Plant Nutritional Status

The nutritional status of the pineapple plant has a large influence on plant growth and, consequently, on yield and fruit quality. For pineapple, plant indicators that reflect plant nutritional status have been identified and, in conjunction with soil analysis, can be used to manage fertilization of the pineapple crop. The alternative to the use of plant indicators and soil analysis is the use of calibrated fertilizer trials in each area where the crop is grown. This practice is more common where pineapple is grown on small farms and where access to technology is limited (Souza, 1999). To sustain growth and obtain good yields, it is important to provide adequate supplies of all nutrients in proper balance. Balanced nutrition based on the principles of best management practices ensures that excess nutrients of one type do not induce deficiencies of others or, in the case of N and P, lead to environmental degradation.

The plant indicators of nutritional status include visual deficiency symptoms and the critical nutrient levels in appropriate reference-plant tissues. This tissue in pineapple is the 'D' leaf, which in most cases is the tallest leaf on the plant. The D-leaf is used because it is the only leaf that can be consistently identified and, as the youngest almost physiologically mature leaf, it reflects

© CAB International 2003. The Pineapple: Botany, Production and Uses (eds D.P. Bartholomew, R.E. Paull and K.G. Rohrbach)

current plant nutrient status with acceptable accuracy. Sideris and Krauss (1936) categorized (Fig. 7.1) leaves as: 'A', present on the propagule at planting and do not elongate after planting; 'B', present on the propagule at planting and elongate after planting; 'C', leaves that develop after planting and are younger than 'B' leaves but older than 'D' leaves; 'D', a whorl of three leaves, including the tallest on the plant; 'E', a whorl of three leaves younger than the 'D' leaves; and 'F', a whorl of three leaves younger than the 'E' leaves. As the plant grows, leaf classification continuously changes, so that 'F' leaves become 'E' leaves, 'E' leaves become 'D' leaves, and so on. A knowledge of the visual symptoms associated with the deficiency of a specific nutrient can help with early detection of nutritional problems in the field. Nutrient levels in leaf tissue provide information about the quantity of nutrients actually absorbed by the plant. However, nutrient deficiencies can have multiple origins, which need precise identification, and several nutrient-deficiency symptoms are not diagnostic.

A diagnosis reference system

The nutritional status of a pineapple plant depends on many factors, including the nutritional status of the propagule, soil

Nutrient Deficiency Pineapple

Fig. 7.1. Groupings of pineapple leaves after Sideris and Krauss (1 936). The numbered sections of each leaf refer to the following tissues: 1, basal non-chlorophyllous; 2, transitional subchlorophyllous; 3, lower chlorophyllous; 4, intermediate chlorophyllous; 5, terminal chlorophyllous. (Drawing modified from Sideris and Krauss, 1936.)

Fig. 7.1. Groupings of pineapple leaves after Sideris and Krauss (1 936). The numbered sections of each leaf refer to the following tissues: 1, basal non-chlorophyllous; 2, transitional subchlorophyllous; 3, lower chlorophyllous; 4, intermediate chlorophyllous; 5, terminal chlorophyllous. (Drawing modified from Sideris and Krauss, 1936.)

nutrient status, the physical and mineral characteristics of the soil, soil water status, root-system development and functionality and numerous physical and biological factors that can influence the efficiency of the root system in extracting soil nutrients. Pineapple readily absorbs all nutrient elements through the leaves (Py et al, 1987), but N, P, K, Mg, Fe, Cu, Zn and B are the ones most commonly applied in solution foliarly (Swete Kelly, 1993). Calcium is normally not applied foliarly because most salts of Ca are relatively insoluble or would render other nutrients in a solution insoluble. Also, calcium is relatively immobile in plants, so foliarly applied calcium may not move to tissues where it is deficient. Where foliar absorption replaces soil uptake, nutrient utilization is still dependent on the physical and biological factors that affect the extraction and utilization of plant nutrients in the soil.

The concept of a pineapple crop log was established in Hawaii in the 1940s (Sanford, 1962), and comprehensive knowledge of nutrient management was developed in many countries in the 1960s and 1970s. The crop log includes soil and plant indices as well as those biological and physical factors of the pineapple crop environment likely to influence growth (Sanford, 1962). The consistent use of the crop log during plant development allows for the detection of factors likely to retard growth and provide growers with the information required to adjust fertilizer applications to fit the requirements of the crop. However, no integrated diagnosis database capable of synthesizing this information is available.

