Response of Ryegrass to Nitrogen Fertilizer under Two Irrigation Systems

The objective of this study was evaluation the effectiveness of the some irrigation systems, and determining the best nitrogen fertilizer level and its effect on some growth characteristics and quality of Italian ryegrass seeds. A field experiment was carried out in two locations, the first is the Khan Atshan pasture station in the Karbala, and the second is the Dikkah pasture station - Khanaqin affiliated to the Forestry and Desertification Control Department - Ministry of Agriculture during the fall season 2021-2022. The experiment was carried out according to a randomized complete block design, in split plots arrangement, with three replications. The main plots included two irrigation systems (solid set sprinkler irrigation and free flow irrigation), and the sub plots included the addition of four levels of nitrogen fertilizer in the form of urea (46% N): 0, 15, 30, and 45 kg N h-1, The results showed that the solid set sprinkler irrigation system was significantly superior to the free flow irrigation system in achieving the highest average of the total chlorophyll content in the leaves 17.69 % and 9.63%, crude protein in the cereal 20.54% and 23.60 % and the percentage of carbohydrates in the cereal 13% and 14% for both experimental location, while the free flow irrigation system was significantly superior in achieving the highest mean of the flag leaf area 4.32% and 5.08% and the dry weight of the plant 13.55% and 46.67% for both location. The results also showed that increasing the added nitrogen fertilizer up to the level of 45 kg h-1 led to a significant increase in each of the flag leaf area cm2 and the total chlorophyll content in the leaves mg g-1, percentage of crude protein in cereals, dry weight of plants, percentage of ash in cereals, and percentage of carbohydrates in cereals in two experiment location.


Introduction
Italian ryegrass Lolium multiflorum Lam.one of the grass crops that is widely grown as fodder for animals in cold and temperate regions because of its high productivity and ability to be digested by animals.Its seeds are also used as food for humans as it is used in the manufacture of brown bread with a high taste and is rich in vitamins and protein, which ranges from 2-9% even if it is less digestible and absorbed than the rest of the grass crops.Its cereals are also used in the manufacture of starch and alcohol, as a concentrated fodder for animals, and its vegetable group in the hay making 1259 (2023) 012118 IOP Publishing doi:10.1088/1755-1315/1259/1/012118 2 industry.Straw is used as a filler in fodder for animals because it has a high fodder value.Ryegrass seeds contain water carbohydrates, nitrogenous substances, and mineral salts, the most important of which are iron and calcium, It is also characterized by its tolerance of drought because the root system of the plant is large and strong, but the lack of moisture during the elongation phase leads to the formation of small spikes of low production [1].water is one of the most important factors determining the growth rates of crop plants, and today, more than ever, we realize the importance of water, especially in arid and semi-arid regions that suffer from a lack of water resources of all kinds, as it is expected that water scarcity will occur due to drought by 2050, which will negatively affect the nutrition of about 67% of the world population as a result of low productivity [2,3].The lack of irrigation water and scarcity of rain in the central and southern regions of Iraq in recent years called for rationalization and control of water use during the growing season with the adoption of modern methods so that every drop of water is preserved, especially in areas that suffer from a decrease of irrigation water [4][5][6][7].In recent decades, those interested in agriculture and irrigation have resorted to non-traditional irrigation methods that rationing water use.Irrigation is represented by adding water to the soil in order to provide plants with moisture and create conditions suitable for plant growth and increased agricultural production.One of the methods used and efficient in solving the problem of water scarcity is to follow Solid set sprinkler irrigation, as it is considered one of the approved systems in the world that achieve high water use efficiency and its use has spread, and the area irrigated using this system in Iraq has become about 150 thousand dunums, but it is still few, and among the most important types used are solid set sprinkler irrigation systems, Center pivot, linear and Side -Role [8].
Fertilizers have an important role in the stages of growth and development of the plant because it is the substrate from which the plant derives nutrients, the most important of which is nitrogen, which is involved in the formation of cells and the formation of amino acids that form protein [9 and 10].Nitrogen is one of the most important main nutrients to increase production, as plants respond to nitrogen fertilizer in a large way, and about half of the nitrogen absorbed is collected by cereals [11,12].[13] indicated that the response of ryegrass to nitrogen fertilization It was very low when fertilizing with more than 40 kg N h -1 when planting in the autumn season and more than 50 kg N h -1 when planting in the spring season, as it was shown that the addition of nitrogen fertilizer every four weeks was the best in terms of productivity compared to fertilization every six weeks .indicated [14] a significant increase in the percentage of ash in wheat cereals was obtained by adding urea fertilizer at high rates.[15] in a study in India found an increase in the percentage of crude protein in the Ryegrass when applying 90 kg N h -1 .[16,17] indicated that the availability of nitrogen since the beginning of growth in the stage (Tillering, Elongation, and Boot) of plants of the Poaceae family affected the meristematic activity of the cells, so their division increased and the free flow area of the leaves expanded accordingly.[18] mentioned that the increase in nitrogen led to an increase in chlorophyll pigment in the leaves and then an increase in the efficiency of the photosynthesis process, which was reflected positively in increasing the leaf area of the wheat plant.For this reason, this study aims to evaluate the effectiveness of the two irrigation systems (solid set sprinkler and free flow) and to determine the best nitrogen fertilizer level and their effect on plant growth and qualitative characteristics of ryegrass seeds.

