Soil Testing for Commercial Vegetables

1. Soil Testing for Commercial Vegetables ANR Update Fall 2008 F.J. Sikora, Ph.D. Division of Regulatory Services

6. Confusion when comparing different soil test reports because of.. different extractants different units expressing results

7. Comparison of 4 extractants for soil test P NAPT sample 2003-110: Rozetta silt loam from Bureau Co., IL. Soil pH = 6.5, CEC = 8.3

8. Different Units • 20 labs report as mg/kg • 15 labs report as lbs/acre • 1 lab reports as lbs/acre-6 inches • 2 labs report as lbs/ppm • 2 labs report as ppm/lbs/acre • 1 lab repors an index • 3 labs reports as kg/ha • 1 lab reports as mg/L Source - NAPT, 2nd quarter 2000

9. UK standard for P and K Mehlich III in lbs/acre ppm x 2 = lbs/acre mg/kg x 2 = lbs/acre

10. Agronomic Threshold High Med Low 5 30 60 V.low 110 100 90 80 Thresholds for vegetable crops Yield (% of maximum) 70 P: 80 lbs/acre K: 300 to 450 lbs/acre Mg: 80 to 200 lbs/acre 60 50 40 0 1 Soil Test P (lbs/acre) Soil Test P (lbs/acre)

13. soil pH Al

16. WHY THERE IS NO SOIL TEST FOR N:

17. ID-36 publication:

19. Number of samples in 2007 16 13 4 79 2 1 1 21 0 8 12 0 0 67 0 105 21 Total = 350

20. Three major vegetables common to all: P, K, pH, Mg Sweet corn Zn Squash and Pumpkins Tomatoes soil Mg needs to be a little higher than other crops (200 lb/ac) Hartz ratio: K/Mg

21. Zn recommendations for Corn

22. as fertilizer as fertilizer

23. (67 samples) as fertilizer as fertilizer

24. (105 samples) as fertilizer as fertilizer

25. Yellow Shoulder Disorder (YSD)

26. Hartz ratio = exchangeable K exchangeable Mg in units of cmolc / kg Critical ratio = 0.35

28. 72% of KY samples 28% of KY samples Apply potassium nitrate in drip irrigation

29. extra

30. Relative Sources of Nutrients Soil Test Sufficiency Level Level soil High 100% fert. soil Med 70-100% fertilizer Low soil 50-70% soil fertilizer V.Low <50% Nutrients External available nutrients from soil required