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This article was produced by Mick English of Australian Horticultural Consultants Pty. Ltd. as a result of his endeavours to determine a suitable fertiliser program for trees at Alstonville.

Reference		(1)	(2)	(3)	(4)	(6) and (9)	(A)	(B)
Year 1	N	4	180	180	75	180	75	100
	P	45	6	6	20	6	20	25
	K	32	18	18	36	18	30	50
Year 3	N	160	108	nil	130	480	120	300
	P	27	45	nil	30	16	30	75
	K	115	135	nil	45	48	45	150
Year 6	N	356	165	not	200	300	250	300
	P	250	55	known	80	100	100	100
	K	468	121	but	110	450	150	200
Year 12	N	712	690	not	330	600	550	600
	P	500	184	much	130	200	220	200
	K	936	506	?	550	800	330	400

(A) and (B) are two grower programs that produced well-grown trees and better-than-average production. Recommended timing to bearing trees has also varied:

(1) 40% 1 month after fruit set (October). 40% after harvest (February) and 20% in March.

(2) 50% 2 weeks prior to harvest and 50% two weeks after.

(3) At or just prior to harvest.

4) 40% of fruit set (Sept.) 60% after harvest (Feb.).

(5) 4 weeks after fruit set to encourage fruit development and 2 weeks after harvest to encourage one growth flush.

Taking the above into account, I have decided to adopt the following fertiliser program for trees that are effectively 7 years old and have a canopy area of 5m.

Application of NPK Fertiliser
There are as many fertiliser recommendations for Lychee as there are authors on the subject. Set out below are the annual applications of NPK (gms/tree) recommended by some authors:

• Correct any soil deficiencies shown up by a soil test undertaken in May by fertigating in June.
• Late June - 100g UREA
• June/ July - Lime, Dolomite or Gypsum as per soil test.
• August - 400g DAP + 200g Muriate of Potash (KCl).
• September - 100g UREA.
• October/November - 100g UREA.
• December - 100g UREA 400g Muriate of Potash (KCl).
• February (after harvest) - 200g KCl + 500g Dynamic Lifter.

All but the lime and Dynamic Lifter will be applied through the irrigation system and the total amounts of each element being applied will be 350g N, 170g P, 210g K. Based on canopy areas, these could be varied up or down by 20%/annum.

Leaf and Soil Standards
Proposed Lychee leaf nutrient standards were first proposed in 1986 and reviewed in a paper presented to ACOTANC in 1988 which also included tentative soil nutrient levels. Recommended Australian standards for leaf and soil have now been suggested by Menzel and Simpson and are:

NUTRIENT	Atom. Wt.	Leaf Standard	Soil Standard
Nitrogen N			mg/kg as NO3
Phosphorus P			100 - 300 mg/kg
Potassium K meq/100g	39	0.70% - 1/10%	0.5 - 1.0
Calcium Ca meq/100g	40	0.60% - 1.00%	3.0 - 5.0
Magnesium mg meq/100g	24	0.30% - 0.50%	2.0 - 4.0
Iron Fe meq/100g		50 - 100 ppm
Zinc Zn		15 - 30 ppm	2 - 15 mg/kg
Copper Cu		10 - 25 ppm	1 - 3 mg/kg
Boron B		25 - 60 ppm	1 - 2 mg/kg
Manganese Mn		100 - 250 ppm	10 - 50 mg/kg

In the Table: mg/kg = ppm: multiply % by 10,000 to convert to ppm: multiply meq/100g by 100 x Atom. Wt to convert to ppm.

The units quoted are those normally used by Incitec in their Reports. Leaf samples should be taken between May and August at panicle emergence, and using the first healthy leaf under the panicle. Eight leaves from each of 20 trees spread through an orchard should give a representative result.

The soil sample should be taken in April/May to give time to undertake any liming as may be necessary before fertiliser applications begin in earnest. The recommended pH range is 5.8 - 6.5 (1: 5 water) and organic carbon should be at least 3%. Lime application for pH correction should be limited to 5 tonnes/hectare when pH falls below 5.5. The recommended soil levels for phosphorus and boron may be difficult to achieve on Alstonville Plateau soils, as may be the low levels of nitrogen, which are very variable throughout the year. A bicarb extractant phosphorus level of 100 ppm is desirable on red soils, any higher may be costly. Boron and nitrogen levels are better judged from leaf levels than from soil analysis.

The ratios of the exchangeable cations, K, Ca and Mg, may not be optimal from the soil standard. The ratio of calcium to magnesium should fall in the range 3 to 6 and magnesium to potassium between 2 and 4. The only loss of potassium to the system occurs when product is harvested and this may only be 15 gms, whereas my suggested program involves applying 210 gms of potassium to a 7 year old tree - well above harvest loss.

The high level of potassium suggested is related to experiments indicating that it may improve flowering. In the long run, this level of potash application will not be sustainable and soil levels should not be allowed to exceed 1 meq/100 g (390 ppm). At this upper level of the range, soil magnesium and calcium levels should be kept above 2 and 6 meq/100 g respectively. As long as the calcium to magnesium ratio is kept within the upper limit of 6 and potassium to magnesium is not more than 0.5, lime rather than dolomite should be applied as it is cheaper. As the upper limits are reached, magnesium oxide should be used to boost magnesium levels.

Don Batten suggested the following note be added in regard to boron. "Boron should be applied as a routine matter on krasnozem soils, unless very close to the sea. The leaf standard for boron is probably a bit low. Our soils are very low in boron and it is readily leached. I apply 4 g Borax/m² in February and July and foliar applications in June and September (0.3% Borax or 0.15% Solubor). Ground application of Solubor can be through fertigation or with Roundup. Foliar application of Solubor can be with Dimethoate for Erinose Mite."

There are two points of difference of opinion between QDPI and NSW Agriculture and are important, which I have been unable to resolve. Resolution is left for the judgement of the individual. Chris Menzel suggests that lime should be applied during the wet season rather than mid-winter. His reason is that the continual rain will activate the material rapidly and less will be lost due to wind. Against this, application just before heavy rain could result in a lot of the surface application being washed away with surface run-off. There is clearly merit in both points of view.

The Queensland recommendation is definitely not to apply any nitrogen after harvest but NSW Agriculture continue to recommend a post-harvest flush be encouraged. Incidentally, Queensland recommends against the use of organic fertiliser on the grounds that the timing of nitrogen release is unpredictable.

The question of Lychee nutrition is not set in concrete but there are now more areas of agreement than disagreement between people who have studied the fruit. It is hoped that the above may give some guidelines on which to base a fertiliser program.

Mick English
Article from Sunshine Coast Subtropical Fruits Association (Inc) Newsletter No.38 November, 1991

DATE: January 1992

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