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Phenological responses of old and modern soybean cultivars to air temperature and soil moisture treatment
Field Crops Research, 21 (1989) 9-18
9
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Phenological Responses of Old and Modern Soybean Cultivars to Air Temperature and Soil Moisture Treatment
J.R. FREDERICK, J.T. WOOLLEY, J.D. HESKETH and D.B. PETERS
Dept. o/Agronomy, University o/Illinois, S-215 Turner Hall, 1102 South Goodwin Avenue, Urbana, Illinois 61801 (U.S.A.) (Accepted 25 October 1988)
ABSTRACT
Frederick, J.R., Woolley, J.T., Hesketh, J.D. and Peters, D.B., 1989. Phenological responses of old and modern soybean cultivars to air temperature and soil moisture treatment. Field Crops Res., 21: 9-18. Soil moisture deficits and low air temperatures frequently result in crop yield losses in the United States. Understanding how older and newer soybean (Glycine max (L.) Merr. ) cultivars differ in phenological development under various environmental conditions may aid in the selection of higher-yielding cultivars and in the development of simulation models for field-grown soybean. In this study, we examined the phenological responses of two widely adapted older ('Dun field' and 'Manchu') and two more-recent ('Clark 63' and 'Williams 82') soybean cultivars to soil moisture deficit and monitored the development of these cultivars as a function of air temperature. These cultivars were grown under drought stress and irrigation on a Flanagan silt loam soil at Urbana, Illinois, in 1984 and 1985. The soil moisture-deficit treatment was begun approximately 2 weeks before initial flowering (R1 stage) and was continued until harvest maturity. Drought stress reduced the final number of mainstem nodes due to a decrease in the rate at which the nodes were produced, but had little effect on the date of termination of node formation. Except for Manchu, no association was observed between the number of nodes produced under irrigation and the magnitude of the decrease in node number due to drought stress. Although the correlation between cumulative growing degree-days and mainstem node formation was high, little difference was found between the old and modern cultivars in their responses to air temperature. A period of low temperatures during early flower formation in 1985 appeared to have partially contributed to a delay in flower appearance of each cultivar. The results from this study show that the old and modern cultivars do not differ in their phenological responses to drought stress. *Contribution from the Dep. of Agronomy, Illinois Agric. Exp. Stn., Univ. of Illinois, and USDAARS, Urbana, IL 61801, U.S.A.
0378-4290/89/$03.50
© 1989 Elsevier Science Publishers B.V.
10 INTRODUCTION Soil moisture deficits and sub-optimal air temperatures are two of the leading causes of crop yield losses in the United States (Boyer, 1982 ). Both of these environmental limitations affect reproductive and vegetative development. Therefore, an understanding of the phenological responses of crop plants to these environmental conditions is needed before crop growth and development can be accurately predicted. The rate of mainstem node formation in soybean (Glycine max (L.) Merr. ) has been shown to depend on the air temperature of the canopy environment (Hesketh et al., 1973 ), with low temperatures inhibiting leaf initiation {Thomas and Raper, 1978; Musser et al., 1983). Reproductive development is affected by low temperatures, with delays in flowering being reported for determinate soybean grown under controlled conditions {Thomas and Raper, 1978; Musser et al., 1983) and for field-grown indeterminate soybean (Major et al., 1975; Seddigh and Jolliff, 1984). Low air temperatures may affect reproductive development by increasing flower abscission (Musser et al., 1986) and by decreasing leaflet photosynthetic rate {Purcell et al., 1987) and stomatal conductance (Musser et al., 1983). Soil moisture deficits have been reported to alter the partitioning of photosynthate in crop plants, resulting in an increase in the root:shoot ratio (Begg and Turner, 1976). Consequently, fewer mainstem nodes in soybean are produced under drought stress (Korte et al., 1983; Kadhem et al., 1985; Muchow, 1985). Decreases in node number, and consequently leaf number, under drought stress would decrease the photosynthetically active leaf area and the interception of radiation by the crop canopy, which may ultimately decrease seed yield (Sinclair et al., 1981; Monteith and Scott, 1982). Whether the number of nodes is decreased depends on the stage of crop development at which the drought stress is imposed, with competition for photosynthate between vegetative and reproductive sinks limiting node and leaf development {Jordan, 1983). Under most soil moisture conditions, higher seed yields may be obtained if the rate of mainstem node appearance is increased, thus allowing a greater period for reproductive growth at each mainstem node. This may particularly be the case for indeterminate soybean, in which the main stem produces a larger proportion of the total seed yield than in determinate soybean {Board, 1987). However, only limited research has been conducted to monitor the effects of prolonged soil-moisture deficit on the rate and the duration of node formation. In the study presented here, we grew two old and two modern soybean cultivars under field conditions, first to monitor throughout the growing season their phenological development as a function of air temperature under drought stress and irrigation, and second to determine whether the widely adapted, old and new soybean cultivars differ in their phenological responses to soil moisture treatment.
