POTATO VARIETAL DIFFERENCES IN PETIOLE NITRATE CONCENTRATION

MISCELLANEOUS REPORTS 77 ISSN 0253-6749 POTATO VARIETAL DIFFERENCES IN PETIOLE NITRATE CONCENTRATION I. Papastylianou and S. Gregoriou AGRICULTURAL RESEARCH INSTITUTE MINISTRY OF AGRICULTURE, NATURAL RESOURCES AND THE ENVIRONMENT NICOSIA CYPRUS JULY 2000

Editor - in Chief Dr A.P. Mavrogenis, Agricultural Research Institute, Nicosia, Cyprus. All responsibility for the information in this publication remains with the author(s). The use of trade names does not imply endorsement of or discrimination against any product by the Agricultural Research Institute. 2

POTATO VARIETAL DIFFERENCES IN PETIOLE NITRATE CONCENTRATION I. Papastylianou and S. Gregoriou SUMMARY Introduced potato varieties selected for specific use (baked, boiled, chips) and high yield under Cyprus conditions were tested for petiole NO 3 concentration (PNC). The study was carried out for two growing seasons aiming to determine varietal differences which could affect the interpretation of nitrogen nutrition diagnostic standards. In the first season petioles from 24 cultivars were sampled from plants 108 days after planting (DAP) and NO 3 -N ranged from 7000 to 25000 mg/kg dry matter. In the second season petioles from 22 cultivars were sampled from plants 60 DAP and NO 3 - N ranged from 22000 to 29000 mg/kg dry matter. Using the PNC as criterion, the rank of the varieties grown in both seasons was the same for seven varieties, while three varieties had different ranking. There was no correlation between PNC and tuber yield of the different varieties. The study concluded that there are significant varietal differences in the PNC of potato, which should be taken into consideration for the interpretation and setting of prognostic standards of nitrate concentrations. ΠΕΡΙΛΗΨΗ Σε ποικιλίες πατατών διάφορης χρήσης (ψητές, βραστές κλπ.), που επελέγησαν για τις ψηλές αποδόσεις τους κάτω από τις κυπριακές συνθήκες, µελετήθηκε η συγκέντρωση νιτρικών στους µίσχους. Η µελέτη έγινε σε δύο συνεχόµενες βλαστικές περιόδους µε σκοπό να διαπιστωθεί κατά πόσο υπάρχουν διαφορές µεταξύ των ποικιλιών αναφορικά µε την συγκέντρωση νιτρικών και αν τέτοιες διαφορές επηρεάζουν τη φυλλοδιαγνωστική µέθοδο. Στην πρώτη βλαστική περίοδο η δειγµατοληψία µίσχων σε 24 ποικιλίες έγινε στις 108 ηµέρες µετά τη φύτευση και η συγκέντρωση νιτρικών κυµάνθηκε από 7000 µέχρι 25000 mg/kg ξηράς ουσίας. Στη δεύτερη περίοδο ή δειγµατοληψία από 22 ποικιλίες έγινε στις 60 µέρες µετά τη φύτευση και η συγκέντρωση νιτρικών κυµάνθηκε από 22000 µέχρι 29000 mg/kg ξηράς ουσίας. ιαβαθµίζοντας τις ποικιλίες ανάλογα µε τη συγκέντρωση νιτρικών στους µίσχους και αντιπαραβάλλοντας τις δύο περιόδους δειγµατοληψίας, από τις 10 ποικιλίες που καλλιεργήθηκαν και στις δύο χρονιές, βρέθηκε ότι επτά είχαν την ίδια διαβάθµιση ενώ τρεις είχαν διαφορετική. εν υπήρχε συσχέτιση ανάµεσα στη συγκέντρωση νιτρικών και την παραγωγή κονδύλων στις διάφορες ποικιλίες. Φαίνεται ότι η συγκέντρωση νιτρικών στους µίσχους ποικίλει από τη µια ποικιλία στην άλλη. Εποµένως, για σκοπούς φυλλοδιαγνωστικής η ποικιλία πρέπει να λαµβάνεται υπόψη. Πρέπει, επίσης, να εξετασθεί κατά πόσον οι διαφορές αυτές επηρεάζουν τα κρίσιµα επίπεδα θρέψης των φυτών. INDRODUCTION Petiole nitrate concentration (PNC) of potatoes has been suggested as an indicator for assessing the nitrogen (N) nutrition status of the crop (Doll et al., 1971; Gardner and Jones, 1975; Roberts and Cheng, 1988; Williams and Maier, 1990; Westcott et al., 1991). However, the validity and accuracy of the method are controversial. Some scientists support the use of the method (Vitosh and Silva, 1996), while others consider that with the present status of knowledge it should not be used as a tool for adjusting top-dressing of N fertilization (Mac Kerron et al., 1995). These contradictions result in NO 3 variability, caused by the same factors which affect PNC. Scientists who adopt the method suggest ways to minimise PNC variability, such as time of sampling, age of the plants, specific plant tissue, etc (Vitosh and Silva, 1996). The opponents of the method seek to explain 3

