Asparragus

Asparagus

Asparagus (Asparagus officinalis L.) is a vegetable crop of the Liliaceous family. It is a perennial plant which is cultivated mainly on temperate climate and with moderate winter.

Its production cycle depends on the variety, climatic conditions and principally on the cultural management applied to the crop. It prefers long days and high light intensity mainly from high temperatures; even though, observations made have indicated that light does not have any direct effect on the stalk (shoot or spear) growing.

The optimum growing average temperature is 19°C with a variation range of +-7°C, being the asparagus growing affected in colder zones (under 10 – 15°C).

The crop has a useful life between 6 and 12 years, depending on the harvest number performed per year. With one annual harvest, usually the plant last between 8 and 10 years. Besides, the plant in older crops, but with two harvests per year, has a life span between 6 and 7 years.

The plant is composed in two parts: the aerial part or canopy, formed by stalks, branches, leaves, flowers, fruits and seeds; and the subterraneous part, which is presented with two types of roots: the principals, which act as storage organs of carbohydrates and the secondary roots or rootles, responsible to the water and nutrients absorption. The crown is found between the root and the stem, which is the connection between both parts. This is a sort of subterraneous horizontal stem (rhizome) over which the vegetative buds sprout that will produce spears (edible part).

The reserves formed in the aerial part are accumulated in the main roots. These reserves play a fundamental role in the spears’ emission for the next season. This, due to that the asparagus yield is not the result of the photosynthetic products generated in the actual season, since it is in direct function of the accumulate reserve quantity of the previous season.

Asparagus is cultivated on a wide range of soil types, obtaining the best results in loam, sandy loam, tilled and soft or spongy or loose soil with good drainage. This crop is tolerant to saline soils, but it is susceptible to acid soils.

Main Nutrients
The application of balanced nutrition aims to ensure adequate aerial and root growth to store as much carbohydrate in specialized organs. Adequate nutrition of the crop is a key factor in obtaining good harvests.

To achieve an appropriate nutrition plan in asparagus is necessary to know the nutrient demand in quantity and type of nutrient. It is also important to know the role of each nutrient for crop growth, yield and quality of production.

The objective of a balanced nutrition application is to assure an adequate aerial and root growing for storing the higher carbohydrate quantity in specialized organs. The adequate nutrition of the crop is a key factor for obtaining a good harvest.

Nutrients requirement for an asparagus planting has an ascending rate from the initial period until the maximum production stage. These requirements comprise nutrients for spears growing, crown, foliar and fruits development.

The following table shows nutrients percent distribution found in different organs in an asparagus planning.

Organ

Fresh biomass

Distribition Percent

(kg/ha)

N

P2O5

K2O

Roots and Crowns

63,840

56

73

59

Foliage

10,640

35

21

34

Spears

6,160

9

6

7

Total

80,640

100

100

100


Generally, 18 elements have been accepted as essential for the plant nutrition: Carbon, Oxygen and Hydrogen (absorbed from the air and water); Nitrogen, Phosphorus, Potassium Calcium, Magnesium and Sulfur (all macronutrients), and Fe, Cu, Zn, Mn, B, Mo, Na y Cl (micronutrients).

It is considered that the macronutrients extraction for the asparagus crop follows a descending order: N > K > Ca > P > S > Mg. For micronutrients, the extraction quantity follows a descending patter: Fe > Zn > Mn > B > Cu.

The following table shows the roles of some very important nutrients in the asparagus crop.

Nutrient

Important characteristics of nutrients

Nitrogen

It is required in large quantity for the plant's tissues formation and for physiological functions performance, and then it is important to assure its availability during the plant biological cycle. It is recommended 3 applications: the first with ammonium Nitrogen, the second with ammonium Nitrogen and Nitrate, and the third, only with Nitrate

Phosphorus

It is required in low quantities for the crop. Among its roles is the root growing stimulation, also influences the asparagus quantity reducing fibrosis and providing flavor, since when there is lack of this nutrient the asparagus becomes insipid.

Potassium

It is required in high quantity for the plants. It intervenes in the carbohydrates transport process within the plants, helping to maintain the spears quality and incrementing resistance to fungi diseases.

Calcium

Due to its immobility within the phloem, it is important to be available for the plant in the soil with the objetive that the plant can absorbed it and conducting it to the mayor growing zones.

Magnesium

It is absorbed in a medium level by the plant, being essential in the photosynthesis process in which organic substances are produced. This will be determinant for obtaining high crop yields.

Boron

Asparagus is a demanding crop of Boron. It requires having certain levels of this nutrient for an adequate formation of its cellular structures. It is observed that the maximum growing in the plant is obtained with concentration of 1.5 ppm under nutritive solution conditions.


