Lime

Lime

Citrus crops, particularly lemon trees, are sensible to frosts. This damage can be very detrimental at fruit formation initiation stage, being affected with temperatures between -0.9°C and -1.4°C. The rest of citrus crops (mandarins, grape fruits and orange tress) are tolerant to temperatures until approximately -2.5°C.

The location of crops is important, since the optimum temperature accumulation (degree days) for growing species directly influences the fruits soluble solid content (sugar content); consequently in warm spring locations, an early and excellent fruit quality is possible to obtain.

In relation to soil requirements, citrus crops need good drainage soils and with an effective depth of 80 cm to develop normal roots, being common to utilize ridges, which allow to establish these crops in thinner soils.

For citrus crops, it is common to utilize technified irrigation for controlling moisture stress, which is particularly damaging at the flowering stage. Also, the utilization of drippers and permanent soil washing to avoid excess salinity at the root zone, due to these crops are very sensible to salinity, being important to avoid water with salt concentration higher than 2mmhos/cm.

Besides, in the irrigation water, carbonates and bicarbonates’ concentrations superior to 2 meq/l requires to acidifying the water to avoid drippers’ blockage. Under the technified irrigation system, it is required about 6.000 m3/ha/year of water in the Quillota zone, Chile.

For a correct rootstock selection, some important criteria to be considered are: the adaptation to the present soil conditions, the productivity looking for, fruit caliber and frost resistance and/or resistance to certain diseases that affect the crop. The rootstock diversity existing in Chile allows finding the best combination to be adapted to different soil conditions in the country.

Nutrients and their role in citrus crops
The following table presents some characteristics of the nutrients and their role in the citrus crops.

Nutrient

Nutrients´main characteristics

Nitrogen

it is a component of many structural, regulator and energetic compounds.
Key compound of chlorophyll, key molecule of the photosynthetic system.
It promotes new buds´s growing after harvesting.
It moves in the phloem, being able to pass from older leaves to younger leaves.
It has influence in the fruit skin thickness.

Phosphorus

It is a compound of many structural and energy transfer compounds.
It is found in phospholipids and the adenosine phosphate.
It is a compound of nucleotides (structural blocks of ADN and ARN).
It has an important role in the root development, flowering and early fruit development periods.
It has mobility in the phloem, with which can be translocated between the tree´ organs.
It has influence in the yield and skin thickness of fruits.

Potassium

An adequate and abundant absortion of Potassium associated with a better fruit quality.
Its availability is important prior flowering.
It has great mobility in the phloem. It intensifies the transport and storage of assimilates from the leaves to the fruits.
It has roles in the weight, fruit size and crops´ yield.

Calcium

It is an essential component of the cellular membranes and walls, which provides resistance to cells aganist decomposition or microorganism attack.
It promotes proteins´ formation.
It does not have mobility within the phloem, therefore it must be readily available in active growing sites and plenty water for its absortion by the roots.
It reduces root attack, promoting root growth and health.
It reduces skin cracks and fruits´ fall.
It is necessary during flowering and fruits development.

Magnesium

It is the essential nutrient as chlorophyll molecular component.
It facilities Phosphorus transport.
It has high mobility within the phloem.

Sulphur

Aminoacid component, being part of the proteins.
It participates in the cholorophyll formation.
It is relative immobile in the phloem, therefore it depends of water availability for its distribution within the plant tissues.

Copper
Iron
Manganese
Zinc
Boron
Molybdenum

They participate in the enzymatic processes, being very important in the chemical synthesis and compounds´ generation of the plants.
Copper: Participates in the photosynthetic and respiration processes. It protects the levels of this in the soil, since chlorides aggravate salinity. Foliar levels of 0.4% indicate an incipient (emerging) toxicity and superior levels to 0.7% indicates a serious toxicity.

Iron: Participates in the chlorophyll formation.

Manganese: Essential in the photosynthesis, respiration and Nitrogen metabolism.

Zinc: Plays a role in the proteins synthesis. It avoids the photo oxidation of the plant tissues.

Boron: Structural component of the pectin and lignin.

Molibdenum and Manganese: Participates in certain Nitrogen transformations.

Absorption of Macro and Micronutrients
The following figure shows the rate of absorption of macronutrients in citrus during fruit growth, Source: Yara / Kynoch South Africa.

Absorption rate of macronutrients in citrus along the fruits´ growing period. Source: Yara/ Kynoch Sudafrica


It is shown that an important increment in the nutrients´ absorption occurs from fruit set until harvesting. Table 1 and Table 2 present the macronutrients´ and micronutriens´absorption respectively, for producing one ton of fresh fruit, in citrus crops.

