GUIDE AND INSTRUCTIONS FOR SOIL AND LEAF SAMPLING FOR TROPICAL AND SUBTROPICAL CROPS

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2 GUIDE AND INSTRUCTIONS FOR SOIL AND LEAF SAMPLING FOR TROPICAL AND SUBTROPICAL CROPS T he purpose of leaf and soil analysis is to determine the nutrient status of a plant on a scientific basis. This information is then used to make fertilizer adjustments or recommendations. Complete analyses are done on LEAF, SOIL, WATER and GROWTH MEDIUM samples. A complete analysis takes 14 days. The following instructions for taking samples must be strictly adhered to since any analytical result is only as good as the sample being analyzed: Samples must be representative of a land or orchard. PREPLANT SOIL SAMPLING A leaf and soil sample must not represent an orchard of more than 3 ha. Should soil variations be apparent in such an orchard, separate leaf and soil samples must be taken. The following instructions must be strictly adhered too: Different cultivars must be sampled separately. Leaf samples must only be taken from trees bearing fruit. For time and position of leaf sample see attached figure. Select approximately 20 healthy trees that are distributed throughout the orchard, homogenous in appearance and representative of the orchard as a whole. Exceptionally good or poor trees must not be sampled. The 20 selected trees must be clearly marked, for example with paint, so that both the soil and leaf samples can be taken from the same marked trees every year. At about shoulder height, where possible, pick four leaves from alternative sides of the tree. A total of about 80 leaves per sample are sufficient. A composite soil sample should be taken from the top-soil (0 to 30 cm) under the drip (tree canopy) of the tree basins. In irrigated orchards samples should be taken in the wetted area of the irrigation under the canopy of the tree. In drip irrigation it should be beneath the dripper. A soil analysis will only indicate the chemical composition of the soil. Physical problems e.g. impermeable layers, ploughsoles etc. can only be identified when test pits are made in the particular area. LEAF AND SOIL SAMPLING IN ESTABLISHED ORCHARDS When a leaf sample from a particular orchard is submitted for the first time, it must be accompanied by a soil sample. Thereafter, it would be advisable to also submit soil samples annually. When making fertilizer adjustments, it is essential to take into consideration the analysis results of both the soil and the leaf samples. 1 In the case of banana leaf samples the third youngest leaf, taken from the top, can be cut with a knife. Sometimes the youngest leaf is small and malformed. In this case the next leaf, which must be at least a meter long, should be regarded as the first leaf. A composite top-soil (0 to 30 cm) soil sample should also be taken 50 cm from the stem, in the plant row. As regards pineapples 10 to 15 D-leaves should be sampled per block. 10 to 15 sub-samples are taken in the top-soil (0 to 30 cm) to make one soil sample. Leaf samples should preferably be collected in the morning, after the dew has dried off. Leaves sampled must be free of sunburn, disease and insect damage. 2

3 Leaf samples should not be taken too soon after a tree has undergone stress or been exposed to any abnormal circumstances such as drought, heat or high rainfall. Wait at least two weeks. PACKING OF SOIL AND LEAF SAMPLES Leaf samples must be placed in clean perforated plastic bags or brown paper bags. After sampling the bag must be tightly closed and leaves must be stored in a refrigerator (not freezer), if samples cannot be delivered immediately. Soil samples should consist of about 2 kg of soil and be placed in a strong plastic or linen bag, avoid paper bags as they break when damp, do not use fertilizer bags as they will contaminate the sample. Topsoil, subsoil and leaf samples must be packed separately and be properly marked. Sample containers must be clearly marked with the block/ orchard number, and in the case of soil top- or sub-soil. The following information must accompany the samples or be filled in on the questionnaire: Name, address and telephone number of farmer. Crop type. Cultivar. Tree age. Orchard / sample no. NB: If leaf samples cannot delivered or couriered within 48 hours to the ITSC research station they must be washed and dried (instructions for this method can be obtained from us). The samples can then be posted to us. Solution A: THE WASHING AND DRYING OF LEAF SAMPLES 250 ml Phosphate free soap (e.g. Deacon 75 or Ekon D.) m Acetic acid CP ml Distilled water. Mix well. Solution B: Add 10 ml of solution A to 1 litre of water and mix well. Procedure: Rinse leaves in: Running tap water Solution B for 3 minutes Running tap water Rinse each leaf in three separate buckets filled with distilled water After every fifth sample, the first bucket with distilled water is replaced and bucket No. 2 becomes No. 1 etc. Lightly rub each leaf with absorbent cotton wool Place leaves in a clean brown paper bag and dry for 48 to 72 hours at 65 C (± 5 C). WATER SAMPLES The correct sampling of water is very important. If the method is incorrect, it will have an effect on the results. Listed are some precautions that are to be followed: Use a clean container that holds at least 500 ml of sample and does not leak when sealed. Rinse the container several times with the sample before filling it. Select the point of collection carefully; Avoid sampling close to the edge of a river or dam Collect the water as close as possible to the intake from where it is pumped for irrigation. 3 4

