MALUMA FERTILISER NORMS AND PRACTICES AA ERNST
SOURCE:
South Africa
Fertilization guidelines based on: –
Sampling for leaf analyses and norms
–
Soils analyses
–
Applciations based on phenological stages -> growth cycle approach
Very few fertilizer applications while tree establishment
Foliar Zn and B application recommended monthly during active shoot growth, specially in young trees
South Africa
Split nitrogen applications recommended: –
Caution for applying nitrogen too early
–
Nitrogen as an important tool to manipulate vegetative and reproductive growth
Critical is the overall nutrient management during summer flush to ensure future productivity
Physiological post-harvest fruit disorder -> “gray pulp” the major problem for local and overseas marketing due to N : Ca ratio imbalances
Calcium as key nutrient to improve fruit quality
Nutrient distribution in Avocado plant – absolute amounts
Variety: Hass; August 2001,
Fruit Leaves
2000
New shoots Branches
Nutrient content in g/tree
1500
Trunk Root & Rootstock
1000
500
0 Nitrogen
Phosphorus
Potassium
Nitrogen is distributed in fruits, leaves, branches and roots. Phosphorus is mainly located in the roots + rootstock and the branches of the tree. Potassium is mainly located in fruits and branches. Source: Rosecrance & Lovatt (2003) - Califoria
Nutrient Removal of Avocado fruits Based on 10 t/ha fresh weight Nutrient
% of dry weight
Kg/ha
Nutrient
ppm of dry weight
Kg/ha
N
0.54
11.3
Na
400
0.8
P
0.08
1.7
B
19
0.04
K
0.93
19.5
Fe
42
0.09
Ca
0.10
2.1
Zn
18
0.04
Mg
0.24
5.0
Mn
9
0.02
Cl
0.07
1.5
Cu
5
0.01
S
0.30
8.0
Yields in New Zealand: 9.4 metric tons/ha (60 to 200 trees per ha) with average fruit size 260 - 290 g/fruit. Source: Lahav, E 1995
The N : K ratio fits to the 12:11:18
Nutrition of Avocado Nitrogen
Nitrogen
Nitrogen has a great influence on growth and yield of avocado
There is a relationship between N concentration in the spring grown (autumn sampled) leaves and the yield of avocado –
The optimum N concentration in the leaf is depending on cultivar – – –
(Embleton, 1959)
“Hass” “Fuerte” Other
= 2.2 – 2.4 = 1.7 – 2.0 = 1.9 – 2.2
A split application in 3-4 rates per year is recommended to prevent losses. Source: The Avocado, 2002 ; Lovatt, 2002
Nitrate absorption is more efficient Autumn
Winter
Spring
Summer
Absorption efficiency (%)
60
Whole tree absorption of Nitrogen was highest for N applied in summer
a
50 ab
40 b b
30 20
a
10
b
a
0 Nitrate Source: Zilkah, S. et al. (2000)
Ammonium
a
Nitrogen deficiency
Nutrition of Avocado Phosphorus
Phosphorus deficiency
Leaf loses lustre and turns reddish brown
Nutrition of Avocado Potassium
Potassium deficiency
Necrosis of leaf margins
Nutrition of Avocado Calcium
Calcium
Calcium related disorders are also internal Calcium distribution problems, mainly between mature and growing regions of the plant and/or in the fruit
Low Avocado fruit Ca levels have been associated with several undesirable fruit characteristics: – – – – – –
Susceptibility to chilling injury Rapid softening/ripening after harvest Flesh discolouration Pulp spot Vascular Browning Susceptibility to Anthracnose
Source: Witney et al. (1990)
Calcium concentration in Avocado fruits 7000
Fruit Ca (mg/kg dm)
6000
Critical Period for Calcium management
5000
in first 11 weeks after fruit set
4000 3000 2000 1000 0 0
5
10
15
weeks after fruit set Source: Witney et al. (1990)
20
25
Calcium concentration in Avocado fruits Proximal end
1 2 20 mm
3
Fruit section
Calcium (µg/g fresh wt)
1
181
2
116
3
73
4
53
5
53
4 The first symptoms of chilling injury are
5
visible at the distal end of avocados, where the Ca concentration is lowest
Distal end Source: Chaplin & Scott (1980)
Calcium and Fruit Quality 26 R2 = 0,61
No° of days to ripen
24 22 20 18 16 14 200
250
300
350
400
450
500
550
Ca concentration in fruits (mg/kg)
Higher Fruit Ca concentration is related to delayed ripening which is increasing fruit Shelf –Life Variety: Hass Source: Hofman et al. (2001)
Calcium and Fruit Quality 5
Anthracnose (1-5)
R2 = 0,77 4
3
2
1 200
250
300
350
400
450
500
550
Ca concentration in fruits (mg/kg)
Higher Fruit Ca concentration is related to a reduced severity of Anthracnose (1= no disease to 5= severe disease) following storage and ripening of “Hass” fruit. Source: Hofman et al. (2001)
60
14
58
12
Calcium in leaf (g/kg dw)
Calcium in fruit (mg/kg fw)
Calcium efficiency varies with rootstock 56 54 52 50 48 46
Hass on Duke 7
Hass on Velvick
10 8 6 4 2 0
Hass on Duke 7
Hass on Velvick
Calcium concentration of Hass avocado leaves and fruit flesh from trees grown on different rootstocks Source: Marques (2000) – from Whiley et al (2001)
Calcium efficiency varies between trees Variety “Hass” Fruit Ca conc (mg/kg)
600
500
400
300
200
100
0
1
2
3
4
5
6
7
8
Individual trees Source: Whiley et al. 2001 – from Vuthapanich et al. 1998
9
10
11
12
13
14
Calcium deficiency
Typical ’tip burn’ of leaf
Magnesium deficiency
Leaves remain green at base and along veins
Sulphur deficiency Sulphur moves slow in plants. Deficiency symptoms therefore manifest in the young leaves.
