Using soil content of plant-available nitrogen as a tool for diagnosing turfgrass damage

Transcription

1 Using soil content of plant-available nitrogen as a tool for diagnosing turfgrass damage Wendy Gelernter and Larry Stowell PACE Turfgrass Research Institute

2 Soil nitrogen A common culprit in turf diagnostics Can cause turf stress when either too low or too high Several conditions can lead to excessive nitrogen and significant turf stress Case studies reviewed Guidelines based on diagnostic samples and soil surveys proposed

3 Conditions that can lead to excessive soil N Over-fertilization High nitrogen content water source Insufficient leaching Anaerobic soils Organic matter release

4 OVER-FERTILIZATION Slow-release N applied May, 2000 prior to laying sod 4/01

5 30 mg/kg N 64 mg/kg N 4/01

6 4/01 OVER-FERTILIZATION Poor sprayer tank agitation led to uneven application rate of CaNO 3

7 77 mg/kg N 22 mg/kg N

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9 NO3 mg/kg 50 0 q1 q2 q3 q4 q5 Turf quality

10 HIGH NITROGEN CONTENT WATER Big Canyon Country Club Jeff Beardsley, CGCS Started pumping recycled water in spring of 1997 Three fairway/roughs remained on domestic water Fairways sampled for soil chemistry at 150 yard mark once or twice per year starting in 1999

11 Trends in Soil Salinity (EC ds/m) Big Canyon CC, 12/98 6/ Recycled 5 Domestic 12/98 6/99 12/99 6/ 0 12/ 0 6/ 1 12/ 1 6/ 2 12/ 2 6/ 3 12/ 3 6/ 4 12/ 4 0 Salinity (ds/m) Value

12 Trends in Plant Available Nitrogen Big Canyon CC, 12/98 6/ Recycled 50 Domestic 12/98 6/99 12/99 6/ 0 12/ 0 6/ 1 12/ 1 6/ 2 12/ 2 6/ 3 12/ 3 6/ 4 12/ 4 0 Nitrogen (mg/kg) Value

13 Big Canyon CC Recycled water contains 18 mg/l NH 4 (Desired < 8mg/l) At 3 acre-feet water/year, approximately 3. 4 lb NH 4 /1000 sq ft delivered from water OM release up to 6 lb N/1000 sq ft/year >9 lb N/1000 sq ft/yr from water + OM; Approximate turf requirement = 8.6 lb N/1000 sq ft/year Therefore, avoid N fertilizers; use domestic water during high water use summer months

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15 INSUFFICIENT LEACHING Precipitation rate lower than expected 0.25 Target rate = 0.22 inches 0.2 Precipication (inches) Precipitation (inches) 0 Good area Poor area

16 Salt and nitrogen accumulation due to lack of sufficient irrigation Parameter Good areas Poor areas Guideline EC (ds/m) <6.0 Plant available N (mg/kg) <20

17 Nitrogen guidelines Based on data from good performing greens and fairways, Nitrate Ammonium Total plant available nitrogen (TPAN) Nitrate & exchangeable ammonium measured via KCl extraction & analysis w/lachat Quick Chem 8000 Flow Injection Analyzer

18 Soil nitrate on good-performing greens and fairways N = 569 greens N = 233 fairways * *

19 Soil ammonium on good-performing greens and fairways N = 570 greens N = 233 fairways * *

20 Soil total plant available nitrogen on good-performing greens and fairways N = 570 greens N = 233 fairways * *

21 Guidelines for soil plant available nitrogen Nitrate (NO 3 ) 3 20 mg/kg Ammonium (NH 4 ) < 7 mg/kg Total plant available nitrogen < 20 mg/kg *Turf damage can result when TPAN<20 mg/kg if NH 4 is > 7 mg/kg

22 A quick test for soil nitrate levels with Hach water test strips: Nitrate levels (mg/kg) = (Dipstick X 1.5) + 2.9

23 Correlation between test strip readings and soil nitrate analyses (KCl extraction) 30 NO3 (mg/kg): Brookside NO3 mg/kg = 1.5 X test strip R = 0.89, P< Test strip Reading

24 Estimating soil NO 3 with Hach test strips Hach water test strips (Cat. # , Hach Co. Mix equal volumes soil and tap water; allow to settle ~ 1 min Dip test strip into soil suspension. Allow strip to develop for 1 minute Lightly rinse with water to remove soil Compare color against guide on container Convert value to mg/kg (NO3 mg/kg = 1.5 X test strip reading + 2.9) Measures nitrate only!

25 Excessive Soil Nitrogen: >20 mg/kg TPAN or >7 mg/kg NH 4 can result in significant turf stress Is more frequent problem than is commonly assumed Courses with well or recycled water with high N (> 8 mg/l) are at risk Courses in arid environments are at risk due to lack of leaching rainfall N release from high OM soils is a risk factor Fairways & roughs at particular risk due to over-fertilization, high %OM, recycled water

26 Avoiding nitrogen stress Monitor soil NO 3, NH 4 and TPAN 1 2 X/year Apply N frequently at low rates <0.5 lb/1000 sq ft for fairways <0.25 lb/1000 sq ft for greens) Use of ammonium-based and slow-release fertilizers should be limited in locations with N problems Increase soil aeration for improved nitrification in soil

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28 % Tissue Nitrogen vs. Total Soil Plant Available Nitrogen KCL extraction