Materials and Methods
A field experiment was carried out in two locations, the first location is the Khan Atshan pasture station in the Karbala, and the second location Dikkah pasture station -Khanaqin affiliated to the Department of Forestry and Combating Desertification -Ministry of Agriculture during the fall season 2021-2022 to study the effect of two irrigation systems and different levels of nitrogen fertilizer and their impact on some growth and specific characteristics of Italian ryegrass seeds.The experiment was carried out according to a randomized complete block design, in split plots arrangement, with three replications.The main plots included two irrigation systems (solid set sprinkler and free flow irrigation), while the sub plots included the addition of four levels of nitrogen fertilizer in the form of urea (46% N), which are: 0, 15, 30 and 45 kg N. h -1 , in three times, the first after the seedlings emerge above the soil free flow and the plant reaches a height of 5-10 cm.The second is a month after the first time, and the third is a month after the second time [19].The experimental land was prepared for tillage, smoothing and leveling and grading, then it was divided into experimental units.The area of the experimental unit was 4 m 2 (2 x 2) m.Each experimental unit contained 10 lines of 2 m in length, and the distance between one line and another was 20 cm.The experiment was fertilized with phosphate fertilizer mixed with soil before planting at a rate of 100 kg P h -1 in the form of triple superphosphate P 2 O 5 45% at once.ryegrass seeds were sown by hand on 5/10/2021 in the first location and on 7/10/2021 in the second location .The experimental land was irrigated immediately after planting and irrigation continued once every two weeks according to the irrigation method used in the two experiments during the growing season.The first experiment was harvested on 6/6/2022 and the second experiment on 10/6/2022, and the growth and qualitative characteristics of the cereal were measured, which are:

Flag Leaf Area cm 2
It was measured when flowering was complete by calculating the average leaf area of ten random plants from the midlines of each experimental unit according to the following equation [20]: Flag leaf area (cm 2 ) = leaf length x maximum width x 0.95

Determination of Chlorophyll in Leaves (mg gm -1 wet weight )
Measured in leaves according to the method of [21] at wave lengths 663 and 645 nm using a spectrophotometer.

Percentage of Protein and Ash in Cereals (%)
Plant samples were taken and dried at a temperature of 70 °C until the weight stabilized, then they were ground and 0.5 gm was taken from them and digested using sulfuric acid and hydrogen peroxide.Nitrogen was measured in the digestion extract as stated in [22] , After that, the percentage of protein was calculated on the basis of the following equation [23].

