Nitrogen Fertilization Effects on Recovery of Bush Beans from Flooding

Nitrogen Fertilization Effects on Recovery of Bush Beans from Flooding Stewart T. Reed Garry G. Gordon

ABSTRACT. Nitrogen loss can be a serious problem to vegetable growers in flood-prone areas. In south Florida. waterlogged soil can cause plant N stress through nitrate leaching. dcnitrification, and reduced N uptake and assimilation. The Comprehensive Everglades Restoration Project will increase water flow into Everglades National Park, resulting in frequent flooding on adjacent agricultural lands. A greenhouse study was conducted to determine effects of nitrogen application method on recovery from flood damage in bush beans (Phaseolus rulgari.c L.). There were three fertilizer treatments: I ) normal: 1/7 N applied preplant, 1 /2 applied at flowering: 2) liquid: daily liquid applications with irrigation water; and 3) Stewart T. Reed is affiliated with the USDA/ARS, Subtropical Horticulture Research Station, 13601 Old Cutler Road, Miami. FL 33158 (E-mail: stewart. reed @ars.usda.gov ). Garry G. Gordon is affiliated with the USDA/ARS, Subtropical Horticulture Research Station, 13601 Old Cutler Road, Miami, FL 33158. The author expresses his sincere appreciation to Dr. David C. Martens for his valuable review and comments on this manuscript. Mention of a trademark, vendor, or proprietary product does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products that may also be suitable. The article was prepared by a USDA employee as part of his/her official duties. Copyright protection under US copyright law is not available for such works, and there is no copyright to transfer. The fact that the private publication in which the article appears is itself copyrighted does not affect the material that is a work product of the US Government, which can he freely reproduced by the public. Address correspondence to Stewart T. Reed at the above address. International Journal of Vegetable Science, Vol. 14(3) 2008 Available online at http://ijvs.haworthpress.com © 2008 by The Haworth Press. All rights reserved. 256 doi: 10.1080/19315260802165183

Stewart T. Reed and Garry G. Gordon

257

foliar: normal fertility treatment plus two foliar spray treatments applied after flooding. Plants were hooded to I cm above the soil surface for 2 or 4 days. drained, and allowed to continue to grow under normal greenhouse conditions. At harvest, plants receiving the liquid treatment had a greater pod fresh weight (FW) than those receiving normal and foliar fertility treatments. From planting through recovery from flooding (day 45), the liquid fertility treatment tended to maintain chlorophyll levels either equal to or greater than those of the loliar and normal treatments. Plants receiving liquid fertilizer tended to have a net photosynthetic rate higher than the other fertility methods and recovered faster, and to higher photosynthetic levels, after flooding. Plants hooded for 2 days and receiving the liquid treatment appeared to have a denser root system and a larger leaf area than the other treatment. These plants probably resisted flood damage longer and were better able to recover from injury, and this likely resulted in higher pod FW than the other treatments. Daily liquid fertility treatments (fertigation) may be an acceptable strategy to mitigate certain effects of 100(1 damage to beans. KEYWORDS. Phascolus vulgaris, bush beans. flooding, nitrogen. photosynthesis

INTRODUCTION The climate in south Florida is characterized by severe thunderstorm activity during the May through October vegetable growing season (United States Department of Agriculture [USDA], 1996). Regional topography is low lying and flat, with shallow soils and a water table near the surface. As a consequence, flooding is a pervasive problem and caused $13 and $77 million in agricultural losses during 1999 and 2000, respectively (Miami-Dade County Cooperative Extension Service, 1999, 2000). The Comprehensive Everglades Restoration Project has been approved to restore historical characteristics of south Florida water flow (Water Resources Development Act, 2000). This will raise the water table in areas adjacent to the Everglades National Park and increase incidences of flooding on agricultural lands. Effective strategies are needed to reduce the risks to vegetable production from flooding. Oxygen movement into waterlogged soil is slow, and as soil organisms deplete existent 0, anaerobic conditions begin to dominate (Drew, 11990 Grable, 1966). Flooding affects soil redox, pH, and metal ion availability.