Fruit is deformed on one side
Nutrition of Avocado Boron
Boron – need
BORON IS REQUIRED PRIOR TO FLOWERING FOR PROPER FERTILIZATION AND FRUIT SET
FOLIAR APPLICATION OF BORON IS NOT ENOUGH: –
ABSORPTION OF BORON BY MATURE LEAVES IS POOR (DUE TO THE WAXY SURFACE),
–
BORON IS TAKEN UP BY YOUNG LEAVES
–
BORON HAS TO BE TRANSLOCATED TO THE INFLORESCENCE
BASE SOIL APPLICATION CAN PREVENT SEVERE BORON DEFICIENCY WITHOUT RISKING TOXICITY EFFECTS
THE SOIL APPLICATION SHOULD BE COMPLIMENTED WITH FOLIAR APPLICATIONS BEFORE FRUIT SET, WHEN NEED IS HIGHEST Source: Robbertse et al., 1992
Boron soil application The effect of soil B application on leaf boron concentrations of Hass grafted to Duke (Mexican or Velvick (Guatemalan) Rootstock. Boron leaf concentration (mg/kg)
60 50 40 Hass/Duke 7
30
Hass/Velvick
20 10 0 0
0.25
0.5
1
2
Boron soil application (kg/ha) Source acc. to: Whiley et al., 1996
3
8
Boron – Critical level for deficiency
DEFICIENCY SYMPTOMS: –
YELLOWING AND DEFORMATION OF LEAVES
–
THICKENING OF NODAL REGIONS ON BRANCHES
–
REDUCED ROOT GROWTH
–
BRANCH AND TRUNK LESIONS
–
REDUCED POLLEN VIABILITY
–
DEFORMED AND SMALLER FRUITS
DEFICIENCY OCCURS AT LEAF BORON CONCENTRATIONS < 25 MG/KG
OPTIMUM LEAF BORON CONCENTRATION –
40-100 MG/KG IN MATURE SUMMER FLUSH LEAVES, BEFORE INFLORESCENCE (ACC. TO ROBBERTSE ET AL, 1995 B > 70 MG/KG)
Source: Whiley et al. 1996 - Australia
Boron deficiency – Cultivars and Rootstocks Rootstock: Cultivar: CULTIVAR
Highly susceptible
Sharwil
Moderate susceptible
Hass
0.5
Reed Moderate tolerant
Fuerte
Boron in leaf (g/kg dw)
BORON DEFICIENCY
Boron uptake efficiency is generally higher for Guatemalan type rootstocks (Edranol, Nabal, Velvick) than those of Mexican type (Duke 7, Topa Topa, Mexicola).
0.4 0.3 0.2 0.1 0
Source: Whiley et al., 1996 Marques (2000) – from Whiley et al. (2001)
Hass on Duke 7 Hass on Velvick
Boron application on B deficient soils 280
Fruit Size (g)
260 240
no B +B
220 200 180 Trial 1
Trial 2
Field Trials: Cultivar Hass, Boron soil applied Leaf boron concentration were also directly correlated to increased Fruit Size Source: Smith et al. (1995)
Boron deficiency
Fruit is deformed on one side
Boron – Critical level for Toxicity
AVOCADO IS ALSO SENSITIVE TO BORON TOXICITY WHICH LEADS TO A VERY NARROW OPTIMUM LEVEL (FAO 1995)
AVOCADO IS SENSITIVE TO IRRIGATION WATER CONTAINING MORE THAN >92 µM BORON –
GUPTA ET AL. (1985)
TOXICITY SYMPTOMS GET VISIBLE IN THE PLANT WITH B CONCENTRATION IN LEAVES > 100 µG/KG –
MIYASAKA ET AL. (1999)
Over aplication of Boron leads to toxicity symptoms 350
Dry weight of new leaves (g) Boron toxicity symptoms visible 35
*
300 Foliar B (mg/kg)
250
*
*
30 25
200
20
150
15
100
10
50
5
0
0 0
3,7
11
22
44
89
178
Added B (mg/kg soil fines)
Over application led to chlorosis symptoms, necrotic spots and a depression of vegetative growth Source: Miyasaka et al (1999)
Dry weight of new leaves (g)
Foliar B (mg/kg)
Over supply of Boron leads to toxicity symptoms Foliar B (mg/kg)
Deformed leaves (%)
350
17,5
300
15
250
12,5
200
10
150
7,5
Plants ok
100 50
5 Boron deficiency symptoms visible
Deformed leaves (%)
Foliar B (mg/kg)
Boron toxicity symptoms visible
2,5
0
0 0
1
10
100
B level in solution (µm)
Deficiency leads to deformed leaves plus “shot-holes” in the leaves Toxicity leads to interveinal chlorosis and necrosis Source: Miyasaka et al (1999)
