Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2005
Volume 8
Issue 4
Topic:
Agronomy
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Helios W. , Kotecki A. 2005. EFFECT OF THE NITROGEN FERTILIZATION AND HARVEST DATE ON THE SEED SOWING VALUE IN PEA, EJPAU 8(4), #11.
Available Online: http://www.ejpau.media.pl/volume8/issue4/art-11.html

EFFECT OF THE NITROGEN FERTILIZATION AND HARVEST DATE ON THE SEED SOWING VALUE IN PEA

Waldemar Helios1, Andrzej Kotecki2
1 Department of Plant Cultivation, University of Agriculture in Wrocław, Poland
2 Department of Plant Cultivation, Wrocław University of Environmental and Life Sciences, Poland

 

ABSTRACT

In a three-factor experiment set up as a ‘split-plot’, at the RZD Pawłowice, in the vicinity of Wrocław, the following were investigated: the effect of: I – pea cultivar: Agra – semi-leafless and ‘Rola’, traditional – bipinnate leaves; II – nitrogen fertilization: 0, 30, 60 kg·ha-1; III – harvest date: green, yellow and full maturity, on the development of the seed sowing value. The cultivars researched did not differ in their germinative energy and germinability, while 1000 seed weight and leachate electroconductivity were higher in ‘Rola’ than in ‘Agra’. There was shown a positive effect of nitrogen fertilization at the dose of 30 kg·ha-1 on 1000 seed weight, while the other parameters of the sowing value did not depend on the sowing value of this factor. As ripening progressed, until full maturity, there was recorded a significant increase in 1000 seed weight, germinative energy and germinability and in vigor measured with the leachate electroconductivity. A positive correlation between 1000 seed weight and germinative energy and germinability of seeds and a negative correlation between the germinative energy, germinability, 1000 seed weight and the leachate electroconductivity after 12 and after 24 hours.

Key words: pea, sowing value, cultivars, nitrogen fertilization, harvest date.

INTRODUCTION

Due to its varied use and a high yielding potential, pea is considered as one of the most important legumes grown in Poland. In 2003 its plantation area covered 13.2 thousand ha, with the average yield of 2.01 t per 1 ha [11]. In Polish agricultural practice the use of pea cultivars yielding potential does not exceed 40%. In 2004 the pea standard yields in the Research Centre for Cultivar Testing (COBORU) experiments amounted to 6.49 t·ha-1 [3]. There are many reasons of low pea seed yields, mostly an inadequate plant density per 1 m2 and a delayed sowing date. This negligence cannot be made up for with any agronomic practices [24].

Only seeds of high quality assure an adequate course of germination, emergence and seedling development, and so affect the right stand density and the right plant ontogeny [28].

In seed production there is recorded a high variation in the seed quality [7], due to genetic (cultivar) variation, maternal variation, namely the place of pod setting on the plant and, as a result, a varied degree of seed [8] and ecological [26] maturity. The sowing value depends on the agronomic practices applied, including nitrogen fertilization.

By fixing free nitrogen, legumes become considerably independent of the fertilization with this nutrient [2]. There is a common belief that higher doses of nitrogen fertilizers applied under legumes are not economically justifiable as they limit the fixation of nitrogen and can prolong the vegetation period. More recent reports show that it is justifiable to apply higher nitrogen doses under high-yielding pea cultivars on less rich soils over cool years [27].

It was demonstrated that papilionaceous plants of a short vegetation period, e.g. pea or bean, which can choose between mineral nitrogen and the nitrogen fixed from the air, used mineral nitrogen [16]. A total accumulation of nitrogen fixed by pea, when exposed to the fertilization of 25-50 kg NO3-·ha-1, amounts to 213-244 kg N·ha-1. About ¼ of the total nitrogen fixed by pea is accumulated prior to flowering, ¼ during flowering, and the other part – after flowering [13]. Nitrogen is most intensively uptaken starting from the stage prior to budding to pod setting and seed filling. As for mineral nitrogen nutrition, its considerable amount is accumulated in plant stems, while the share of nitrogen transported to seeds decreases along with an increase in its dose [12].

