The Response of Morphological Traits of Sugar Beet (Beta vulgaris L) To Different Irrigation Methods and Nitrogen Fertilization Ratios

Introduction

Water is a valuable natural resource, both renewable and non-re- newable, while maintaining its sustainability [1]. Also, water sup- ply, in almost all regions of the world, is the main limiting factor that is most important for crop production, due to the demand of water for the rapid industrial sector and high population growth. Water is the main element in economic growth and poverty reduc- tion [2-4]. Agriculture is the largest freshwater user on the planet [5].

Beta vulgaris L. belongs to the family Chenopodiaceae and is a biennial herbaceous plant that completes its life cycle in two years. It grows vegetatively in the first year, where the root is formed at the maximum size, and sugar and other nutrients are stored in it, and the stem is a disc. In the second year, if the roots are left in the field, the plant completes its life cycle, so the stems will elongate and bear a large number of flowers, which turn to fruits [6].

The cultivated area and production of sugar beet crop ranged be- tween 2002 and 2013 at about 32.562 hectares, with a production of 1437.921 tons in 2006, and 26014 hectares and a production of 1805184 tons, for the year 2011, respectively [7].

Sugar beet is grown in the Syrian Arab Republic in several dates: Autumn time: it starts from October 15 to November 15, and is planted in the governorates of Hama, Idlib, Aleppo, Raqqa, and Deir Ezzor.

Winter: starts from January 15 to February 15, and is grown in the governorates of Hama, Idlib, Aleppo, and Raqqa [8].

Summer: it starts from July 15 to August 15 [6].

It is a new planting date that avoids high temperatures that deteri- orate the sucrose stored in the roots and allows the application of a crop rotation that contributes to a better investment of agricultural lands and extends the operating period of the sugar factory for a longer period in the governorates of Raqqa and Deir Ezzor.

The use of water in irrigation must be rationalized and methods should be adopted that increase yields and improve the quality of production [9]. The development of irrigation methods and tech- niques and rationalization of water use has become an urgent ne- cessity that must be taken as one of the main priorities in develop- ing irrigated agriculture and improving its production [10].

Davidoff and Hanks, indicated that the water requirement of sugar beet ranges between 550-750 mm [11]. They added that irrigation increases root yield but reduces sucrose. Furrow irrigation of sugar beet crop causes many problems be- cause of water gatherings such as the spread of diseases and avail- able nitrogen leaching, so soil moisture is a determining factor for the productivity of this plant, especially since surface irrigation does not provide a homogeneous distribution of water to a large extent, and from here it is necessary to control and manage the available water to control this problem, reduce irrigation water losses and raise the efficiency of its consumption [12-14].

The nitrogen element is one of the major elements needed by the plant and determined for production in sugar beet [15]. It is very important in the mineral nutrition of the plant, because of its im- portance in the formation and composition of proteins, and in the synthesis of nucleic acids. It is also included in the synthesis of photosynthetic chlorophyll pigments, so it is an important and nec- essary component of photosynthesis and respiration [16].

El-Geddawy and Makhlouf confirmed that increasing the nitrogen fertilization of sugar beet increases root dimensions (length and diameter), the percentage of impurities (Brix), the production of the shoot and the actual sugar yield, and in return it reduces the percentage of sucrose [17]. Several studies in Egypt showed that adding nitrogen fertilizer between 214 and 262 kg N/ha in clay or sandy soils gives the best productivity indicators of roots, actual sugar yield and qualitative traits [18-21].

The study of Pytlarz-Kozicka, showed that the increase in nitrogen fertilization rate from 90 to 180 kg N/ha increased insignificantly the root production, while it decreased the sucrose percentage in the roots [22].

Sharaf and Masri et al. exhibited that the positive effect of increas- ing nitrogen fertilization rate is on leaf area index, root weight of the plant, the percentage of impurities, root production and actual sugar yield, while the percentages of sucrose and purity were neg- atively affected [23,24].