11 MATERIALS AND METHODS
Phenological data were collected at Urbana, Illinois, in 1984 and 1985 from plants grown on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. This soil has a high soil water-table and a profile conducive to deep rooting, which allowed the soil moisture-deficit treatment to increase gradually during reproductive development (Frederick, 1987). Treatments were assigned in a split-plot factorial arrangement in a randomized complete block design with three replications. The two soil moisture treatments {soil moisture deficit and natural rainfall plus supplemental irrigation) represented whole plots, with indeterminate soybean cultivars as subplots. Cultivars evaluated were 'Manchu' (released 1911 ), 'Dunfield' (1927), 'Clark 63' (1963) and 'Williams 82' (1982). Manchu, Dunfield, and Williams 82 are classified as Maturity Group III cultivars and Clark 63 as an early-maturing member of Group IV. These cultivars were selected on the basis of their seed yield stability over environments and because of their adaptation to Illinois soybean-production regions. Williams has previously been observed to have a high stability in yield over test environments compared to other modern cultivars (Cooper, 1981; Specht et al., 1986). The wide adaptation of Williams to Midwest production regions has been suggested to be partially due to its low sensitivity to less than optimum water conditions (Specht et al., 1986). On the other hand, the wide adaptation of Clark, the recurrent parent of Clark 63, has partially been attributed to its tolerance to low night temperatures (Van Schaik and Probst, 1958). The stability of yield over test environments of Manchu and Dunfield has been shown to be equal to that of more-recent cultivars (Wilcox et al., 1979). Manchu and Dunfield were also selected for this study because they were widely grown in Illinois until they were replaced by superior cultivars (Wilcox et al., 1979), and because they represent two of a limited number of soybean introductions that form the genetic base of a large number of recently developed cultivars (Specht and Williams, 1984). The soybean seed was hand-planted on 29 May and 30 May in 1984 and 1985, respectively, in 76-cm-spaced rows as described by Frederick (1987). After emergence the soybean stands were thinned to 26 plants m-1 row. Because soil moisture deficit develops slowly in this soil, the soil moisture deficit treatment was initiated approximately 2 weeks before first flowering (Fehr et al., 1971 ) and was continued until harvest maturity. On days rainfall occurred, wetting of the soil was prevented by stretching polyethylene film between the soybean rows, thus diverting most of the rainwater to a collection system. The film was folded up on days when no precipitation occurred. When 7 days occurred with less than 25 mm of rain, the plots receiving natural rainfall were irrigated using garden dripper hoses. Irrigation was applied four times in 1984 (33-34, 52-53, 78-79, and 91-92 days after planting) and once in 1985 (43-44
12 days after planting). Irrigation was continued until the upper 15 cm of soil was saturated, as indicated by gypsum blocks placed at that depth (Frederick, 1987). To avoid differences in lodging effects among cultivars, lodging was prevented by twine placed on both sides of the crop row. Vegetative and reproductive development (Fehr et al., 1971 ) were monitored weekly throughout the growing season. Ratings were made twice weekly during the week before and the week after initial flowering (R1 stage) and the termination of vegetative mainstem growth, and once weekly for the remainder of the growing season. Growth stages were monitored on two sets of 10 plants from each cultivar within a replication. The mean of the 20 plants in each subplot was used in the growth-stage analysis. Data collected during the apparent linear phase of node appearance were analyzed by linear regression analysis to determine the relationship between node formation and cumulative growing degree-days. The mean of 20 plants in each subplot was used in the linear-regression analysis. Growing degree-days (°Cd) for each day were estimated as the average of the daily maximum and minimum temperature, with a minimum growth threshold temperature of 10°C and temperatures above 30 ° C being counted as 30 ° C. Air-temperature data were collected at a weather station located approximately 200 m from the experimental site. The date of initial flowering (R1 stage ) and the final number of mainstem nodes produced were analyzed as a split-plot factorial to determine if there were significant treatment differences. A Waller-Duncan's LSD was calculated to compare cultivars within each soil moisture treatment for those variables in which a significant cultivar effect was observed. Significance for the LSD was set at a k ratio of 100: 1. RESULTSAND DISCUSSION Precipitation was below normal in 1984 with near-normal air temperatures (Frederick, 1987). In contrast, many of the days in 1985 were overcast (irradiance lower than in 1984) with above-normal rainfall and below-normal air temperatures observed in that year. Soil moisture potentials of both soil moisture treatments were lower in 1984 than in 1985 at all soil depths (Frederick, 1987 ). In the drier year of 1984, average seed yield of Williams 82 and Clark 63 under irrigation was 43% higher than the average yield of the older cultivars, but no significant differences in seed yield were observed among cultivars under drought stress (Frederick, 1987). Similar trends were observed in 1985, with the newer cultivars yielding 19% more than the older cultivars under irrigation, but under drought stress having only a greater yield than Dunfield. Average seed yield decreases due to drought stress were 30 and 8% in 1984 and 1985, respectively. Mainstem node-number responses to soil moisture treatment are shown in Table 1. Averaged over all cultivars, final node numbers were reduced 26 and 11% by soil moisture deficit in 1984 and 1985, respectively. Dunfield had the
13 TABLE 1 Effect of soil moisture t r e a t m e n t on m a i n s t e m node n u m b e r of each soybean cultivar in 1984 a n d 1985 Cultivar
1984 D1
1985 I
D/I
D
I
(%)
D/I
(%)
Williams 82 Clark 63 Dunfield Manchu
10.3 11.2 10.2 10.9
14.2 15.3 14.6 13.8
72.5 73.2 69.9 79.0
13.6 14.8 13.1 12.9
15.2 16.9 15.0 14.1
LSD 2
--
--
--
Effects 3
M**
1.4 M**
1.2 C**
89.5 87.6 87.3 91.5
' T r e a t m e n t s : D = drought stress, I = irrigation. 100) for comparison of cultivars within a soil moisture t r e a t m e n t . 3M, C, a n d M × C represent significance of soil moisture, cultivar, a n d interaction effects, respectively, with * a n d ** indicating significance at the 0.05 a n d 0.01 levels, respectively. T r e a t m e n t effects not listed were not significant. 2 L S D (k----
greatest percentage decrease in node number in both years and Manchu the least, although cultivar differences in the reduction of the number of nodes were small. These responses are similar to those reported in other studies in which an increase in the number of mainstem nodes was observed for several indeterminate cultivars when irrigation was applied during early flowering or throughout reproductive development (Korte et al., 1983; Kadhem et al., 1985 ). Across years in our study, little association was observed between the number of nodes formed under irrigation and the percentage reduction in node number due to drought stress, with the exception of Manchu, which had the fewest number of nodes and smallest decrease due to drought stress. The responses of mainstem node number to cumulative ° Cd for the droughtstressed and irrigated plants in 1984 and 1985 are shown in Figs. 1 and 2, respectively. In both years, the decrease in final node number due to drought stress was primarily the result of a reduction in the rate at which the nodes were produced. The termination of node appearance was only slightly hastened by drought stress even in the drier year of 1984. The time of cessation of node formation was similar among cultivars in 1984, but in 1985 the termination of node formation was slightly earlier for the older cultivars. Since the older cultivars reached physiological maturity earlier than the modern cultivars in both years (Frederick, 1987), there was little association between the termination of reproductive and vegetative growth for the cultivars we examined. Averaged over cultivars, the terminal nodes appeared 72 and 75 days after planting in
14 20
20 I: Y = - 6 . 1 0 D: Y = - 3 . 5 9
+ 0.0229X + 0.0161X
r 2 = 0.99 r 2 = 0.86
1: Y = - 5 . 5 8 D: Y = - 3 . 4 2
+ 0.0223X + 0.0159X
r 2= 0.99 r 2 = 0.96
16
16 ~2
Z
I "
12
~12 22 7_
D•
4
.
