Soil Fertility Dynamics

Transcription

1 Soil Fertility Dynamics T. Scott Murrell Director, Northcentral U.S. National Alliance of Independent Crop Consultants, 2013 Annual Meeting, Jacksonville, FL Jan

2 IPNI Nutrient Evaluation Efforts Soil Test Summaries Nutrient Use GIS

3 Median Bray P-1 equivalent soil test levels, 2010

4 Change in median Bray P equivalent soil test levels from 2005 to 2010

5 Soil test P distribution in 2010 compared to 2005 for the Corn Belt (12 states plus Ontario) 30% 25% 20% 15% 10% 5% 0% Corn Belt P million samples million samples Median (2010) (2005) Bray P1 Equivalent, ppm

6 nugis.ipni.net 1987 P 2 O 5 Balance

7 nugis.ipni.net 1992 P 2 O 5 Balance

8 nugis.ipni.net 1997 P 2 O 5 Balance

9 nugis.ipni.net 2002 P 2 O 5 Balance

10 nugis.ipni.net 2007 P 2 O 5 Balance

11 Change in soil test level Expected changes in soil test levels based upon nutrient budgets + Application > removal ~ 0 Application removal Application < removal -

12 Annual change in median P, ppm Annual change in median soil P level for 12 Corn Belt states as related to state P balance, y = x r² = 0.62 IA NE IN OH MN KS SD MO KY -1.5 MI IL 11 lb P 2 O 5 / ppm WI NuGIS balance*, lb P 2 O 5 /A/yr *NuGIS is a GIS nutrient balance model (IPNI, 2010).

13 Median soil test K levels in 2010

14 Change in median soil K level from 2005 to 2010

15 Soil test K frequency distribution in 2001, 2005 and 2010

16 nugis.ipni.net 1987 K 2 O Balance

17 nugis.ipni.net 1992 K 2 O Balance

18 nugis.ipni.net 1997 K 2 O Balance

19 nugis.ipni.net 2002 K 2 O Balance

20 nugis.ipni.net 2007 K 2 O Balance

21 Soil Test Potassium: Difficulties with Identifying Trends Changes that occur are not consistently predictable What could be contributing to this variability?

22 P removal (lb P 2 O 5 /acre) Soil P decrease (ppm) Long-term crop removal and soil test P trends Years of corn/soybean rotation P Removal 43 lb P 2 O 5 / ppm Soil P decrease Villavicencio and Mallarino, Personal communication

23 K removal (lb K 2 O/acre) Soil K decrease (ppm) Long-term crop removal and soil test K trends 0 Years of corn/soybean rotation lb K 2 O / ppm K Removal Soil K Decrease Villavicencio and Mallarino, Personal communication

24 Contributors to soil test K variability: Sampling variability

25 Short-range variability of soil test K: Across and down Nutrient stratification Banding 4 yr. ago Banding this year Banding 2 yr. ago

26 Depth (in.) Depth control: Important in reduced tillage systems No-till field with 10-yr history Tama silt loam 8 in ppm 4 in ppm in in. 330 Robbins and Voss, 1991 (IA)

27 Frequency (50 total) Core number: Impact on variability 40 True average cores per sample Soil test P category upper limit (ppm) 20 cores per sample

28 Contributors to soil test K variability: Sampling frequency

29 Soil test level Sampling frequency: Affects ability to detect trends Sampled every 42 1 years Increasing or decreasing? Crop year

30 Concept of a monitoring strip Area where intensive measurements are taken each season Soil tests Plant tissue tests Nutrient deficiency symptoms Grain nutrient content Diseases Insects Management practices etc.

31 K visual deficiency symptom index Visual symptoms of K deficiency are a useful diagnostic tool Deficiency Symptom Index: 0 = None 1 = Moderate 2 = Severe Soil test K (ppm) Wittry and Mallarino, Iowa State University

32 Example of K deficiency symptoms: soybean

33 Contributors to soil test K variability: Leaching of K from plant residue

34 Corn stover K content (lb K 2 O/acre) Changes in corn stover K content after physiological maturity harvest Days since physiological maturity Oltmans and Mallarino Personal communication.

