining nutrient deficiencies. • Fact: Need to make certain that correct plant part (ex: upper four leaves, stem, whole plant) is sampled.

20. Tissue Testing: What does it show? • Nutrient status of plants at the time of sampling, indicating deficient or adequate soil nutrient supplies. • Unseen deficiencies and may confirm visual symptoms of deficiencies. • Toxic levels of metals or excessive nutrients; critical for determining forage nitrate toxicity. MontGuide fact sheet # 200205 orhttp://www.montana.edu/wwwpb/pubs/mt200205.html

21. Types and Methods of Tissue Testing Lab Plant Analysis vs. Cell Sap, In-Field Analysis • Lab Tissue testing is an accurate, quantitative analysis of specific nutrients. • Results take more time to obtain and samples need to be collected carefully. • Cell Sap analyses with in-field instruments are qualitative analyses, often indicating very low, low, medium or high nutrient levels in the plant. • Immediate results allow for possible fertilizer adjustments when used with historical soil analyses and fertilizer records.

22. How to Sample for Lab Analysis 1) Sample when symptoms first appear 2) In the same field or area, collect similar samples of plant materials from plants that appear abnormal and also collect samples of healthy plants for comparative analysis. 3) Make sure that symptoms are not due to factors such as drought stress, insect or disease damage or mechanical injury. 4) Collect the correct parts, clean by brushing or with distilled water, pat dry and mail to the lab in a paper bag or envelope.

23. Sample collection Flynn et al. 2004. Sampling for Plant Tissue Analysis. New Mexico State University Extension. Guide A-123

24. What’s happening with this spring wheat crop? What would you recommend? Previous fall soil sampling measured 76 lb N/ac Tissue tests report: N at 1.7% P at 0.3% K at 2.8% Ca at 0.41% Mg at 0.25% S at 0.14 % All micronutrients at sufficient levels. Photo courtesy of The Mosaic Co. Website accessed 05/17/2006

25. Sufficiency Values for Plant Growth Adapted from Soil Fertility Handbook, Oklahoma State University.

26. Tissue Testing in Conjunction with Soil Testing • Soil testing analyzes current and future availability. • When both are used, fertilization practices can be adjusted to specific plant needs for optimal yield.

27. QUESTIONS?

28. More myths about fertilizers • Myth: You can get something from nothing • Fact: It takes about 2-3 lb N to get a bu of wheat. • Myth: Low nutrient solutions can take N out of the air, or mobilize soil nutrients. • Fact: Low nutrient solutions can not take N out of the air, and appear to have little to no effect (at rates prescribed) on mobilizing soil nutrients.

29. ‘Plant Food’ vs. Fertilizer Affects on Winter Wheat Yield a b b b b b Jackson. 2005. unpub. data Fertilizer: 16-30-0 with seed, 64-0-25 applied broadcast while planting. M1: 38 oz/ac of Monty’s Seed Starter 4-15-12 applied to the seed. M2: 48 oz/ac of Monty’s Seed Starter 4-15-12 applied to the seed, plus 16 oz/ac of Monty’s All Purpose Growth 8-16-8 M3: 58 oz/ac of Monty’s Seed Starter 4-15-12 applied to the seed, plus 16 oz/ac of Monty’s All Purpose Growth 8-16-8, plus 16 oz/ac of Monty’s Root & Bloom 2-15-15 Humic Acid (dry product) 64 oz/ac.

30. ‘Plant Food’ vs. Fertilizer Affects on Winter Wheat Protein Content a b b b b b Jackson. 2005. unpub. data Fertilizer: 16-30-0 with seed, 64-0-25 applied broadcast while planting. M1: 38 oz/ac of Monty’s Seed Starter 4-15-12 applied to the seed. M2: 48 oz/ac of Monty’s Seed Starter 4-15-12 applied to the seed, plus 16 oz/ac of Monty’s All Purpose Growth 8-16-8 M3: 58 oz/ac of Monty’s Seed Starter 4-15-12 applied to the seed, plus 16 oz/ac of Monty’s All Purpose Growth 8-16-8, plus 16 oz/ac of Monty’s Root & Bloom 2-15-15 Humic Acid (dry product) 64 oz/ac.