258 INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE

Plant responses to flooding include, but are not limited to: reduced stern growth, inhibition of leaf elongation, epinasty, chlorosis, reduced rates of CO2 assimilation, reduced nutrient uptake, increased production of adventitious roots, wilting, and an increased susceptibility to attack by pathogens and predators (Aloni and Rosenshtein, 1982; Bradford and Dilley, 1978; Bradford and Hsiao, 1982; Kozlowski, 1977; Kuo and Chen, 1980; Nunez et al., 1999; Sundstrom and Pezeshki, 1988). In areas prone to periodic flooding, plant N stress can result from a number of flood-related causes. Nitrate leaching and denitrification can directly reduce soil N (Freney et al., 1985; Hodgson and MacLeod, 1988). Soil oxygen depletion or pathogenic organisms can decrease root activity and N uptake (Jackson and Drew, 1984; Sojka and Stolzy, 1980). Reduced photosynthesis can reduce N assimilation (Bradford, 1983). Supplemental applications of N have been only partially successful in counteracting negative effects of flooding on plants. Surface-applied calciurn nitrate to flooded barley plants (Hordeum vidgare L. cv. Alfa) resulted in shoot weight and chlorophyll content similar to non-flooded plants (Drew et al., 1979). However, in cotton (Gossypiuin liirsutum L.), waterlogging was shown to reduce N uptake and the physiological efficiency of absorbed N (Hearn and Constable, 1984; Hodgson and MacLeod, 1988). When applied to soil at high rates, N was most effective at reducing flood damage in cotton. A high N application rate would not be advisable in areas adjacent to protected lands like the Everglades. Plant responses to foliar applications are inconsistent. Where soil N is limiting, the high N application rates needed cannot be applied without risking leaf burn (Haq and Mallarino, 2000; Hodgson and MacLeod, 1988). Fertigation with N may be an appropriate means to help reduce detrimental effects of flooding on crops. A greenhouse study was initiated to determine the comparative performance of fertilization method on growth of bush bean (Phaseolus vulgaris L.) flooded for 2 or 4 days. MATERIALS AND METHODS The experiment was begun in February 2002 (winter). There were three fertility treatments and two flood durations. Four Mirada, TG5863, hush bean seeds were planted on 1 February in 15-L (25.4-cm-diameter) pots containing approximately 10 L of a commercial potting mix (Atlas Peat and Soil Inc., Boynton Beach, Fla.). The potting mix consisted of 50 17c sand and 50% peat fortified with a nutrient mix (9.0% Mg, 2.0% Mn,


259

0.23% Cu, 6.75% Fe, and 0.69% Zn as sulfates). Pots were watered daily at 7 AM and 2 ivi. The irrigation system was set to deliver I L water per pot per irrigation generally resulting in through-flow. Ten days after planting (DAP), plants were thinned to one plant per pot. Fertility treatments used are listed in Table 1. The normal treatment (normal) received a total of 1.36 g N, 0.56 g P, and 2.53 g K. This treatment corresponds to a surface-applied fertility rate of 176 kg•ha' N. The foliar treatment (foliar) received the same fertility treatment as the normal plus a foliar application equivalent to 4.2 mg of N per pot (0.54 kg . ha 1 N) applied the day flooding ended and a second application 48 h later. The liquid treatment (liquid) received daily applications beginning 10 DAP applied with the morning irrigation. The total N applied to the liquid treatment was 1.47 g per pot (190 kg . ha' N). Pots were not fertilized during flooding. The fertigation application rate was based on rates commonly applied by south Florida producers (5.6 kg-ha'-day N; Hochmuth, 2000). Fertigation resulted in it greater total N application than the other treatments, equivalent to 3 days of additional applications. Fertility rates were planned assuming 42 days time from planting to harvest. Liquid applications continued until the first harvest, which occurred at 45 DAP, 3 days latter than anticipated. Growth stage was determined by an adaptation of the method developed at Iowa State (Ritchie et al., 1985) for soybeans (Glvcine max (L.) Merr.). Vegetative growth stages (VI—Vn) were determined on the main stem by the number of nodes above the unifolioate node with unfolded

TABLE 1. Nitrogen (N), Phosphorus (F), and Potassium (K) application rate, form of fertilizer, and days after planting (DAP) applied to 1 5-L pots Treatment

N

Application in g/Pot

Form

OAF

10-10-10 solid KNO 3 liquid CaHPO4 liquid 10-10-10 solid KNO 3 liquid CaHPO4 liquid KNO 3 spray 10-10-10 liquid

