LEAF & SOIL SAMPLING AND ANALYSIS TO ADJUST CITRUS FERTILIZER PROGRAMS. Mongi Zekri

Transcription

1 LEAF & SOIL SAMPLING AND ANALYSIS TO ADJUST CITRUS FERTILIZER PROGRAMS Mongi Zekri

2 Improving fertilizer efficiency Evaluation of leaf and soil analysis data. Adjustment of N rates to the level based on expected production and recommendations. Selection of fertilizer formulation to match existing conditions. Proper calibration and maintenance of equipment. Careful placement of fertilizer within the root zone. Timing to avoid the rainy season. Split application, and good irrigation management to maximize production and minimize leaching.

3 IMPORTANCE OF SOIL TESTING IN FLORIDA Soil tests in Florida are mainly important for ph, P, Ca, Mg, and maybe Cu.

4 The soil sample must represent the field. Each soil sample should consist of cores. The time of year for soil sampling is not that critical.

5 WHEN & HOW TO SAMPLE? Soil samples can be taken at the same time leaf samples are collected to save time and money and reduce the number of trips across the field. 16 to 20 soil cores should be taken to a depth of 6-8 inches within the irrigated zone close to the dripline of 16 to 20 trees.

6 SAMPLE HANDLING Mix the soil cores together in a plastic bucket. Sub-sample the mixed soil to fill the paper bag. Samples should be air-dried before shipping to a soil testing laboratory.

7 SOIL TESTING - FINAL THOUGHTS Soil testing is most effective when done annually. Choose a lab you trust and stick with it. Soil analysis results should answer these questions: - Does the grove need to be limed? - Is the soil Ca and Mg status OK? - Is the soil P status OK? - For old groves, what s the Cu status?

8 Mehlich1 soil test interpretations Adequate values for Florida sandy soils Element ppm P Mg Ca Cu 3-5 parts per million (ppm) x 2 = lbs/acre

9 LEAF SAMPLING & TESTING

10 IMPORTANCE OF PLANT ANALYSIS Plant Analysis was demonstrated and proven to be an extremely useful tool for: Assessing fertilizer needs, Detecting low levels of nutrients before severe deficiencies occur, Identifying nutritional problems.

11 CAUTION Standard procedures for leaf sampling must be followed because improperly collected leaf samples may provide misleading information about the nutritional status of the trees and the fertilizer programs.

12 LEAF SAMPLE COLLECTION The sample must properly represent the block of trees in question spring cycle leaves (from trees, at least one leaf from each tree quadrant), 4 to 6- month old from nonfruiting shoots should be collected in July-Sept before fall fertilization from uniform trees of similar age, same cultivar and rootstock and under the same fertilizer program. Sampled trees should be mapped so that samples can be collected from the same trees every year.

13 SAMPLING TECHNIQUES Trees at the edge of the block and at the end of rows should not be sampled because they may be coated with soil particles and dust or have other problems. Do not include diseased, insect damaged, or dead leaves in a sample. Use good judgment. Select only one leaf from a shoot and remove it with its petiole (leaf stem).

14 Start here Finish here 8-10 trees from each side

15 8-10 trees from each side

16 HANDLING LEAF SAMPLES Samples should be collected in paper bags, protected from heat (stored in portable ice chests), and placed in a refrigerator for overnight storage if they cannot be shipped the same day of collection.

17 EVALUATION The best indication of successful fertilizer management practices is having leaf nutritional standards within the optimum range.

18 Optimum Leaf Mineral Concentrations (%) for Citrus N P K Ca Mg S *4-6-month-old spring cycle leaves from non-fruiting terminals.

19 Optimum Leaf Mineral Concentrations (ppm) for Citrus Mn Zn Fe B Cu 6-16 Mo *4-6-month-old spring cycle leaves from non-fruiting terminals.

20 /SS/SS47800.pdf SL 253

21 BOTTOM LINE People collecting samples should be trained individuals and should know how to sample correctly. Leaf testing is valuable for all nutrients. Soil testing has value for ph, P, Ca, Mg, and maybe Cu.

22 FINAL THOUGHT If you make the effort to collect and have leaf and soil samples analyzed, use the information to make fertilization, liming, or soil amendment decisions.

23 THANK YOU!

24 Why 4-to-6-month old spring flush? Effect of leaf age on nutrient concentration

25 WHY NON-FRUITING TWIGS? Type N P K Ca Mg percentages in spring flush leaves Nonfruiting Fruiting

26 HANDLING LEAF SAMPLES For macronutrient analysis, leaves do not need to be washed.

27 COMPARING LEAF WASHING METHODS for macronutrients Method N P K Ca Mg percentages in spring flush leaves Wash Rinse *A. K. Alva and D. P. H. Tucker, Proc. Fla. State Hort. Soc, 1997

28 PREPARATION FOR ANALYSIS Leaves that have been recently sprayed with micronutrients for fungicidal (Cu) or nutritional (Mn, Zn) purposes should not be analyzed for those micronutrients. For more accurate micronutrient determination, samples require hand washing. Is it better to wash leaves when they are still in a fresh condition.

29 COMPARING LEAF WASHING METHODS for micronutrients Method Cu Fe Mn Zn ppm in spring flush leaves Wash Rinse *A. K. Alva and D. P. H. Tucker, Proc. Fla. State Hort. Soc, 1997

30 Summary- Improving fertilizer efficiency Evaluation of leaf and soil analysis data. Adjustment of N rates to the level based on expected production and recommendations. Selection of fertilizer formulation to match existing conditions. Proper calibration and maintenance of equipment. Careful placement of fertilizer within the root zone. Timing to avoid the rainy season. Split application, and good irrigation management to maximize production and minimize leaching.