Verifying the functional value of seeds is also important due to a high price of certified seeds. Unfortunately, the lab germinability does not always correlate with the field emergence capacity and a further plant development [20]. For that reason, frequently, besides the germinative energy and germinability, the seed vigor is determined using other methods. It is more and more popular to research it with the conductometric test of seeds. The leachate electroconductivity test allows one to determine seeds of a lower vigor in the sowing material of a similar germinative energy and germinability [20].

The aim of the present research was to define the effect of the cultivar, nitrogen fertilization and harvest date on 1000 seed weight, germinative energy and germinability and on seed vigor. It was assumed that the sowing value of pea seeds changes significantly during ontogeny, and depends on the genetic factor and pre-sowing nitrogen fertilization.

MATERIAL AND METHODS

The research was carried out over 2000-2002 at the Agricultural Experiment Station, Pawłowice, in the vicinity of Wrocław, on the soil representing autogenic soils, brown-earth, lessive type, subtype: typical, formed from light loam on medium loam, representing a good wheat agricultural soil suitability complex, IIIb soil valuation class. Prior to sowing the seeds were dressed with Dithane M-45 80 WP. The seeds sown were certified (Pb), ‘Agra’ and ‘Rola’ cultivars.

The experiments were established following the ‘split-plot’ design and involved three variable factors, which were, successively: I – pea cultivars; II – pre-sowing nitrogen fertilization: 0, 30, 60 kg·ha-1; III – harvest dates: at green, yellow and full maturity. Prior to the experiment, the following were determined: seed purity, germinative energy and germinability of the seeds sown. 100 germinating seeds were sown per 1 m2, 4-6 cm deep, at the row spacing of 15 cm. Due to a high soil richness in phosphorus and potassium, no fertilization with these macroelements was applied. The sowing value parameters were determined for mean samples of 4 replications with the following methods:

The length of respective pea development phases and the vegetation period was a product of cultivar properties and weather conditions. Mean for three research years the vegetation period in ‘Agra’ was 11 days longer than in ‘Rola’ (Table 1). The process of seed development (from the end of flowering to the beginning of green maturity) was longest in the humid and cool year of 2001, and the shortest in 2000 and it was slightly cultivar-specific.

Table 1. Length of respective pea development stages against weather conditions (2000-2002 means for cultivars)

Specification

2000

2001

2002

2000-2002 means for cultivars

Agra

Rola

Agra

Rola

Agra

Rola

Agra

Rola

Sowing – emergence

Number of days

14

14

20

19

21

20

18

18

Mean daily temperature, oC

9.4

9.4

5.6

5.4

4.6

4.4

6.2

6.1

Total precipitation, mm

16.3

16.3

37.5

35.2

2.7

2.7

18.8

18.1

Emergence – beginning of flowering

Number of days

42

35

47

42

47

42

45

40

Mean daily temperature, oC

16.0

16.1

14.5

14.3

15.0

14.4

15.1

14.9

Total precipitation, mm

99.7

80.1

64.8

52.8

71.3

63.2

78.6

65.3

Flowering

Number of days

15

14

15

13

12

14

14

14

Mean daily temperature, oC

19.9

17.4

15.4

15.1

16.1

17.1

17.2

16.6

Total precipitation, mm

5.9

25.5

46.9

28.2

38.4

10.2

30.4

21.3

End of flowering – green maturity

Number of days

11

11

15

17

14

11

13

13

Mean daily temperature, oC

17.8

18.5

19.3

17.1

20.6

17.0

19.3

17.5

Total precipitation, mm

10.5

4.7

43.4

51.2

39.9

72.8

31.3

42.9

Green maturity – yellow maturity

Number of days

6

7

11

10

10

10

9

9

Mean daily temperature, oC

14.7

20.5

18.9

20.5

18.0

21.5

17.6

20.9

Total precipitation, mm

4.0

6.5

96.4

45.8

27.1

3.4

42.5

18.6

Yellow maturity – full maturity

Number of days

24

9

8

8

6

9

13

9

Mean daily temperature, oC

16.5

16.0

20.4

17.9

20.3

18.2

17.9

17.3

Total precipitation, mm

107.5

4.5

26.5

76.7

5.3

27.3

46.4

36.2

Vegetation period

Number of days

112

90

116

109

110

106

112

103

Mean daily temperature, oC

15.9

15.9

14.5

14.1

14.4

14.1

14.9

14.6

Total precipitation, mm

243.9

137.6

315.5

289.9

184.7

179.6

248.0

202.4

Similar trends were recorded for the length of development stage from green to yellow maturity. The greatest differences over research years in both cultivars concerned the length of the period from yellow to full maturity, due to a very high total precipitation in 2000 (111.5 mm), which lasted 24 days in ‘Agra’ and only 9 days in ‘Rola’. In 2001 the length of that period in both cultivars was 8 days. In the last research year in ‘Agra’, due to higher temperature and lower precipitation, the stage was shorter than in ‘Rola’. Also in that year both cultivars reached full maturity earliest.