In the absence of previous studies, on the recommendations for cultivating sugar beet in Syria in summer time, in Hama gover- norate, and where studies were limited to determining the dates of planting and harvesting, it was necessary to implement this re- search to find out the best agricultural treatments that contribute to improving the properties of soil and increasing yields regarding maintaining a high percentage of sugar for this crop in Syria, tak- ing into consideration irrigation method and nitrogen fertilization.

The research aims to study the effect of irrigation method and ni- trogen fertilization rate on some qualitative characteristics (root length and diameter, root and shoot fresh weight and plant fresh weight) of genetically monogerm sugar beet.

Introduction

Water is a valuable natural resource, both renewable and non-re- newable, while maintaining its sustainability [1]. Also, water sup- ply, in almost all regions of the world, is the main limiting factor that is most important for crop production, due to the demand of water for the rapid industrial sector and high population growth. Water is the main element in economic growth and poverty reduc- tion [2-4]. Agriculture is the largest freshwater user on the planet [5].

Beta vulgaris L. belongs to the family Chenopodiaceae and is a biennial herbaceous plant that completes its life cycle in two years. It grows vegetatively in the first year, where the root is formed at the maximum size, and sugar and other nutrients are stored in it, and the stem is a disc. In the second year, if the roots are left in the field, the plant completes its life cycle, so the stems will elongate and bear a large number of flowers, which turn to fruits [6].

The cultivated area and production of sugar beet crop ranged be- tween 2002 and 2013 at about 32.562 hectares, with a production of 1437.921 tons in 2006, and 26014 hectares and a production of 1805184 tons, for the year 2011, respectively [7].

Sugar beet is grown in the Syrian Arab Republic in several dates: Autumn time: it starts from October 15 to November 15, and is planted in the governorates of Hama, Idlib, Aleppo, Raqqa, and Deir Ezzor.

Winter: starts from January 15 to February 15, and is grown in the governorates of Hama, Idlib, Aleppo, and Raqqa [8].

Summer: it starts from July 15 to August 15 [6].

It is a new planting date that avoids high temperatures that deteri- orate the sucrose stored in the roots and allows the application of a crop rotation that contributes to a better investment of agricultural lands and extends the operating period of the sugar factory for a longer period in the governorates of Raqqa and Deir Ezzor.

The use of water in irrigation must be rationalized and methods should be adopted that increase yields and improve the quality of production [9]. The development of irrigation methods and tech- niques and rationalization of water use has become an urgent ne- cessity that must be taken as one of the main priorities in develop- ing irrigated agriculture and improving its production [10].

Davidoff and Hanks, indicated that the water requirement of sugar beet ranges between 550-750 mm [11]. They added that irrigation increases root yield but reduces sucrose. Furrow irrigation of sugar beet crop causes many problems be- cause of water gatherings such as the spread of diseases and avail- able nitrogen leaching, so soil moisture is a determining factor for the productivity of this plant, especially since surface irrigation does not provide a homogeneous distribution of water to a large extent, and from here it is necessary to control and manage the available water to control this problem, reduce irrigation water losses and raise the efficiency of its consumption [12-14].

The nitrogen element is one of the major elements needed by the plant and determined for production in sugar beet [15]. It is very important in the mineral nutrition of the plant, because of its im- portance in the formation and composition of proteins, and in the synthesis of nucleic acids. It is also included in the synthesis of photosynthetic chlorophyll pigments, so it is an important and nec- essary component of photosynthesis and respiration [16].

El-Geddawy and Makhlouf confirmed that increasing the nitrogen fertilization of sugar beet increases root dimensions (length and diameter), the percentage of impurities (Brix), the production of the shoot and the actual sugar yield, and in return it reduces the percentage of sucrose [17]. Several studies in Egypt showed that adding nitrogen fertilizer between 214 and 262 kg N/ha in clay or sandy soils gives the best productivity indicators of roots, actual sugar yield and qualitative traits [18-21].