10 27 27 10 27 27 32 and 34 35

P K

0.28 0.53 Normal 0.64 2.00 0.72 0.28 0.28 0.53 Foliar 0.64 2.00 0.72 0.28 0.0117 0.0042 Liquid 0.042 0.0179 0.0345


leaflets. Emergence was designated VE and the VC growth stage began once unifolioate leaves unfolded. Reproductive growth stage began with the opening of the first flower on the main stem (RI). Growth stages R2 through R5 were designated as follows: R2, all flower above the fourth trifolioate node; R3, pod 5 mm long on the main stem; R4, pod 2 cm long oil main stem; and R5, pod on main stem with seed 3 mm long. Four wooden tanks with waterproof liners were constructed to hold 15 pots each during flooding. At 30 DAP (V4 growth stage) pots were placed in tanks and flooded to 2 cm above the soil surface for a duration of either 2 or 4 days. Pots were removed from tanks and allowed to drain. Plants were then maintained under normal greenhouse conditions. Plant growth stage was monitored daily and chlorophyll concentration, plant height, and photosynthesis weekly. Chlorophyll measurements were taken with a Minolta Chlorophyll Meter, SPAD-502 (Spectrum Technologies Inc., Plainfield, ill.) and photosynthesis by an ADC LCA-4 Automatic Microclimate System (Dynarnax Inc., Houston, Tex.) with light intensity set at 2,100 pimol/m.s'. Chlorophyll and photosynthesis were measured on the uppermost fully expanded leaf, which is the leaf directly below the last newly unfolded leaf. On the day flooding began, and a week after flood termination, one randomly selected plant from each treatment was sacrificed for N analysis. The first harvest began when 50/c of pods oil were >8 cm in length, at 45 DAP. and a second at 53 DAP. All pods, ^!8 cm in length were carefully cut and removed at each harvest. Leaf area was determined with a CI-202 portable leaf area meter (CID, Inc., Vancouver, Wash.). Pod fresh weight (FW), the number of pods produced, and shoot dry weight (DW) were determined. The study was repeated in June 2002 (summer), using an 80-20 (v/v) sand-peat potting mix to simplify root extractions. Pots were thinned to two plants per pot and the normal fertilizer treatment consisted of 0.64 g N applied at 7 DAP, 0.18 g KH 7 PO41 plus an additional 0.64 g N applied at 35 DAP. The liquid treatment received daily fertilizer applications beginning 10 DAP and ending 42 DAP. The equivalent of 1.5 days of extra N was applied to the liquid treatment. Flood treatments began at 22 DAP, the V4 growth stage. Measurements were made on individual plants and reported as data per plant. Pods were harvested three times at 46, 53, and 63 DAP. Each planting was analyzed separately because of differences in the number of plants per pot. Analysis of variance was performed using the


261

General Linear Model procedure of SAS (SAS Institute, 1999). Where an interaction was present, it was used to explain results. Means separation was determined by linear contrasts. Data accumulated over time were presented as line graphs and means separated using standard error of the means. In the summer planting there was a high mortality rate following 4 days of flooding; consequently, the 2-day and 4-day flood treatments were analyzed separately. Pots were arranged in a completely randomized design with five replications for each treatment. RESULTS Genera! Characteristics—Winter Planting Results from an analysis of variance for effects of fertilizer treatment (F), days of flooding (D), interaction (F x D), and the complete model (F + D + F x D) for each growing season are presented in Table 2. The model Y = F + D + F x D was significant at the 0.05 level for all characteristics measured except number of pods and shoot N for the winter growing season. Bush beans planted in winter reached the V4 growth stage between 27 and 33 DAP (Table 3). The first flower appeared between the V4 and VS growth stage for all treatments (data not shown). For the winter crop, there were no differences in the time required for bush beans to flower, or the DAP when pods were ready for harvest, between plants subjected to 2 or 4 days of flooding. TABLE 2. Significance (P> F) for effects of fertilizer treatment (F), days of flooding (D), interactions (F x D), and the complete model (F + D + F x D) on development characteristics of bush bean grown in a greenhouse Source

Fertilizer treatment (F) Days of flooding (D) Interaction (F x D) Model (F + D + F x D) Summer 2 days Fertilizer treatment (F) Summer 4 days Fertilizer treatment (F)

Shoot dw Leaf Area Pod fw No. of Pods Shoot N 0.4901

0.8672 0.0988

0.9536

0.7916 0.7546

0.0668 0.5291

0.5633 0.5062

0.2022 0.2599 0.8187 0.4089 0.3778 0.9366 0.3840 0.5963 *

0.4529

0.3647 0.5524

and *** significant at P 5 0.05, P5 0.01, and P^ 0.001 levels, respectively, ANOVA.