•
~
WILMAMS 82
•
CLARK 63
J
z
400
200
~'"
A
600
800
1000
0 200
4;0
6;0
a;o
1;oo
20,
20I: Y = - 5 . 0 7 D: Y = - 2 . 2 2
+ 0.0223X + 0.0148X
r2= 0.98 r2 = 0.93
16
16!
I: Y = - 5 . 1 7 D: Y = - 3 . 4 1
+ 0.0219X + 0.0166X
r2= r2=
0.98 0.96
y-'l j.
12: D
Z ~ 8 o Z
8~ 4
DUNFIELD
|
200
400
600
1300
1000
C U M U L A T I V E G R O W I N G D E G R E E DAYS
4 ~ 01 200
|
-
400
MANCHU
600
800
1000
C U M U L A T I V E G R O W I N G D E G R E E DAYS
Fig. 1. Node number as a function of cumulative growingdegree-days (base temperatureof 10 °C) for the irrigated (I) and drought (D )-treated Williams 82, Clark 63, Dunfield, and Manchu soybean plants in 1984. 1984 and 1985, respectively, with these dates corresponding to an accumulation of 940 and 895 °Cd. Therefore, the higher temperatures in 1984, in addition to earlier flowering dates, may have contributed to an earlier termination of node formation in that year. For all cultivars, soil moisture treatments, and years, regression r 2 values were high (range of 0.86 to 0.99) for the apparent linear region of node formation (Figs. i and 2 ). Although not presented, similar linear trends were also found for mainstem node number versus the number of days after planting because the accumulation of degree-days was relatively constant throughout most of the growing season in both years. In 1984, soil moisture deficit reduced the rate at which the nodes were initiated and the final number of nodes produced. However, only small differences were observed among cultivars in the magnitude of the rate reduction. Among cultivars, little association was also observed between the rate of node appearance (Figs. 1 and 2) and the final number of mainstem nodes produced (Table 1 ), indicating that the duration of node formation was also important in determining the final node number. In 1985 similar trends were found, but the differences in appearance rate between drought-stressed and irrigated plants were smaller. Times of initial flowering (R1 stage) are shown in Table 2. The number of
15 20,
20~- I: Y = -3.88 + 0.0209X r2 = 0.97 D: Y = -4.26 + 0.0199X r2 = 0.97 16
I: Y = -4.12 + 0.0216X r 2 = 0.99 D: Y -3.90 + 0.0207X r 2 0.99
12
~12
~
I"
-'"" "
M ,.
S 82
CLARK 63
Z
200 20 r~ r.l
460
I: Y = - 3 . 8 3 D: Y = - 3 . 5 1
660
860
+ 0.0213X + 0.0196X
zoo
1000
460
860
16oo
20 DII Y = -3.72 + 0.0205X r 2 : 0 . 9 9 Y - -3.67 + 0.0201X r2-- 0.99 16 ..
r2= 0.99 r2 = 0.97
16
12
~12
I D I
Z r--, o z
660
, y .,-""
"
•
8 •~
4
E
L
i
D
MANCHU lb
200
460
660
86o
o 200
16oo
•
460
660
860
1600
CUMULATIVE GROWING DEGREE DAYS
CUMULATIVE GROWING DEGREE DAYS
Fig. 2. Node number as a function of cumulative growing degree-days (base temperature of I0 °C) for the irrigated (1) and drought (D )-treatedWilliams 82, Clark 63, Dunfield, and Manchu soybean plants in 1985.
TABLE 2 Effect of soil moisture treatment on initial flowering date (days after planting) for each soybean cultivar in 1984 and 1985 (cumulative °Cd in parentheses) Cultivar
1984 D1
Williams 82 Clark 63 Dunfield Manchu LSD 2
Effects3
39 42 44 37
1985 I
{503) (551) (576) (487)
3 M*
40 43 46 39
D (515) (562) (606) ( 503 )
2 C**
52 55 54 50
I (613) (646) (635) (583)
3
51 53 55 50
(598) (624) (646) ( 583 )
3 C**
1Treatments: D -- drought stress, I = irrigation. 100) for comparison of cultivars within a soil moisture treatment. 3M, C, and M X C represent significance of soil moisture, cultivar, and interaction effects, respectively, with * and ** indicating significance at the 0.05 and 0.01 levels, respectively. Treatment effects not listed were not significant. 2LSD (k----
16 days to, and the number of cumulative ° Cd needed for, first-flower appearance were only slightly reduced by soil moisture deficit in 1984. The lack of responses in 1985 and small responses in 1984 probably occurred because the soil moisture treatment was initiated only 2 weeks before the R1 stage and a significant soil moisture deficit had not developed during the flower-formation period. Over both years, little association was found between the number of nodes formed and the onset of flowering. Averaged over all cultivars in 1984, the R1 stage was observed at vegetative (V) stages 5.7 and 7.2 under drought stress and irrigation, respectively. On the other hand, the R1 stage for the drought-stressed and irrigated plants was observed at the V8.3 and V8.8 stages, respectively, in 1985. In both years, the number of nodes that had formed by the time of initial flowering under irrigation was greatest for Dunfield, followed by Clark 63, Williams 82, and Manchu. However, under soil moisture deficit the ranking of the cultivars differed between years. Therefore, under the conditions of this experiment, flower appearance was independent of the stage of vegetative development. These data agree with the results of Thomas and Raper ( 1984 ), which showed that flower formation was independent of the vegetative stage in which the plants were photo-induced. In 1984, average initial flowering occurred after 529 (9 July) and 547 (11 July) ° Cd had accumulated for the drought-stressed and irrigated plants, respectively. In contrast, 619 (22 July) and 613 (21 July) °Cd had accumulated before initial flowering was observed for the drought-stressed and irrigated plants in 1985. To help explain this difference, data of Table 3 show the degreedays accumulated and air temperature data for days 13 through 60 after planting in both years. Between days 12 and 21 in 1985, a period of low temperatures caused a reduction in the rate of degree-day accumulation. On the other hand, no decrease in the accumulation of degree-days was observed during the same time period in 1984. The average daily degree-days accumulated during this period were approximately twice as great in 1984 as in 1985. In contrast, the average degree-days accumulated per day for days 21 through 60 were s i m i l a r between years. Because the lengths of both the flowering delay and the period TABLE3 Temperature
