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DOI https://doi.org/10.18551/rjoas.2018-05.39
THE ROLE OF SEED SIZE AND NITROGEN IN THE DEVELOPMENT OF GLYCINE MAX (L.) MERRILL
Trindade Aneceto Mascarenhas
Master's Program in Agriculture, Faculty of Agriculture, University of Brawijaya & Betano Institute of Polytechnic, Indonesia E-mail: babuloaneceto78@gmail.com
ABSTRACT
This research aimed to study the role of sink capacity approached from genotype with the seed size in the development and the result of soybean (Glycine max (L.) Merrill). This research was conducted during October 2017 - January 2018 at Indonesian Legume and Tuber Crops Research Institute of East Java. The experimental field sat at 400 meters above sea level, its type of soil was regosol with brown-gray color. This research result concluded that there was no interaction between seed size and nitrogen dose to the growth or result of soybean, sink capacity approached from seed size has an influence on the growth and the result of soybean: plant height, total leaves, weight of wet stover, weight of dry stover, total root nodules, number of nodes, number of productive branches, harvest dates, number of pods per sample, weight of 100 g seed.
KEY WORDS
Seed size, nitrogen, soybean, plant growth, legumes.
Soybean (Glycine max (L.) Merrill) is one the important food crops in Indonesia because of containing nutrition which among other is protein reaching up to 30 - 50%, carbohydrate by 35% and fat by 15%. Soybean is one of the sources of vegetable protein, as the raw material of agro industry like tempeh, tofu, tauco, soy sauce, soybean milk and for livestock food needs (Rohmah and Saputro, 2016). The massive soybean utilization causes the domestic demands are getting higher regarding the increase of total people and society's knowledge. This continuously-increasing demands cannot be fulfilled yet by domestic production since the productivity of soybean is still low and tends to not be stable. Soybean production in 2015 was amounting to 963.183 ton ha-1, while the soybean needs per year were less than of 2,300,000 ton seeds. The lack of those needs must be completed by an importing policy (Anonymous, 2015).
One of the obstacles of soybean culture is the problem variety since every variety has a different genetic variation so that resulting in a different characteristic of production ability. For that matter, variety selection holds an important role in the soybean cultivation to achieve high productivity level. Therefore, the use of high-quality variety is the most basic way to increase plant production Sumarno and Hananto (as quoted in Efendi, 2010).
One of the physiological approaches for plant productivity improvement is using the concept of source and sink. The source is an organ or tissue generator or photosynthates exporter, while the sink is the importer or the receiver of photosynthate. Sink capacity and source strength is a physiological characteristic considered the main controller of soybean result. The main source of soybean is leaves, while its main sink is seed.
Seed is one of the factors that determine the success of plant cultivation whose role cannot be changed by another factor since it functions as plant material and genetically potential. Haznah's (2013) research shows that seed size has a significant influence on the plant growth. Large seed influences the best height growth compared to the medium and small seed. Good seed growth will bring the good growth and the result as well.
Indonesia's soybean is categorized having higher protein content than imported soybean. The protein content of local soybean is 39-40% while imported soybean is only 3537% Banaszkiewica (as quoted in Sarama, Anas, and Asrida, 2014). High content of protein of soybean seed indicates that soybean needs high trace element, but soybean's needs of
nitrogen is different depending on the variety cultivated, thus, Efficiency of Nitrogen Uptake (ENU) in soybean needs to be known to determine the dose of fertilizer use which is in accordance with plant needs, to increase the efficiency of nitrogen uptake by soybean and the resulting productivity.
This research aims to: (1) learn sink capacity approached from genotype with seed size to the result and growth of soybean (Glycine max (l.) Merrill), (2) learn the role of source strength approached by nitrogen providence to the growth and result of soybean (Glycine max (L.) Merrill).