RESULTS

A varied pattern of precipitation and temperature conditions, the harvest date and nitrogen fertilization demonstrated a significant effect on 1000 seed weight of both cultivars tested.

The three-year seed size mean in ‘Rola’ was greater than that of ‘Agra’. There was observed a significant increase in 1000 seed weight due to fertilization with 30 kg N·ha-1. Irrespective of the cultivar, the fertilization level and weather course, 1000 seed weight increased regularly along as the ontogenetic plant development progressed, reaching the maximum value at full maturity. The greatest 1000 seed weight was recorded in 2000, and the lowest - in 2002 (Table 2).

Table 2. Functional value of pea seeds (2000 – 2002 means for factors and years)

Specification

1000 seed weight
g

Germinative energy
%

Germinability
%

Electroconductivity
µS·cm-1·g-1

after 12 hours

after 24 hours

Cultivar

Agra

204 b

69.4 a

71.2 a

42 b

66 b

Rola

211 a

70.1 a

71.2 a

52 a

75 a

kg N·ha-1

0

203 b

70.2 a

71.4 a

50 a

74 a

30

210 a

69.6 a

70.9 a

44 a

70 a

60

211 a

69.6 a

71.3 a

45 a

67 a

Development stage 

green

126 c

15.0 c

16.4 c

89 a

132 a

yellow

232 b

96.4 b

97.8 b

28 b

42 b

full

266 a

98.0 a

99.5 a

23 b

37 b

Year

2000

215 a

71.3 a

72.6 a

49 a

72 a

2001

211 b

71.6 a

72.9 a

42 a

64 b

2002

197 c

66.4 b

68.1 b

50 a

75 a

Means followed by the same letters did not differ significantly at a = 0.05; ns – non-significant differences

1000 seed weight was determined by the interaction between the nitrogen fertilization and the maturity stage and there was recorded a decrease in the rate of increase of that character during the seed ontogeny. By the yellow maturity there had been observed no significant differences in 1000 seed weight due to nitrogen fertilization. Between yellow and full maturity 1000 seed weight increase rate was much greater in fertilized plants (Fig. 1).

Fig. 1. 1000 grain weight depending on the interaction between nitrogen fertilization and development stage
Means followed by the same letters did not differ significantly at a = 0.05

From green to yellow maturity the 1000 seed weight increase rate was greatest in 2002, while the lowest – in the first research year. In 2001 between green and full maturity there were recorded the highest differences in 1000 seed weight (Fig. 2).

Fig. 2. 1000 grain weight [g] depending on the interaction between development stage and years

The germinative energy and germinability of seeds depended mostly on the maturity stage at which they were collected. A slightly lower effect was recorded for weather conditions. The cultivar factor and nitrogen fertilization did not differentiate those parameters of the seed quality. As the seed ontogeny progressed, the germinative energy and germinability increased and the greatest differences were demonstrated between green and yellow maturity. The percentage of germinating seeds was highest in the first two research years. The above features depended on the interaction between the years and the cultivars. In the first research year high precipitation at the end of the vegetation period and prolonged ripening period resulted in poorer seed germination in ‘Agra’, as compared with that in ‘Rola’. Over the last research year a greater germinative energy was recorded in ‘Agra’ than in ‘Rola’ seeds (Figs 3-4). In all the research years, in both cultivars, as early as over yellow maturity, a high germinability was recorded. The seeds collected over the green maturity germinated significantly poorer (Fig. 5).

