Nitrogen utilization by Typha latifolia L. as affected by temperature and rate of nitrogen application

Aquatic Botany, 27 (1987) 127-138

127

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

N I T R O G E N U T I L I Z A T I O N BY T Y P H A L A T I F O L I A L. AS A F F E C T E D B Y T E M P E R A T U R E A N D R A T E OF N I T R O G E N APPLICATION

K.R. REDDY 1and K.M. PORTIER 2

1University of Florida, IFAS, Central Florida Research and Education Center, P.O. Box ~09, San[ord, FL 32771 (U.S.A.) 2University of Florida, IFAS, Department of Statistics, GainesviUe, FL 32611 (U.S.A.) (Accepted for publication 13 August 1986)

ABSTRACT Reddy, K.R. and Portier, K.M., 1987. Nitrogen utilization by Typha latifolia L. as affected by temperature and rate of nitrogen application. Aquat. Bot., 27: 127-138. Greenhouse and growth chamber studies were conducted to evaluate growth and N utilization by Typha latifolia L. in flooded organic soil under varying temperatures and rates of N additions. Elevation of temperature from 10 to 25 ° C increased shoot biomass yields by 275%. Root biomass yields were lowest at 10 °C and increased linearly as a function of temperature. Shoot/root ratios were low (0.72-0.82) at lower temperatures (10-15 ° C) and ratios increased by about three times at higher temperatures {20-30 °C). Biomass yields were increased by addition of N fertilizers, while the shoot/root ratios were directly related to plant-available N present in the soil. Fertilizer 15N uptake (expressed as % of applied N) by the whole plant was 5.3% at 10 ° C, 37.5% at 20°C and at 30°C decreased to 20.8%. Fertilizer N accumulation in shoots was 2.1-29.8% of applied N, while roots accumulated 3.2-7.7%. Under greenhouse conditions, N uptake by T. lati[olia was found to increase with increased rate of N application. Fertilizer N uptake by both shoots and roots was in the range of 61-77%. Plants cultured in growth chambers were affected by low light conditions resulting in poor growth and low fertilizer 15N uptake, as compared to plants grown under greenhouse conditions. Added fertilizer N was the major source of N during the early part of the growing season, while soil organic N was the major and perhaps the sole source of N during the latter part of the growing season.

INTRODUCTION

Recent energy crises have renewed interest in plant biomass as an alternate energy source. High productivity of wetlands and marshes has promoted the suggestion of Typha spp. (cattails) as an energy crop (Morton, 1975; Pratt and Andrews, 1980). Biomass of Typha spp. cultivated in flooded organic soils was found to range from 25 to 30 Mg ha-1 year-1 in Minnesota (Pratt and Andrews, 1980), while in Florida yields often exceed 40 Mg ha-1 year-1 0304-3770/87/$03.50

© 1987 Elsevier Science Publishers B.V.