METHODS OF RESEARCH
This research was conducted in October 2017 until January 2018 at Indonesian Legume and Tuber Crops Research Institute (ILETRI) in Kendal Payak Village, Pakisaji Subdistrict, Malang District - East Java. The experimental field sat at 400 meters above sea level, its type of soil was regosol with brown-gray color. The average weather was 22 - 280C. The average humidity was 83.2 % per year, the average relative humidity was 82-93.5% and the average rainfall was 1.255-1.845 m3 dt-1. Materials used to conduct this research were 6 varieties, i.e. Brawijaya 1 and Grobogan variety (large seed), Brawijaya 2 and Gema variety (medium seed), Tidar and Ringgit variety (small seed), fertilizer urea, TSP fertilizer, KCL fertilizer and manure, insecticide, pesticide.
This research used Randomized Complete Block Design (RCB) arranged in a factorial way with 3 repetitions within treatment placement in an experimental plot. The treatment consisted of 2 factors, the first factor was the seed size with 3 levels: Small Seed (Brawijaya 1 and Grobogan), Medium Seed (Brawijaya 2 and Gema), Small Seed (Tidar and Ringgit), the second factor was nitrogen dose: N1 (50 kg N ha-1, 50 kg P ha-1, 50 kg K ha -1), N2 (manure, 100 kg N ha-1, 50 kg P ha -1, 50 kg K ha). The entire total of the experimental plot was 36 plots.
The field research was processed using a plow. Weed and stover were sunk into the ground and then left for a week, and was processed once again using a harrow. The next step was making a 1.6 x 3.7 m bed. Among the bed was created a drainage channel by 30 cm x 50 cm deep. The plantation was conducted using dibble, within a 2 cm deep, the planting distance was 40 cm x 15 cm, every planting whole was grown one similar plant. The ingrown seed was replaced after 4-7 days old. Fertilizer application was applied based on the treatment. N1 (50 kg N ha-1, 50 kg P ha-1, 50 kg K ha -1) treatment, fertilizer application was conducted 3 times, the first fertilizer application was doing when planting time, consisting of 9.8 gram of urea, 29.6 gram of TSP and 29.6 gram of KCL for each plot; the second and the third fertilizer application was applying nitrogen fertilizer by 9.8 gram/plot. N2(manure, 100 kg N ha-1, 50 kg P ha -1, 50 kg K ha), fertilizer application was conducted three times; the first application was at the planting stage consisting of manure by 1.776 kg/plot, nitrogen fertilizer by 19.73 gram/plot, TSP and KCl was 29.6 gram/plot for each; the second and the third application was using nitrogen fertilizer for each 19.73 gram/plot.
Plantation maintenance covers: (1) irrigation was carried out by damming drainage channels among the dam until the water flood the bed, and then was opened again. Flooding can be carried out every week or 5 times when it 0,14, 28, 42 and 56 days old after planting, or 3 times at 0, 14, and 28 days after planting, (2) replacing was carried out a week after planting to replace dead seeds or having bad growth with the new ones have been prepared with various condition, (3) hand weeding was carried out 2 times, that was 2-4 weeks after planting and the flower bloom, (4) pest and disease handling was carried out if there was an attack indication by spraying pesticide. The observation was applied to the 8 samples. The changer observed in this research was: (1) plant height, (2) numbers of pods per sample, (3) total leaves, (4) leaf area, (5) weight of wet stover, (6) weight of dry stover, (7) total root nodules, (8) number of nods, (9) number of productive branches, (10) chlorophyll content, (11) short flowering, (12) harvest dates, (13) numbers of pods per sample, (14) seed weight per sample, (15) weight of 100 seeds.
RESULTS OF STUDY
Plant Height. There was no interaction between the combination of seed size and N dose to the plant height. Seed size had an influence on the plant height by 3, 4, 5, 6 weeks after planting (WAP), Nitrogen dose had an influence on plant height by 4, 5, and 6 WAP. The average plant height can be seen in Table 1. The research result revealed that the large seed represented by Brawijaya 1 and Grobogan variety produced higher plant than that of medium seed (Brawijaya 2 and Gema variety) and small seed (Tidar and Ringgit variety) on average. Table 1 above indicates that the average highest plant height is obtained in V1 treatment (Brawijaya 1).
