Effects of nitrogen and phosphorus nutrition on the growth of asparagus seedlings

Scientia Horticulturae, 21 (1983) 105--112

105

Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands

EFFECTS OF NITROGEN AND PHOSPHORUS NUTRITION ON THE GROWTH OF ASPARAGUS SEEDLINGS

K.J. FISHER ~ and B.L. BENSON

Department of Vegetable Crops, University of California, Davis, CA (U.S.A.) Present address: Department of Horticulture and Plant Health, Massey University, Palmerston North, New Zealand (Accepted for publication 2 March 1983)

ABSTRACT Fisher, K.J. and Benson, B.L., 1983. Effects of nitrogen and phosphorus nutrition on the growth of asparagus seedlings. Scientia Hortic., 21 : 105--112. N was applied at 50, 100 or 150 mg 1-~ in factorial combination with P at 7.5, 15 or 22.5 mg 1-I to asparagus seedlings. There were 6 successional harvests. N and P increased shoot dry weight by increasing mean dry weight and number of shoots. Increasing P had no effect on shoot growth at 50 mg 1-1 N. N increased root dry weight (crown and roots) by increasing root number, whereas P decreased root dry weight due to a decrease in mean root dry weight. N increased total plant dry weight, but P had no effect. N and P increased the partitioning of dry weight to the shoots, while partitioning to the roots increased with time. Plant analysis revealed that 2.6--2.7% N and 0.29-0.36% P, on a dry-weight basis, were present in the shoots at the later harvests with the higher concentrations of N and P. 100--150 mg 1-~ N in combination with 15 mg l -I P produced a seedling suitable for transplanting into commercial fields at 6 weeks from emergence. Keywords: Asparagus officinalis L.; dry weight; partitioning; tissue analysis; transplants.

INTRODUCTION

Asparagus seedlings have been used in California (Benson et al., 1978) and New Jersey (Ombrello and Garrison, 1978) to establish commercial fields, and in the United Kingdom (Williams, 1979) on an experimental basis. The planting of seedlings conserves seed, reduces the likelihood of early disease problems, and allows for the establishment of a uniform line of plants at the desired plant population. Comparison between yields of crown and seedlings in the second year after planting has produced conflicting results; Benson ( 1 9 7 9 ) f o u n d crowns produced the higher yield, whereas Williams (1979) found that seedlings were most desirable. The seedling technique of establishment appears to have potential, but there have been no detailed studies on methods of producing plants. The 0304-4238/83/$03.00

© 1983 Elsevier Science Publishers B.V.

106 present study examined the effects of N and P levels on the growth and development of asparagus seedlings. MATERIALS AND METHODS Pre-germinated seed of the California hybrid 'UC 157' was sown on 3 June 1981, in a 50:50 peat:vermiculite medium to which 3 kg of ground limestone per m 3 had been added. All nutrients were supplied in the treatment solutions. The seedlings were raised in a commercially available plastic plant tray. The cells o f these trays were 7 cm deep, contained 45 cm 3 of media and were arranged at a density of 542 plants per m 2 . The trays were placed on wire mesh so that the roots would be air-pruned, and the treatments were applied from 11 June, when 50% of the seedlings had emerged. From 3 to 19 June, the plants were grown in a shade house, and from the latter date until the end of the experiment, they were grown in a greenhouse having a minimum temperature of 18°C with fan ventilation operating at 29°C. There were 3 levels of N (50, 100 or 150 mg 1-1) in factorial combination with 3 levels of P (7.5, 15 or 22.5 mg 1-1) and 6 harvests. The K source was KNO3, which supplied 40 mg 1-1 of N to all treatments. The remaining N was supplied as NH4NO3 and NH4H2PO4, the latter was also the source of P. The levels of the other major elements were 110 mg 1-1 K, 24 mg 1-1 Mg and 40 mg 1-' Ca. Trace elements were also supplied. The plants were watered as required to achieve container capacity, always using the complete treatment solutions. Dally watering was carried out for much of the experiment. Plants were harvested on a weekly schedule, the first harvest was on 18 June and the last on 23 July. A split plot randomized block design was used, providing 6 blocks, 9 nutritions (main plots), 6 harvests (sub-plots) and 5 plants per plot, and 1620 plants. There was a single row of guard plants, which were relocated after every harvest, surrounding each main plot. At each harvest, data on length of the longest shoot per plant, shoot and storage r o o t number, and shoot and root dry weights were recorded. The root dry weight included the crown. The data on a per-plot basis were converted to a per-plant basis, and the m e t h o d of orthogonal polynomials was used to determine the best fit of regression lines. Dried plant material was ground through a 1-mm sieve, and total nutrients were then determined after digestion of a 0.1-g sample with sulphuric acid (selenium catalyst) using an autoanalyser and an atomic absorption s p e c t r o p h o t o m e t e r (O'Neill and Webb, 1970). RESULTS AND DISCUSSION g r o w t h . - - There were significant interactions (P < 0.05} between N and P for several aspects of shoot growth (Fig. 1 a--d). The pattern was n o t always clear-cut, b u t the following generalizations could be made.