Plant Dry Weight ( gm plant -1 )
According from the weight of the ten plants from the midlines of each experimental unit, then divided by the number of plants of the experimental unit, which includes the dry matter of all parts of the plant above the free flow of the soil after air drying the sample and weighting it with a sensitive balance [24].

Estimation of the Percentage of Carbohydrates in Cereals (%)
The data were analyzed according to the analysis of variance, and the means were compared using the least significant difference test (L.S.D 0.05) in Genstat.

Flag Leaf Area cm 2
The results of Figure (1and 2) indicate that the free flow irrigation treatment was significantly superior in achieving the highest average area of the flag leaf in the both locations of the experiment, which reached 18.22 cm 2 and 20.07 cm 2 , and the irrigation by solid set spray gave the lowest average of 17.48 cm 2 and 19.88 cm 2 .The reason for that It is due to the role of water, which is one of the environmental factors that have priority in influencing the stages of emergence, formation and growth of plant organs, as it plays a major role in increasing the availability of nutrients.NPK supports cell growth, division, and stability of photosynthesis, as well as being a solvent and a carrier medium for these substances to various parts of the plant, including leaves, as well as the energy source needed for photosynthetic processes in any organic food that is manufactured.This was agreed with [3,25].While the nitrogen fertilization had a significant effect for both locations on the average of this characteristic, as the level of 45 kg N.h -1 gave the highest average of 18.99 cm 2 for the first location and 20.99 cm 2 for the second location , while the control treatment gave the lowest average area of the flag leaf amounted to 16.72 cm 2 and 19.22 cm 2 for both locations sequentially.This may be due to the availability of nitrogen since the beginning of plant growth in the stage of (Tillering, Elongation, and Boot) and because nitrogen is necessary in all the vital processes that take place inside the plant, as it greatly affects the meristematic activity of the cells, so their division increases and expands accordingly to the free flow area of the leaves, In addition, the increase in nitrogen increases the chlorophyll pigment in the leaves and thus increases the efficiency of the photosynthesis process, which is reflected positively in increasing the leaf area of the plant [16 and 26].The results of the same figure showed that there was a significant effect of the interaction between irrigation methods and levels of nitrogen fertilization in the effect on the flag leaf area of the plant cm 2 at the first experiment location.As the interaction of the free flow irrigation with the level of fertilization of 45 kg N.h -1 gave the highest average of 19.13 cm 2 and 21.13 cm 2 , while this average decreased to 16.43 cm 2 and 18.43 cm 2 when the treatment of solid set spray irrigation and the level of fertilization 0 kg N.h -1 interaction.

The Total Chlorophyll Content in the Leaves (mg.gm -1 )
The results of Figure (3 and 4) indicate that there is a significant increase in the total chlorophyll content of the leaves at The pasture station of Khan Atshan and Dikka pasture station using solid set sprinkler irrigation method.as it gave the highest mean for this characteristic, which reached 1.53 and 1.48 mg.gm -1 , respectively, while the average total chlorophyll content decreased to 1.30 and 1.35 mg.gm -1 when treated with free flow irrigation.This may be due to the decrease in the leaf area when the solid set sprinkler irrigation treatment was treated (Fig. 1and 2), which led to a decrease in the efficiency of the plant in photosynthesis, which was reflected in the accumulation of quantities of unused chlorophyll in it, This agreed with [27].The results of the same figure indicate that there is a significant increase in the total content of chlorophyll when increasing the levels of nitrogen fertilization, as the addition of the level of 45 kg N.h -1 in the first location achieved the highest average for this characteristic, reaching 1.60 mg.g -1 , and the level achieved 30 kg N.h -1 in The second location had the highest average of 1.67 mg.gm -1 , while the mean for this trait decreased to 1.20 and 1.05 mg.gm -1 , respectively, in the comparison treatment and for both location s. in the comparison treatment and for both location s, and this may be due to the fact that nitrogen is one of the compounds included in the composition of the chlorophyll molecule, which led to an increase in its concentration in the flag leaf by increasing the level of nitrogen fertilization, and this is consistent with [16, 26 and 28].The results also show that there is a significant interaction between irrigation methods and fertilization levels in the effect on the average of this trait, as the interaction of the solid set sprinkler irrigation treatment with the level of 45 kg N.h -1 gave the highest mean of 1.80 and 1.76 mg.gm -1 , while the average of this trait decreased to 1.10 and 1.00 mg.gm -1 when the free flow irrigation treatment interaction ped with the level of nitrogen fertilization 0 kg N.h -1 for both locations .