128 (Reddy and Bagnall, 1981). The efficiency of Typha spp. as a solar energy collector and its capacity to grow under flooded conditions, makes it an excellent choice as a biomass crop on flooded organic soils or wetlands. The success of a Typha spp.-based biomass production system depends on high rates of growth and nutrient use efficiency throughout the year. In order to optimize this system, a better understanding of environmental and nutrient requirements of Typha spp. is needed. Temperature and N availability in the soil are probably among the most important environmental and soil factors controlling growth and nutrient utilization by Typha spp. (Dykyjova et al., 1972; Adriano et al., 1980; Cary and Werts, 1984). Changes in temperature also alter soil microbial activity, thus influencing plant-available N in the soil. Plant-available N in a flooded organic soil planted with Typha spp. is derived from two sources (1) added fertilizer and/or wastewater N and (2) mineralization of soil organic matter. In order to quantitatively determine the applied N (fertilizers or wastewater) use efficiency of Typha spp., it is necessary to use I~N so that the external source of N can be distinguished from soil N. MATERIALSAND METHODS Soil used in the study was obtained from the plow-layer of an organic soil (Lithic Medisaprist, euic, hyperthermic) from the Central Florida Research and Education Center's experimental farm in Zellwood, Florida. The soil had a total N content of 2.65%, total C content of 45.3% and pH of 7.6 Temperature controlled growth chambers were used to evaluate N utilization by T. latifolia L. at different temperatures. Twenty plastic containers each with 500-cm 2 surface area and 12-1 volume were filled with organic soil and flooded. Two 45-day-old T. lati[olia seedlings were transplanted to each container and placed in growth chambers maintained at 10, 15, 20, 25 or 30 ° C each with a 14-h photoperiod of 200/zE m-2 s-1. Typha seedlings used in the study were grown from seed in a nursery bed. Fertilizer N as ( NH4 ) 2SO4 labeled with 4.36 atom % 15N excess was added to each container at a rate of 10 g N m -2 (500 mg N per pot). This was accomplished by injecting equal amounts of N solution at six locations at three depths (3, 6 and 9 cm) to ensure uniform distribution of N in the soil. A floodwater depth of 3 cm was maintained during the growing period. At 45 days, T. latifolia plants were removed from the containers and shoots were separated from roots plus rhizomes. Dry matter content of the shoots and roots plus rhizomes was determined after 72 h of drying at 70°C. The second experiment was conducted in a greenhouse to determine the effect of rate of fertilizer additions on N utilization by T. latifolia. Triplicate containers filled with known amounts of organic soil and planted with 45-dayold seedlings were used for each treatment. All plastic containers were placed in a greenhouse provided with cross ventilation. Fertilizer N as (NH4)2SO4

129 containing 4.5 atom % excess 15N, was applied at 0, 5, 10 and 20 g N m -2, as described in the previous experiment. This study was initiated on 10 June 1982, and continued for a period of 3 months. Daily maximum, minimum and average air temperatures during the study period were 32.6 _+0.7 ° C, 22.5 + 0.7 ° C, and 27.5+_0.5°C, respectively. Solar radiation during the same period was 1.82+_0.14X10 v J m -2 day -1. At the end of 30, 60 and 90 days, plants were harvested and shoots and roots plus rhizomes separated. Component dry weights, total Kjeldahl N and labeled N content of the plants were determined. The difference between total N uptake and labeled N uptake was calculated as the contribution of soil N to the plant. Plant samples were ground to pass through a 20-mesh sieve before analysis. Total Kjeldahl N was determined by digestion followed by steam distillation. Labeled N content of the samples was determined using an isotope ratio mass spectrometer (Micromass 602E). Linear, quadratic and cubic contrasts of" temperature, time and N rate-effects were examined for statistical significance using the general linear model. Calculations were performed using S.A.S. (1982) on an IBM 4341. RESULTS

Biomass yield Growth of T. lati[olia in growth chambers was significantly affected by temperature (Table I ) and shoots were found to be more sensitive than roots and rhizomes with maximum biomass yield obtained at 25 ° C. Overall, rates of biomass (g m -2 per 5°C rise in temperature) for shoot, root and total plant were 2.57 _+0.49, 0.61 + 0.17 and 3.20 _+0.64, respectively. Typha latifolia cultured in flooded organic soil responded to the addition of N fertilizer, indicating that the labile pool of organic N present in the soil was not adequate to support maximum biomass yields (Table II). Statistical analysis indicates that overall biomass yield increased linearly as a function of N added and in a curvilinear (quadratic) fashion as a function of time after planting. The quadratic nature of the time after planting curve is seen in the large increases in biomass yield at 60 days, followed by little or no significant increase in the next 30 days. The linear effect of N added was observed at each sampling date, but was most obvious at 60 days. Although shoot biomass did not increase after 60 days, increase in root rhizome biomass at 90 days was significant. Shoot/root ratios were found to be highest (1.83-3.04) at 30 days and decreased to a value of 0.58-0.68 at the end of 90 days.