00) CD 0-

0 a

r--CC\ (DC) r- UO)N-Q •(N- LUU C'JCCJ C\JC'JC\J

z

CL 0 (0 -C 0

.0

0 ci)

•0

-Q

Ea.0

E

zo

.0 (0 0 -U2 'U)C'J (DU(DN-U) Lt)N- ddd

CO U) co CU U)

C)

U) ..— 0 - 0

(I)

a)-

CL

.0 -0

22

.

-E c\J c0

U) -J

Co

.0

COCUCO0.0.0 .0(0(0 (N LC)N( D r co0) U) 0 C') U)'N- N-r-(')COC')--,--

.0 a)CacU.0.0cU .0(0.0 'CJ(D CO0 oo

N -r o 0.21

C)

C/)

>

.2 .

(I) -

0 0 r Eco

(')0 QC'? It) t It) It) C -cli C") C') C') co co co C') C') Cl) co

LL

Ch 0

C oz

co

>-.-

000000 000 LflLU(O 000000 000

0

C Ca 0 C 0) (I)

Ch

cu U)0

ID

E' 00 c'J

-'t C\JC\JC'J ttI

>

CL

0.0

0 0 U-

00) C U)

E Ca

a) F-

262

ci)

CO.0 co

I-

Ca C U)

0

0

-J

LU 0 0 V

Cl)

C

= U)

w

0. U) 0 x U)

0 C

Cci D 0)C

w

.0

>

c CZ ci)

0 ci

E E Cd) Q)

0 co

-D

0 0 .0 00 (0(0(00.0.0 .0(0.0 LC C\C 0'O

t CD U-

CO Er

(1) Cd) (0 (0

• 0_o_0LL 0 0-0 •00fl -j

LL -i Z LL 0) (1)

z

0(/1 co (J)0) >0 N 0


263

There was a 100% survival rate for all treatments during the winter planting (Table 3). There were no significant fertilization effects in the winter (Table 2). Plants flooded for 2 days had a greater shoot dry weight than did plants flooded for 4 days. Leaf area and pod weights were greater in plants flooded for 2 days than in those flooded for 4 days. Pod number was similar for all treatments. Pod FW across flood treatments followed the order liquid > normal > foliar fertility treatment. Shoot N content followed the order foliar = normal > liquid. General Gharacteristics—Summer Planting The high mortality rate after 4 days of flooding rendered any differences due to fertilization treatment of no practical importance. Therefore, in the summer the 2-day flooding treatments were analyzed separately from the 4-day flooding treatments. There were no significant differences between treatments in the time required to reach the V2 growth stage. All plants flowered after the V6 growth stage (data not shown). Flooding for 4 days delayed flowering by more than 7 days beyond that for plants flooded for 2 days (Table 3). Some plants exposed to flooding for 4 days survived for several days after flooding before dying. These plants were slower in developing and the average time to flowering was increased. Once these plants died, the healthier, more rapidly developing survivors resulted in a faster mean time to reach R4 than the time to reach RI growth stage. With the 4-day flood treatment, only a few plants survived and produced pods. For plants flooded for 2 days during the summer, fertilizer treatment affected plant development (Table 2). Fertilizer treatment had no affect on plants flooded for 4 days. The plants flooded for 2 days and receiving the liquid treatment had the greatest shoot DW, leaf area, pod FW, and pod number (Table 3). However, leaf area was significantly different only at P = 0.0668 level. Leaf area in the liquid treatment was 1.4 x that in the normal and 2.1 x that in the foliar treatment. Leaf area likely was a major factor in greater DW and pod FW from the liquid treatment. Both pod FW and the number of pods followed the order liquid > normal > foliar. Between fertility treatments, shoot N was not significant] y different. At the beginning of each planting, an extra pot in each treatment was included for post-flood root analysis. The plants flooded for 2 days and receiving the liquid treatment had root densities >1.5 and >1.4 x greater than the other 2-day flooding treatments in the winter and summer, respectively (data not shown).