32. Myth: Liquid fertilizers work much better than granular fertilizers • Fact: While in some cases liquid fertilizers work better than granular, once granular fertilizers dissolve, the two are essentially identical. • Fact: Foliar applying liquid metal micronutrients CAN be more effective than soil applied granular. WHY? • Fact: Liquid fertilizers, due to expense of hauling water, are almost always more expensive per unit of nutrient.

33. Liquid and Solid Fertilizers Havlin et al. 2005 and Nutrient Management Module 10 (MSU Extension pub. 4449-10)

34. Liquid fertilizers could be the right choice IF… • A high value crop needs immediate corrective fertilizer. • Equipment and water are available. • Weeds are being sprayed anyways. • Confirmed micronutrient deficiencies are occurring; applying liquid provides soluble micronutrients which are absorbed by the plant instead of sorbing or precipitating when applied to the soil.

35. QUESTIONS?

36. Myth: 50-70% of applied urea will volatilize • Fact: Volatilization amounts will depend highly on temperature, pH, moisture, application method, residue, etc., and appear to be fairly low in Montana based on N source comparisons. • Fact: Urea will volatilize if applied on moist, warm soil, and not incorporated within a few days, so well thought out application is necessary.

37. Factors Affecting Volatilization • Soil pH and Temperature • Wind • Cation Exchange Capacity (CEC). WHY? • Buffering capacity (resistance to pH change) • Soil moisture/humidity • Rainfall/Irrigation following fertilization (depth in soil) • Ground cover/vegetation/residue. WHY? • Soluble and Exchangeable Calcium Bottom line: Large number of factors make volatilization amounts VARIABLE and difficult to predict.

38. 1. Soil pH and Temperature Effects on Relative Amount of Ammonia in Soil Solution

39. 2. Wind • SO, avoid applying if have high winds in forecast. Ammonia Loss Fillery et al., 1984 Wind Speed

40. 3. Cation Exchange Capacity • As CEC increases, volatilization rates generally decrease (Fenn and Kissel, 1976). Why? 1. Less NH4+ in solution to volatilize 2. Increased pH buffering capacity (next slide)

41. 4. Buffering Capacity

42. 5. Effect of Soil Water Content

43. 6. Rainfall/Irrigation • 1/10 inch of rain/irrigation dissolves fertilizer, allowing volatilization. • 1/2 inch of rain/irrigation pushes dissolved fertilizer about 2 in. into soil, essentially stopping volatilization if within about 2 days of fertilization (Meyer et al., 1961; Lloyd, 1992)

44. Effect of Incorporation Depth Urea Rate=100 lb N/ac Texture = silt loamSoil pH = 6.5Temp. = 75o F

45. 7. Effect of Grass Residue

46. Effect of Residue, Cont’d • Volatilization was found to be approximately 2 times higher in the upper 1.5 inches under no-till than under conventional tilled systems (Dick, 1984).

47. 8. Exchangeable Ca2+ Decreases Volatilization (Fenn and Kissel, 1976) Why? Calcium can tie up a carbonate ion, preventing pH rise AND open up 2 exchange sites for ammonium. Implication: Less concern with volatilization on soils with high exchangeable Ca levels (generally indicated by high CEC). Good news for MT. Doesn’t matter though if urea doesn’t reach soil.

48. Note • Grant Jackson and I, and three other faculty from ID and WA, have finished a final draft of a urea management guide. It is now out for review, with an anticipated publication time of this Fall.

49. Conclusions • The question, Should I fertilize?, will largely be answered by economics (Duane Griffith will cover this afternoon) • Nitrogen use efficiency can be improved with good placement and timing, reasonable yield goals, and a ‘balanced’ fertility program. • Tissue testing can be useful in verifying nutrient deficiencies, but is not useful in determining fertilizer amounts. • Low nutrient liquid fertilizers (less than 2 lb nutrient/ac) do not increase yield or protein over control treatments. • Liquid fertilizers and granular fertilizers are generally equally effective, yet each has its advantages and disadvantages. • Urea volatilization can be minimized with well thought-out placement and timing.