Nitrogen content of the plant tissue Nitrogen content in the shoots was found to be maximum (30.9 and 31.5 mg g- 1) at 15 ° C (Fig. 1). Increasing the temperature to 30° C or decreasing to

130 TABLE I Effect of temperature on dry matter production (g dry wt. m -2) of T. latifoliacultivated in flooded organic soil (fertilizer N applied= 10 g N m -2) Temperature (°C)

Shoots

Roots and rhizomes

Total

Shoot/root ratio

10 15 20 25 30

17 37 130 157 137

24 34 57 61 58

41 82 187 218 195

0.72 0.82 2.30 2.58 2.36

< 0.01 < 0.01 NS

< 0.01 < 0.01 < 0.01

< 0.01 < 0.01 NS

Source of variability Temperature Linear Quadratic

D.f. 4 1 1

NS = not significant at the 0.05 level. 10°C lowered the tissue N, resulting in a statistically significant quadratic trend. A significant linear decrease in root tissue N was observed as the temperature was increased from 10 to 30°C. The rate of N addition to the soil altered the shoot a n d root tissue N concentrations ( Table III). No simple statistical model was found to describe the N and time after planting effects. T h e N concentration in the shoots varied as a curvilinear function of N added. An increase in N c o n t e n t with added N was observed at 30 days after planting, while an opposite t r e n d was observed at 60 and 90 days. For root N content, a linear decline was observed as a function of time after planting with the same N added effect as for shoots.

Nitrogen (soil and fertilizer N) uptake by the plant Data on the uptake of N (final N in the tissue - initial N in the seedlings) by T. latifolia at the end of 45 days after planting, as influenced by temperature, are presented in Fig. 2. A significant quadratic t r e n d was observed in shoots with m a x i m u m N accumulations (4.1 g N m -2) at 20 a n d 25°C and minima (0.5-1.1 g N m -2) at 10 and 15°C. Nitrogen accumulation in roots showed a significant linear t r e n d with uptake rates of 0.6-1.2 g N m-2. Nitrogen uptake by the whole p l a n t was found to be in the range of 1.1-5.3 g N m -2 (11-53 kg N h a - 1) during the 45-day growth period. At 30 days after planting, N accumulation in shoots was increased in proportion to N application (Fig. 3) with 2.4 and 13.4 g N m -2 at N application rates of 10 a n d 20 g N m -2, respectively. At high rates of N additions (10 and

131 T A B L E II Dry m a t t e r production (g dry wt. m -2) of T. lati[olia as influenced by the addition of nitrogen to flooded organic soil T i m e after planting (days)

Nitrogen added (g N m -2)

Shoots

Roots a n d rhizomes

Total

Shoot/root ratio

30

0 5 10 20

185 360 733 659

101 147 241 240

286 507 974 899

1.83 2.45 3.04 2.75

60

0 5 10 20

522 628 965 1328

378 808 1186 1323

900 1436 2151 2651

1.38 0.78 0.81 1.00

90

0 5 10 20

599 633 822 1363

1006 1138 1415 2005

1605 1801 2237 3368

0.60 0.58 0.58 0.68

Time Linear Quadratic

Df 2 1 1

< 0.01 < 0.01 < 0.01

< 0.01 < 0.01 < 0.01

< 0.01 < 0.01 < 0.02

Nitrogen Linear Quadratic

3 1 1

< 0.01 < 0.01 NS

< 0.01 < 0.01 NS

< 0.01 < 0.01 NS

T i m e × nitrogen Lin. × lin.

6 1

0.06 0.01

0.04 < 0.01

0.04 < 0.01

Source of variability

N S = n o t significant at t h e 0.05 level.