The Percentage of Crude Protein in Cereals %
The results of Fig. ( 5 and 6) show an increase in the average percentage of crude protein in cereals when treated with solid set sprinkler irrigation, as it reached 9.27% and 10.27%, while the percentage of crude protein decreased to 7.50% and 8.52% when treated with free flow irrigation in both locations, this may be due to the rapid transfer of nitrogen from the rest of the plant to the cereals, with low relative humidity, which was reflected in the increase in protein content.[30], This is agree with [29].
Increasing levels of nitrogen fertilizer led to an increase in the percentage of protein in cereals (Fig. 5  and 6), as it gave the level 45 kgN.h -1 had the highest average of 10.37% and 11.37%, while the control treatment gave the lowest average of 6.14% and 7.17% for both location s, respectively.The increase in the percentage of protein in cereals by increasing the levels of added nitrogen fertilizer is due to the role of nitrogen in maintaining the balance of nitrogen metabolism in the plant tissue of wheat, as it contributes to building protein and supplying chloroplasts and the rest of the vital membranes with it, which contributes to delaying their aging and limiting their demolition.It also compensates for the demand The upper parts of the organic nitrogen, as the formation of organic nitrogen in the plant tissue increases due to the processes of building and forming the spike cereals and the beginning of the formation of protein granules in the endosperm of the cereal, which results in an increase in the ability of the leaves, especially the flag leaf, to produce soluble protein, which accumulates later in the cereal in the form of a stored protein.Agrees with [31] and [32].The interaction of Solid set sprinkler irrigation with the fertilizer level of 45 kg N.h -1 resulted in achieving the highest average protein percentage in both location, which reached 11.37% and 12.37%, while it decreased to 5.60% and 6.67% when the interaction between the irrigation treatment and the fertilizer level 0 kg N.h. - sequentially.) that there is a significant effect of the irrigation method on the average dry weight of the plant, as the irrigation gave the highest average of 1.76 g. plant -1 for the first location and 0.66 g. plant -1 for the second location , while irrigation by solid set spray gave the lowest average of 1.55 g. plant -1 for the first location and 0.45 g.plant -1 for the second location , and the reason for this may be due to the fact that water is one of the most important factors determining the growth rates of crop plants, and it is one of the necessary factors for the occurrence of division and elongation of plant cells [33].These results agree with [34 and 35] in the occurrence of a decrease in dry weight of wheat plants when subjected to water stress.
The results of the same figer show an increase in the average dry weight with an increase in the levels of nitrogen fertilizer for both location s, as it reached the level of 45 kg.N.h -1 had the highest average of 1.77 and 0.67 g.plant -1 , while the control treatment achieved the lowest average of 1.52 g.plant -1 and 0.42 g.plant -1 , respectively, as nitrogen is an essential and indispensable element and nitrogen nutrition controls the growth rate of the plant during the vegetative phase [27].It is noted from the results of Fig. (7 and 8) that there are no significant differences between the irrigation method and the levels of nitrogen fertilizer in the effect on average plant dry weight.) that there is a significant effect of the irrigation method on the average percentage of ash in the cereals , as solid set sprinkler irrigation achieved the highest average of 1.33% and 1.43%, while it decreased to 1.03% and 1.13% when free flow irrigation for both location s, respectively.The results are also shown in the Fig. ( 9 and 10) that there is a significant effect of nitrogen fertilizer levels on the average percentage of ash in cereals , as the level was given as 45 kg.N.h -1 had the highest average, reaching 1.41% and 1.51%, respectively, while the average decreased to 0.86% and 0.95% in the control treatment, respectively, for both locations.The rate of absorption of elements by plants, part of which will be transferred to the cereals , and the reason may be attributed to the high level of nitrogen giving the highest average area of the flag leaf, which led to an increase in the manufacture of nutrients that are transferred to the cereals , and led to an increase in the percentage of ash resulting from them [36].This result agreed with [37], who obtained a significant increase in the percentage of ash in wheat cereals by adding urea fertilizer, especially at high rates.The results of same figer indicate that there is no significant effect of the interaction of irrigation methods treatment and nitrogen fertilizer levels to affect the average of this characteristic for both locations.showed that there was a significant effect of the irrigation method on the average percentage of carbohydrates in cereals for both experimental locations, as the irrigation by solid set sprinklers gave the highest average of 66.92% and 61.92%, while it decreased to 59.67% and 54.68 when free flow irrigation.this is consistent with [29].
The results of the same Figer show an there is a significant effect of nitrogen fertilizer levels on the average percentage of carbohydrates in cereals , as the level gave 45 kg.N.h -1 had the highest average of 67.67% and 62.67%, while the average decreased to 59.