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Fig. I. Interactions between N and P for shoot growth (means of 6 harvests). (a) Shoot number. Y ffi2.57 + 0.0029x (7.5 m g I-' P) Y = 2.44 + 0.0063x (15 m g l -' P) Y = 2 . 8 1 + 0.0022x (22.5 m g l-~ P) (b) Mean shoot dry weight.

Y = 0.018 + 0.00053x -- 0.0000023x 2 (7.5 m g 1-~ P) Y = 0.029 + 0.00021x -- 0.0000004x 2 (15 m g l-~ P) Y = 0.014 + 0.00058x -- 0.0000021x 2 (22.5 m g l-~ P)

(c) Shoot dry weight. Y = 0.079 + 0.00115x -- 0.0000039x ~ (7.5 m g I-' P) Y = 0.039 + 0.00194x -- 0.0000055x 2 (15 m g l-~ P) Y = 0.003 + 0.00316x -- 0.00001Pat 2 (22.5 m g I-~ P) (d) Dry weight partitioned to shoot.

Y = 54.9 + 0.134x -- 0.00056x 2 (7.5 m g I-~ P) Y = 48.8 + 0.282x -- 0.00104x 2 (15 m g l-~ P) Y = 5 0 . 1 + 0 . 2 9 6 x -- 0.00112x 2 (22.5 m g l-' P)

N increased shoot n u m b e r , m e a n shoot dry weight, shoot dry weight a n d % dry weight partitioned to the shoot (P < 0.001, P < 0.001, P < 0.001 a n d P < 0.01, respectively). T h e r e w a s a nfl or limited response to P at 5 0 m g l-I N for m e a n shoot dry weight, shoot dry weight a n d dry weight partitioned to the shoot. It appeared, therefore, that the l o w level of N w a s an important limiting factor to plant growth. A t the higher concentrations of N, there w a s usually a positive response to increasing P. S h o o t dry weight is d e t e r m i n e d b y the c o m b i n e d effects of shoot n u m ber a n d m e a n shoot dry weight, a n d thus shoot dry weight m o s t clearly

108

demonstrates the effects described above. These increases in shoot growth were achieved, at least in part, by increased partitioning of dry weight to the shoot. There was no interaction between N and P with respect to shoot length. Here, the length of the longest shoot per plant increased with N (Fig. 2a) (P < 0.01), whereas P had no effect. 20"

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Fig. 2. R e l a t i o n s h i p b e t w e e n N and P concentrations and seedling g r o w t h ( m e a n s o f 6 harvests). (a) N c o n c e n t r a t i o n and s h o o t length. Y = 1 4 . 0 6 + 0 . 0 7 5 x - - 0 . 0 0 0 2 8 x 2 (b) N c o n c e n t r a t i o n and storage r o o t number. Y = 4 . 2 2 + 0 . 0 0 6 x (c) P c o n c e n t r a t i o n and m e a n root dry weight. Y = 0 . 0 1 9 8 - - 0 . 0 0 0 1 6 x (d) N and P c o n c e n t r a t i o n s and r o o t dry weight. Y ffi 0 . 0 9 7 3 + 0 . 0 0 0 1 4 x ( N ) Yffi 0 . 1 3 0 - - 0 . 0 0 1 2 x (P) (e) N c o n c e n t r a t i o n and total plant dry weight. Y = 0 . 1 4 3 + 0 . 0 0 2 1 x - - 0 . 0 0 0 0 0 6 7 x ~

