Optimal Management of Nitrogen Fertilization in some Yield Traits of Corn Plant in Gypsum Soil

A field experiment was conducted in the fields of the College of Agriculture - University of Tikrit during the autumn season for the year (2022) to find out the effect of nitrogen fertilizer fractionation on the growth of corn in gypsum soil.Where the experiment included three factors, the first factor, five dates for nitrogen fertilizer fractionation, symbolized by the letter T (T1, the first appointment / half of the quantity at planting and the other half after (30) days of planting, and T2, the second appointment / one-third of the quantity at planting and two-thirds after (30) days of cultivation and T3 third date / one-third of the quantity at planting and one-third after (30) days of cultivation and a third after the passage of (60) days of cultivation and T4 the fourth date / one-fifth of the quantity when planting, fifty-five after the passage of (30) days of cultivation and fifty after the passage of (60) days of cultivation and T5 the fifth date / two-fifths at planting and fifty after a month of cultivation and one-fifth of the quantity After the passage of (60) of cultivation. The second factor is two levels of nitrogen fertilizer, denoted by the symbol N, namely (N1) (320) kg N ha-1 and (2N) (360) kg N ha-1. The third factor is Adding method, denoted by the symbol M, the BroadcastingM1 method) and the Bands(M2) method. All the results showed that the retail treatment of the fourth appointment, T4, excelled in all traits, and the second level, N2 (360) kg N ha-1, gave the highest significant difference in all traits, and the addition of the second method, M2 (Bands method), also gave excelled in all studied traits.The results showed that the treatment T4N2M2 gave the highest values in the studied traits (the number of rows per ear, the number of grains per ear, the weight of 500 grains, and the total grain yield), as it reached (18.01) row cob-1, (739) grain cob-1, (163.01) gm, and (14.08)) ton ha-1, respectively.


Introduction
The yellow corn crop (Zea mays L.) is one of the important major grain crops in global production in many countries of the world, including Iraq, which ranks third in terms of cultivated area after wheat and rice, and its productivity is constantly evolving [1].It is one of the most important crops of increasing importance in the food industry because it provides the basics of food security.Many food products are made from its grains that are used in human nutrition.It is also involved in many 1259 (2023) 012027 IOP Publishing doi:10.1088/1755-1315/1259/1/012027 2 industrial fields, including the manufacture of dyes, ceramics, paper and cork [2].Its importance is also due to its high productivity and its adaptability to different environmental conditions.The Iraqi environment is one of the suitable environments for the production of corn, but its productivity is still low compared to global production [3].Therefore, Iraq needs to double the production of maize and expand its cultivation.As the cultivated area for the year 2016 amounted to a total of 55,837 thousand dunums, with an average production of 1,133 tons of e -1 [4], compared to the average yield of agriculturally developed countries such as the United States of America 11.07 tons.ha - , Turkey 10.75 tons.ha-1and Egypt 8.00 tons.ha - [5] Fertilizers have an important role in the stages of growth and development of the plant, being the substrate from which the plant derives nutrients, the most important of which is nitrogen, which enters the structure of cells, which is a basic element in the formation of compounds, the most important of which are amino acids that form protein [6].Nitrogen is one of the basic elements for plant growth, and the crop's need for this element is not limited to a specific stage of growth.Water and nutrients from the soil on the other hand, but in the later stages it is necessary to improve the quality of agricultural crops [7].Therefore, the aim of this study was to reach the best fractionation of nitrogen fertilizer batches, as well as to determine the best rate and method of adding nitrogen to influence the growth and yield of corn in gypsum soil, in interaction with the fractionation of fertilizer batches.