data during the period of flowerformation (days after planting) in 1984and 1985
T e m p e r a t u r e (days 1 3 - 2 0 ) : Average maximum Average minimum Mean d e g r e e - d a y s day-': Days 13-20 Days 21-60
1984
1985
31.3 ° C 18.9 ° C
21.5 ° C 12.0 ° C
13.4 12.5
6.8 12.3
17
of low temperatures were similar in 1985, it appears that the low temperatures may have contributed to a delay in flower formation. These data are in agreement with other workers who have observed that low temperatures occurring during early phenological development of chamber-grown soybean result in delays in initial flowering (Musser et al., 1986). In contrast, it can be seen from our data in Fig. 1 and 2 that the number of nodes formed after 300 ° Cd had accumulated (after low-temperature period) was similar between years, indicating a linear relationship between cumulative ° Cd and mainstem node formation. The results from this study have provided insight into the phenological responses of several field-grown soybean cultivars to soil moisture treatment. Although soil moisture deficit reduced the rate of appearance and the final number of mainstem nodes, it had little effect on the date of termination of node formation. A high correlation was found between cumulative growing degree-days and mainstem node formation, but little difference was observed between the old and modern cultivars in their response to air temperature. The data indicate that low-temperature stress occurring early in flower development may delay flower appearance. The small differences in node appearance rate and initial flowering between the old and modern cultivars suggest that future seed yield increases may be achieved in soybean without changing their phenological development. REFERENCES
Begg, J.E. and Turner, N.C., 1976. Crop water deficits. Adv. Agron., 28: 161-217. Board, J.E., 1987. Yield components related to seed yield in determinate soybean. Crop Sci., 27: 1296-1297. Boyer, J.S., 1982. Plant productivity and environment. Science, 218: 443-448. Cooper, R.L., 1981. Development of short-statured soybean cultivars. Crop Sci., 21: 127-131. Fehr, W.R., Caviness, C.E., Burmood, D.T. and Pennington, J.S., 1971. Stage of development descriptions for soybeans, Glycine max (L.) Merrill. Crop Sci., 11:929-931. Frederick, J.R., 1987. Agronomic, phenological, and physiological responses of old and modern soybean varieties to soil moisture deficit. Ph.D. Thesis, University of Illinois, Urbana, 82 pp. Heketh, J.D., Myhre, D.L. and Willey, C.R., 1973. Temperature control of time intervals between vegetative and reproductive events in soybean. Crop Sci., 13: 250-254. Jordan, W.R., 1983. Whole plant response to water deficit: an overview. In: H.M. Taylor, W.R. Jordan, and T.R. Sinclair (Editors), Limitations to Efficient Water Use in Crop Plants. American Society of Agronomy, Madison, WI, pp. 289-317. Kadhem, F.A., Specht, J.E. and Williams, J.H., 1985. Soybean irrigation serially timed during stages R1 to R6. I. Agronomic responses. Agron. J., 77: 291-298. Korte, L.L., Specht, J.E., Williams, J.H. and Sorensen, R.C., 1983. Irrigation of soybean genotypes during reproductive ontogeny. II. Yield component responses. Crop Sci., 23: 528-533. Major, D.J., Johnson, D.R., Tanner, J.W. and Anderson, I.C., 1975. Effects of daylength and temperature on soybean development. Crop Sci., 15: 174-179. Monteith, J.L. and Scott, R.K., 1982. Weather and yield variation of crops. In: K. Blaxter and L. Fowden {Editors), Food, Nutrition and Climate. Applied Science Publishers, Barking, Great Britain, pp. 127-149.
18
Muchow, R.C., 1985. Canopy development in grain legumes grown under differentsoilwater regimes in a semi-aridtropicalenvironment. Field Crops Res., 11: 99-109. Musser, R.L.,Thomas, S.A. and Kramer, P.J.,1983. Short and long term effectsof root and shoot chillingof Ransom soybean. Plant Physiol.,73: 778-783. Musser, R.L.,Kramer, P.J.and Thomas, J.F.,1986.Periodsof shoot chillingsensitivityin soybean flower development, and compensation in yieldafterchilling.Ann. Bot.,57: 317-329. Purcell,L.C.,Ashley,D.A. and Boerma, H.R., 1987.Effectsof chillingon photosyntheticcapacity, and leafcarbohydrate and nitrogen statusof soybean. Crop Sci.,27" 90-95. Seddigh, M. and Jolliff,G.D., 1984. Night temperature effectson morphology, phenology, yield and yieldcomponents of indeterminate field-grownsoybean. Agron. J.,76: 824-828. Sinclair,T.R., Spaeth, S.C. and Vendeland, J.S.,1981. Microclimate limitationsto crop yield.In: M.H. Miller,D.M. Brown, and E.G. Beauchamp (Editors),Breaking the Climate/Soil Barriersto Crop Yield.Univ. of Guelph, Ontario,Canada, pp. 3-27. Specht, J.E. and Williams,J.H., 1984.Contribution of genetictechnology to soybean productivity - retrospectand prospect.In W.R. Fehr (Editor),Genetic Contribution to Yield Gains of Five Major Crop Plants.American Society of Agronomy, Madison, WI, Spec. Publ. 7, pp. 49-74. Specht, J.E.,Williams,J.H. and Weidenbenner, C.J.,1986. Differentialresponsesof soybean genotypes subjectedto a seasonalsoilwater gradient.Crop Sci.,26: 922-934. Thomas, J.F. and Raper, C.D., Jr.,1978. Effect of day and night temperatures during floralinduction on morphology of soybeans. Agron. J.,70: 893-898. Thomas, J.F. and Raper, C.D., Jr.,1984. Photoperiod regulationof floralinitiationfor soybean plants at differentages.Crop Sci.,24: 611-614. Van Schaik, P.H. and Probst, A.H., 1958. Effectsof some environmental factorson flower production and reproductiveefficiencyin soybeans. Agron. J.,50: 192-197. Wilcox, J.R.,Schapaugh, W.T. Jr.,Bernard, R.L., Cooper, R.L., Fehr, W.R. and Niehaus, M.H., 1979. Genetic improvement of soybeans in the Midwest. Crop Sci.,19: 803-805.