The study of Pytlarz-Kozicka, showed that the increase in nitrogen fertilization rate from 90 to 180 kg N/ha increased insignificantly the root production, while it decreased the sucrose percentage in the roots [22].

Sharaf and Masri et al. exhibited that the positive effect of increas- ing nitrogen fertilization rate is on leaf area index, root weight of the plant, the percentage of impurities, root production and actual sugar yield, while the percentages of sucrose and purity were neg- atively affected [23,24].

In the absence of previous studies, on the recommendations for cultivating sugar beet in Syria in summer time, in Hama gover- norate, and where studies were limited to determining the dates of planting and harvesting, it was necessary to implement this re- search to find out the best agricultural treatments that contribute to improving the properties of soil and increasing yields regarding maintaining a high percentage of sugar for this crop in Syria, tak- ing into consideration irrigation method and nitrogen fertilization.

The research aims to study the effect of irrigation method and ni- trogen fertilization rate on some qualitative characteristics (root length and diameter, root and shoot fresh weight and plant fresh weight) of genetically monogerm sugar beet.

Materials and Methods

Site of Experiment

The experiment was carried out at Taizin Irrigation Research Station, Hama Research Center, General omission for Scientific Agricultural Research, Syria. The center is located within the first stability zone, at longitude of 35.9º and latitude of 36.52º and its height above sea level is 270 m, with an average rainfall of 400 mm/year.

Variety

The study was carried out on a variety of genetically monogerm hybrid of sugar beet, this variety is called Dita, which is recom- mended for cultivation in autumn, winter and summer dates, and its source is the General Commission for Scientific Agricultural Research GCSAR. Table (1) shows its most important productive and technological characteristics.

Table 1: Productive and technological characteristics of the studied variety.

Planting Method

The land was prepared for cultivation, with a first plowing at a depth of 30 cm and a second plowing at a depth of 20 cm. Then, organic fertilizers were added at a rate of 5 m3. dunums-1, at a rate of 13.33 tons/ha. Then the land was plowed with a cultivator, and it was leveled, and the soil was planned, taking into account the following:

Experimental plot length (row length): (6 m), width: (3 m), and area: (18 m2), while the distance between rows: (50 cm), between plants: (20 cm), and between replicates: (1.5 m).

The planting was done manually during summer time (beginning of September) at a depth of 2-3 cm and at a rate of 2 seeds in each hole, in order to allow the process of thinning and replanting to obtain the required plant density. The number of irrigation times throughout the agricultural season (6 times). Thinning and replant- ing were also done before the plant reached the stage of the second pair of true leaves, with manual hoeing of for weeding, at a rate of 3 times during the growing season. The nitrogen fertilizer was added according to the studied rates for two times, in each time half the studied amount of the three fertilizer rates, the first before planting, specifically between the second and third plowing ac- cording to the soil analysis, and the second was added during the period of emergence of the second pair of true leaves (the fourth true leave).

The following studied quantities of fertilizers were added accord- ing to the soil analysis:

Phosphorous fertilizer: Triple super phosphate (46% P2O5) was not added, because the soil has a good content of this element.

Potassium fertilizer: Potassium sulfate fertilizer (50% K2O) was added at a rate of 80 kg. ha-1, which is equivalent to 40 kg K2O/ ha.

Boron fertilizer: (10% effective boron) was added at a rate of 2 kg/ha.

Studied Variables

Irrigation Methods (sprinkle, foggy, drip and furrow):

A- Furrow irrigation: Six rows were planted for each treatment in each replicate, where the distance between lines is 50 cm, and 20 cm between plants on the same row.

B- Sprinkler Irrigation: It consists of 8 sprinklers for three rep- etitions, the distance between the sprinklers is 12 x 6 m, with a discharge of 1.25 m3/h at a pressure of 3 bar, the sprinkler radius is 6 m on a stand with a height of 75 cm.

C- Surface drip irrigation: the irrigation rows are spaced 50 cm apart, and the experimental plot consists of six rows.