the factors involved in PNC variability and give more accurate and reliable suggestions for further N application (Mac Kerron et al., 1995). One important factor that affects PNC is the cultivar. For some crops the genotypic effect on tissue nitrate concentration exists but it does not affect the diagnostic value of the tissue nitrate concentration (Papastylianou, 1987). For potatoes, there is a contradiction in using the PNC as a diagnostic tool of the N nutrition status since in other studies it is shown that the genotypic factor could be critical (Lewis and Love, 1994), while in other studies the genotypic differences were small and unimportant for diagnostic purposes (Williams and Maier, 1990; Vitosh and Silva; 1996). The objective of the present study was to examine PNC variability in a set of potato cultivars with tubers suitable for different final uses (baked, boiled, chips), which were selected for high yield under Cyprus conditions. MATERIALS AND METHODS The study was conducted for two growing seasons (1995 and 1996) with varieties selected for high yield and desirable tuber quality characteristics under Cyprus growing conditions. In 1995, 24 varieties and in 1996, 22 varieties were planted in randomized complete block designs with provision for two liftings with four replications at each lifting. Ten varieties were present in both years of the study. Planting in December was done in rows 65 cm apart with a 20-cm spacing within the row. Each plot consisted of 4 rows, each having 24 plants. Plot size was 2.6 m x 4.8 m. Fertilizer (14-22-9) at the rate of 1500 kg/ha was applied at planting. Irrigation by minisprinklers was provided when required, so that optimum water conditions were maintained. The soil of the site was Terra rosa (Luvisol 50% clay, 15% silt, 25% fine sand, 10% coarse sand, 1% organic matter and 8.4 ph). Yield of tubers was recorded by harvesting the middle two rows. Tuber specific gravity was determined with a potato hydrometer (Smith, 1968) on mixed sized samples of 3629 g each. The specific gravity was converted into dry matter by using conversion tables (Vakis, 1978). Samples were collected 4 at 108 days after planting (DAP) in 1995 and at 60 DAP in 1996. Samples were collected in the morning 2 to 3 h after sunrise. Twenty of the youngest fully expanded leaves (usualy the 4th from the top) were collected at random from each plot. Nitrate was extracted with 0.2 N copper (II) sulphate solution (Hadjidemetriou, 1982) and determined potentiometrically with a specific NO 3 -ion electrode. Petioles were analysed for nitrate concentration after being dried (60 o C) to constant weight and ground (1 mm sieve). RESULTS There were up to 40%, differences in tuber yield between cultivars in both years of the study. Tuber yield ranged from 40 to 66 t/ha in both years, with cultivar yield being consistent in the two seasons except for the variety Burren which gave higher tuber yield in the second season (Tables 1 and 2). Yield differences at the two liftings were very small in 1995 (Table 1) with variety Burren increasing its yield at the second lifting by 8 t/ha. In 1996 (Table 2), several varieties increased their yield by circa 8 t/ha at the second lifting. Dry matter of tubers ranged from 16.66 to 21.87% in 1995 and from 16.33 to 18.60% in 1996. The varieties grown in 1995 with tuber dry matter above 19% were not included in the 1996 season. Petiole Nitrate concentration in the different varieties grown in 1995 for plants at 108 DAP, ranged from 7.000 to 25.000 mg NO 3 - N/kg dry matter, and in the 1996 study for plants at 60 DAP from 22.000 to 29.000 mg NO 3 -N/kg dry matter. Comparing the rank of the ten varieties present in both seasons with regard to their PNC, seven of them (Marabel, Spunda, Nicola, Cynthia, Cara, Exquisa, and Burren) maintained the same relative position, two (Akira and Armada) ranked at a lower position and one (Arinda) at a higher position in 1996. There was no relationship between PNC and tuber yield. DISCUSSION Genetic variability of the different varieties grown was clearly demonstrated by the