9
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Phenological Responses of Old and Modern Soybean Cultivars to Air Temperature and Soil Moisture Treatment
J.R. FREDERICK, J.T. WOOLLEY, J.D. HESKETH and D.B. PETERS
Dept. o/Agronomy, University o/Illinois, S-215 Turner Hall, 1102 South Goodwin Avenue, Urbana, Illinois 61801 (U.S.A.) (Accepted 25 October 1988)
ABSTRACT
Frederick, J.R., Woolley, J.T., Hesketh, J.D. and Peters, D.B., 1989. Phenological responses of old and modern soybean cultivars to air temperature and soil moisture treatment. Field Crops Res., 21: 9-18. Soil moisture deficits and low air temperatures frequently result in crop yield losses in the United States. Understanding how older and newer soybean (Glycine max (L.) Merr. ) cultivars differ in phenological development under various environmental conditions may aid in the selection of higher-yielding cultivars and in the development of simulation models for field-grown soybean. In this study, we examined the phenological responses of two widely adapted older ('Dun field' and 'Manchu') and two more-recent ('Clark 63' and 'Williams 82') soybean cultivars to soil moisture deficit and monitored the development of these cultivars as a function of air temperature. These cultivars were grown under drought stress and irrigation on a Flanagan silt loam soil at Urbana, Illinois, in 1984 and 1985. The soil moisture-deficit treatment was begun approximately 2 weeks before initial flowering (R1 stage) and was continued until harvest maturity. Drought stress reduced the final number of mainstem nodes due to a decrease in the rate at which the nodes were produced, but had little effect on the date of termination of node formation. Except for Manchu, no association was observed between the number of nodes produced under irrigation and the magnitude of the decrease in node number due to drought stress. Although the correlation between cumulative growing degree-days and mainstem node formation was high, little difference was found between the old and modern cultivars in their responses to air temperature. A period of low temperatures during early flower formation in 1985 appeared to have partially contributed to a delay in flower appearance of each cultivar. The results from this study show that the old and modern cultivars do not differ in their phenological responses to drought stress. *Contribution from the Dep. of Agronomy, Illinois Agric. Exp. Stn., Univ. of Illinois, and USDAARS, Urbana, IL 61801, U.S.A.
0378-4290/89/$03.50
© 1989 Elsevier Science Publishers B.V.
10 INTRODUCTION Soil moisture deficits and sub-optimal air temperatures are two of the leading causes of crop yield losses in the United States (Boyer, 1982 ). Both of these environmental limitations affect reproductive and vegetative development. Therefore, an understanding of the phenological responses of crop plants to these environmental conditions is needed before crop growth and development can be accurately predicted. The rate of mainstem node formation in soybean (Glycine max (L.) Merr. ) has been shown to depend on the air temperature of the canopy environment (Hesketh et al., 1973 ), with low temperatures inhibiting leaf initiation {Thomas and Raper, 1978; Musser et al., 1983). Reproductive development is affected by low temperatures, with delays in flowering being reported for determinate soybean grown under controlled conditions {Thomas and Raper, 1978; Musser et al., 1983) and for field-grown indeterminate soybean (Major et al., 1975; Seddigh and Jolliff, 1984). Low air temperatures may affect reproductive development by increasing flower abscission (Musser et al., 1986) and by decreasing leaflet photosynthetic rate {Purcell et al., 1987) and stomatal conductance (Musser et al., 1983). Soil moisture deficits have been reported to alter the partitioning of photosynthate in crop plants, resulting in an increase in the root:shoot ratio (Begg and Turner, 1976). Consequently, fewer mainstem nodes in soybean are produced under drought stress (Korte et al., 1983; Kadhem et al., 1985; Muchow, 1985). Decreases in node number, and consequently leaf number, under drought stress would decrease the photosynthetically active leaf area and the interception of radiation by the crop canopy, which may ultimately decrease seed yield (Sinclair et al., 1981; Monteith and Scott, 1982). Whether the number of nodes is decreased depends on the stage of crop development at which the drought stress is imposed, with competition for photosynthate between vegetative and reproductive sinks limiting node and leaf development {Jordan, 1983). Under most soil moisture conditions, higher seed yields may be obtained if the rate of mainstem node appearance is increased, thus allowing a greater period for reproductive growth at each mainstem node. This may particularly be the case for indeterminate soybean, in which the main stem produces a larger proportion of the total seed yield than in determinate soybean {Board, 1987). However, only limited research has been conducted to monitor the effects of prolonged soil-moisture deficit on the rate and the duration of node formation. In the study presented here, we grew two old and two modern soybean cultivars under field conditions, first to monitor throughout the growing season their phenological development as a function of air temperature under drought stress and irrigation, and second to determine whether the widely adapted, old and new soybean cultivars differ in their phenological responses to soil moisture treatment.
