Soil Fertility 101? Ray Weil

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1 NutrientSmart - Guelph, Ontario January 2018 Soil Fertility 101? Ray Weil

2 Guiding principles of soil fertility management Soils are complex, integrated systems. Soils are alive! C drives the food web. Soils are 3-D use the whole profile. Each nutrient has its cycle fertilizer can supplement, not supplant. Economic and environmental optima often allow a win win. Lots of dollars still going down the drain.

3 Soils are complex, integrated systems.. Soil Chemistry Soil Biology Plant root root physiology Soil Physics Soil types formation Landscape, ecology

4 Soils are alive roots are part of a community Washed roots Rhizosphere soil sheaths Root cap cells spilling C Mucigel Root hairs

5 Soil Pests Beneficial bacteria Crop roots Crop roots Beneficial nematodes Mycorrhizal partners

6 Soils are three-dimensional Use the full profile Which nutrient & water reservoir do you want supporting your crops?

7 Each nutrient has its soil cycle P fluxes for 106 Ohio fields, Kg P/ha P in Solution 0.2 Iron, Aluminum -phosphates 0.3 Calciumphosphates Organicphosphorus

8 Forms of watersoluble phosphorus News Flash! It s not all orthophosphate (H 2 PO 4 ). From Weil & Brady (20017) using means for 14 unfertilized pastures on alluvial Vermont Inceptisols in Young et al. (2013)]

9 Chelate iron or aluminum to release P. Increased root absorptive surface area Encourage colonization by mycorrhizal fungi that help plants take up P Six plant strategies to enhance P availability Six basic strategies that plant roots may employ to enhance their uptake of various forms of phosphorus from soils. Dissolve Ca P compounds with acid exudates Exude phosphatase enzymes to release P from organic compounds Exude substances to stimulate P-solubilizing rhizobacteria.

10 Root-Fungi alliance (Mycorrhizae) is a game changer for plants.

11 Best case correlation data for two common P soil tests Sawyer, J.E., and A.P. Mallarino Differentiating and understanding the Mehlich 3, Bray, and Olsen soil phosphorus tests. 19th Annual Crop Pest Management Short Course, University of Minnesota.

12 Drainage water P, mg / L Agronomic optimum Total P Concentration In Drainage Water Broadbalk Experiment, England Olsen soil test P, mg/kg From: Heckrath etal 1995

13 Nutrient Input-Output Balance on a Farm N fixation Fertilizer Deposition Manure/Compost Feed: grain, hay, salts NH 3 volatilization NO x losses Manure sales Sales: crops, animals, milk Erosion Bedding Leaching Runoff

14 Fast etal Better Crops/Vol. 93 (No. 1) Phosphorus buildup sins of our grandfathers

15 Lake Erie Algal Bloom, Annual Total P Loading to Lake Erie

16 Ca 2+ & ionic Strength Reduce Dispersion No Gypsum Gypsum applied to soil surface Ohio soil photos: Darrell Norton

17 Before During rain Gypsum on surface No till Gypsum Turbotilled into soil Water Hi -P Lo -P Preferential flow Bypass flow Macro-pore flow Ca 2+ precipitates soluble P

18 Cover crops can 1. solubilize P 2. bring P to surface P

19 North America: ~ 6500 Tg N imported as fertilizer ~ 4500 Tg N exported as grain Internationally Traded N (A) fertilizer (31 Tg N), (B) grain (12 Tg N), (C) meat (0.8 Tg N). J N Galloway et al. Science 2008;320:

20 N Use Efficiency (harvested /applied) Goal: high NUE and Yields Where we want to be. Yield (kg N ha -1 yr -1 ) Zhang et al

21 Interpretation of field responses to make nutrient application recommendations Economists quadratic model : Y= a+bx+cx 2

22 Corn Crop Response to N Fertilizer 200 lbs N/ 158 bu ~ 1.25 lbs N/ bu of yield Y= a+bx=cx 2 Recommended optimum = 220 kg/ha From Cerrato and Blackmer, 1990.

23 Corn Crop Response to N Fertilizer 105 lbs N/ 158 bu ~ 0.65 lbs N/ bu of yield Recommended optimum = 110 kg/ha

24 On average, Maryland farmers are ahead of other regions in nitrogen management Using less fertilizer with manadatory nutrient management plans ( lb N/bu expected yield) Split applications of N Soil N tests (PSNT) Adapt-N and other computer models to predict N needs.

25 Nitrogen Use and Corn Yield Trends in Maryland

26 Next level Good start

27 Barley cover crop responding at Thanksgiving to UAN side-dressed to corn previous June But Maryland, too, still has a leaky N system 5 ft 2 corn rows apart? Leftover N from June side-dressing being used by rye cover crop in Nov.

28 Veihmeyer, F.J An improved soil sampling tube. Soil Science 27:

29 Transect of 8-10 cores per farm 1 ft 2 ft 1 ft 2 ft 2 ft 2 ft 2 ft 2 ft

30 Crop Corn Soybean * * * * * Crop Corn Soybean Depth, cm NH 4+ -N Depth, cm Kg N /ha in each 15 cm layer * * * NO 3- -N Means of 20 profiles. Paired side-by-side soybean & cornfields on 4 farms in PG, Howard and Kent Counties. Fall * Ammonium-N, kg/ha Nitrate-N, kg/ha

31 EARLY planting is essential for fall cover crop activity August 0m 1m 2m

32 Depth (cm) Depth (cm) Soil nitrate Nov 2015 b b b a b a a a b a (0.09) NO 3 -N (kg/ha) Apr 2016 b b b ab a b ab a b ab a b a a b ab a (0.08) a a Letter indicates sig different NO 3 - N in layer (p < 0.05, unless noted) NO 3 -N (kg/ha)

33 Field Suction Lysimeters Sample Soil Pore Water 4 ft Deep Data collected from February - April 3 replications 60 x 300 plots Covers planted 15 Sept. 1. No cover 2. Sole rye 3. Sole radish 4. Triticale, radish, & clover mixture 5. Triticale, radish, & clover mixture, planted two weeks later

34 Even cover crop frost-killed in December impacted pore-water nitrate at 100 cm deep in February-March-April

35 Nitrate in sandy soil pore water, 90 cm deep on 22 Feb Triticale-clover-radish mix planted 15 Aug 30 Sept EPA Std

36 Down the drain? Changes (1960 to 2010) in ph & potassium concentrations in rivers across the US. Potassium In rivers K Fertilizer? Kaushal, et al Freshwater salinization syndrome on a continental scale. Proc. Natl Acad. of Sciences.

37 Keys to effective nutrient mgt with cover crops: Plant early get deep roots in Fall Include brassica + legume + grass Kill late let covers work for you in Spring

38 Lots to think about Soils are integrated systems. Soils are alive! Soils are deep. Each nutrient has its cycle Fertilizer can supplement, not supplant. Economic and environmental win-win. Lots of dollars still going down the drain.

39 Thanks for your attention. And remember: Start where you are. Use what you have. Do what you can. - Arthur Ashe