Fig. 3. Germinative energy depending on the interaction between cultivars and years

Fig. 4. Germinability depending on the interaction between cultivars and years

Fig. 5. Germinability depending on the interaction between development stage and years

The seed vigor measured with the leachate electroconductivity test, irrespective of the factors studied and weather conditions, assumed higher values after 24 than after 12 hours. There was shown a significant effect of the genetic factor and the maturity stage on the development of seed vigor after 12 hours, and the effect of the research years, cultivars and the maturity stage on leaching of exudates after 24 hours. On average for three-research years ‘Agra’ seeds assumed lower values of leachate electroconductivity than ‘Rola’ seeds (Table 2). In 2000 a high total precipitation from yellow to full maturity resulted in higher values of electroconductivity after 12 and after 24 hours in ‘Agra’, which reached full maturity earlier than ‘Rola’. Over the successive research years a lower electroconductivity was recorded in ‘Agra’ (Figs 6-7). The leaching of exudates depended mostly on the maturity stage. As the seeds were ripening, the vigor was increasing and the greatest differences in the values of leachate electroconductivity were observed between green and yellow maturity stages. The course of weather differentiated the leachate electroconductivity significantly after 24 hours, while – after 12 hours it did not differ significantly over respective research years. The highest values of leachate electroconductivity after 24 hours coincided with 2002, and the lowest – with 2001 (Table 2).

Fig. 6. Electroconductivity after 12 hours [µS·cm-1·g-1] depending on the interaction between cultivars and years

Fig. 7. Elecroconductivity after 24 hours [µS·cm-1·g-1] depending on the interaction between cultivars and years

The first two research years recorded a high variation in the values of leachate electroconductivity of the seeds harvested at the green and yellow maturity. In 2001 a high total precipitation at the end of the vegetation period in both cultivars increased electrolytes leaching after 12 and 24 hours in seeds harvested at the full maturity than those collected at the yellow maturity (Figs 8-9).

Fig. 8. Electroconductivity after 12 hours [µS·cm-1·g-1] depending on the interaction between development stage and years

Fig. 9. Electroconductivity after 24 hours [µS·cm-1·g-1] depending on the interaction between development stage and years

Significant dependences were noted between respective parameters of the sowing value of pea seeds. The germinative energy and germinability increased along with an increase in 1000 seed weight. The inverse was observed for the germinative energy, germinability and 1000 seed weight and the leachate electroconductivity after 12 and after 24 hours (Fig. 10).

Fig. 10. Correlation between pea seed sowing value parameters

DISCUSSION

As the ontogeny continues, there is observed an increase in the sowing value of seeds whose basic parameters are: 1000 seed weight, germinability and germinative energy as well as the results of leachate electroconductivity test.

In the present research the seeds of ‘Rola’ were bigger than ‘Agra’ seeds. Nitrogen fertilization can show a diverse effect on 1000 seed weight in pea. Songin and Czyż [23] demonstrated that 1000 seed weight did not depend on nitrogen fertilization. Ziółek and Kulig [27], on the other hand, demonstrated that 1000 seed weight decreased due to nitrogen fertilization, which must have been due to a high soil richness in nitrogen in these experiments. In the present research 1000 seed weight was higher as a result of a pre-sowing fertilization with nitrogen.

A high level of nitrogen fertilization generally enhances the development of seeds and its sowing-and- reproductive value [6]. The seeds obtained from plants showing insufficient nitrogen availability show a low biological value [10]. In the present research there was recorded an effect of nitrogen fertilization neither on the germinative energy and germinability of seeds nor on the leachate electroconductivity. An excessive fertilization with nitrogen results in the formation of small seeds, of a low specific density and a low sowing value [6]. According to Decleire and Sorogera [4] plump seeds showed a greater vigor, while the shrunk ones produced poor seedlings. Also Taweekul et al. [25] demonstrated that vigor is significantly correlated with 1000 seed weight.

The harvest date shows a considerable effect on 1000 seed weight. In the present research it increased from green to full maturity by 211%. Similar results were recorded by Kulig et al. [14].