11 MATERIALS AND METHODS
Phenological data were collected at Urbana, Illinois, in 1984 and 1985 from plants grown on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll) soil. This soil has a high soil water-table and a profile conducive to deep rooting, which allowed the soil moisture-deficit treatment to increase gradually during reproductive development (Frederick, 1987). Treatments were assigned in a split-plot factorial arrangement in a randomized complete block design with three replications. The two soil moisture treatments {soil moisture deficit and natural rainfall plus supplemental irrigation) represented whole plots, with indeterminate soybean cultivars as subplots. Cultivars evaluated were 'Manchu' (released 1911 ), 'Dunfield' (1927), 'Clark 63' (1963) and 'Williams 82' (1982). Manchu, Dunfield, and Williams 82 are classified as Maturity Group III cultivars and Clark 63 as an early-maturing member of Group IV. These cultivars were selected on the basis of their seed yield stability over environments and because of their adaptation to Illinois soybean-production regions. Williams has previously been observed to have a high stability in yield over test environments compared to other modern cultivars (Cooper, 1981; Specht et al., 1986). The wide adaptation of Williams to Midwest production regions has been suggested to be partially due to its low sensitivity to less than optimum water conditions (Specht et al., 1986). On the other hand, the wide adaptation of Clark, the recurrent parent of Clark 63, has partially been attributed to its tolerance to low night temperatures (Van Schaik and Probst, 1958). The stability of yield over test environments of Manchu and Dunfield has been shown to be equal to that of more-recent cultivars (Wilcox et al., 1979). Manchu and Dunfield were also selected for this study because they were widely grown in Illinois until they were replaced by superior cultivars (Wilcox et al., 1979), and because they represent two of a limited number of soybean introductions that form the genetic base of a large number of recently developed cultivars (Specht and Williams, 1984). The soybean seed was hand-planted on 29 May and 30 May in 1984 and 1985, respectively, in 76-cm-spaced rows as described by Frederick (1987). After emergence the soybean stands were thinned to 26 plants m-1 row. Because soil moisture deficit develops slowly in this soil, the soil moisture deficit treatment was initiated approximately 2 weeks before first flowering (Fehr et al., 1971 ) and was continued until harvest maturity. On days rainfall occurred, wetting of the soil was prevented by stretching polyethylene film between the soybean rows, thus diverting most of the rainwater to a collection system. The film was folded up on days when no precipitation occurred. When 7 days occurred with less than 25 mm of rain, the plots receiving natural rainfall were irrigated using garden dripper hoses. Irrigation was applied four times in 1984 (33-34, 52-53, 78-79, and 91-92 days after planting) and once in 1985 (43-44
12 days after planting). Irrigation was continued until the upper 15 cm of soil was saturated, as indicated by gypsum blocks placed at that depth (Frederick, 1987). To avoid differences in lodging effects among cultivars, lodging was prevented by twine placed on both sides of the crop row. Vegetative and reproductive development (Fehr et al., 1971 ) were monitored weekly throughout the growing season. Ratings were made twice weekly during the week before and the week after initial flowering (R1 stage) and the termination of vegetative mainstem growth, and once weekly for the remainder of the growing season. Growth stages were monitored on two sets of 10 plants from each cultivar within a replication. The mean of the 20 plants in each subplot was used in the growth-stage analysis. Data collected during the apparent linear phase of node appearance were analyzed by linear regression analysis to determine the relationship between node formation and cumulative growing degree-days. The mean of 20 plants in each subplot was used in the linear-regression analysis. Growing degree-days (°Cd) for each day were estimated as the average of the daily maximum and minimum temperature, with a minimum growth threshold temperature of 10°C and temperatures above 30 ° C being counted as 30 ° C. Air-temperature data were collected at a weather station located approximately 200 m from the experimental site. The date of initial flowering (R1 stage ) and the final number of mainstem nodes produced were analyzed as a split-plot factorial to determine if there were significant treatment differences. A Waller-Duncan's LSD was calculated to compare cultivars within each soil moisture treatment for those variables in which a significant cultivar effect was observed. Significance for the LSD was set at a k ratio of 100: 1. RESULTSAND DISCUSSION Precipitation was below normal in 1984 with near-normal air temperatures (Frederick, 1987). In contrast, many of the days in 1985 were overcast (irradiance lower than in 1984) with above-normal rainfall and below-normal air temperatures observed in that year. Soil moisture potentials of both soil moisture treatments were lower in 1984 than in 1985 at all soil depths (Frederick, 1987 ). In the drier year of 1984, average seed yield of Williams 82 and Clark 63 under irrigation was 43% higher than the average yield of the older cultivars, but no significant differences in seed yield were observed among cultivars under drought stress (Frederick, 1987). Similar trends were observed in 1985, with the newer cultivars yielding 19% more than the older cultivars under irrigation, but under drought stress having only a greater yield than Dunfield. Average seed yield decreases due to drought stress were 30 and 8% in 1984 and 1985, respectively. Mainstem node-number responses to soil moisture treatment are shown in Table 1. Averaged over all cultivars, final node numbers were reduced 26 and 11% by soil moisture deficit in 1984 and 1985, respectively. Dunfield had the
13 TABLE 1 Effect of soil moisture t r e a t m e n t on m a i n s t e m node n u m b e r of each soybean cultivar in 1984 a n d 1985 Cultivar
1984 D1
1985 I
D/I
D
I
(%)
D/I
(%)
Williams 82 Clark 63 Dunfield Manchu
10.3 11.2 10.2 10.9
14.2 15.3 14.6 13.8
72.5 73.2 69.9 79.0
13.6 14.8 13.1 12.9
15.2 16.9 15.0 14.1
LSD 2
--
--
--
Effects 3
M**
1.4 M**
1.2 C**
89.5 87.6 87.3 91.5
' T r e a t m e n t s : D = drought stress, I = irrigation. 100) for comparison of cultivars within a soil moisture t r e a t m e n t . 3M, C, a n d M × C represent significance of soil moisture, cultivar, a n d interaction effects, respectively, with * a n d ** indicating significance at the 0.05 a n d 0.01 levels, respectively. T r e a t m e n t effects not listed were not significant. 2 L S D (k----
greatest percentage decrease in node number in both years and Manchu the least, although cultivar differences in the reduction of the number of nodes were small. These responses are similar to those reported in other studies in which an increase in the number of mainstem nodes was observed for several indeterminate cultivars when irrigation was applied during early flowering or throughout reproductive development (Korte et al., 1983; Kadhem et al., 1985 ). Across years in our study, little association was observed between the number of nodes formed under irrigation and the percentage reduction in node number due to drought stress, with the exception of Manchu, which had the fewest number of nodes and smallest decrease due to drought stress. The responses of mainstem node number to cumulative ° Cd for the droughtstressed and irrigated plants in 1984 and 1985 are shown in Figs. 1 and 2, respectively. In both years, the decrease in final node number due to drought stress was primarily the result of a reduction in the rate at which the nodes were produced. The termination of node appearance was only slightly hastened by drought stress even in the drier year of 1984. The time of cessation of node formation was similar among cultivars in 1984, but in 1985 the termination of node formation was slightly earlier for the older cultivars. Since the older cultivars reached physiological maturity earlier than the modern cultivars in both years (Frederick, 1987), there was little association between the termination of reproductive and vegetative growth for the cultivars we examined. Averaged over cultivars, the terminal nodes appeared 72 and 75 days after planting in
14 20
20 I: Y = - 6 . 1 0 D: Y = - 3 . 5 9
+ 0.0229X + 0.0161X
r 2 = 0.99 r 2 = 0.86
1: Y = - 5 . 5 8 D: Y = - 3 . 4 2
+ 0.0223X + 0.0159X
r 2= 0.99 r 2 = 0.96
16
16 ~2
Z
I "
12
~12 22 7_
D•
4
.