20 g N m - 2 ) , N accumulation in shoots decreased after 60 and 90 days. No significant differences were observed in the t r e a t m e n t receiving 5 g N m -2. However, plants grown in the soil with no added fertilizer accumulated an additional 3.4 g N m -2 after a 60-day growth period. Accumulation of N in root biomass was linear in both N applied and time after planting. At the end of 90 days, root biomass accumulated 6.8 and 15.0 g N m -2 at an N application rate of 0 and 20 g N m -2, respectively.

Uptake of fertilizer nitrogen Fertilizer N accumulation in shoots was found to be m a x i m u m at 20 ° C. A non-significant decline in N uptake was observed at high temperatures (25

132

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Shoots

[3)

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Roots

\

end

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o

"-

Z

8 0

I

5

10

I

I

I

15 20 25 Temperature, C

I

30

Fig. 1. Nitrogen content of the Typha spp. cultivated in flooded organic soil as influenced by ambient air temperature. Plants were cultured in temperature-controlled growth chambers for 45 days. Fertilizer N applied= 10 g N m -2 (500 mg N per pot).

and 30 oC ). Temperature effects on fertilizer N uptake by roots were minimal, although significant linear and quadratic trends were found with N accumulation in the range of 3.2-7.7% of the added N. Uptake of fertilizer N by the whole plant was found to be in the range of 5.3-37.5% of added N (Table IV). Accumulation of fertilizer N in the shoots was found to increase with increased rate of N application to the soil (Fig. 3). Similar trends in 15N assimilation were also recorded for roots. Distribution of ISN (expressed as % of added N) in the plant after 30 days indicates that about 47-62% occurred in shoots, 4-5% in rhizomes and 3-4% in roots. Accumulation of added N by the whole plant was in the range of 55-71% after 30 days and 61-77% after 60 days. During a 60-day period, 15N remaining in the soil was in the range of 23-39%.

Accumulation o[ native soil nitrogen Accumulation of native soil N in shoots and roots was calculated from the difference between total N and 15N assimilation (Fig. 2). Total soil N uptake in 45 days by the whole plant was found to be 0.78 g N m -2 (7.8 kg N ha -1) at 10 oC and 3.79 g N m - 2 (37.9 kg N h a - 1) at 25 oC. Uptake of soil N in plants was significantly affected by temperature. Soil N uptake by shoots was in the range of 3.93-6.65 g N m -2 (39.3-66.5 kg N h a - l ) at all harvests (Fig. 3). Although soil N uptake in roots was low (0.98-1.80 g N m -2) at 30 days, at the end of 90 days it had increased significantly (6.6-10.4 g N m - 2 ) . Soil N uptake by the whole plant was in the range of 8.4-11.8 g N m -2 at 60 days and 11.2-15.4 g N m -~ at 90 days. Addition of fertilizer N (10 and 20 g N m -2) considerably enhanced the uptake of native

133 TABLE III Nitrogen content of the plant tissue at different levels of fertilizer additions to flooded organic soil planted with T. latifolia Time after planting (days)

Nitrogen added (g N m -2)

Shoots (mg N g - ' )

Roots and rhizomes (mg N g-~)

30

0 5 10 20

13.3 14.3 17.7 21.4

9.9 9.4 11.1 11.3

60

0 5 10 20

11.5 10.4 9.3 9.4

7.1 7.3 8.6 6.5

90

0 5 10 20

10.8 9.5 8.8 8.6

6.8 6.8 6.6 7.4

Df 2 1

NS NS

0.01 0.01

Quadratic

1

NS

NS

Nitrogen Linear Quadraticj

3 1 1

0.01 0.01 NS

0.01 0.01 NS

Time × nitrogen Lin. X lin. Lin. X quad.

