FERTILIZING. Correct time is during October and November. Sample young, fully developed, hardened off leaves.

Transcription

1 FERTILIZING Macadamias need to be fertilized from planting. Although in small quantities it must be done to ensure good growth. The trees do grow slowly and have to be helped to grow bearing wood in as short a time as possible. Leaf Sampling Correct time is during October and November. Sample young, fully developed, hardened off leaves. A leaf sample should represent a planting of not more than 3 ha. Different cultivars should be sampled separately Leaves should be taken from healthy tree, free of sunburn, deficiency symptoms, insect damage and disease symptoms. Leaves should be sampled in the morning after the dew has dried off. Do not sample after heavy rainfall, wait at least 2 weeks for the nutritional levels to stabilize. Select healthy trees well distributed throughout the planting. Mark the selected trees and use the same trees every year. Sample 4 leaves per tree at shoulder height.

2 MACADAMIA SOIL AND LEAF ANALYSIS NORMS SOIL ph [H O] 5.0 to 6.0 ph [KCI] 4.0 to 5.0 P [Phosphorous] 20 to 80 ppm K [Potassium] 80 to 150ppm 0.2 to 0.4 meq % Ca [Calcium] 400 to 800 ppm 2.0 to 4.0 meq % Mg [Magnesium] 100 to 200ppm 0.8 to 1.6 meq % Na [Sodium] <40 ppm <0.2 meq % TOTAL CEC 3.2 to 6.2 meq % NOTE: ppm = parts per million = mg/kg = milligrams per kilogram meq % = milli equivalents % or per 100g soil 1 meq % Ca = 200 ppm Ca 1 meq % Mg = 120 ppm Mg 1 meq % K = 390 ppm K 1 meq % Na = 230 ppm Na TOTAL CEC = Total Cation Exchange Capacity = Sum of Ca + Mg + K + Na as meq % Work towards increasing total CEC as high as possible and an ideal balance between Ca, Mg, K and Na as percentage of total CEC as follows:- Ca Mg K Na 72.5% of total CEC 15% of total CEC 7.5% of total CEC <5% of total CEC LEAF N [Nitrogen] 1.2 to 1.5% P [Phosphorous] 0.07 to 0.09% K [Potassium] 0.40 to 0.60% Ca [Calcium] 0.60 to 0.90% Mg [Magnesium] 0.09 to 0.11% S [Sulphur] 0.20 to 0.40% B [Boron] 50 to 90 ppm Zn [Zinc] 15 to 30 ppm Cu [Copper] 5 to 10 ppm Mn [Manganese] 150 to 250 ppm

3 MACADAMIA FERTILIZER GUIDELINES 1 PREPLANT Your only chance to modify soil ph and phosphorous levels to a decent depth in the rooting zone [0.5 to 1m]. If ph [H 0] is less than 5.0:- it takes 5 tons of lime per hectare to raise ph [H20] by one ph unit in a heavy [clay] soil, and 2.5 tons/ha in a sandy soil. Broadcast the lime prior to ripping/discing. If soil P is <5 ppm:- apply at least 1 ton/ha single superphosphate broadcast prior to ripping/discing. BOTH Ca [major constituent of lime materials] and P move extremely slowly through the soil. Hence your only chance to improve levels of these two elements through the rooting zone of the trees is to mix them well into the soil prior to planting. 2 AT PLANTING Macadamias will benefit greatly from the addition of 1 litre well composted chicken or kraal manure and 25 grams single superphosphate, mixed into the planting hole soil at planting. 3 YOUNG TREES [0-3 years] Do not apply any fertilizer for the first 6 weeks after planting, then use the following failsafe guide:- Nitrogen: Apply 25 to 50g N per tree per age of tree per annum. See Nitrogen application guide for macadamias. Phosphorous and Potassium: Best applied up to age 3 in the ratio of N:P:K of 4:1:2. Eg, if a tree aged 1 receives 50g N/year than the N:P:K application for the year will be 50:12,5:25g/tree of N:P:K. This is easiest applied as a ready made fertilizer mixture. If straights are used then the

4 phosphate should all be applied in March and the potassium split between March and August. As much of the young tree N:P:K requirement as possible should be applied as organic manure. Calcium, Magnesium and trace elements: It should not be necessary to apply any lime to young trees up to age 3, if ph was corrected before planting. If lime is required, do not apply more than 500kg/ha to trees 3 years old or less. Trace elements [zinc and boron especially] can be applied to young trees using foliar sprays. 4 BEARING AGE TREES [4 years +]: Nitrogen: See nitrogen application guide for macadamias. Change N:P:K ratio to 5:1:5. Eg: if a 5 year old tree needs 250g N/yr then the N:P:K application for the year will be 250:50:250 g/tree N:P:K. Easiest applied as a commercially available 5:1:5 mixture. Applying as much as possible of the N:P:K requirements using an organic source will again be beneficial. Calcium and Magnesium: If soil ph and calcium levels are low apply agricultural lime as a top dressing at no more than 1 ton/ha year. If soil ph is satisfactory but calcium levels are low, apply gypsum at no more than 1

5 ton/ha/year. If ph and calcium and magnesium levels are low, apply dolonitic lime at no more than 1 ton/ha/year. Sulphur: If leaf sulphur levels are low, choose fertilizers containing sulphur in the fertilizer programme, such as single superphosphate, gypsum, ammonium sulphate and potassium sulphate. Boron If leaf levels are low apply up to 4 foliar sprays of solubor at 1 gram/litre between September and December. Even if leaf boron levels are within the norms of ppm B, at least one pre-blossom spray of solubor at 1 gram/litre should be applied to aid fruit set. Soil applications of borax can be made according to the following table: Zinc: Apply a foliar spray of zinc nitrate at 150ml per 100l water annually preblossom. Alternatively apply zinc sulphate to the soil in July as follows:- Zinc foliar Zinc sulphate Level [ppm] gram/m2 canopy area <

6 Copper: Apply pre-blossom foliar spray of copper oxychloride at 400 grams/100l. Copper can also be applied to the soil using copper sulphate at 30kg/ha broadcast under the drip area. Major Nutrient content of common fertilizers used in macadamias:- Fertilizer N% P% K% S% Ca% Mg% Urea 46 Ammonium sulphate LAN 28 Potassium Chloride 50 Potassium sulphate Single superphosphate Mono-ammonium phosphate Agricultural Lime Dolomitic Lime Gypsum :1:5 [36]