Materials and Methods
A factorial field experiment was conducted during autumn season for the year (2022) in the fields of the College of Agriculture -University of Tikrit to know the effect of nitrogen fertilizer fractionation on the growth and yield of corn in gypsum soil.The experiment included three factors, the first being five dates for nitrogen fertilizer fractionation, symbolized by the letter T. Thirty (30) days of cultivation.The third date is T3/ 1/3 the quantity at cultivation, 1/3 after (30) days of cultivation, 1/3 after (60) days of cultivation, and the fourth date is T4/ 1/5 the quantity at cultivation and 2/5 after (30) day of cultivation and 2/5 after (60) days of cultivation and the fifth date is T5/ 2/5 when planting, 2/5 after a month of cultivation, and 1/5 of the quantity after (60) of cultivation.The second factor is the level of addition and is symbolized by the letter N. The first level is N1 (320) kg NH-1, and the second level is N2 (360) kg NH-1.The third factor is the method of addition and is symbolized by the letter M. The first method is M1 / the broadcasting method and the second method is M2 / the Bands method.Urea fertilizer was used 46% as a source of nitrogen .Soil samples were taken from the site of executing the experiment from the surface layer (0-30) cm and mixed well.One representative sample of the field soil was taken, then air dried and sieved through a sieve with a diameter of pit(2 mm) and a sample was taken from it to conduct some physical and chemical analyzes on it.(1) makes it clear.The soil was well moistened to facilitate the process of plowing, leveling and the necessary smoothing that I did.The land was divided into three sectors, and each sector was divided into plot(experimental units).The area of one experimental unit was (3 m x 3 m), with an area of (9) square meters, and a distance of (75 cm) was left ) between an experimental unit and another and (100) cm between each sector and another to prevent the transfer of nitrogen fertilizer between the panels, after that the drip irrigation system was installed in the experimental field .The seeds were sown on 7/20/2022, and (2) seeds were placed in each pit in the form of straight lines, using corn grains (Zea mays L.), the American Jameson cultivar, imported.The distance between one pit and another was (25 cm), and the distance between the lines within each experimental unit was (75 cm), with an average of (4) lines in each experimental unit and one line included (11) plants in an average of (44) plants per Experimental unit.The experiment was applied using the randomized complete block design (R.C.B.D) and with three replicates, one replicates included (20) experimental units, and the transactions were distributed randomly to experimental units, and the total number of experimental units was (60).The field was watered according to the plant's need, and after two weeks of germination, the number of plants was reduced to one plant per pot.The service and weeding operations were conducted manually for the weeds in the experimental field for all the experimental units in a homogeneous manner and for several times, so that the experimental land was almost free of weeds, and the process of controlling the corn stalk borer insect was carried out by using the granular diazinon pesticide with a concentration of (10%) twenty days after germination by feeding for the growing apices of the yellow corn stalk [8],The crop service operations continued until the plants were harvested on 11/20/2022, after random samples consisting of ten plants were taken from each experimental unit.Some trait of the yield were studied, namely the number of grains per cob, the number of rows per cob, the weight of 500 grains, and the total grain yield.
Table 1.Some chemical and physical properties of the soil before planting.