D- Foggy irrigation: drain sprinklers of 50 l/h, where the spacing of sprinklers (mine sprinklers) is 3 m, the pressure is 1 bar, and the sprinkler radius is 3 m on a stand of 30 cm.

Irrigation was carried out every 5 days according to the amount of evaporation from the glass basin. The area of the experimental plot is 9 m2.

The total area of the experiment: (9 * 12) * 3 + the distances be- tween the factors and the replicates = 1291 m2.

Nitrogen Fertilizer

It was noticed from the soil analysis (Table 2) that the soil content of available nitrogen is low, and urea fertilizer (effective N 46%) was used at four rates: (no addition, 200, +25% (250) and -25% (150) kg/ha) as a pure unit of nitrogen, which is equivalent to (0, 434, 445, 326 kg urea/ha).

Table 2: Soil analysis of the experiment site at Taizin Research Station in Hama

Studied Traits

Experiment plants were lifted at the harvest time (middle of March) after about 195 days, and samples of the crop (3 plants) at the stage of full maturity of the roots were taken from each ex- perimental plot from each of the replicates of the experiment to estimate each of:

1- Root Length (cm)

After topping, which was done by a horizontal cut just below the thick disc stem and the vegetative system was excluded, and the thin wedge root was cut (the taper end of the root) after leaving a distance of 1 cm from the root end, a longitudinal section was made from the middle of the root tip, then the distance was mea- sured by means of a graduated ruler, located vertically from the top of the root to its end.

2- Root Diameter (cm):

the measurement was taken horizontally with a ruler for the lon- gest distance between the two ends of the root (after cutting it ver- tically from the middle to calculate the length).

3- Fresh root weight per plant (g).

4- Fresh shoot weight per plant (g).

5- Plant weight (g).

Experiment Design and Statistical Analysis:

Field experiment was carried out according to a randomized com- plete block design with three replications. The sources of variance (ANOVA) were analyzed for the main factors and their interaction according to the least significant difference (L.S.D) was estimated at 5% level of significance, and coefficient of difference (C.V%) was calculated using the statistical program Genestat v.12 [25].

Results and Discussion

Effect of Irrigation Methods and Nitrogen Fertilization Rates on the Morphological Traits:

1- Root length (cm)

Table (3) shows that there is a significant effect of irrigation meth- od on this trait, where the sprinkler irrigation method gave the low- est value root length (24.39 cm), but foggy irrigation method gave the highest (27.06 cm), this may be attributed to the homogeneous distribution of irrigation water to the plants [26]. Also, Table (3) exhibits an existence of a significant effect of nitrogen fertilization on this trait, between nitrogen fertilization levels (Table 3), where the treatment (N1=200 kg N/ha) gave the highest value (27.11 cm), but the treatment (N0) gave the lowest value (24.87 cm), this may be due to the role of nitrogen in improving the meristematic activity which contribute to the increase in number of cells in addi- tion to cell enlargement. Also, enhancing net assimilation rate and dry matter accumulation which in turn incrementing root length and diameter as well as root fresh weight [27].

The beet plant gave the highest root length (28.11 cm) when fol- lowing furrow irrigation and adding 200 kg nitrogen/ha.

                 Table 3: Effect of irrigation methods and nitrogen fertilization rates on root length (cm) of sugar beet.

* Means that there are significant differences at 0.05 level of probability, ns means that there are no significant differences at 0.05 level of probability.

2- Root diameter (cm)

Table (4) shows that there is a significant effect of the irrigation method on this trait. The sprinkle irrigation method gave the low- est value of root diameter (8.89 cm), while the other irrigation methods did not differ significantly in the effect on this character- istic. The results of the statistical analysis showed that there were significant differences (p≥0.05) on root diameter between nitrogen fertilization levels (Table 4). The highest value of root diameter (10.19 cm) was achieved when using the furrow irrigation method and adding 250 kg of nitrogen/ha.