6 1 1

0.01 0.01 0.01

NS 0.02 0.02

Source of variability Time Linear

NS = not significant at the 0.05 level.

soil N at the end of 30 days. Nitrogen supplied by the soil at high rates of lSN additions was in the range of 6.7-9.3 g N m -2 as compared to 3.4 g N m -2 by the control where no N was added. At all temperatures evaluated, plants derived more N from the fertilizer than from the soil. Fertilizer N contributed about 50-71% of the total uptake, while the soil N contributed only about 29-50% of the total uptake. Fertilizer N contribution to plant uptake was found to be directly proportional to the rate of N application. Plants derived more fertilizer N during the first 30 days of the growth period. As the growing season progressed, the percentage of N

134 4 04 I

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Shoots ~--~ Soil N [] Fertilizer N Roots and Rhizomes

.'.

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soil

Jim

Fertilizer N

10

N

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Temperature,

25

30

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Fig. 2. Fertilizerand soil nitrogenutilization by T. latifolia cultivatedin floodedorganicsoil as influencedby ambient air temperatures.Plants werecultured in temperature-controlledgrowth chambersfor a periodof 45 days.FertilizerN applied= 10 g N m-2 (500 mg N per pot). derived by plants from fertilizer N decreased and the N derived from soil N increased. Plants grown on both fertilized and unfertilized soil were more dependent on organic N mineralization after 60 and 90 days. DISCUSSION

This study reveals the effects of growth determining factors, i.e. temperature and soil and fertilizer N on the quantity and quality of Typha spp. biomass. Air temperature showed a striking effect on growth and N uptake of Typha spp. with an optimum at 25 oC. Optimal growth for T. orientalis Presl was found to occur at 25°C, with yields at 16 and 20°C being about 33 and 66%, respectively, of that at 25 oC ( Cary and Weerts, 1984 ). However, Adriano et al. (1980) found slightly better growth of T. latifolia at 32 than at 25 ° C. In natural and cultivated stands, shoot growth of Typha is significantly reduced during cooler months, and during this period below-ground portions (rhizomes) increase in weight (Linde et al., 1976). This observation was noted in the data presented in Table I, where shoot/root ratios were <1.0 at 10-15°C, and the ratio increased to 2.6 at a temperature of 25 ° C. Active rhizome growth during winter months has an excellent practical significance when wetlands containing Typha spp. are used for wastewater treatment. Plant-available N in the soil was shown to influence the shoot/root ratio, and overall biomass yields. In our study, shoot/root ratios were found to be higher 30 days after fertilizer application, and the ratio decreased significantly

135

20 shoot,

30 days

Soil N L~ Fertilizer N ~oots and R h i z o m e s r ~

15 10

i

soil.

I

I

I

['---7

I

5 O4

o

~E 20 o~ 15 d _~

•10

~

5

e-

0

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0

9 0 days

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0 5 10 20 Nitrogen a d d e d , g N m - 2 Fig. 3. Fertilizer and soil nitrogen utilization by T. latifolia as influenced by rates of N application to flooded organic soil. Plants were cultured under greenhouse conditions.

TABLE

IV

Effect of ambient air temperature on labeled N uptake by T. latifoEa cultivated in flooded organic soil (fertilizer N applied= 10 g N m -2) Temperature

Plant uptake ( % added ~SN )