Conclusion
It is clear that the solid set sprinkler irrigation system was more efficient in affecting the qualitative characteristics of ryegrass cereal, and it is effective in reducing the amount of water used to irrigate the plant, especially in the Khan Atshan pasture station, which is characterized by being a desert area compared to the Dikkah pasture station, except for the flag leaf area characteristic, which increased significantly when the free flow irrigation system, and this increase was reflected in the dry weight of

Figure 1 .
Figure 1.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in flag leaf area (* The pasture station of Khan Atshan).

Figure 2 .
Figure 2. Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in flag leaf area (* Dikka pasture station).

Figure 3 .
Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in total chlorophyll content in the leaves mg.gm -1 .(* The pasture station of Khan Atshan).

Figure 4 .
Figure 4. Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in total chlorophyll content in the leaves mg.gm -1 .(*Dikkapasture station).

Figure 5 .
Figure 5.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in the percentage of crude protein in cereals.(* The pasture station of Khan Atshan).

Figure 6 . 7 3. 4 .
Figure 6.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in the percentage of crude protein in cereals.(*Dikka pasture station).

Figure 7 .
Figure 7. Effect of two irrigation systems and nitrogen fertilizer levels and their interactions in dry weight of the plant (gm.plant -1 ).(* The pasture station of Khan Atshan).

Figure 9 .
Figure 9.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions percentage of ash in the cereal (* The pasture station of Khan Atshan).

Figure 10 . 9 3. 6 .
Figure 10.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions percentage of ash in the cereal (*Dikka pasture station).
17% and 54.19% in the comparison treatment in two experimental locations sequentially.The results of Fig. (11 and 12) indicate an increase in the percentage of carbohydrates in cereals when the treatment of solid set sprinkler irrigation and the level of 45 kg N.h -1 , as it reached 73.67% and 68.67%, respectively, while the interaction of the treatment of free flow irrigation and the level 0 kg N.h -1 gave the lowest average of 56.67% and 51.70%, respectively, for both experimental locations.

Figure 11 .
Figure 11.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions percentage of Carbohydrates in cereals (* The pasture station of Khan Atshan).

Figure 12 .
Figure 12.Effect of two irrigation systems and nitrogen fertilizer levels and their interactions percentage of Carbohydrates in cereals (*Dikka pasture station).