Number of Rows Per Cob (row.cob -1 )
The results in Table (2) show that the addition of nitrogen fertilizer led to a significant increase in the number of rows in corn cobs.Raising the fertilizer level from (320) kg Nha -1 to (360) kg Nha -1 resulted in a significant increase in the number of rows per cob, as it reached (16.16, 16.86) row cob -1 , respectively.The reason for excelled the N2 level may be due to excelled of the level in the rate of abortion in the ovaries, which leads to an increase in the rate of fertilization and pollination, and thus the number of rows per cob [9] and this result is consistent with [10] and [11].The results of the same table show that the method of adding nitrogen fertilizer significantly affected the trait of the number of rows per cob , where the method of adding Bands gave the highest average of (16.60) cm, while the addition of the Broadcusting method gave an average of (16.43) cm.The reason for this is that the quantities of fertilizer added by the method of bands, grooves, or local fertilization and at depths are distributed in a regular and homogeneous manner for each plant within the root growth space, which reduces the loss obtained by different loss methods.As for the addition of fertilizer by the Broadcasting method, the added nitrogen is lost due to the presence of empty spaces between the lines and also within the same line between the plants, especially in the early stages of growth, which are characterized by the lack of sufficient root density to occupy the spaces, as the root system is small and unable to absorb the nutrients present at great distances from the root system [12].Also, because the fertilizer added by the Bands method led to an increase in the amount of ready nitrogen, which led to an increase in the leaf area and the amount of accumulated dry matter, and thus an increase in the average number of rows in cobs.Fragmentation of nitrogen fertilizer led to a significant increase in the trait of the number of rows per cob, where treatment T4 gave (17.44) cm, while treatments T1, T2, T3, and T5 gave an average of 15.29, 16.14, 17.05, and 16.65, respectively.The reason for the excelled of the T4 treatment in most of the factors is due to the abundance of nutrients contained in the fertilizer in this treatment, which was reflected in the improvement of crop performance through division and expansion of cells in addition to increasing the rate of leaf area trait and leaf area index and thus increasing the surface area exposed to light and thus improving conditions growth, which was reflected in the increase in the rate of this trait, and this is in line with the findings of [13] Those who explained that there was a significant effect of fertilization on trait of the number of rows per cob, and this led to an increase in the treatment (T4) adding nitrogen fertilizer in three batches (1/5 at planting, 2/5 after one month, and 2/5 after two months).The results in Table (2) indicate that the triple interaction between the study factors (level of application, application method, and fertilizer fractionation) showed a significant increase, where treatment M2N2T4 gave the highest average of (18.01) row cob-1, while treatment M1N1T1 gave the lowest average of (14.11) row cob -1 , an increase of 27.63%.T1: Adding nitrogen fertilizer in two batches (half when planting and half after a month.T2: Adding nitrogen fertilizer in two batches (1/3 at planting and 2/3 after a month.T3: Adding nitrogen fertilizer in three batches (1/3 at planting, 1/3 after one month, and 1/3 after two months.T4: Adding nitrogen fertilizer in three batches (1/5 at planting, 2/5 after one month, and 2/5 after two months.T5: Adding nitrogen fertilizer in three batches (2/5 at planting, 2/5 after one month, and 1/5 after two months Averages with similar letters, there is no significant difference between them according to the Duncan test at the probability level of 5% The results in Table (3) show that the addition of nitrogen fertilizer led to a significant increase in the number of grains per cob of corn, where raising the fertilizer level from (320) kg Nha -1 to (360) kg Nha -1 resulted in a significant increase in the weight of 500 grains.It reached (626,589) (cob grain -1 ), respectively.The reason for this is that the increase in nitrogen leads to an increase in the leaf area during the vegetative growth stage, which increases the rate of carbon metabolism and reduces the number of aborted grains.This is consistent with [14], who noticed the effect of nitrogen fertilizer significantly superior to the level of addition of 200 kg N -1 on the levels 0 and 100 kg ha -1 .And the average number of grains is 279, 438, and 467 grains for the addition levels 0, 100, and 200 kg Nha -1 , respectively.With an increase of 67.4 and 6.6% for the level of 200 kg N ha -1 compared to the levels 0 and 100 kg N ha -1 , and also these results agreed with what was reached by [15] of the presence of a positive correlation between nitrogen and the number of grains in cob, and this is also consistent with what was reached [16] It is noted from the results in Table (3) that the method of adding nitrogen fertilizer significantly affected the number of grains per ear, as the method of adding Bands gave the highest average of (631) grains .cob - .While the addition of the Broadcasting method gave an average of (584) grains cob -1 .Perhaps this excelled is due to the fact that this method reduced the contact area between the fertilizer and the soil in a greater way compared to other methods used, which increased the readiness of the element in the soil, and in turn this abundance of the element was reflected in The number of grains per row.Fragmentation of nitrogen fertilizer led to a significant increase in the number of grains per cob, where treatment T4 gave (690) grain.cob - , while treatments T1, T2, T3, and T5 gave an average of 518, 581, 632, and 616 grains.cob - , respectively.The reason for the increase in the number of grains per cob may be attributed to the availability of added nitrogen in the stages of emergence and development of flowering plants, the flowering stage, pollination, and the growth of grains, which reduced the competition between them, which helped increase the number of cob [17].A significant response was obtained from the cultivars to the time of adding nitrogen, where the cultivar (Al-Fajr 1 + A6) gave the highest average number of grains per cob, which amounted to 650.00 cob seeds.This is consistent with [18], which found that the time of nitrogen addition gave the highest average of the number of grains per cob in the sixth fragmentation treatment (A6), which includes a quarter of the fertilizer recommendation a week after emergence + half of the fertilizer recommendation at the 8-leaf stage + a quarter of the fertilizer recommendation at the appearance of the silk Where it reached 611.33 grains cob -1 , While the time of adding the second fragmentation treatment (A2), which includes half of the fertilizer recommendation a week after emergence + half of the fertilizer recommendation at the stage of 8 leaves, gave the lowest average for this trait amounted to 502.50 (grains cob -1 ).It is clear from the results in Table (3) that the triple interaction between the study factors (the level of addition, the method of application, and the fractionation of fertilizer) led to a significant increase, where the treatment M2N2T4 gave the highest average of (739) grains cob -1 , while the treatment M1N1T1 gave the lowest average of (480) grains cob -1 ), with an increase of 53.95%.T1: Adding nitrogen fertilizer in two batches (half when planting and half after a month.T2: Adding nitrogen fertilizer in two batches (1/3 at planting and 2/3 after a month.T3: Adding nitrogen fertilizer in three batches (1/3 at planting, 1/3 after one month, and 1/3 after two months.
T5: Adding nitrogen fertilizer in three batches (2/5 at planting, 2/5 after one month, and 1/5 after two months Averages with similar letters, there is no significant difference between them according to the Duncan test at the probability level of 5%

