Soil Testing in Tomatoes

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?