1. Soil Testing in Tomatoes
Jim Rideout
Extension Specialist
Soil Fertility

2. The Main Idea
Maintain growth while applying only those nutrients which can not be supplied by the soil in adequate amounts

3. Other Reasons
Routine monitoring can spot nutrient problems before they become nutrient deficiencies
Mountain soils are extremely variable
Fertility can be considered part of a good IPM program

4. How Tomatoes Differ from Agronomic Crops
May have drip fertigation
Must manage calcium
Need to consider source of nutrients
Earliness and quality are important
High value per acre

5. Soil Analysis Basics

6. NCDA&CS Agronomic Division
Soil
Plant tissue
Irrigation water
Nutrient solutions
Nematode assay

7. What Does Soil Analysis Measure ?
The extractable nutrient concentration in a soil sample
Does not measure the total nutrient concentration
Estimates the ability of the soil to supply nutrients to a crop
Optimized for annual row crops

8. Recommendation Philosophies
Crop Response
Nutrient Replacement (maintenance)
Nutrient Buildup
Cation Balancing
NC Recommendations
– Crop response + some maintenance

9. Soil Sampling Methods

10. Importance of Collecting a Representative Soil Sample
One acre of soil, 6” deep, weighs about 2,000,000 pounds
Weight of soil in box about 1 pound
Weight of sample analyzed is about 2.5 g (1/10) of an ounce

11. Selecting Areas for Routine Sampling
Areas should be less than 5 acres
Similar soil type and crop history
Similar fertilization history
Keep blocks same year to year

12. Soil Sample Handling Mix cores well in clean plastic bucket
Fill box to line
Do not oven-dry sample
Send sample in for analysis as soon as possible

13. Stick With Your Lab Different reporting units
Different soil extracting solutions
Different yield assumptions
Different recommendation philosophies

14. NCDA Sample Volume 252,025 soil analyses last year
Turnaround time varies by month
7 to 10 days in summer
February 2004:
5 to 6 weeks

16. New codes
Will reduce lime recommendation to account for un-reacted lime

17. Interpretation of Results

18. Now What Do I Do?

19. Crop Information

20. Basic Soil Information

21. Soil pH and Lime

22. Lime Recommendations Actual pH Acidity (buffer pH)
Target pH (6.5 for tomato)
Residual credit for applied lime
CANNOT make an accurate lime recommendation based on pH alone

23. Nitrogen
Based on crop code,
not on test results

24. NCDA Index System Unique to North Carolina
Converts nutrients to common units for interpretation
Used for P, K, Mn, Zn, Cu, S
Similar to index used for tissue

25. Soil Interpretation Indices

26. Phosphorus and Potassium

27. Calcium and Magnesium Expressed as percent of CEC
May determine the type of lime needed
Need to consider CEC for gypsum applications

28. Calcium and Magnesium

29. Micronutrients and Sulfur

30. Salinity Information

31. Additional Information

33. Fruit Calcium

34. Causes of Low Fruit Calcium
Low soil calcium
Low soil pH
Nutrient imbalances
Excessively wet or dry soil
Large fruit
Variety differences

35. Cation Balance and Fruit Calcium
Must balance calcium, potassium and magnesium in the soil
Excessive potassium fertilization can reduce fruit calcium content
Excessive magnesium fertilization from dolomitic lime can reduce fruit calcium content

36.
+K +K
Ca ++
K+ K+
+K +K
Ca ++
Ca ++
++ Mg
K+ K+
Ca ++
++ Mg
+H +H
Ca ++

37. Questions?