Table 1. Yield (t/ha) and dry matter content of tubers and petiole nitrate concentration of 24 potato varieties in the 1995 growing season Days to lifting 127 136 Petiole nitrate Origin Yield Dry matter Yield Dry matter concentration Variety of seed (t/ha) (%) (t/ha) (%) 108 DAP (mg/kg) Cynthia France 64.3 65.0 16.88 16.99 15323 Spunta Holland 63.8 64.2 16.66 16.66 14991 Arinda Holland 62.1 62.1 17.20 18.28 20284 Armada Holland 61.4 61.3 16.99 16.99 7093 Cicero Holland 61.3 63.7 17.64 17.42 14983 Akira Holland 60.5 61.3 17.85 17.74 14206 YP 83-040 Holland 59.9 61.1 18.28 17.96 21662 Marabel Germany 57.9 57.7 17.64 17.20 12575 Nicola Holland 57.2 56.7 17.96 17.85 17057 Provento Holland 56.8 54.1 17.64 17.74 16807 Cara Ireland 56.1 57.0 17.53 17.85 20926 Donald Holland 55.6 56.1 20.30 20.62 13042 Exquisa Holland 55.4 52.1 19.14 19.03 19019 Helena Germany 55.2 54.3 17.53 17.31 9455 Glamis Scotland 54.6 58.4 18.49 18.49 16984 Anna Ireland 53.0 55.0 17.74 17.96 25429 Brodick Scotland 51.9 50.7 20.83 20.93 22328 Regina Germany 51.2 50.8 16.88 16.55 15811 Othello Scotland 50.1 54.1 17.10 16.88 20062 Lady Rosetta Holland 48.7 49.8 21.87 21.77 15108 Burren Ireland 48.5 56.8 17.10 16.77 15528 Likaria Germany 45.9 48.2 17.96 18.28 7999 Carlingford UK 44.5 45.3 17.64 17.74 20587 Olivia Holland 40.5 40.4 18.71 19.03 9807 SEM 1.77 1.38 - - 1656 high differences in tuber yield. Nitrogen availability was not a limiting factor for productivity, since a high rate of N was used. The non limiting N supply, was also obvious by the high tuber yield obtained by some varieties, while, under the same conditions, tuber yield of other varieties was much lower. This genetic variability in yield is of particular importance to this study since it must be examined how varieties with similar or different tuber yield potential behave, as far as PNC is concerned, and how the range of PNC observed might affect the critical level which defines the status of nitrogen nutrition. Under similar nitrogen availability the varieties tested showed high variability in PNC, in both seasons. The differences in the PNC range between the two seasons was due to the different stage of growth at which sampling was done. It is known that NO 3 in plants drops with aging. In the present study in the 1996 season, with sampling at 60 DAP, all varieties had PNC above 20.000 mg/kg dry matter. The upper levels of PNC, at this stage of growth, are indicative of excessive N nutrition as it was determined in many studies (Roberts and Cheng, 1988; Williams and Maier, 1990). In the 1995 season with sampling at 108 DAP the PNC ranged from 7000 to 25000 mg/kg dry matter and this range is by far wider than the PNC range of 7000 to 16000 m/kg, which indicates sufficiency of N at this stage of growth (Gardner and Jones, 1975; Porter and Sisson, 1991). Even though the lower conncetration is near the level which denotes defficiency of N, the higher concentration indicates excessive N supply. Such a case is not economical and it is a potential source for pollution of the underground water. Differences in PNC observed between cultivars could be due either to a different behaviour of the cultivars in accumulating nitrate under sufficient N supply or to different N requirements. In the first case, the critical nitrate range should be established for each cultivar, while for the second case the critical range could be the same. Based on previous studies (Williams and Maier, 1990; Westcott et al., 1991) the range of PNC which was obtained in the 1995 study is too wide, ranging from the zone of deficient N nutrition to excessive supply of N. Since N supply was uniform for all culti- 5