                     Table 4: Effect of irrigation methods and nitrogen fertilization rates on root diameter (cm) of sugar beet.

*, ** Means that there are significant differences at 0.05 and 0.01 levels of probability, ns means that there are no significant differenc- es at 0.05 level of probability.

3- Root fresh weight/plant (g)

Table (5) shows that there is a significant effect of the irrigation method on this trait. The furrow irrigation method had a signif- icant effect on increasing the root weight of the plant, as it gave the highest value (1139.5 g). The results of the statistical analysis showed that there were significant differences (p≥0.05) on root weight between nitrogen fertilization levels (Table 5). In general, it was observed that this trait increased with the increase of nitrogen fertilization up to the rate of N2, then this trait began to decrease with the increase of nitrogen fertilization. The highest value of root weight (1463 g) was achieved when using the furrow irrigation method and adding 250 kg of nitrogen/ha.

  Table 5: Effect of irrigation methods and nitrogen fertilization rates on root fresh weight/plant (g) of sugar beet.

** Means that there are significant differences at 0.01 level of probability, ns means that there are no significant differences at 0.05 level of probability.

4- Shoot fresh weight/plant (g)

Table (6) shows that there is no significant effect of irrigation methods factor on the shoot weight/plant.

The analysis of variance (Table 6) shows a significant effect of the rate of nitrogen fertilizer addition on the shoot weight per plant, where the highest value in the treatment (N2 = 250 kg N/ha) was (585.0 g), and in contrast the lowest value was (313.1 g) (Table 6).

Table 6: Effect of irrigation methods and nitrogen fertilization rates on shoot fresh weight/plant(g) of sugar beet.

**Means that there are significant differences at 0.01 level of probability.

5- Plant Weight (g)

Table (7) shows that there is a significant effect of the irrigation factor methods on plant weight, where the highest value of the plant weight (1665 g) was reached when the furrow irrigation method was followed.

The analysis of variance table (Table 7) shows that there is a signif- icant effect of increasing the nitrogen fertilization rate in increas- ing the value of this trait compared with the no-addiction treat- ment (N0 =no addition) (1077 g), where the highest value of the treatment was (N2 = 250 kg N/ha) (1693 g) (Table 7). This was confirmed by both that the increase in nitrogen fertilization leads to an increase in plant weight [28,29].

Table 7: Effect of irrigation methods and nitrogen fertilization rates on plant weight (g) of sugar beet.

** Means that there are significant differences at 0.01 level of probability.

6- Water Consumption (m3/ha) Provided to Sugar Beet in Summer Time Using Four Irrigation Methods:

Table (8) shows that the water consumption of beet planted in sum- mer time was high when following surface irrigation with a value of (5350 m3/ha), while it decreased by 28% in sprinkle irrigation, 32% when following foggy irrigation, and by 34.5% in drip irriga- tion, this means that the percentage of savings water provided to the crop was the highest when using drip irrigating, followed by foggy method and finally the sprinkle irrigation method. report- ed that drip irrigation system resulted in higher water saving than sprinkler and furrow systems in sugar beet fields [30].

                                               Table 8: Water consumption (m3/ha) of sugar beet under four irrigation methods

Conclusion

The use of drip irrigation saves water consumed by 34.4% didn’t differ significantly in its effect on root length and diameter com- pared to furrow irrigation, but furrow irrigation gave significantly higher values of root and shoot and plant weight, where the per- centages of increase attained to values of 22, 14 and 20% respec- tively.

The nitrogen fertilization level of 250 kg N/ha significantly in- creased the morphological traits, which indicated the importance of nitrogen fertilization in increasing the efficiency of plant in the photosynthesis process and increasing the percentage of dry matter accumulation, and this reflected positively on the morphological characteristics of the plant [31-37].

Recommendations

The experiment recommends continuing the implementation of this experiment for another season to confirm the results before generalizing them due to the importance of these factors on the morphological traits of sugar beet.

References