109

R o o t growth. -- N increased storage root number (Fig. 2b) (P < 0.001), but

had no effect on mean root dry weight. P decreased mean root dry weight (Fig. 2c) (P < 0.001), but had no effect on root number. As a result of these responses, N increased (P < 0.01) and P decreased (P < 0.001) root dry weight (Fig. 2d). As the plants were divided at harvest into shoots and roots (crown plus roots), the pattern of partitioning of dry weight to the roots was the reverse of that for the shoot (Fig. ld). Thus, increases in N and P decreased partitioning to the root. Increases in partitioning to the roots at low N levels have been reported in studies with many crops (Brouwer, 1962). T o t a l p l a n t dry weight. -- N increased both shoot and root growth, and this resulted in an increase in total plant dry weight (Fig. 2e) (P < 0.05). The increased partitioning of dry weight to the shoot shows that the increase in shoot growth was proportionally greater than the increase in root growth. P had no effect on total plant dry weight. Thus, the increase in shoot dry weight must have been compensated for by the decrease in root dry weight. These changes in shoot and root dry weights increased the partitioning of dry weight to the shoot. T i m e o f harvest. - - The length of the longest shoot per plant increased with time (Fig. 3a) (P < 0.01). Shoot numbers increased in a linear manner (Fig. 3b) (P < 0.001), while the weekly increase in storage root numbers increased (Fig. 3c) (P < 0.001) over the same period. This contrast between shoot and root growth also occurred with mean dry weight (Fig. 3d). Here, the weekly increase decreased with the shoot (P < 0.001), but increased with the root (P < 0.001). Loge dry weights for total plant, shoot and root (P ,~ 0.001) are presented in Fig. 3e. The slope of loge dry weight against time at any point on these curves is the relative growth-rate at that point (Hunt, 1978). From Week 3 onwards, the relative growth-rate of the total plant fell, as did that of the component organs. The relative growth-rate of the shoot fell faster than that of the root. This was to be expected, due to the changes in number and mean dry weights of shoots and roots outlined above. The data for partitioning of dry weight between shoot and root (Fig. 3f) showed the same trend. That is, from Week 3 onwards, the proportion of dry matter partitioned to the root steadily increased. Benson and Takatori (1980) have reported similar changes in shoot and root numbers and dry-weight partitioning over a 6-week period. Tissue analysis. - - There was no significant difference in % N on a dryweight basis between the 100 and 150 mg 1-1 N levels for shoot tissue. In other cases the % N or P in the plant tissue increased significantly (P < 0.05) as the nutrient levels increased (Fig. 4 a--d). The percentages of both nutrients fell during Weeks 1--4 and then levelled off.

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Fig. 3. R e l a t i o n s h i p b e t w e e n t i m e o f h a r v e s t a n d s e e d l i n g g r o w t h ( M e a n s o f 9 n u t r i t i o n a l treatments). (a) S h o o t l e n g t h . Y = 2.34 + 6 . 0 8 x - - 0 . 3 4 8 x 2 (b) Shoot number. F = 0.28 + 0.77x (c) S t o r a g e r o o t n u m b e r . Y = 0.31 + 0 . 7 0 x + 0 . 1 3 5 x 2 (d) Mean dry weight. Y = --0.014 + 0.0228x -- 0.0013x 2 (shoot) Y'= 0 . 0 0 0 4 + 0 . 0 0 3 2 x + 0 . 0 0 0 3 9 x 2 ( r o o t ) (e) L o g e d r y w e i g h t . Y = - - 5 . 7 4 + 1 . 6 7 x - - 0 . 1 3 2 x 2 ( t o t a l ) Y = --6.18 + 1.75x --0.151x 3 (shoot) Y = --6.82 + 1.55x -- 0.103x 2 (root) (f) P a r t i t i o n i n g o f d r y w e i g h t . H a r v e s t s 1 - - 3 n o t s i g n i f i c a n t f r o m e a c h o t h e r ; all o t h e r d i f f e r e n c e s s i g n i f i c a n t (P < 0.01).