Table 1 - The Average Plant Height of the Influence of Seed Size and Nitrogen Dose in the Various
Observation Ages
Treatment Plant Height (WAP)
3 4 5 6
Type of Variety
V1 18.60 e 28.56 d 40.35 c 55.40 c
V2 16.85 cd 26.13 c 38.63 c 51.96 c
V3 17.42 de 26.77 cd 40.75 c 55.69 c
V4 15.15 b 21.44 b 33.25 b 45.58 b
V5 11.71 a 18.15 a 28.29 a 39.73 a
V6 15.44 bc 23.31 b 34.38 b 46.46 b
LSD 5% 1.414 2.325 3.928 4.250
Nitrogen Dose
N1 15.67 23.38 a 34.78 a 47.73 a
N2 16.05 24.74 b 37.10 b 50.54 b
LSD 5% nd 1.343 2.268 2.454
Note: the same number in the same column shows no significant difference according to the LSD test of 5% level; nd = no significant difference at LSD test of 5% level.
According to Table 1, the supply of 100 kg N ha-1 results in higher plant and very significance different compared to the fertilizer supply of 50 kg N ha-1. This research result revealed that the higher the dose of nitrogen supplied, the higher the soybean height.
Total Leaves. There is no interaction between the combination of seed size and N dose to the soybean total leaves. Seed size had a significant influence on the total leaves at 3, 4, 5, and 6 WAP, N dose had a significant influence on the total leaves at the age of 3 and 4 WAP. The average total leaves can be seen in Table 2.
Table 2 - The Average Total Leave of the Influence of Seed Size and Nitrogen Dose on the various
observation Ages
Treatment Total leaves (WAP)
3 4 5 6
Type of Variety
V1 10.42 a 15.56 a 23.40 a 32.94 a
V2 12.33 b 18.06 b 30.46 b 40.63 bc
V3 10.98 a 16.31 ab 26.88 a 38.44 abc
V4 9.33 a 14.27 a 22.23 a 35.73 ab
V5 9.63 a 14.46 a 25.13 a 43.83 c
V6 12.42 b 18.06 b 31.31 b 44.40 c
LSD 5% 1.875 2.441 4.857 6.790
Nitrogen Dose
N1 10.29 a 15.40 a 25.53 37.88
N2 22.41 b 16.85 b 27.60 40.78
LSD 5% 1.083 1.409 nd nd
Note: the same number in the same column shows no significance different according to the LSD test 5%; nd = no significant difference at LSD test 5%.
According to table 2, at the age of 3 and 5 WAP, the average total leaves of V2 (Grobogan variety) and V6 (Ringgit variety) is no significance different, however; the average total leaves of those two varieties was significance different with other fourteen varieties. The
average total leaves of V1, V2, V4 and V5 was not significance different. At the age of 4 WAP, the average total leaves in V2 (Grobogan variety), V3 (Brawijaya 2) and V6 (Ringgit variety) was no significance different, however; the average total leaves of those three varieties was significance different with other three varieties (V1 = Brawijaya, V4 = Gema, V5 = Tidar). At the age of 6 WAP, V5 (Tidar) and V6 (Ringgit) produced the highest total of leaves, but was no significance different with V2 (Grobogan) and V3 (Brawijaya 2). The average lowest total leaves were resulted by V1 plant (Brawijaya 1), even though no significance difference with V3 (Brawijaya 2) and V4 (Gema). The research result showed that generally small and large seed produced relatively more leaves than that of medium seed. Nitrogen dose gave the average total leaves significance different. The application of 100 kg N ha-1 resulted the average total leaves was more than the supply of 50 kg 100 kg N ha-1.
Leaf Area. Treatment combination of seed size and nitrogen dose revealed the occurrence of interaction in the observation result of leaf area. Seed size also had no influence on leaf area of soybean. Nitrogen dose had an influence on leaf area. According to Table 3, the application of 100 kg N ha-1 resulted in the average leaf area from the supply of 50 kg N ha-1.