Plants exposed to 2 days of flooding lost an average of approximately 25% of their leaf area. This leaf area was replaced by subsequent growth during recovery from flooding. However, plants from the 4-day flood treatment lost 50% or more of their leaf area. Many plants died shortly after termination of the 4-day flood treatment. Plants that survived 4-day floods were not able to replace the lost leaf area with new growth by harvest. Chlorophyll—Winter Planting Results from an analysis of variance for the effects of frtili,er treatment (F), days of flooding (D), interaction (F x 1)), and the complete model (F + D + F x D) on chlorophyll content for several da) s during each growing season are presented in Table 4. lii the winter, flooding began on day 30 and was terminated on day 32 and day 34 for the 2-day and 4-day flood treatments, respectively. Prior to flooding, leaf chlorophyll was similar for all treatments (Table 5). After flooding, chlorophyll content in all but the 2-day liquid treatment began to decline slightly. On day 45, 15 days after flooding, all but the normal 4-day flood treatment had similar chlorophyll content. Across flood treatments, a liquid fertilizer application caused plants to maintain the highest chlorophyll levels. TABLE 4. Significance (P> F) for effects of fertilizer treatment (F), days of flooding (D), interactions (F x D), and the complete model (F + D + F x D) on chlorophyll content in bush bean grown in a greenhouse Source

Winter Day 30 Day 33 Day 38 Day 41 Day 45

Fertilizer treatment (F) Days of flooding (D) Interaction (FxD) Model (F+D+FxD) Source

*** * 0.3270 * 0.847 * * *** 0.0615 0.5098 0.2054 0.5488 0.7526 0.3149 *** * 0.6733 *

Summer Day 21 Day 28 Day 35 Day 42 Day 49 Day 56

Fertilizer treatment (F) *** ** 0.1202 0.0802 Days of flooding (D) 0.7547 0.0552 0.4705 *** ** Interaction (FxD) 0.0805 0.5129 0.8991 0.3182 0.4882 0.8794 *** * Model (F+D+FxD) *** 0.0758 and —significant at P:^ 0.05, Pc^ 0.01, and P!^ 0.001 levels, respectively, ANOVA.


265

TABLE S. Chlorophyll content in bush bean leaves as influenced by flooding and nitrogen fertilization Fertilizer Flood Treatment Duration (days) Winter Foliar Liquid Normal Foliar Liquid Normal

Chlorophyll Content (SPAD units)

Day 30 Day 38 Day 41 Day 45 28.5 b 30.5 ab 31.1 a 32.2 33.8 a 35.0 a 32.1 a 31.8 27.8 b 27.0 bc 29.5 a 32.5 26.7 b 27.2 c 29.6 a 34.3 28.7 b 29.3 b 30.3 a 30.6 25.3 b 22.8 c 22.5 b

Day 21 Day 28 Day 35 Day 42 Day 49 Summer Foliar 2 27.0 b 28.6 b 30.8 a 29.6 27.4 Liquid 2 30.5 a 33.7 a 29.9 a 29.0 31.3 Normal 2 25.6 b 30.6 ab 24.6 b 29.5 31.9

Z values in columns followed by the same letter are not significantly different, P < 0.05, linear contrast.

After flood termination, both the liquid and foliar treatments generally maintained a chlorophyll content significantly greater than that of the normal fertilizer treatment.

Chlorophyll-Summer Planting Unlike the winter planting, chlorophyll content during the summer varied between treatments prior to flooding (Table 5). Plants receiving daily liquid fertilizer generally had the highest chlorophyll content. In the summer, plants were flooded on day 22 and flood termination was on day 24. The chlorophyll content after flooding was not different within 2-day flooding treatments. There were no differences in post-flood chlorophyll content within the 4-day treatment (data not included in Table 5).

Photosynthesis- Winter Planting Prior to flooding on day 30, plants had a mean photosynthetic rate (net CO, assimilation) of 16.8 imol CO 1/rn 2 s. In all treatments, photosynthesis was reduced below preflood levels for at least 10 days after initiation of flooding (Figure 1A). By day 45, the 15th day after flood initiation, plants flooded for 2 days and treated with liquid and foliar fertility treatments


FIGURE 1. Effects of flood duration and fertilizer treatments on photosynthetic recovery. Values for all days except day 30 in the winter and day 40 in the summer are significant at P !!^ 0.05. Bars represent the standard error for each treatment mean at each growth stage. Flood initiation began after net 00 2 readings were made on day 30 and 22 for the winter and summer plantings, respectively. The letters F, L, and N stand for the foliar, liquid, and normal treatments, respectively; the numbers stand for either 2 or 4 days of flooding. A

25 1

• F-2 o F-4 -v- [-2

a 20 E 15 0

-5 428

25

E 0

o 0

Winter

30 32 34 36 38 40 42 44 46 Days

B

Summer

20

15

E

0

• F-2 -v-- L-2 -.- N-2

01 20 22 24 26 28 30 32 34 36 38 40 42 44 46 Days


267

had fully recovered photosynthetic rates to that of the prefiood plants. Plants receiving daily liquid applications of fertilizer tended to maintain the highest photosynthetic rates during recovery from a 2-day flood and they reached rates equivalent to preflood levels fastest. At both flood durations, only plants treated with normal fertilizer failed to recover photosynthetic capability.