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Fig. 4. Relationship between time of harvest and % N and P present in shoot and root tissue (dry weight basis). (a) % N in shoot, SE 0.19. (b) % P in shoot, SE 0.018. (c) % N in root, SE 0.18. (d) % P in root, SE 0.019. SE (30 df) are for comparing harvests within the same nutrient concentration. N and P are given in mg 1-1 .

The following nutrient ranges were achieved at the later harvests from the 100--150 mg 1-1 N and 15--22.5 mg 1-1 P treatments. The data for these treatments were selected because it was considered t h a t these treatments provided adequate nutrition for the seedling.

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Geraldson et al. (1973) reported 2.4--3.8% N and 0.3--0.35% P on a dry-weight basis as the c o m m o n nutrient range f o u n d in mature asparagus fern. The N concentrations in the shoot reported here for seedlings are within this range, although much narrower, while the P concentrations compare closely.

112 implications. - - If as large a seedling as possible is the intention at planting, th en 150 mg 1-1 N should be applied, as this p r o d u c e d the plant with the greatest total plant dry weight. However, the m ore vigorous s h o o t growth achieved by this t r e a t m e n t m ay n o t be favoured by some seedling producers, who would consider the 100 mg 1-1 N level more acceptable. P had no e f f e c t on plant dry weight. The lowest level of P partitioned m o r e dry weight to the roots, which m a y be desirable at transplanting. It is also possible that u n d e r conditions of reduced P availability, a higher level o f P may be m or e beneficial t o the seedling during establishment, since P is readily translocated f r om older t o y o u n g e r tissue (Seatz and Stanberry, 1963). As a c om pr om i s e , the 15 mg 1-1 P level is r e c o m m e n d e d . On the basis o f these results, where plants were fed at each watering, it is suggested t ha t 100- - 150 mg 1-1 N in c o m b i n a t i o n with 15 mg 1-1 P will p r o d u c e a seedling suitable for transplanting into commercial fields. Such plants had 5 shoots, 9--11 storage roots with the longest s h o o t 26--28 cm long, and a total dry weight of 0.70--0.75 g.

Practical

ACKNOWLEDGEMENTS The n u t r i e n t analysis o f the plant material was carried out by Dr. M. Prasad and T.M. Spiers o f the Levin Horticultural Research Centre, Ministry o f Agriculture and Fisheries, Levin, New Zealand. REFERENCES Benson. B.L., 1979. Evaluation of asparagus plantation establishment with 10-week-old seedlings and year-old crowns. In: Asparagus Research 1978--79. Veg. Crops Ser. No. 207, Dep. Veg. Crops, U.C., Davis, pp. 2--4. Benson, B.L. and Takatori, F.H., 1980. Partitioning of dry matter in open-pollinated and F 1 hybrid cultivars of asparagus. J. Am. Soc. Hortic. Sci., 105: 567--570. Benson, B., Souther, F., Takatori, F. and Mullen, R., 1978. Establishing asparagus plantations with seedling plants. Calif. Agric., 32: 10--11. Brouwer, R., 1962. Nutritive influences on the distribution of dry matter in the plant. Neth. J. Agric. Sci., 10: 399--408. Geraldson, C.M., Klacan, G.R. and Lorenz, O.A., 1973. Plant analysis as an aid in fertilizing vegetable crops. In: L.M. Walsh and J.D. Beaton (Editors), Soil Testing and Plant Analysis. Soil Sci. Soc. Am., pp. 365--379. Hunt, R., 1978. Plant Growth Analysis. Studies in Biology No. 96. Edward Arnold, London, pp. 67. Ombrello, T.M. and Garrison, S.A., 1978. Establishing asparagus from seedling transplants. HortScience, 13: 663--664. O'Neill, J.V. and Webb, R.A., 1970. Simultaneous determination of nitrogen phosphorus and potassium in plant material by automatic methods. J. Sci. Food Agric., 21: 217--219. Seatz, L.F. and Stanberry, C.O., 1963. Advances in phosphate fertilisation. In: M.H. McVichar, G.L. Bridger and L.B. Nelson (Editors), Fertiliser Technology and Usage. Soil Sci. Soc. Am., pp. 155--187.

Williams, J.R., 1979. Studies on the propagation and establishment of asparagus. Exp. Hortic., 31: 50--58.