Table 3 - The Average Leaf Area of the Influence of Seed Size and Nitrogen Doze
Nitrogen Dose Leaf Area (cm2)
N1 918.98 a
N2 1,353.07
LSD 5% 364.121
Note: the same number in the same column shows no significance different according to the LSD test 5%; nd = no significance different at LSD test 5%.
Weight of Wet Stover. Treatment combination of seed size and nitrogen dose showed an interaction towards soybean's weight of wet stover. Seed size had a significant influence on the weight of wet stover at all observation ages, while nitrogen dose had a significant influence on the weight of wet stover at the age of 6 WAP.
Table 4 - The Average Wet Stover Weight of the Influence of Seed Size and Nitrogen Dose
T t t Wet Stover Weight
_lreatment_4 WAP_6 WAP_
Type of Variety
V1 20.06 e 75.03 c
V2 16.06 de 68.10 bc
V3 14.26 cd 73.53 c
V4 11.75 bc 63.75 ab
V5 6.33 a 58.41 a
V6 10.16 ab 65.85 abc
LSD 5% 4.047 9.603
Nitrogen Dose
N1 12.37 64.50 a
N2 13.83 70.40 b
LSD 5% nd 5.544
Note: The same number in the same column revealed no significance difference at 5% LSD test.
According to Table 4, large seed, Brawijaya 1 (V1) and Grobogan (V2) variety, resulted in heavier wet stover weight than that of medium and small size, later on, medium size like Brawijaya 2 (V3) and Gema (V4) variety resulted in heavier wet stover weight than that of small seed, that was Tidar (V5) and Ringgit (V6). Nitrogen supply by 100 kg N ha-1 (N2) provided heavier wet stover weight than the supply of nitrogen by 50 kg N ha-1 (N1).
Weight of Dry Stover. Treatment combination of seed size and Nitrogen dose did not show an interaction to the dry stover weight of soybean. Seed size had a significant influence on dry stover weight at the age of 4 WAP, while the Nitrogen dose had no significant influence on dry stover weight. According to table 5, large seed, Brawijaya 1 (V1) and Grobogan (V2) variety resulted in heavier dry stover weight than that of medium and small
seed, moreover; medium seed like Brawijaya 2 (V3) and Gema (V4) resulted in heavier dry stover weight than small seed, that was Tidar (V5) and Ringgit (V6).
Table 5 - The Average Dry Stover Weight of The Influence of Seed Size and Nitrogen dose
Type of Variety Dry Stover Weight At The Age of 4 WAP
V1 4.92 e
V2 4.20 de
V3 3.76 cd
V4 2.97 bc
V5 1.59 a
V6 2.66 b
LSD 5% 0.868
Note: the same number in the same column shows no significance different according to the LSD test 5%; nd = no significance different at LSD test 5%.
Total Root Nodules. Treatment Combination of seed size and Nitrogen dose did not indicate interaction to the total root nodules. Seed size had a significant influence on total root nodules at all observation ages, while nitrogen dose had a significant influence on total root nodules at an observation of 4 WAP. According to Table 6, it could be explained that large and medium seed resulted in more average total root nodules than that of smaller one. The lowest total root nodules were gotten from smaller seed. The average total root nodules resulted in the supply of 50 kg N ha-1 nitrogen was higher and significance different from the 100 kg N ha-1 nitrogen supply.
Table 6 - The Average Total Root Nodules of the Influence of Seed Size and Nitrogen Dose
Total Root Nodules
4 WAP 6 WAP
Type of Variety
V1 26.71 b 78.33 b
V2 29.13 b 74.54 b
V3 32.50 b 67.21 ab
V4 27.79 b 81.50 b
V5 16.17 a 52.38 a
V6 18.38 a 64.08 ab
LSD 5% 8.286 19.033
Nitrogen Dose
N1 28.40 b 74.43
N2 21.82 a 64.92
LSD 5% 4.784 nd
Note: the same number in the same column shows no significance different according to the LSD test 5%;
nd = no significance different at LSD test 5%.