Weight of 500 Grain (g)
The results in Table (4) show that the addition of nitrogen fertilizer led to a significant increase in the weight of 500 grains of corn, where raising the fertilizer level from (320) kg N ha -1 to (360) kg N ha -1 resulted in a significant increase in the weight of 500 grains.It reached (142.83,150.37) g, respectively.The reason for this may be due to the level 360 kg NH-1 plants excelled in the number of leaves and leaf area, and thus the increase in the efficiency of photosynthesis in the processing of grains with their requirements of the processed food needed to fill them, increase their size, and then increase their growth [19], These results agreed with what was found by [20] in increasing seed weight by increasing the level of nitrogen fertilizer application.It also agrees with [21] who concluded that the treatment of 200 kg N.ha -1 excelled in the weight of 300 grains of corn.The results in Table (4) showed that the method of adding nitrogen fertilizer significantly affected the trait of 500 grains, where the Bands method gave the highest average of (148.78)g, while the Broadcusting method gave an average of (144.42)g.Perhaps the reason for this excelled is that the fertilizer using the Bands method was prepared for the plant and thus benefited from it perfectly and in sufficient quantity for its needs, which led to an increase in the contact points between the root and the fertilizer, and then the formation of a good root system, and this is indicated by each of [22].Fragmentation of nitrogen fertilizer led to a significant increase in the weight of 500 grains, where treatment T4 gave (156.46)grams, while treatments T1, T2, T3, and T5 gave an average of 135.93, 141.83, 148.19, and 150.59 g, respectively.The excelled of some levels significantly over others may be due to the efficiency of nitrogen fertilization distribution differed from one level to another, and it was found that the first and then the third levels shared that they had the highest amount of nitrogen fertilization for the period after 30 days of cultivation, compared with the other levels and they achieved the highest significant mean for the weight of 500 grains [23].
It was also shown [24] that the corn plant is more responsive to nitrogen fertilization for the period after 30 days of germination.These results agree with [25], [26], and [27].The reason may also be due to the fact that the addition of nitrogen at late growth stages of the crop coincided with the stage of growth and filling of grains, and this led to an increase in the transfer of photosynthesis products from the source to sink, which led to Increasing the size of the seeds [28] and this led to an increase in the treatment T4) adding nitrogen fertilizer in three batches (1/5 at planting, 2/5 after one month and 2/5 after two months).The results in Table (4) indicate that the triple interaction between the study factors (level of application, application method, and fertilizer fractionation) resulted in a significant increase, as treatment M2N2T4 gave the highest average of (163.01)gm, while treatment M1N1T1 gave the lowest average amounted to (128.01) gm, with an increase of 27.34%.T1: Adding nitrogen fertilizer in two batches (half when planting and half after a month.T2: Adding nitrogen fertilizer in two batches (1/3 at planting and 2/3 after a month.T3: Adding nitrogen fertilizer in three batches (1/3 at planting, 1/3 after one month, and 1/3 after two months.T4: Adding nitrogen fertilizer in three batches (1/5 at planting, 2/5 after one month, and 2/5 after two months.T5: Adding nitrogen fertilizer in three batches (2/5 at planting, 2/5 after one month, and 1/5 after two months Averages with similar letters, there is no significant difference between them according to the Duncan test at the probability level of 5%