•
~
WILMAMS 82
•
CLARK 63
J
z
400
200
~'"
A
600
800
1000
0 200
4;0
6;0
a;o
1;oo
20,
20I: Y = - 5 . 0 7 D: Y = - 2 . 2 2
+ 0.0223X + 0.0148X
r2= 0.98 r2 = 0.93
16
16!
I: Y = - 5 . 1 7 D: Y = - 3 . 4 1
+ 0.0219X + 0.0166X
r2= r2=
0.98 0.96
y-'l j.
12: D
Z ~ 8 o Z
8~ 4
DUNFIELD
|
200
400
600
1300
1000
C U M U L A T I V E G R O W I N G D E G R E E DAYS
4 ~ 01 200
|
-
400
MANCHU
600
800
1000
C U M U L A T I V E G R O W I N G D E G R E E DAYS
Fig. 1. Node number as a function of cumulative growingdegree-days (base temperatureof 10 °C) for the irrigated (I) and drought (D )-treated Williams 82, Clark 63, Dunfield, and Manchu soybean plants in 1984. 1984 and 1985, respectively, with these dates corresponding to an accumulation of 940 and 895 °Cd. Therefore, the higher temperatures in 1984, in addition to earlier flowering dates, may have contributed to an earlier termination of node formation in that year. For all cultivars, soil moisture treatments, and years, regression r 2 values were high (range of 0.86 to 0.99) for the apparent linear region of node formation (Figs. i and 2 ). Although not presented, similar linear trends were also found for mainstem node number versus the number of days after planting because the accumulation of degree-days was relatively constant throughout most of the growing season in both years. In 1984, soil moisture deficit reduced the rate at which the nodes were initiated and the final number of nodes produced. However, only small differences were observed among cultivars in the magnitude of the rate reduction. Among cultivars, little association was also observed between the rate of node appearance (Figs. 1 and 2) and the final number of mainstem nodes produced (Table 1 ), indicating that the duration of node formation was also important in determining the final node number. In 1985 similar trends were found, but the differences in appearance rate between drought-stressed and irrigated plants were smaller. Times of initial flowering (R1 stage) are shown in Table 2. The number of
15 20,
20~- I: Y = -3.88 + 0.0209X r2 = 0.97 D: Y = -4.26 + 0.0199X r2 = 0.97 16
I: Y = -4.12 + 0.0216X r 2 = 0.99 D: Y -3.90 + 0.0207X r 2 0.99
12
~12
~
I"
-'"" "
M ,.
S 82
CLARK 63
Z
200 20 r~ r.l
460
I: Y = - 3 . 8 3 D: Y = - 3 . 5 1
660
860
+ 0.0213X + 0.0196X
zoo
1000
460
860
16oo
20 DII Y = -3.72 + 0.0205X r 2 : 0 . 9 9 Y - -3.67 + 0.0201X r2-- 0.99 16 ..
r2= 0.99 r2 = 0.97
16
12
~12
I D I
Z r--, o z
660
, y .,-""
"
•
8 •~
4
E
L
i
D
MANCHU lb
200
460
660
86o
o 200
16oo
•
460
660
860
1600
CUMULATIVE GROWING DEGREE DAYS
CUMULATIVE GROWING DEGREE DAYS
Fig. 2. Node number as a function of cumulative growing degree-days (base temperature of I0 °C) for the irrigated (1) and drought (D )-treatedWilliams 82, Clark 63, Dunfield, and Manchu soybean plants in 1985.