Number of Nodes. Treatment combination of seed size and nitrogen dose did not show
interaction to the number of nodes. Seed size and Nitrogen dose had a significant influence
on the number of nodes.
Table 7 - The Average Number of Nodes of the Influence of Seed Size and Nitrogen Dose
Treatment Number of Nodes
Type of Variety
V1 16.48 bc
V2 13.21 a
V3 17.52 c
V4 14.21 ab
V5 27.50 d
V6 26.04 d
LSD 5% 3.031
Nitrogen Dose
N1 18.05 a
N2 20.27 b
LSD 5% 1.750
Note: The same number in the same column revealed no significance difference at 5% LSD test.
According to the Table 7, it could be explained that small seed resulted in a higher number of nodes than that of medium and small seed on average. The lowest number of nodules was obtained within the larger seed, which was Grobogan variety (V2), even though no significance different from the number of nodes at Gema variety (V4). Tidar (V5) and Ringgit (V6) variety, those two resulted in a larger number of nodules. The average number of nodules obtained in the supply of 100 kg N ha-1 nitrogen was higher by 20.27 nodes and significance different from nitrogen supply by 50 kg N ha-1 that was 18.05 nodes.
Total productive Branches. Treatment combination of seed size with nitrogen dose did not show an interaction to the total productive branches. Seed size and nitrogen dose of each has a significant influence on the total of productive branches.
Table 8 - The Average Total Productive Branches of the Influence of Seed Size and Nitrogen Dose
Treatment Total productive Branches
Type of Variety
V1 3.21 b
V2 2.23 a
V3 3.35 b
V4 3.15 b
V5 4.17 c
V6 4.29 c
LSD 5% 0.506
Nitrogen Dose
N1 3.20 a
N2 3.60 b
LSD 5% 0.292
Note: The same number in the same column shows no significance different according to 5% LSD test.
Table 8 shows that the seed of Grobogan variety (V2) resulted in the lowest average of total productive branches, Tidar (V5) and Ringit (V6) variety produced the highest average of total productive branches. The application of 10 kg N ha-1 resulted in the lowest average of total productive branches.
Chlorophyll Content. Treatment combination of seed size and Nitrogen dose indicated the interaction to the chlorophyll content of soybean, so did the separated treatment of seed size. Nitrogen dose separately revealed the significance influent of chlorophyll content.
Table 9 - The Average Chlorophyll Content of the Influence of Seed Size and Nitrogen Dose
Nitrogen Dose
N1 1.94 a
_N2_2.15 b_
LSD 5% 0.189
Short Flowering. Treatment Combination of seed size and Nitrogen dose did not indicate an interaction to the short flowering of soybean, so did each separated nitrogen dose.
Harvest Dates. Treatment Combination of seed size and nitrogen dose did not indicate an interaction to the harvest dates. Each seed size and Nitrogen dose separately had an influence on the harvest dates.
Table 10 - The Average Harvest Dates of the Influence of Seed Size and Nitrogen Dose
Treatment harvest dates (DAP)
Type of Variety
V1 86.33 b
V2 80.00 aa
V3 86.50 b
V4 77.50 a
V5 79.00 a
V6 98.17 c
LSD 5% 4.212
Nitrogen Dose
N1 83.22 a
N2 85.94 b
LSD 5% 2.432
Note: the same number in the same column revealed no significance different according to the test of 5% LSD.
Table 10 explains that the seed of Grobogan (V2), Gema (v4) and Tidar (v5) variety resulted in quicker harvest dates, followed by Brawijaya 1 (V1) and Brawijaya 2 (V3) variety. Ringgit (V6) variety had lower harvest dates, that was 98.17 dap. Nitrogen supply of 100 kg N ha-1 caused longer harvest dates on average than the supply of 50 kg N ha-1 nitrogen.