4 Let the water run for some time before it is collected from a pipe or borehole. Seal the container immediately after the sample has been taken, water samples should be analysed as soon as possible after sampling. If it is not possible to deliver the sample immediately it should be kept in the fridge until it can be delivered to the laboratory. The following information should be written on the container: sample date, sample name and source of water. Samples can be sent to the following address: or delivered to: Soil Science Laboratory Soil Science laboratory ARC-ITSC ARC-ITSC Private Bag X11208 Corner of Bosch Street and Nelspruit Kanyamazane Rd R Nelspruit CROP AVOCADO BANANA CITRUS COFFEE TIMES OF LEAF SAMPLING TIME OF SAMPLING 6 8 month old leaves - February to April October to April when 50 % of the orchard has flowered March to April Full bloom - October to November GINGER 105 days after planting - GRANADILLA GUAVA LEMON LITCHI MACADAMIA Approximately mid-december September to December 5 months after pruning February September to November 3 month old leaves - October to November COMPOST (Growth medium) ANALYSIS A good growing medium needs to continuously supply plant roots with balanced proportions of water; air and nutrients. A complete analysis consists of a chemical analysis, a physical analysis and the determination of the C:N ratio. The chemical analysis will provide information on the nutrients available to the plants. The physical analysis comprises determination of air filled porosity, water holding capacity and wettability. The C:N ratio indicates the decomposition level of the medium. OTHER ANALYTICAL LABORATORY SERVICES Nematode analyses Nematodes or roundworms occur in the soil and roots of most crops. Nematodes severely damage root systems of plants and therefore affect the normal uptake of nutrients and water. Crops such as banana and pineapple, as well as many vegetables and ornamentals are very susceptible to nematodes. Root and soil samples should therefore be taken regularly for testing. These are analysed and corrective measures are recommended. Pathology services Pathology is the study of the processes underlying disease abnormality or dysfunction of plants. At the ARC-ITSC, diseases of tropical and subtropical crops and the causal agents are identified. Avocados and citrus are indexed for viruses and viroids. Advice on control measures is provided. Pest Management Consultancy The Pest Management Division assists farmers by assessing insect-related problems. Suitable monitoring and cost effective control measures are then recommended. Why is it essential to do these analyses? It allows the producer to: Determine the nutrients required for an orchard. Make the correct fertilizer application. This will ensure better fruit quality and higher yields. Detect deficiencies and malnutrition timeously. 5 6

5 LEAF / FRUIT / COMPOST ANALYSIS: (EXCL. VAT) RANDS (R) (INCL.VAT) Standard Leaf (includes preparation): N, P, K, Ca, Mg, Zn, Cu, Mn, Fe, B Standard Manure (includes preparation): % moisture, N, P, K, Ca, Mg, Zn, Cu, Mn, Fe, B Preparation: wash, dry, grind Avocado Fruit Preparation: Several fruit per sample Single Element (price/element): P, K, Ca, Mg, Zn, Cu, Mn, Fe, B, Na, Cl Total Nitrogen - N Total Sulphur - S % Moisture SOIL CHEMICAL ANALYSIS: Standard Soil (includes preparation): ph, resistance, K, Ca, Mg, P, Al, Na Preparation: dry, mill, sieve ph (water or KCl) and Resistance Cations (price/element): K, Ca, Mg, Na Micro Elements (price/element): Zn, Cu, Mn, Fe, Cl Aluminum - Al Phosphorus - P Percentage Carbon (%C) and Organic Matter - Walkey Black Method SOIL PHYSICAL ANALYSIS: % Sand, Silt, Clay Water Retention Curve (easily available water: 0-100kPa) Computer determination WATER ANALYSIS: Standard Irrigation Water: ph, EC, K, Ca, Mg, Na, Cl, TDS, SAR, Carbonate, Bi-carbonate, Adjusted SAR, Irrigation class Standard Drinking Water: ph, EC, K, Ca, Mg, Na, Cl, TDS, Carbonate, Bi-carbonate, Zn, Cu, Mn, Fe, B, S,N, P, Co, Ni and Total Coliform and E. Coli count Single (price/element): ph, EC, K, Ca, Mg, Na, Cl, Zn, Cu, Mn, Fe, Co, Ni, Carbonate, Bicarbonate Single (price/element): Nitrogen (N), Phosphorus (P), Boron (B), Sulphur (S) Total Coliform and E. Coli count GROWTH MEDIUM (POTTING SOIL) ANALYSIS: (preparation included) Standard Chemical: % moisture, ph, EC, K, Ca, Mg, Na, Cl, Zn, Cu, Mn, Fe, N, P, B Standard Physical: Air filled porosity, waterholding capacity and wettability Single (price/element): ph, EC, Ca, Mg, K, Na, Zn, Cu, Mn, Fe, Co, Ni, Cl, % Moisture, NO 2, NO 3, NH 4, SO Single (price/element): Nitrogen (N), Phosphorus (P), Boron (B) Lime Requirement Curve Total Nitrogen C:N Ratio

6 ARC-ITSC Corner of Bosch and Kanyamazane Rd R2296, Nelspruit Private Bag X11208, Nelspruit, 1200 Tel.: Fax: Website: Analytical Laboratory Services: Soil, Leaf and Water Analyses: Mrs Yvette Abercrombie Nematode Analyses: Dr Mieke Daneel Pathology services: Ms Zama Dlamini Pest Management Consultancy: Mr Arthur Sippel TAKE NOTE Discount: samples = 5 % discount 100+ samples = 10 % discount

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