(°c) 10 15 20 25 30

Shoots

Roots

Total

2.1 6.0 29.8 23.8 16.7

3.2 6.5 7.7 6.3 4.1

5.3 12.7 37.5 30.1 20.8

< 0.01 < 0.01 NS

< 0.01 < 0.01 < 0.01

< 0.10 < 0.01 NS

Source of variability Temperature Linear Quadratic

D.f. 4 1 1

136

90 days afterfertilizerapplication.Results presented by Dykyjova et al. (1972) indicate that the shoot/root ratio of Typha spp. shiftswith growth in favor of the root biomass. Reduced plant-available N in the culture medium increased the growth of roots of Typha spp. (Bonnewell and Pratt, 1978) and Spartina patens (Ait) Muhl. (Valielaet al.,1976), thus decreasing shoot/root ratios. Typha spp. are an efficientcollectorof solar energy and out-produce many agronomic crops (Pratt and Andrews, 1980). This plant can be grown on marginal lands not suitable for food production, is highly productive, grows naturallyin monocultures and has few pest problems. Biomass yieldsof Typha spp. cultivated in flooded organic soils of central Florida were about 45 M g ha-i year-i. These yield estimates were based on the aboveground portion of plants obtained in 3 harvests (Reddy and Bagnall, 1981). The shoot/root ratio of these plants was in the range of 1.0-1.7, indicating a significantamount of biomass in the soil. Low fertilizerN use efficiencyby T. latifoliaat low temperatures was due to poor growth of plants, and increased fertilizerN use efficiencyat higher temperature was due to high growth rates.At low temperatures, most of the fertilizer N added was probably stillpresent in the soil,because of the slow rates of biochemical (nitriflcation-denitrification)and physico-chemical processes (NH3 volatilization)functioning in the soiland overlying floodwater (Reddy and Patrick, 1984). However, as the temperature increases,the rates of these processes will also increase,resultingin significantN loss from the soil. Most of the fertilizerN uptake occurred during the first30 days of growth with littleor no additional uptake at 60 and 90 days (Fig. 3 ). This indicates that after 30 clays fertilizerN was not present in the soil in plant-available form, and that most of the fertilizerN had been absorbed by the plants,immobilized into soil organic matter or lost from the system (Reddy and Patrick, 1984). Patrick and Reddy (1976) also reported that fertilizerN added to the soil,rapidly disappeared in 4-6 weeks afterthe planting of rice,and about onethird of the added N was recovered in the plant, the remaining being lostfrom the system. They attributed these losses to nitrification-denitrificationreactions, since more fertilizerN was present in the inorganic form during the first 4-6 weeks than could be immediately utilizedby the plants. Soil N uptake toward the end of the growing season was much higher than fertilizerN uptake. This was due to depletion of fertilizer,and mineralization of soil organic N (Reddy, 1982) or N2 fixation (Biesboer, 1984). Addition of fertilizerN increased the uptake of soilN, primarily due to enhanced microbial activity and subsequent N mineralization of organic N (Broadbent, 1965; Nommik, 1968). The annual N uptake rate was about 1032 kg N ha -I year -I for Typha spp. cultivatedon flooded shallow organic soils (Reddy and Bagnall, 1981 ).A much higher N uptake (2630 kg N ha- Iyear- i) by Typha spp. was reported by Boyd (1970). These results suggest that N can be limiting when Typha spp. are

137

cultivated on shallow organic soils. Results shown in Table II indicate significant response to N application by Typha spp., cultivated in organic soils. The economics of N additions for growing biomass crops, however, will be dependent on the value of the biomass produced and its ultimate utilization ( Morton, 1975) for some beneficial purposes. ACKNOWLEDGEMENTS

Florida Agricultural Experiment Stations Journal Series No. 6500. This paper reports results from a project that contributes to a cooperative program between the Institute of Food and Agricultural Sciences (IFAS) of the University of Florida and the Gas Research Institute (GRI), entitled "Methane from Biomass and Waste".

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138 drainage water treatment. In: 2nd International Gas. Res. Conf. Proc. Govt. Inst., Inc. Rockville, MD, pp. 376-390. Reddy, K.R. and Patrick Jr., W.H., 1984. Nitrogen transformations and loss in flooded soils and sediments. CRC Crit. Rev. Environ. Control. 13: 273-309. S.A.S. Institute, 1982. S.A.S. User's Guide: Statistics. S.A.S. Instiute, Cary, NC, 583 pp. Valiela, I., Teal, J.M. and Persson, N.Y., 1976. Production and dynamics of experimentally enriched salt marsh vegetation: below ground biomass. Limnol. Oceanogr., 21: 245-252.