Number of Pods per Sample. Treatment combination between seed size and nitrogen dose revealed an interaction to the number of pods per sample. Each of seed size and nitrogen dose showed a significant influence on the number of pods per sample. Table 11 indicates that the seed of Grobogan (V2) variety produces the lowest average number of pods per sample compared to other varieties. Tidar (V5) and Ringgit (V6) variety results in the highest average of the number of pods per sample.
Table 1 - The Average Number of Pods per Sample of the Influence of Seed Size and Nitrogen Dose
Treatment_Number of Pods Per Sample
Type of Variety
V1 56.63 b
V2 30.67 a
V3 51.69 b
V4 47.69 b
V5 84.83 c
V6 79.13 c
LSD 5% 9.187
Note: The same number in the same column shows no significance different according to 5% LSD test.
Weight of Seed per Sample. Treatment combination between seed size and nitrogen dose did not show an interaction towards weight of seed, so did the separated seed size treatment. Nitrogen dose separately indicated a significant influence on weight seed per sample.
Table 12 - The Average Weight Seed per Sample of the Influence of Seed Size and Nitrogen Dose
Nitrogen Dose Weight Seed per Sample
N1 11.18 a
N2 13.02 b
LSD 5% 1.110
Note: The same number in the same column shows no significance different based on the 5% LSD test; nd = no significance different at the 5% LSD test.
Table 12 shows that the supply of 100 kg N ha-1 nitrogen resulted in a higher average weight of seed than the supply of 50 kg N ha-1 nitrogen.
100 Seeds Weight. Treatment of seed size and nitrogen dose jointly did not indicate an interaction towards weight of 100 seeds. Seed size is significance different, while nitrogen dose did not significantly influence the weight of 100 seeds. Table 13 indicates that the seed of Grobogan (V2) variety produces the highest average of 100 seeds weight compared to other varieties. Tidar (V5) and Ringgit (V6) produce the lowest average of 100 seeds weight.
Table 13 - The Average of 100 Seeds Weight of the Influence of Seed Size and Nitrogen Dose
Treatment 100 Seeds Weight
Type of Variety
V1 12.22 b
V2 21.77 c
V3 11.87 b
V4 11.05 b
V5 6.08 a
V6 6.47 a
LSD 5% 1.927
Note: The same number in the same column shows no significance different based on the 5% LSD test; nd = no significance different at the 5% LSD test.
DISCUSSION OF RESULTS
Actually, the research result shows that the larger the seed size, the higher the plant and the more the total leaves. This is caused by a larger seed has a much more food reserve, thus resulting in much more energy for the growth process. This is line with what Magagula and Ossom's (2011) have explained that seed growth is truly influenced by total food reserves stored within the seed. Rahmawati and Saemong (2010) have also explained that seed size shows a food reserve, protein, mitochondria, speed/respiration ability/ ATP production and growth potential. Haznah's (2013) research revealed that seed size has a significant influence on the plant height growth from seed.
Leafe is the main source of the assimilate-producer plant. High-low source activity is characterized by photosynthesis ability. Photosynthesis activity is in relation to the source capacity characterized by a growth rate of leaf area index and chlorophyll content, which play an important role in determining soybean ability to absorb radiation and water photolysis process. This is in line with what Purnawati and Manshuri (2015) have said, through a photosynthesis process, plant assimilates carbon dioxide, assimilates result is then spread to all plant part for growth and development process. Assimilate is resulted from source, playing a role to hold metabolism, the source also functions to supply non-photosynthetic plant.
Assimilate produced by leaf is then translocated through phloem into the sink. Sink needs assimilate to its growth and the remaining is kept. The amount of photosynthates resulted by leaf is directly proportional to the sink size, divided into the vegetative and reproductive sink. Leaf activity improvement influences photosynthate quantity translocated into the sink, as a result, the sink size is getting larger, indicated by wet stover weight and dry stover weight, total root nodules, number of nodes, total productive branches, total nodes per sample and seed weight. Seed size has an influence on the rate growth and production. The amount of protein content within a plant is among other influencing growth rate and root development so that the root will grow bigger and result in a heavier weight.