Copper deficiency
Leaf is deformed and cups up
Iron deficiency
Veins remain dark green
Manganese deficiency
Interveinal yellowing with brown necrotic spots
Nutrition of Avocado Zinc
Application of Zn increases leaf Zn status Foliar Zn conc (µg/g)
1992 - Start
1993
1994
120 100 80 60 40 20 0 ZnSO4 soil
ZnSO4 irrigation
Zinc-sulfate was soil banded and through the irrigation system applied. Variety: Hass, commercial orchard, California All trees had a leaf Zn concentration < 50µg/g at the beginning; grown on calcareous soils Source: Crowley et al. (1996)
Application of Zn increases leaf Zn status Foliar Zn conc (µg/g)
June
July
August
September
October
100 80 60 40 20 0 Control
ZnSO4 via soil
Zinc-sulfate was soil applied (3.2 kg ZNSO4/tree = 1.14 kg Zn/tree) in May. Variety: Hass, commercial orchard, California All trees had a leaf Zn concentration < 50µg/g at the beginning; grown on Calcareous soils
Source: Crowley et al. (1991) – from Hofshi (2001)
Zinc
DEFICIENCY SYMPTOMS – – –
INTERVEINAL YELLOWING (MOTTLED LEAVES) SHORTENED INTERNODES DEFORMED (ROUND) AND SMALLER FRUITS
DEFICIENCY OCCURS AT LEAF ZINC CONCENTRATIONS < 20 MG/KG
OPTIMUM LEAF ZINC CONCENTRATION –
30-150 MG/KG IN MATURE SUMMER FLUSH LEAVES, BEFORE INFLORESCENCE
OCCURS MAINLY IN CALCAREOUS SOILS
Source: Crowley et al., 1991; Hofshi, 2001
Zinc deficiency
Zinc deficiency
Nutrition of Avocado Other effects
Salt toxicity
Chloride toxicity Sodium toxicity
Nutrition of Avocado Analysis
Leaf Sampling in Avocado (Southern Hemisphere)
For nutrient monitoring sample in March-April to coincide with cessation of the season's growth. Sampling Time: April to May, when the summer flush has ceased. Plant Part: 2nd - 4th leaf from the terminal bud (blade plus petiole). Collect From: Shoots that are not flushing nor fruiting. Select at shoulder height - exclude boundary trees. Quantity per Sample: 4-8 leaves from each of 20 trees selected at random. Ring of buds between the previous and present year´s growth
Source: National department of agriculture, South Africa Koen & du Plessis (1992)
Leaf Analysis Standards – various Countries Unit %
Australia 2.2 - 2.6
California 2.2 - 2.4
New Zealand 2.2 - 2.6
South Africa 2.2 - 2.4
Mexico 2.2 - 2.6
Phosphorus
%
0.08 - 0.25
0.08 - 0.44
0.08 - 0.25
0.08 - 0.15
0.08 - 0.25
Potassium
%
0.75 - 2.0
1.0 - 3.0
0.8 - 2.0
0.75 - 1.25
0.71 - 2.0
Calcium
%
1.0 - 3.0
1.0 - 4.5
1.0 - 3.0
1.0 - 2.0
1.0 - 3.0
Magnesium
%
0.25 - 0.8
0.25 - 1.0
0.25 - 0.8
0.4 - 0.8
0.25 - 0.8
Sulphur
%
0.2 - 0.6
0.2 - 0.6
0.2 - 0.6
0,2- 0,6
0.2 - 0.6
Sodium
%
> 0.25
> 0.25
> 0.25
> 0.25
Chlorine
%
> 0.25
> 0.25
> 0.25
> 0.25
Boron
ppm
40 - 60
12 - 100
35 - 80
50 - 80
50 - 100
Copper
ppm
5 - 15
5 - 15
5 - 15
5 - 15
5 - 15
Iron
ppm
50 - 200
50 - 300
50 - 200
50 - 150
50 - 200
Manganese
ppm
30 - 500
30 - 700
30 - 500
30 - 250
30 - 500
Zinc
ppm
40 - 80
30 - 250
30 - 150
30 - 100
30 - 150
Nitrogen
University of California DANR Analytical Lab
Right Nutrition at the right time
The fruit Size of avocado is higher related to the number of cells than to the cell size in fruits –
It is important to maximize cell division in fruit during the first 7-8 weeks after fruit set –
Moore-Gordon et al. 1997
Cowan et al 1997, 2001
The two key trace elements involved in this process are Zinc and Boron.
Source: Wolstenholme, 2001; Whiley, 2001_b