TABLE 2 Effect of soil moisture treatment on initial flowering date (days after planting) for each soybean cultivar in 1984 and 1985 (cumulative °Cd in parentheses) Cultivar
1984 D1
Williams 82 Clark 63 Dunfield Manchu LSD 2
Effects3
39 42 44 37
1985 I
{503) (551) (576) (487)
3 M*
40 43 46 39
D (515) (562) (606) ( 503 )
2 C**
52 55 54 50
I (613) (646) (635) (583)
3
51 53 55 50
(598) (624) (646) ( 583 )
3 C**
1Treatments: D -- drought stress, I = irrigation. 100) for comparison of cultivars within a soil moisture treatment. 3M, C, and M X C represent significance of soil moisture, cultivar, and interaction effects, respectively, with * and ** indicating significance at the 0.05 and 0.01 levels, respectively. Treatment effects not listed were not significant. 2LSD (k----
16 days to, and the number of cumulative ° Cd needed for, first-flower appearance were only slightly reduced by soil moisture deficit in 1984. The lack of responses in 1985 and small responses in 1984 probably occurred because the soil moisture treatment was initiated only 2 weeks before the R1 stage and a significant soil moisture deficit had not developed during the flower-formation period. Over both years, little association was found between the number of nodes formed and the onset of flowering. Averaged over all cultivars in 1984, the R1 stage was observed at vegetative (V) stages 5.7 and 7.2 under drought stress and irrigation, respectively. On the other hand, the R1 stage for the drought-stressed and irrigated plants was observed at the V8.3 and V8.8 stages, respectively, in 1985. In both years, the number of nodes that had formed by the time of initial flowering under irrigation was greatest for Dunfield, followed by Clark 63, Williams 82, and Manchu. However, under soil moisture deficit the ranking of the cultivars differed between years. Therefore, under the conditions of this experiment, flower appearance was independent of the stage of vegetative development. These data agree with the results of Thomas and Raper ( 1984 ), which showed that flower formation was independent of the vegetative stage in which the plants were photo-induced. In 1984, average initial flowering occurred after 529 (9 July) and 547 (11 July) ° Cd had accumulated for the drought-stressed and irrigated plants, respectively. In contrast, 619 (22 July) and 613 (21 July) °Cd had accumulated before initial flowering was observed for the drought-stressed and irrigated plants in 1985. To help explain this difference, data of Table 3 show the degreedays accumulated and air temperature data for days 13 through 60 after planting in both years. Between days 12 and 21 in 1985, a period of low temperatures caused a reduction in the rate of degree-day accumulation. On the other hand, no decrease in the accumulation of degree-days was observed during the same time period in 1984. The average daily degree-days accumulated during this period were approximately twice as great in 1984 as in 1985. In contrast, the average degree-days accumulated per day for days 21 through 60 were s i m i l a r between years. Because the lengths of both the flowering delay and the period TABLE3 Temperature
data during the period of flowerformation (days after planting) in 1984and 1985
T e m p e r a t u r e (days 1 3 - 2 0 ) : Average maximum Average minimum Mean d e g r e e - d a y s day-': Days 13-20 Days 21-60
1984
1985
31.3 ° C 18.9 ° C
21.5 ° C 12.0 ° C
13.4 12.5
6.8 12.3
17
of low temperatures were similar in 1985, it appears that the low temperatures may have contributed to a delay in flower formation. These data are in agreement with other workers who have observed that low temperatures occurring during early phenological development of chamber-grown soybean result in delays in initial flowering (Musser et al., 1986). In contrast, it can be seen from our data in Fig. 1 and 2 that the number of nodes formed after 300 ° Cd had accumulated (after low-temperature period) was similar between years, indicating a linear relationship between cumulative ° Cd and mainstem node formation. The results from this study have provided insight into the phenological responses of several field-grown soybean cultivars to soil moisture treatment. Although soil moisture deficit reduced the rate of appearance and the final number of mainstem nodes, it had little effect on the date of termination of node formation. A high correlation was found between cumulative growing degree-days and mainstem node formation, but little difference was observed between the old and modern cultivars in their response to air temperature. The data indicate that low-temperature stress occurring early in flower development may delay flower appearance. The small differences in node appearance rate and initial flowering between the old and modern cultivars suggest that future seed yield increases may be achieved in soybean without changing their phenological development. REFERENCES
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Muchow, R.C., 1985. Canopy development in grain legumes grown under differentsoilwater regimes in a semi-aridtropicalenvironment. Field Crops Res., 11: 99-109. Musser, R.L.,Thomas, S.A. and Kramer, P.J.,1983. Short and long term effectsof root and shoot chillingof Ransom soybean. Plant Physiol.,73: 778-783. Musser, R.L.,Kramer, P.J.and Thomas, J.F.,1986.Periodsof shoot chillingsensitivityin soybean flower development, and compensation in yieldafterchilling.Ann. Bot.,57: 317-329. Purcell,L.C.,Ashley,D.A. and Boerma, H.R., 1987.Effectsof chillingon photosyntheticcapacity, and leafcarbohydrate and nitrogen statusof soybean. Crop Sci.,27" 90-95. Seddigh, M. and Jolliff,G.D., 1984. Night temperature effectson morphology, phenology, yield and yieldcomponents of indeterminate field-grownsoybean. Agron. J.,76: 824-828. Sinclair,T.R., Spaeth, S.C. and Vendeland, J.S.,1981. Microclimate limitationsto crop yield.In: M.H. Miller,D.M. Brown, and E.G. Beauchamp (Editors),Breaking the Climate/Soil Barriersto Crop Yield.Univ. of Guelph, Ontario,Canada, pp. 3-27. Specht, J.E. and Williams,J.H., 1984.Contribution of genetictechnology to soybean productivity - retrospectand prospect.In W.R. Fehr (Editor),Genetic Contribution to Yield Gains of Five Major Crop Plants.American Society of Agronomy, Madison, WI, Spec. Publ. 7, pp. 49-74. Specht, J.E.,Williams,J.H. and Weidenbenner, C.J.,1986. Differentialresponsesof soybean genotypes subjectedto a seasonalsoilwater gradient.Crop Sci.,26: 922-934. Thomas, J.F. and Raper, C.D., Jr.,1978. Effect of day and night temperatures during floralinduction on morphology of soybeans. Agron. J.,70: 893-898. Thomas, J.F. and Raper, C.D., Jr.,1984. Photoperiod regulationof floralinitiationfor soybean plants at differentages.Crop Sci.,24: 611-614. Van Schaik, P.H. and Probst, A.H., 1958. Effectsof some environmental factorson flower production and reproductiveefficiencyin soybeans. Agron. J.,50: 192-197. Wilcox, J.R.,Schapaugh, W.T. Jr.,Bernard, R.L., Cooper, R.L., Fehr, W.R. and Niehaus, M.H., 1979. Genetic improvement of soybeans in the Midwest. Crop Sci.,19: 803-805.