35 Soybean tissue K content (lb K 2 O/acre) Changes in soybean tissue K content after physiological maturity harvest Days since physiological maturity Oltmans and Mallarino Personal communication.

36 Percent of initial K remaining Amount of water affecting K leaching from residue Non-irrigated Irrigated by overland flow (2 in. every 7-21 days) Water, inches Schomberg, H.H. and J.L. Steiner Soil Sci. Soc. Am. J. 63:

37 Contributors to soil test K variability: Soil moisture

38 Potassium fixation Dehydrated K ion Hydrated K ion Planar positions Clay mineral layer Interlayer positions Edge positions Havlin et al., 1999

39 Wetting/drying cycles impact variability Sample Treatment Fixed K Exchangeable K meq/100g Drummer (Dekalb) Dry Wet Drummer (Urbana) Dry Wet Cisne (Brownstone) Dry Wet Stucki, 1996 (IL)

40 Soil test K (ppm) Soil moisture (%) Seasonal variation in soil test K Soil test K Soil moisture J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A Month of the year Ebelhar et al Personal communication. Soil test values are ammonium acetate extractable.

41 How the scientific community is responding to variability in soil test K Two primary efforts have been underway to address K variability: Conduct new crop response trials Re-examine the effect of drying soils prior to analysis

42 Scientific response to soil test K variability: Updated crop response trials

43 Corn grain relative yield (%) Very low Low Optimum High Very high Changes in soil test K critical levels: Categories used previously Iowa, U.S Soil test K (ppm) Mallarino, A.P

44 Corn grain relative yield (%) Very low Low Optimum High Very high Changes in soil test K critical levels: Categories used previously Iowa, U.S Many other soils Canisteo, Colo, Ely, Nicollet, Tama, Webster Soil test K (ppm) Mallarino, A.P

45 Corn grain relative yield (%) Very low Low Optimum High Very high Changes in soil test K critical levels: Categories currently used Iowa, U.S Many other soils Canisteo, Colo, Ely, Nicollet, Tama, Webster Soil test K (ppm) Mallarino, A.P

46 Scientific response to soil test K variability: Re-examining the effect of drying soils prior to analysis

47 Soil test K (ppm) Monitoring soil test K over time: Effects of drying the soil sample lb K2O/acre 108 lb K2O/acre K applications discontinued Field moist Air-dried Years of corn/soybean rotation Mallarino, A.P. Personal communication. Soil test values are ammonium acetate extractable.

48 Soil test K (ppm) Effect of sample drying on soil test K y = x R² = Harpster silty clay loam Clarion loam y = x R² = Soil moisture (%) Luebs, R.E. et al Soil Sci. Soc. Am. Proc 20: Note: curve fitting and statistics not performed by the authors.

49 Soil test K (ppm) Dowdy, R.J. and T.B. Hutcheson, Jr Soil Sci. Soc. Am. Proc. 27: Initial soil test K levels affect changes as soils are dried Bedford: no K added Bedford: K enriched Soil moisture (%)

50 Corn relative yield (%) Keeping samples moist may improve the relationship of soil test K to yield response 110 Dried Clay loam Loam Silty clay loam Soil test K (ppm) Barbagelata and Mallarino Personal communication.

51 Corn relative yield (%) Keeping samples moist may improve the relationship of soil test K to yield response 110 Moist Clay loam 70 Loam Silty clay loam Soil test K (ppm) Barbagelata and Mallarino Personal communication.

52 Summary Soil test P levels are declining in the Midwest, and these declines can be explained by mass balance Soil test K levels are declining in many states in the Midwest, but declines are not explained by mass balance perhaps because of high variability Causes of soil test K variability: Sampling variability Sampling frequency Leaching of K from crop residues Soil moisture Drying of soil samples prior to analysis Scientific response: Update crop response data Investigate drying of soils prior to analysis