As a result, an asparagus crop conducted in Chile, indicated that for producing 1 ton of spears, the crop extracted the following total rate of nutrients:

P2O5/ha

K2O/ha

S/ha

MgO/ha

CaO/ha

Fe/ha

Mn/ha

Cu/ha

Zn/ha

B/ha

5.0 kg

17.0 kg

1.5 kg

1.8 kg

5.0 kg

111 gr

27 gr

8 gr

50 gr

20 gr


These values vary according various trails conducted with this crop, which explains different climate, edaphic and moisture conditions in each location, also variety, age, and crop management used. A general possible statement is that the N and K extractions are relatively of the same order (high requirement).

A useful tool to determine the crop’s nutritional requirements is the foliar analysis method, which can be compared with the critical range of nutritional values for the crop, and analyzed taking into consideration the available historical results for each location.

The following table shows that climate variations and crop methods influence the nutrients content of the asparagus plant. This table presents results obtained from foliar analysis conducted on asparagus crop in Chile, Peru, Spain and United States.

Element

Chile (1)

USA (2)

Spain (3)

Peru (4)

Nitrogen %

2.50 - 3.50

2.40 - 3.80

2.20 - 2.95

2.50 - 4.00

Phosphorus %

0.20 - 0.30

0.30 - 0.35

0.10 - 20

0.25 - 0.60

Potassium %

1.70 - 2.50

1.50 - 2.40

2.95 - 3.1

1.75 - 4.50

Calcium %

0.50 - 1.60

0.40 - 0.50

0.67 - 0.98

1.50 - 3.50

Magnesium %

0.20 - 0.30

0.15 - 0.20

0.76 - 1.35

0.20 - 0.60

Iron ppm

120 - 680

ND

70 - 120

400 - 750

Manganese ppm

16 - 112

10 - 100

ND

50 - 200

Zinc ppm

16 - 28

20 - 60

20 - 90

100 - 200

Cooper ppm

10 - 22

-

10 - 95

10 - 30

Boron ppm

ND

50 - 100

8 - 110

20 - 40


Macro and Micronutrients concentrations in the asparagus crop foliage obtained from foliar analysis results conducted in different countries. - Sources: (1): Fundación Chile, 1987; (2): Campell, R.C., 1979; (3) San Agustín, 1989 y (4): Sánchez, J., 1992.

In general, the nutrients concentration in the foliage is larger in Peru, this is due to the tropical dry conditions (arid climate) existing, long days present, constant supply water and nutrients.
Nutritional Recommendation
An adequate supply of nutrients to plants should incorporate both macronutrients and micronutrients. SQM in the selection of specialty plant nutrition (SPN) that offers the following alternatives available according to the route of application (fertigation, soil or foliar):

The following table presents an example of a fertirrigation program of an asparagus planting with different ages and harvesting number per year in Peru.

Condition/Dose (kg/ha)

N

P2O5

K2O

CaO

MgO

B (salt)

Mic EDTA

a. Minor than 2 years
- One harvest per year.
- More than one harvest per year.

250

200

180

120

250

220

80

40

40

20

5

3

10

5

a. Older than 2 years
- One harvest per year.
- More than one harvest per year.

350

250

150

120

350

2280

60

40

30

20

5

3

15

10


As follows, the most common fertilizers sources utilized in fertirrigation in Peru are presented in the following table - Source: Burt,et.al. (1998), quoted and summarized by Sánchez, J.

Fertilizer

Purity (%)

Chemical Form

Solubility g/100 ml

Saline Index

Index (A) or (B)

Nitrogen

- Urea
- Ammonium Nitrate
-Ammonium Sulphate

46N
33N
21N

CO(NH2)2
NH4NO3
(NH4)2SO4

1033
1920
730

75
105
69

80 (A)
60 (A)
110 (A)

Phosphorus

-Phosphoric Acid
Monoammonium Phosphate

61 P2O5
12 N-61 P2O5

H3PO4
NH4H2PO4

Alta
626

-
30

-
55 (A)

Potasic

-Potassium Nitrate
-Potassium Sulphate
-Potassium Chloride

13 N-44 K2O
50 K2O
60 K2O

KNO3
K2SO4
KCl

316
110
340

74
46
116

23 (B)
N
N

Other

-Calcium Nitrate
Magnesium Sulphate
Boric Acid
Solubor

15 N-26 CaO
16 MgO
17.5 B
20.0 B

Ca(NO3)2
Mg SO4 7H2O
H3 BO3
Na2B8O13 - 4H2O

1220
77
6.4
22

61
44
-
-

21 (B)
N
-
-

Multimicross: Different concentrations, chelate agent, actual commercial brand.