Photosynthesis—Summer Planting Prior to flooding, plants receiving the liquid fertility treatment had the highest photosynthetic rates (Figure 113). By day 28 all plants exposed to a 2-day flood had recovered to preflood photosynthesis levels. For days 32 to 35, plants receiving either liquid or foliar fertilization after a 2-day flood maintained a higher photosynthetic rate than the normal fertility treatment. The survival rate for plants receiving the 4-day flood treatment was between 25 and 66%. Several plants lost all but their upper most leaves, making readings on fully developed leaves impossible. Photosynthesis did not return to preflood levels until day 40.

Transpiration— Winter Planting Prior to flooding, the average transpiration rate for all 2-day treatment plants was 5.1 mol H20/m 2 's' (Figure 2A). For the 8 days following cessation of flooding, transpiration averaged 0.5 mol H 2 O/m2 's 1 . Between days 38 and 42, plants treated with the liquid fertilizer after 2 days of flooding maintained a higher transpiration rate and recovered faster than plants in the other treatments. By day 42, only plants treated with liquid fertilizer after 2 days of flooding had recovered transpiration rates to preflood levels.

Transpiration—Summer Planting The reduction in transpiration as a result of flooding was not as great during the summer as the winter planting (Figure 213). After 2 days of flooding, the plants treated with liquid, foliar, and normal treatments all recovered by day 35. In plants treated with 4 days of flooding, meaningful transpiration measurements were hampered by the high mortality and severe leaf loss in surviving plants. Recovery from the 4-day flood was slow; transpiration values approaching preflood levels were not reached until day 40. Given the low pod fresh weight (Table 3) and slow recovery of photosynthesis and transpiration,


FIGURE 2. Effects of flood duration and fertilizer treatments on transpiration. Values for days 30 through 42 in the winter and days 26, 28, and 35 in the summer planting are significant at P :^ 0.05. Bars represent the standard error for each treatment mean at each growth stage. Flood initiation began after readings were made on day 30 and 22 for the winter and summer plantings, respectively. The letters F, L, and N stand for the foliar, liquid, and normal treatments, respectively; the numbers stand for either 2 or 4 days of flooding.

7-

A Winter

6-

E

o

-•- F-2

o

F-4 -i- L-2 A L-4 -- N-2 a N-4

Z C 0 0 C I0

28 30 32 34 36 38 40 42 44 46

Days 7

B Summer

6

0 0

C

20 22 24 26 28 30 32 34 36 38 40 42 44 46

Days


269

the 4-day flood treatment appeared to he too severe for any fertilizer treatment effect to he worthwhile.

DISCUSSION Agreenhouse study was conducted to determine the effects of N fertilization on recovery from flood damage in hush beans. Flood duration reduced shoot DW, leaf area, and pod FW in the winter study. In the summer study, a high plant mortality and negligible pod production were the results of a 4-day flood treatment. This left any advantage due to fertilization treatment of no practical importance. The average outdoor temperature during the summer study was 27°C compared to 21°C in the winter and likely influenced the response to flooding in the summer. A 4-day flood reduced shoot dry DW, leaf area, and pod FW to it greater extent than it 2-day flood. These findings are in agreement with Scott et at. 1989). who reported that canopy height, dry matter accumulation, and yield in soybeans decreased linearly with flood duration. l3acanamwo and Purcell (1999) found flood-induced N deficiency reduced shoot N content and led to a reduction in dry matter accumulation compared to non-flooded controls. They concluded that improving N availability might be an effective means to improve tolerance to flooding. In this study, after a 4-day flood no fertilization treatment had a significant impact on bean yield. There were no significant differences on plant growth characteristics between fertilizer treatments for plants flooded for 2 days in the winter. However, the liquid treatment did have the highest pod FW and produced the most pods. In the summer planting, plants flooded for 2 days and receiving the liquid treatment had the highest shoot DW, leaf area, pod FW, and number of pods. There was a greater stress put on plants during the summer flooding as indicated by the high mortality rate for a long period of inundation. There was a difference between the amount of N applied to the liquid and normal fertilizer treatments. Liquid treatments received the equivalent of an extra 2.6 days of N due to the flood-induced delay in plant growth. A first harvest occurred when 50% of pods contained seeds 3 mm in length. At this stage, pod fresh weight accumulation slows. The extra N provided in the liquid treatments likely had no effect on numbers of pod in the first harvest and a small effect on their fresh weight. The additional N most likely reduced flower abortion in plants treated with liquid.