Table 2. Yield (t/ha) and dry matter percent of tubers and petiole nitrate concentration of 22 potato varieties in the 1996 growing season Days to lifting 127 136 Petiole nitrate Origin Yield Dry matter Yield Dry matter concentration Variety of seed (t/ha) (%) (t/ha) (%) 60 DAP (mg/kg) Burren Ireland 66.1 67.4 16.33 16.77 23448 Fabula Holland 59.7 61.8 16.33 16.66 22833 Armada Holland 59.0 61.6 16.33 16.66 23838 Mondial Holland 58.9 66.7 16.33 16.77 24228 Spunta Holland 58.4 61.9 16.33 16.77 22011 Arinda Holland 58.1 62.1 16.88 17.64 23680 Cynthia France 57.5 65.7 16.55 16.99 25473 Akira Holland 56.9 61.1 17.20 18.07 26783 Ovatio Holland 56.3 60.1 18.28 18.60 25608 Aurora UK 54.4 60.3 16.33 16.88 * Cara Ireland 53.1 61.6 16.77 17.53 28665 Inova Holland 52.7 59.7 18.17 18.28 29346 Nicola Holland 52.5 58.0 18.28 18.39 26108 Glamis Scotland 49.1 57.2 16.99 17.42 * Doppenberg Holland 47.0 50.6 16.99 17.20 24810 Carlingford UK 46.9 47.3 16.88 16.99 * Marabel Germany 46.0 51.3 17.53 17.85 23012 Cicero Holland 44.9 52.0 16.44 16.99 * Exquisa Holland 42.0 48.9 17.20 18.17 26638 Colleen Ireland 41.6 42.0 17.96 18.28 28862 Colette Germany 40.3 44.0 16.55 16.77 * Saxon UK 40.3 44.8 16.33 16.77 23495 SEM 2.28 2.80 - - 897 * = Plants did not reach sampling stage. vars and a uniform rate was applied, the sources of variation must be due to the cultivar. Even though a wide critical nutrient range is expected whenever the average PNC of many cultivars is used to establish the critical range (Williams and Maier, 1990), the present data show that critical nutrient range should be established for each cultivar or for groups of cultivars having similar trends of PNC under similar conditions. Due to the cultivar differences in PNC shown in this study it is now considered that it might not had been proper to use the critical nitrate range established (with different cultivars) in other studies to compare the N nutritional status of cultivars grown in this study. However, at present there are no cultivar specific critical ranges and the existing ones are used. In the future it must be examined whether cultivar differences denote also different critical ranges. ACKNOWLEDGEMENTS We thank Ph. Theophylactou, N. Onouphriou, Georgia Constantinou and M. Elia for technical assistance. REFERENCES Doll, E.C., D.R. Christenson, and A.R. Wolcott. 1971. Potato yields as related to nitrate levels in petioles and soils. American Potato Journal 48:105-112. Gardner, B.R., and J.P. Jones. 1975. Petiole analysis and the nitrogen fertilization of Russet Burbank potatoes. American Potato Journal 52:195-200. Hadjidemetriou, D.G. 1982. Comparative study of the determination of nitrates in calcarous soils by the ion-selective electrode, chromotropic acid and phenoldisulphonic acid methods. Analyst 107:25-29. Lewis, R.L., and S.L. Love. 1994. Potato genotypes differ in petiole nitrate - nitrogen concentration over time. Hortscience 29:175-179. Mac Kerron, D.K.L., M.W. Young, and H.V. Daries. 1995. A critical assessment of the value of petiole sap analysis in optimizing the nitrogen nutrition of the potato crop. Plant and Soil 172:247-260. 6

Papastylianou, I. 1987. Effect of wheat and barley varietal differences in nitrate concentration on plant analysis interpretation. Fertlizer Research 12:157-163. Porter, G. A., and J.A. Sisson. 1991. Petiole nitrate content of Maine-grown Russet Burbank and Shepody potatoes in response to varying nitrogen rate. American Potato Journal 68:493-505. Roberts, S., and H.H. Cheng. 1988. Estimation of critical nutrient range of petiole nitrate for sprinkler-irrigated potatoes. American Potato Journal 65:119-124. Smith, O. 1968. Potatoes: Production, storing. Processing. Avi Publications Co., Westport, Conn., USA. Vakis, N.J. 1978. Specific gravity, dry matter content and starch content of 50 potato cultivars grown under Cyprus conditions. Potato Research 24:171-181. Vitosh, M.L., and G.H. Silva. 1996. Factors affecting potato petiole sap nitrate tests. Communication in Soil Science Plant Analysis 27:5-8. Westcott, W.P., V.R Stewart, and R.E. Lund. 1991. Critical petiole nitrate levels in potato. Agronomy Journal 83:844-850. Williams, C.M.J., and N.A. Maier. 1990. Determination of the nitrogen status of irrigated potato crops. 1. Critical nutrient ranges for nitrate - nitrogen in petioles. Journal of Plant Nutrition 13:971-984. 7

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