Total Grain Yield (tons ha -1 )
The results in Table (5) show that the addition of nitrogen fertilizer led to a significant increase in the grain yield trait of corn, as raising the fertilizer level from (320) kg N ha-1 to (360) kg N ha -1 led to a significant increase in the weight of 500 grains.It reached (11,063,9,919) tons.ha - , respectivelyThe reason for the increase is due to the fact that the addition of fertilizer led to the regulation of vital activities and the encouragement of good root and vegetative growth, which led to an increase in the absorption of nutrients coupled with an increase in the process of photosynthesis and food stocks (carbohydrates and proteins).Which was reflected on the grain yield, and this is consistent with the results of [29], which found that the addition of nitrogen fertilizer led to a significant increase in the yield of the wheat crop, and also agrees with [30]The results in Table (5) show that the method of adding nitrogen fertilizer significantly affected the number of grains per cob, where the method of adding Bands gave the highest average of (11.064) tons ha -1 , while the addition of the Broadcasting method gave an average of (9.917) tons ha -1 The reason may be due to the increase in the available of nitrogen in the soil where a result of adding nitrogen fertilizers using the Bands method, which led to an increase in its absorption by the plant.These results agree with what was obtained [31].This is that the productivity of fertilizer increases with the local addition and at depths because the addition by the Bands method provides nitrogen in an amount It is greater in the soil and reduces its loss by volatilization, which makes the plant get enough of the fertilizer and then improves productivity, and this is consistent with [32] and [33] as they showed that by increasing the levels of nitrogenous fertilizer, the productivity of the fertilizer increases.Fragmentation of nitrogen fertilizer gave a significant increase in the grain yield , where treatment T4 gave (12.67) tons.ha - , while treatments T1, T2, T3, and T5 gave an average of 8.225, 9.652, 11.002, and 10.906 tons .ha - , respectively.The difference in the fractionation treatments for adding nitrogen fertilizer may be significant in terms of grain yield due to the fact that some fractionation treatments are more efficient than others in supplying plants with nitrogen at critical times when the plant needs it or at times when the plant is more responsive to nitrogen than others, and thus a decrease in the amount of wasted nitrogen and an increase in the amount of nitrogen absorbed by the plant, and this was reflected in the excelled of some treatments on others, and these results agree with what was reached by [24] and [34].The results of Table (5) indicate that the triple interaction between the study factors (the level of addition, the method of application, and the fractionation of fertilizer) resulted in a significant increase, where the treatment M2N2T4 gave the highest average of (14.08) tons ha -1 , while the treatment M1N1T1 gave the lowest average amounted to (7.182) tons ha -1 with an increase of 96.04%.Table 5.Effect of nitrogen fertilizer fractionation, level and method of its application on grain yield (ton ha -1 ) of corn.addition.when planting and half after a month.T2: Adding nitrogen fertilizer in two batches (1/3 at planting and 2/3 after a month.T3: Adding nitrogen fertilizer in three batches (1/3 at planting, 1/3 after one month, and 1/3 after two months.T4: Adding nitrogen fertilizer in three batches (1/5 at planting, 2/5 after one month, and 2/5 after two months.T5: Adding nitrogen fertilizer in three batches (2/5 at planting, 2/5 after one month, and 1/5 after two months.Averages with similar letters, there is no significant difference between them according to the Duncan test at the probability level of 5%

Conclusions
From the results of the study, we can conclude the following:  The fourth date for dividing the application of nitrogen fertilizer (one fifth of the quantity at planting andtwo month after cultivation and fifty after two months of cultivation (significantly superior and gave the highest values in all studied traits. The best level of fertilizer is the second level N2(360 kg.h -1 ) this indicates that the soil the gypsum soil is poor in elements and responds greatly to the addtition of fertilizers. The best way to add nitrogen fertilizer is the second application M2 the packet method as it was significantly superior in all studied yield characteristics ( at rows per ear , number of grains per ear , and weight of 500 grain and total grain yield ).

Table 2 .
Effect of nitrogen fertilizer fractionation, level and method of adding it on the number of rows per cob(row.cob - ) of corn.

Table 3 .
Effect of nitrogen fertilizer fractionation, level and method of applying it on the number of grains per cob(grains cob -1 ) of corn.

Table 4 .
Effect of nitrogen fertilizer fractionation, level and method of application on the weight of 500 grains (g) of corn.