Whereas all treatments tended to have a greater yield in the last harvest, the liquid treatment produced 4.6 and H. . 1 more pods/plant than the normal and foliar treatments, respectively. As a general trend with pod FW, the liquid outperformed the normal and foliar fertility treatments. From planting through recovery from flooding (day 45), the liquid fertility treatment tended to maintain the highest chlorophyll levels. During the winter study, plants receiving the liquid treatments recovered photosynthesis rates faster and to a higher level after flooding. Lakitan et at. (1992) imposed a 4-day flood on snap beans at 27 DAP. Photosynthesis was measured 10 days into recovery from flooding and no statistically significant difference was found between these values and preflood rates. Photosynthesis rate was compared here to preflood rates and it was concluded that plants receiving liquid and foliar treatments after it 2-day flood fully recovered their photosynthetic capacity 13 and 4 days after flood termination in the winter and summer, respectively. When the foliar, liquid, and normal treatments are combined, per pod fresh weights were 1.82 g and 2.37 g for the winter and summer plantings, respectively. Given the longer time between full recovery and harvest in the summer as opposed to the winter, it is not surprising that in the summer pod FW from 2-day flood treatments reached a greater per pod weight than in winter. A short recovery time gives a plant a longer time to partition photosynthate to pods production before harvest. Kahn et al. (1985) found black beans recovered from flooding by partitioning dry matter to roots. This is in agreement with Schumacher and Smucker (1984) and Lakitan et al, (1992), who reported that upon recovery from flooding the highest rate of growth was observed for adventitious roots. A high level of soil N was found by Voisin et al. (2002) to promote proliferation of small pea (Pisuin sath'wn L.) roots in the upper 20 cm of soil rather than overall increases in dry weight. During recovery, fertigation provides a readily available source of N to the roots. This may have contributed to the rapid recovery in plants treated with the liquid fertilizer. Continuous liquid N application during reproductive growth also may have contributed to pod FW in the liquid treatment. The liquid treatment encouraged dense root growth. In the field dense root growth especially near the surface where 02 limitations should be less, flood damage may be less severe. Additional research is needed to determine effects that root distribution in soil has on plant recovery after flooding. The precise role fertigation can play in mitigating adverse effects of flooding is not yet clear. Nevertheless, fertigation may be an appropriate management strategy in flood-prone areas.