The crop log, as embodied in the work of Nightingale (1942a,b) and more completely characterized by Sanford (1962), includes indices related to the actual determination of nutrient deficiencies and those that measure other factors that may have a direct or indirect effect on the nutrition of pineapple plants. The first set of indices include soil analysis, plant visual deficiency symptoms and plant analyses. The second set of indices include growth rates, plant pests, moisture status and weather. Thus the crop log not only identifies those nutrients that are limiting, but also provides information on why they are low. For example, the presence of a nematode or fungus infestation of roots or inadequate soil moisture could explain why a nutrient element is deficient in a plant even when levels of a given element in the soil are satisfactory.

To ensure that growth is optimum, it is essential to identify all the factors that directly or indirectly affect the uptake, translocation and utilization of nutrients. Soil indices always include the levels of P, K, Ca and Mg and pH, but may also include soluble Al and Mn and salinity. Where nitrate in fruits is a concern, soil N may also be analysed (Swete Kelly, 1993). When properly developed and calibrated, soil analyses provide an estimate of the quantity of fertilizer to be applied at planting and during early growth, indicate the levels of nutrient element reserves in the soil and indicate possible toxicities that could restrict plant growth.

Opinions about soil nitrogen analyses vary. In Hawaii, soil N analysis was not considered to be useful because the results were too variable (Sanford, 1962). Also, pineapple plants had a low requirement for N during early growth, so the relationship between soil N and early growth was poor. However, in Australia (Sinclair, 1993), both initial soil N as nitrate and nitrate present after a 2-week incubation period are provided for growers to guide them in applying nitrogen fertilizer prior to planting. Since growers often tend to over- rather than underfertilize, soil N analyses help to reduce the problem of high nitrate in fruit at harvest (Sinclair, 1993).

Plant indices for N, P, K, Ca, Mg and Fe have been developed using the 'D' leaf, but may include other elements as well (Table 7.1). If measured, N and Fe are analysed on the middle one-third of the green tissue of this same leaf. However, plant N status is assessed visually in Hawaii and Australia, using plant colour, as described by Nightingale (1942a), because N levels in

Table 7.1. Norms proposed for 'D'-leaf mineral element content.

Element

Basal white*1"

Whole leaf* inflorescence emergence

Vegetative

Induction

Deficient

N

15-17 g kg-1

P

110

200

<100

~1.0 g kg-1

K

3000-3500

3000

2000

22-30 g kg-1

Ca

150

150

90

8-12 g kg-1

Mg

250-270

250-270

90

~3.0 g kg-1

Zn

10 mg kg-1

Cu

8 mg kg-1

Mn

50-200 mg kg-1

Fe

100-200 mg kg-1

B

30 mg kg-1

*Units are in mg kg-1, fresh-mass basis. tData from Glennie, 1977; Swete Kelly, 1993. ♦Data from Dalldorf and Langenegger, 1978.

pineapple leaves can change quickly and so were not found to be a reliable measure of long-term plant nitrogen status.

Tissue element norms for P, K, Ca and Mg for 'Smooth Cayenne' were developed for the middle one-third of the white basal tissue of the 'D' leaf in Hawaii and Australia, because the results can be expressed on a fresh mass basis, thus simplifying calculation of the final results (Table 7.1). The fresh mass of basal tissue can be used because changes in the dry-matter content of this tissue with changing plant water status are small, typically only 1.0-1.5% (Sanford, 1962). The analyses are usually made on ten 'D' leaves sampled from a crop logging station comprised of about 100 plants in a representative part of the field.

Tissue element norms have also been developed for the entire 'D' leaf (Py et al., 1987; Table 1) because it was believed that nutrient element levels in leaf basal tissue were more indicative of movement within the plant and were too sensitive to daily rhythms and to variations in the soil solution. Because whole-leaf water content can vary significantly, results must be calculated on a dry-mass basis. There is little evidence to show that one method is superior to the other and it is clear from a long history of use that either method allows for the early detection and correction of nutrient-element insufficiencies.

Few data are available on possible differences among cultivars. Optimum levels of N, P and K in 'Red Spanish' pineapple appear to be slightly higher than those for 'Smooth Cayenne' (Samuels and Gandia-Diaz, 1960). While published data were not found for pineapple hybrids, tissue levels of nitrate-N, P, K, Mg and B were higher for the hybrid '53-116' developed by the Pineapple Research Institute of Hawaii than for the 'Smooth Cayenne' clone Champaka F153 at the same level of applied nutrients (Anon., 1965). It should not be assumed that the nutrient requirements of hybrids will be the same as those for 'Smooth Cayenne'.

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Responses

  • Yohannes
    Which leaf is used for assessment of nutrients requirements of pineapple crop?
    2 years ago

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