It is viability, determined with the germinative energy and germinability, which is a very important character of the sowing value of seeds [9]. In the present research these parameters depended most of all on the maturity stage and less considerably on the weather conditions. Along with ripening the germinative energy and germinability of seeds increased. Bedford and Matthews [1] recorded that 50% of morphologically unripe fresh pea seeds germinated already after 23 days after pollination. However their fast desiccation resulted in a decrease in germinability to 0%. The analysis of quality parameters of pea seeds carried out by Ziółek et al. [28] revealed that the seeds reached their physiological maturity 3 weeks after the completion of flowering. According to Prusiński [21], the seeds become tolerant to desiccation without losing viability more or less in the middle of their development, which is when the moisture of pea seeds decreases below 65%. Matthews [15] observed, however, that pea seeds become resistant to desiccation when they contain 65-85% of water and their quality is enhanced along with further desiccation. All that was confirmed by the present research in which at the moisture of 70% the seed germinability was 16%, and along with desiccation it increased to 99.5 % at full maturity. Reports by Ellis et al. [5] demonstrated also that pea seed desiccation up to 45-50% increased the seed quality (measured as the size of seedlings at the end of the germination test), however no further increase in quality was observed when the moisture decreased below that level. In the present research at the yellow maturity at the moisture of 56% the germinability reached 97.8% and it was only 1.7% lower than it was at full maturity when the content of water in seeds remained at 19%. Seeds can acquire the germinability without the completion of ontogeny [28] as pea seeds reach the physiological maturity once their moisture drops to 45-50% [19].

One of the most important functional characters of seeds is vigor which can be measured by electrolyte leaching, which well reflects the extent of physiological damage of seeds and the susceptibility to stress during germination [22]. The electroconductivity test is also very helpful in identifying these seeds whose germinability is still high but their vigor – low. Low-vigor seeds should not be sown under stress, while very low-vigor seeds should not be sown at all [19]. The amount of electrolytes leached depends mostly on the state of seed maturity and the degree of aging [Ziółek et al. 1997]. The more mature the seeds, the greater the vigor [18]. In the experiments reported by Prusiński [18], vigor was enhanced by the delay in the harvest date up to 21 days after the completion of flowering. In the present research high values of leachate electroconductivity of unripe pea seeds were due to a low percentage of germinable seeds. Once the seeds became resistant to fast desiccation without losing viability, a clear drop in the leachate electroconductivity was recorded. Similar results were noted by Prusiński [20]. An excessive delay in the harvest date, besides losses caused by pod-shedding, can lead to aging of seeds on parent plants [28], which is one of the main reasons of a decreased vigor [17]. High air temperature and humidity and multiple desiccation – seed imbibition in pods decrease the seed viability as a result of intensive respiration [19].

The rate of seed vigor decrease is closely correlated with air temperature and humidity and the total precipitation over ripening [28]. An increased leachate electroconductivity was observed both during and after seed aging before a significant decrease in their laboratory germinability was noted [20]. Despite a high germinability of seeds, their vigor decreases already after a few-day delay in the harvest [19], which was observed in the present research in 2001 when high precipitation during seed ripening increased the leachate electroconductivity between yellow and full maturity. However the germinative energy and germinability of pea seeds increased up to full maturity.

CONCLUSIONS

  1. The cultivars researched demonstrated differences neither in the germinative energy nor in the germinability, while 1000 seed weight and leachate electroconductivity were higher in ‘Rola’ than in ‘Agra’.

  2. There was observed a positive effect of fertilization with nitrogen at the dose of 30 kg·ha-1 on 1000 seed weight, while the other sowing value parameters did not depend on that factor.

  3. A three-year mean, as ripening progressed, up to full maturity, 1000 seed weight of pea seeds, the germinative energy and germinability increased significantly. There was also noted a significant increase in vigor measured as the leachate electroconductivity between the green and yellow maturity.

  4. A positive correlation was demonstrated between 1000 seed weight and the germinative energy and germinability of seeds and a negative correlation between the germinative energy, germinability, 1000 seed weight and the leachate electroconductivity after 12 and after 24 hours.


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  28. Ziółek W., Kulig B., Pisulewska E., 1997. Dynamika zmian parametrów jakościowych nasion grochu siewnego w zależności od sposobu i terminu zbioru [Dynamics of pea seed quality changes parameters depending on the harvest method and date]. Zesz. Nauk. AR we Wrocławiu, Rolnictwo 308, 49-58 [in Polish].


Waldemar Helios
Department of Plant Cultivation,
University of Agriculture in Wrocław, Poland
C. K. Norwida 25, 50-375 Wrocław, Poland
email: helios@ekonom.ar.wroc.pl

Andrzej Kotecki
Department of Plant Cultivation,
Wrocław University of Environmental and Life Sciences, Poland
pl. Grunwaldzki 24a, 50-363 Wrocław
email: andrzej.kotecki@up.wroc.pl

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