271

LITERATURE CITED Aloni, B. and G. Rosenshtein. 1982. Effect of flooding on tomato cultivars: The relationship between proline accumulation and other morphological and physiological changes. Physiol. Plant. 56:513-517. Bacanamwo. M. and L.C. Purcell. 1999. Soybean dry matter and N accumulation responses to flooding stress. N sources and hypoxia. J. Exp. Bet. 50:689-696. Bradford. K.J. 1983. Effects of soil flooding on leaf gas exchange of tomato plants. Plant Physiol. 73:475-479. Bradford, K.J. and D.R. Dilley. 1978. Effects of root anaerohiosis on ethylene production. epinasty. and growth of tomato (Lvcopersicou escu/entwn) plants. Plant Physiol. 61:506-509. Bradford. K.J. and T.C. Hsiao. 1982. Stomatal behavior and water relations of waterlo gged tomato (Lrcopersicon e.cu1entwn) plants. Plant Physiol. 70:1508-1513. Drew, M.C. 1990. Sensing soil oxygen. Plant Cell Environ. 13:681-693. Drew, MC., E.J. Sisworo. and L.R. Saker. 1979. Alleviation of waterlogging damage to young barley plants by application of nitrate and a cytokinin. and comparison between the effects of waterlogging, nitrogen deficiency, and root excicion. New Phytol. 82:315-329. Freney, JR., J.R. Simpson, O.T. Denmead. W.A. Muirhead. and R. Leuning. 1985. Transformations and transfers of nitrogen after irrigating a cracking clay soil with a urea solution. Aust. J. Agric. Res. 36:685-694. Grable, A.H. 1966. Soil aeration and plant growth. Adv. Agron. 18:57-106. Haq. M.U. and A.P. Mallarino. 2000. Soybean yield and nutrient composition as affected by early season foliar fertilization. Agron. J. 92:16-24. Hearn. A.B. and G.A. Constable. 1984. Irrigation for crops in a suhhumid environment. VII. Evaluation of irrigation strategies for cotton. Irrig. Sci. 5:75-94. Hochmuth, G.J. 2000. Nitrogen management practices for vegetable production in Florida. University of Floridallristitute of Food and Agricultural Sciences. llodesoii. A.S. and D.A. MacLeod. 1988. Seasonal and soil fertility effects on the rcspm1c of %¼.mtcrlogged cotton to loliar-applied nitrogen fertilizer. Agron. J. 8ft25 t 1 n5. Jack'uim. NI B. and M.C. l)rcw. 1984. Effects of flooding on growth and metabolism of herbaceous plants. pp. 47-128. In: T.T. Kozlowski (ed.). Flooding and plant growth. Academic Pmcss, New York. Kahn. A.B., P.J. Stofiella. R.F. Sandstcd. and R.W. Zohel. 1985. Influence of flooding on root morphological components of young black beans. J. Amer. Soc. Hort. Sci. 110:623-627. Kozlowski. I.T. 1977. Responses of woody plants to flooding and salinity. Tree physiology monograph No. I. Heron Publishing, Victoria, British Columbia. Kimo. C.G. and B.W. Chen. 1980. Physiological responses of tomato cultivars to flooding. J. Amer. Soc. Hort. Sci. 1(15:751-755. Lakitan. B., D.W. Wolfe. and R.W. Zohel. 1992. Flooding affects snap bean yield and genotypic variation in leaf gas exchange and root growth response. J. Amer. Soc. Hort. Sci. 117:711-716.

272 INTERNATIONAL JOURNAL OF VEGETABLE SCIENCE Miami-Dade County Cooperative Extension Service. 1999. Preliminary Miami-Dade County Agricultural loss estimates from flooding IS October, 1999. Miami-Dade County Cooperative Extension Service in cooperation with Farm Service Agency. University of Florida. and United States Department of Agriculture. Homestead, FL. Miami-Dade County Cooperative Extension Service. 2000. Preliminary Miami-Dade County Agricultural loss estimates from flooding 9-10 December. 2000. Miami-Dade County Cooperative Extension Service in cooperation with Farm Service Agency. University of Florida, and United States Department of Agriculture, Homestead. FL. Ndnez, R.E., B. Scheffer, J.B. Fisher, A.M. Coils, and J.H. Crane. 1999. Influence of flooding on net CO 2 assimilation, growth, and stem anatomy of Anona species. Ann. Bot. 84:771-780. Ritchie, SW., H.E. Thompson. and G.O. Benson. 1985. How a soybean plant develops. Special Report No. 53. Iowa State University of Science and Technology Cooperative Extension Service, Ames, Iowa. SAS Institute. 1999. SAS for Windows. SAS Institute. CaLy, N.C. Schumacher, T.E. and J.M. Smucker. 1984. Effects of localized anoxia on Piwseolus lu/garis L. root growth. J. Exp. Boi.35:l039-1047. Scott, HI)., J. DeAngulo, M.B. Daniels. and L.S. Wood. 1989. Flood duration effects on soybean growth and yield. Agron. J. 81:631-636. Sojka. R.E. and L.H. Stoizy. 1980. Soil oxygen effects on stomatal response. Soil Sci. 130:350-358. Sundstrom, F.J. and S.R. Pezeshki. 1988. Reduction of Capsicum annuwn L. growth and seed quality by soil flooding. HortScience 23:574-576. United States Department of Agriculture. 1996. Soil survey of Dade County area. Florida. USDA-NRCS, Washington. D.C. Voisin, AS., C. Salon, N.G. Munier-Jolain. and B. Ney. 2002. Effect of mineral nitrogen nutrition and biomass partitioning between the shoot and root of pea (Piston salii'wn L.). Plant Soil 242:251-262. Water Resources Development Act. 2000. Title VI. section 601. Public Law No. 106-541 of the 106th Congress of United States of America.