Generally, two applications are made; in the first, 70% of N, 80% of P2O5 and 30% K2O are supplied; in the second, the remaining quantities are applied. In relation to micronutrients, the addition of 5 to 10 kg of Fe, Cu, Zn, Mn and Mo would be enough for supplying the demand for a normal crop harvest. The distribution of this mixture will be 60% in the first application and the remaining 40% in the second application.

It is possible to perform additional fertilizer applications of macro or micronutrients for correcting specific deficiencies which could arise during the crop development. These can be applied through fertirrigation (general application) or by foliar system (specific area application).
Important edaphic and moisture
Important edaphic and moisture factors for the asparagus crop

The following table presents some considerations in relation to edaphic and moisture factors which are important for the asparagus crop.

Programa nutritivo de SQM. Incluye cantidades más altas de K, Ca y B.

Factors

Optimum

Favorable

Unfavorable

EDAPHIC

TEXTURE

Sandy loam

Sand - Sandy loam

Cilt - Clay

PERMEABILITY

Moderate Rapid

MOderate

Slow - Rapid

DEPH

Greater than 1.5 m

0.75 - 1.50 m.

Lower than 0.75 m.

DRAINAGE

Good

Table of water < 1m. de prof.

Table of water < 1 m. de prof.

REACTION (pH)

6.5 - 7.8

6.0 - 6.5 - 7.8 - 8.3

< 6.5 and > 8.3

SALTS

< 4.1 dS/m

4.1 - 10 dS/m

> 10 dS/m

FERTILITY (N, P, K)

3 parameters in high level

2 parameters in high level

min 1 parameters in high level

BORON

< 10 ppm

10 - 15 ppm

> 15 ppm

HYDROUS E.C.

< 3 dS/m

3.0 - 6.0 dS/m

> 6.0 dS/m

SAR

< 3

3.0 - 8.0

> 8.0

BORON

< 3

2.0 - 5.0 ppm

> 5.0 ppm


Asparagus is a draught tolerant crop to, but if this is present during the harvesting stage, the crop could be affected on the spears’ quality by diminishing their diameter and turgidity. Besides, if the objective is maximum crop yield, the ideal is to have the soil at moisture field capacity(*), allowing a good water supply to the plant which also will allow an adequate nutrients’ availability to the plants. Besides, salts in the soil will be maintained under the crop’s tolerance level. This last aspect is especially important for arid zones.

The vegetative period of the asparagus is 12 months in the case of direct planting and 9 months in nursery planting. Each year, after finishing the harvest, the stalks and leaves growing is initiated, this stimulates photosynthesis until the plant reaches its maximum development. Photosynthetic products are translocated to the rhizomes and roots where are accumulated. Buds which will originate spears are formed exclusively with the accumulated reserves by this process.

(*): Agronomic term. This is the water content which the soil is capable to hold after being submitted to saturation or being abundantly irrigated, then leaving it at free drainage.
Development stages
Development stages

In the development of an asparagus planting several stages can be defined:

a) Development of “garras” between the planting and formation of plants (one or two years).

b) Accumulation of reserves where the vegetative expansion is promoted to have the greatest possible quantity of nutritive substances, which will be translocated to the thick roots (principals) where are accumulated (two to three years).

c) Productive phase starting from the third year. In this phase three stages can be differentiated:

• Spears’ recollection period.

• Vegetative development period.

• Resting period.

The dry weight evolution of crowns, in locations with annual harvest, is shown in the Figure 1.
Sampling period
Figure 1. Dry Weight Evolution of Crowns during 10 months in locations with only one annual harvest. - Source: Woolley, et.al. 1999, modified by Sánchez, J.

There is a rather high loss of carbohydrates´ dry weight of the total stored reserves from the senescence stage onwards.

In location with two or more annual harvests, with active growing plants during all year (e.g. Peru), there is an additive accumulation of carbohydrates when each generation of sprouts mature. This is managed by forcing plants through draught stress application, which made possible to harvest in any period of the year (Figure 2).

Growing / Accumulation
Figure 2. Growing curve and reserves´ accumulation from an asparagus planting that produces more than an annual production, in relation to time. - Source: Sánchez, 1998.
Results from some trails conducted in asparagus crops which demonstrate the effect of certain nutrients in the crops development are presented as follows

Nutrients´ balance and crop’s yield... Read more.
Phenological Stage


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All the information is given to the best of SQM's knowledge and is believed to be accurate. Your conditions of use and application of the suggested products and recommendations are beyond our control. There is no warranty regarding the accuracy of any given data or statements. SQM specifically disclaims any responsibility or liability relating to the use of the suggested products and recommendations and shall under no circumstances whatsoever, be liable for any special, incidental or consequential damages which may arise from such use.