 

N

P2O5 (=P)

K2O (=K)

MgO (=Mg)

CaO (=Ca)

S

Oranges

1773

506 (223)

3194 (2651)

367 (220)

1009 (726)

142

Mandarins

1532

376 (165)

2465 (2045)

184 (110)

706 (508)

111

Limon and Lime

1638

366 (161)

2086 (1772)

209 (125)

658 (473)

74

Grapefruit

1058

298 (131)

2422 (2010)

183 (110)

573 (413)

90

Table 1. Absorbed macronutrients quantity (g) by citrus crops for producing one ton of fresh fruit - Fuente: IFA (after Koo, 1958; Chapman, 1968; Malavolta; 1989)

 

Fe

Mn

Zn

Cu

B

Oranges

3.0

0.8

1.4

0.6

2.8

Mandarins

2.6

0.4

0.8

0.6

1.3

Lemon and Lime

2.1

0.4

0.7

0.3

0.5

Grapefruit

3.0

0.4

0.7

0.5

1.6

Table 2. Absorbed micronutrients quantity (g) by citrus crops for producing one ton of fresh fruit. - Fuente: IFA (after Koo, 1958; Chapman, 1968; Malavolta; 1989)
Foliar Concentrations
Various foliar concentrations are presented and their interpretation according to the nutritional development of citrus.

The following figure shows different concentrations of main macronutrients in the leaves (NPK) and the interpretation of each level according to the nutritional development for the specie.

Specie

 

Deficient (MB)

Low (B)

Normal (N)

High (A)

Excess (MA)

 

N

< 2,30

2,30 - 2,50

2,51 - 2,80

2,81 - 3,00

> 3,00

Oranges

P

< 0,10

0,10 - 0,12

0,13 - 0,16

0,17 - 0,20

> 0,20

 

K

< 0,50

0,50 - 0,70

0,71 - 1,00

1,01 - 1,30

> 1,30

 

N

< 1,80

1,81 - 2,00

2,00 - 2,40

2,41 - 2,60

> 2,60

Lemons

P

< 0,70

0,70 - 0,085

0,085 - 0,115

0,115 - 0,14

> 0,14

 

K

< 0,50

0,50 - 0,75

0,75 - 1,10

1,10 - 1,60

> 1,60

 

N

< 2,20

2,21 - 2,40

2,41 - 2,70

2,71 - 2,90

> 2,90

Clementinos

P

< 0,09

0,09 - 0,11

0,12 - 0,15

0,16 - 0,19

> 0,19

 

K

< 0,50

0,50 - 0,70

0,71 - 1,00

1,01 - 1,30

> 1,30

Table. Specific foliar range of N, P and K for dripping irrigation in citrus crops.

Element

Deficient (MB)

Low (B)

Normal (N)

High (A)

Excess (MA)

N

< 1,80

< 1,80 - 2,00

< 2,00 - 2,40

< 2,40 - 2,60

> 2,60

P

< 0,07

< 0,07 - 0,085

< 0,085 - 0,11

< 0,115 - 0,14

> 0,14

K

< 0,50

< 0,50 - 0,75

< 0,75 - 1,10

< 1,10 - 1,60

> 1,60

Presents different concentrations of secondary elements and microelements in the leaves and the interpretation of each level according the nutritional development for the specie.

Element

Very low

Low

Normal

High

Very high

Ca

< 1,60

1,6 - 2,9

3,0 - 5,0

5,1 - 6,5

> 6,5

Mg

< 0,15

0,15 - 0,24

0,25 - 0,45

0,46 - 0,90

> 0,90

S

< 0,14

0,14 - 0,19

0,20 - 0,30

0,31 - 0,50

> 0,51

Fe

< 35

35 - 36

61 - 100

101 - 200

> 200

Zn

< 14

14 - 25

26 - 70

71 - 300

> 300

Mn

< 12

12 - 25

26 - 60

61 - 250

> 250

B

< 21

21 - 30

31 - 100

101 - 260

> 260

Cu

< 3

3 - 5

6 - 14

15 - 25

> 25

Mo

< 0,06

0,06 - 0,09

0,10 - 3,0

3,1 - 100

> 100

In fertirrigation application, the most common nutrients applied are urea, ammonium nitrate, potassium nitrate, soluble potassium sulphate, phosphoric acid and magnesium sulphate. Via foliar application, sulphates, zinc and magnesium oxides or chelates are the most used.
Test Oranges in Sofruco Agricultural Society

For the present research study an orchard of the “La Rosa Sofruco S.A.” farm was selected. This orchard had the necessary characteristics for the study: The proper variety (Valencia: the most planted in Chile); being in full production, considering the great potassium demand by the fruit; homogenous threes, with excellent management and sanitary control; besides, presenting the lowest possible ... Read More.

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