The relationship between source capacity from the top of an active leaf and sink capacity influence dry goods production and determine field production (Kato et al, 2003). The sink's assimilate needs is a factor that determines photosynthesis rate, in addition to the environmental factor. After the canopy completely grows, CER is still able to increase and decrease in light to the sink needs change. If the sink strongly absorbs the assimilate, it causes carbohydrate gradient between source and sink is getting higher, this stimulates source to be more productive Gifford and Evans (as quoted in Yudiwanti et al, 2007). At the first of vegetative growth, the young foliage and root are the major sink in which at the part of the plant, the canopy dominates more root to obtain assimilate. At the reproductive stage, the growth and development of fruit and seed dominate canopy growth (Mardlaw, 1991).
The result of the future research shows that nitrogen dose has an influence on the height plant, total leaves, leaf area, root dry weight, wet stover weight, total root nodules, number of nudes, harvest dates, total productive branches, total nodes per sample and seed weight per sample. This is initiated by the sufficiency of nitrogen that can accelerate photosynthesis process so that the formation of leaf organs becomes quicker, and stomata conductivity towards CO2 and respiration rate. Even though given that trace nitrogen contained in the leaf does not directly play role in the photosynthesis, but this element is a photosynthesis compilation, the raw material in the photosynthesis process. According to Wibowo et.al (2012), total leaf area illustrates photosynthesis process running. The larger the total leaf area, the higher the photosynthesis process running, so that the formed photosynthesis will be much more.
This is supported by Hardianti's (2016) opinion that one of the factors influencing soybean growth is nitrogen element within the soil, in which needs for nitrogen must be sufficient for plant growth. According to Salisbury and Ross (1995), Adisarwanto (2005), that nitrogen is also an element of chlorophyll compilation as a machine of the photosynthesis process. Nitrogen is also a factor influencing photosynthesis rate. Limited nitrogen stock will prevert the formation chlorophyll and decrease the photosynthesis rate, as well as disturb plant metabolism. The similar opinion was proposed by Prawiranata et. al (1991), that
nitrogen element supply can increase photosynthesis rate so that can stimulate plant's vegetative growth. The increase of nitrogen amount within the soil results in a large amount of protein within the plant.
CONCLUSION
There is no interaction between seed size and nitrogen fertilizer dose to the growth or soybean result (Glycine max (L.) Merrill).
Sink capacity approached from seed size had an influence on the growth and soybean result: (1) plant height, (2) total leaf, in which at the age of 6 WAP, V5 (Tidar) and V6 (Ringgit) result in the highest total leaves, while the lowest total leaves resulted by V1 (Brawijaya 1), (3) root wet weight, in which V1 (Brawijaya 1 variety) and V2 (Grobogan variety) produce the heaviest weight, (4) root dry weight, large seed represented by Brawijaya 1 (V1) and Grobogan (V2) variety has a heaviest root dry weight, (5) wet stover weight, Brawijaya 1 (V1) and Grobogan (V2) variety result in heavier wet stover weight, (6) dry stover weight is larger, that is Brawijaya (V1) and Grobogan (V2) result in heavier dry stover weight, (7) total root nodules, large and medium seed produce larger total root nodules on average than that of the small, (8) number of nodes, (9) number of productive branches, (10) harvest dates, (11) number of pods per sample, (12) weight of 100 seeds.
Source strength approached by nitrogen dose has an influence on soybean growth: (1) plant height, in which the highest average is obtained from the supply of 100 kg N ha-1, (2) total leaves, the highest average is obtained from the application of 100 kg N ha-1, (3) leaf area, the highest average is obtained from the application of 100 kg N ha-1 (4) root dry weight, the highest average is obtained from the application of 100 kg N ha-1, (5) wet stover weight, the highest average is obtained from the application of 100 kg N ha-1 (6) total root nodules, the highest average is obtained from the application of 50 kg N ha-1, (7) number of nodes, (8) total productive branches, (9) chlorophyll content, (10) harvest dates, (11) number of pods per sample, (12) seed weight per sample.
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