Soil Testing Labs. Soil Testing. Soil Testing Gardens and A Comparison of Three Garden Soil Test Kits With a Soil Testing Lab

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1 Soil Testing Labs Soil Testing Gardens and A Comparison of Three Garden Soil Test Chris Augustin NDSU Extension Soil Health Specialist Minot, ND Chris.Augustin@ndsu.edu NDSU Soil Testing Lab Soil Testing Lab 1360 Bolley Drive Fargo ND (701) AGVISE Labs Highway 15 W; P.O. Box 510 Northwood, ND Ag Soil Science 54 th St. NW. Minot, ND Soil Testing 6 or more samples in your lawn or garden 811 Remove non-soil (grass, thatch, leaves, plastic, etc.) layer from surface of sampling location and sample the soil to a depth of 6 inches Place the soil from each area into a bucket and mix them all together. This becomes the composite sample for your lawn or garden Place about 1 pint into a soil sample bag Fill out the Lawn and Garden Information Sheet and include with sample X Don t worry days Lawn Shady, Lawn Sunny, Back Garden, Front Garden 1

2 ph effects nutrient availability If you don t use a ND lab, make sure you have an Olsen phosphorus test done. lbs/ac vs. ppm O.M. can be important for herbicides Salts over 0.5 can be a problem Fertilizer Application Soil Test Issue Garden Lawns Needs N 4-5 lbs N as lb/1000 ft 2 (late August, mid-may, late June) Needs P 4-5 lbs P 2 O 5 as lbsp 2 O 5 /1000 ft 2 Needs K 4-5 lbs K 2 O as lbs K 2 O/1000 ft 2 ph < 7 Apply ~6 lbslime/400 ft 2 Plant adaptive species Organic Matter < 3% Add compost or peat moss and mix soil E.C. > 0.5 Improve drainage, plant salt Improve drainage, plant tolerant plants, or move garden adapted cultivars Adapted from Evaluating, Preparing and Amending Lawn and Garden Soil How do I pick a fertilizer? Incorporate or water after application How do I pick a fertilizer? N-P-K = 46%N = 11%N, 52% P 2 O = 60% K 2 O Generic fertilizers are fine. Plant only cares if there is NO 3, H 2 PO 4, and K. Knowing how to read a fertilizer test will save you money and reduce environmental impacts. Compost and manure are the natural and original Slow Release fertilizer. Split applications of fertilizer are more efficient than Slow Release fertilizers. 2

3 How much do you apply? 20 lbsn & 5 lbsp 2 O 5 /1000 ft 2, No K 2 O needed and is the fertilizer Raised bed area is 100 ft 2 Determine P first 5lbsN needed/1000 ft 2 8% = 62.5 lbsfert lbsfert. x 0.10 (account for smaller area) = Apply 6.3 lbsfertfor P2O5 6.3 x 24% = 1.5 lbsn How much do you apply? 30 lbsn/1000 ft 2 x 0.1 = 3 lbsn needed -1.5lbs N from Need 1.5 lbsn 1.5 lbsn/100 ft 2 13% = 0.2 lbsfert Apply 0.2 lbs and 6.3 lbs fertilizer Also applying 1 lbsk 2 O N is a leaky nutrient Proper timing and split applications of N tend to be more effective than fertilizer additives. Denitrification is about 1-3% per day. Leaching depends on soil texture and form of N Rainfall and Urea Loss Estimates *Rainfall (in) Daysafter application N Volatilization Loss (%) to to *1/2 inch rain needed for full urea incorporation Adapted from Fox and Hoffman, Pennsylvania Garden Test Comparison Study Certified lab tests have been studied and scrutinized by university and testing lab personnel for years. Certified labs perform tests that have shown to be most consistent for a region. Garden soil testing kits are cheap and offer quick results. However, these tests haven t been compared to certified lab tests. Is there a difference between the garden test kits and certified testing lab? 3

4 Zahill Williams Zahl Forman Heimdal Bearden Glyndon Belfield Reeder Mandan Buse Svea Barnes Fargo Determining Soil Type Web Soil Survey Soil Web 4

5 Luster leaf rapitest LaMotte Complete Soil Test Kit Luster leaf rapitetst4-way Analyzer We compared the individual garden test kit with the. Each test had 3 reps. Mean soil test results. Nitrat ph P e 2 O 5 K 2 O Soil Test lbs/ac ----ppm---- NDSU Soil Testing Lab LaMotte Complete Soil Test Kit *** Rapitest Soil Test Kit *** 143.5*** Rapitest 4-Way Analyzer 6.1*** 8.8*** 1.4*** 23.4*** ***Significantly different at the 99.9% confidence level 5

6 Times Different Soil Tests Were Similar to The at the 95% C.L. ph Nitrate P 2 O 5 K 2 O Occurrence Where SoilTests Soil Test Were Similar (16 different soils) LaMotte Complete Soil Test Kit Rapitest Soil Test Kit Rapitest 4-Way Analyzer Rapitest *** Svea LaMotte *** 46.1*** 4-way Analyzer 6.2** 6.4*** 1.0*** 20.0*** LaMotte * 41.7* 27.6*** Williams Rapitest 6.5** 0.0*** * 4-way Analyzer 6.5** 4.9*** 0.8*** 15.1*** way Analyzer *** 23.6*** Zahill Rapitest * 16.0** 139 LaMotte *** *** way Analyzer * 1.5** 26.7*** Zahl LaMotte ** 37.5* 37.6*** Rapitest 6.6* 0.0*** *** *USDA-NRCS, Rapitest * 13.5*** 147.0*** Compost** 4-way Analyzer 6.3*** *** 17.8*** LaMotte 8.0* 0.0* *** LaMotte *** 50.0** 189.1** Fargo Rapitest *** 16.0*** 201.0*** 4-way Analyzer 5.9*** 13.6*** 2.2*** 34.9*** LaMotte * *** Forman 4-way Analyzer 5.9* 14.1** 2.3** 32.0*** Rapitest 6.4** 86.7* ** LaMotte 8.0* *** 67.9* Glyndon Rapitest 6.9** ** 4-way Analyzer 6.1*** 10.7** 1.7*** 26.9*** *USDA-NRCS, 2019; **Mountain West Products, 2019; Rapitest 7.4* * Barnes LaMotte 8.0*** *** 42.2*** 4-way Analyzer 6.1*** 9*** 1.4*** 25.3*** Rapitest 7.4* 111*** 16.0*** 171.7** Bearden LaMotte 8.0*** *** 129.4*** 4-way Analyzer 6.3** 9.3*** 1.5*** 24.9*** LaMotte *** 12.5*** 63.2*** Belfield 4-way Analyzer *** 1.3*** 20.4*** Rapitest 6.4*** ** 155*** LaMotte *** 28.3*** Buse Rapitest 7.3*** 80.7* 16*** 112.7* 4-way Analyzer 6.1*** 10*** 1.6*** 25.3*** *USDA-NRCS,

7 Rapitest *** 147.0*** Heimdal LaMotte 7.0* *** 4-way Analyzer 6.1** 8.4*** 1.4*** 20.9*** LaMotte *** Mandan Rapitest 6.7*** 105.0** 15.2*** 139.0*** 4-way Analyzer 5.9*** 11.3*** 1.8*** 37.3*** LaMotte *** Potting Soil** Rapitest * 147.0*** 4-way Analyzer 6 7.1* 1.1*** 20.9*** LaMotte Reeder *** Rapitest * 147*** 4-way Analyzer 6 7.1* 1.1*** 20.9*** *USDA-NRCS, 2019; **Oldcastle Lawn & Garden, Inc., 2019 Conclusions In some instances, the soil garden test kits provided similar soil test results to the certified soil testing lab. However, garden soil test kits tended to measure less nutrients than the certified soil testing lab. North Dakota soils tend to have high levels of potassium. All garden soil test kits underestimated soil potassium levels. Using the garden soil test kits instead of a certified soil testing lab may cause over application of fertilizers. Unless, fertilizer recommendations are calibrated for the garden soil test kit. Several other garden soil test kits are available. Many of the untested kits have similar extraction solutions as the ones tested. If using an untested kit, the extraction solutions should be noted by the user to determine if the kit is comparable to a certified testing lab. Summary Soil test LaMotte appears to be the most accurate garden soil test kit. Potassium was inaccurate. EccoConceptstest uses same reagents. Rapitestwas good for nitrogen and ph. 4-way Analyzer results were different from all tests. garden test is $