Okra productivity and nutrient concentrations in the vegetative and fruiting parts as a result of mineral fertilization and fertilizer application sites

A field experiment was carried out in one of the farms in the district of Al-Suwaira-Wasit governorate for the 2021 agricultural season. To find out the effect of adding levels of NPK and the places of addition on their concentrations in the vegetative and fruiting part and the productivity of the okra crop. Six treatments were produced from the fertilizers levels, and the addition distances are C2D2, C2D1, C1D2, C1D1, C0D2, and C0D1. With three replications, experimental units become 18 units. A completely randomized block design (RCBD) was used to distribute treatments. The dry weight and root diameters of the plant were taken, and the NPK concentrations were estimated in the vegetative part at the end of the season, as well as the NPK concentrations in the fruiting part of the first and last fairies and the cumulative yield was taken. The results showed a significant effect of NPK levels on nitrogen and phosphorous concentrations in the vegetative and fruiting parts, while the effect was not significant on potassium concentration. The position of the fertilizer application did not significantly affect the concentration of NPK in the plant. The second level of fertilization, C2, had a significant effect on the dry weight of the plant, while the fertilization levels had no significant effect on the diameter of the roots. Fertilizer levels had a significant effect on yield.


Introduction
Soil fertility is affected by many factors that lead to the depletion of its nutritional content, and at the forefront of these depletion factors is the plant consumption resulting from continuous cultivation without compensating for the lack of nutritional content with mineral or organic fertilization.There are other less effective depletion factors, which are leaching, volatilization, water and wind erosion.Mineral fertilization comes at the top of the measures taken to address the lack of soil nutrients due to the high content of mineral fertilizers, their high solubility, and the appearance of their rapid effect on plants after use for a few days.It must be taken into account that the quantities used of fertilizers should be according to the plant's needs and what is in the soil to avoid negative effects on the environment and reduce costs 1 .
Mineral fertilizers are salts of mineral elements added to the soil or sprinkled on plants to nourish the plant and increase soil fertility.Its high content of nutrients characterizes it compared to organic fertilizers.It is necessary to follow some sober management methods such as quantity, quality, method and time of addition to make maximum use of the fertilizer and reduce its negative effects on plants and soil.The pH of the fertilizer used should contrast with the soil pH, and its salt index is low and has high solubility.Compound fertilizers are preferred over fertilizers that contain One element and preferably fertilizers with a high nutrient element content and fertilizers that withstand storage conditions, that do not hydrate and then agglomerate.Other specifications are preferred in mineral fertilizers, for example, that they be slow-release so that they supply the plant with its nutritional needs throughout its stay in the field to avoid the problems of volatilization, leaching, fixation and precipitation, with the need for the fertilizer price to be appropriate 2 .Adding fertilizers is significant because some nutrients are immobile or less mobile.This point should be taken into consideration.The movement of nutrients in the soil is necessary for nutrient management to increase plant growth and yield and maximize the benefit of using nutrients for the plant.The absorption of nutrients by plant roots needs direct contact Between the ions and the surfaces of the roots.There are three mechanisms for the arrival of nutrients to the root surfaces: diffusion, mass flow and root interception 3 .Recognizing the movement of nutrients in the soil when added in the form of fertilizers is important in determining the method of adding fertilizer.If the nutrient is mobile or little mobile in the soil, adding fertilizer containing this nutrient should be near the area of roots spread.At the same time, the process is more straightforward when adding mobile nutrients because they will move towards the roots after adding irrigation water and dissolving the fertilizer 4 .Okra (Abelmoschus esculentus L.) is one of the most important plants of the Malvaceae family.It grows well in both wet and dry conditions.It contains 2% protein, 0.2% fat, 1.4% fiber, folic acid, vitamin K and an average amount of vitamin A. Among its benefits, it contributes to reducing the risk of breast cancer through lectin protein and folic acid, reduces the level of harmful cholesterol in the body, improves the energy level in the body and reduces the feeling of fatigue and exhaustion, resists constipation, helps the viscous texture in the treatment of mucous membranes, contributes to resistance Osteoporosis by vitamin K found in okra, regulating blood sugar level and finally improving the health of pregnant and lactating women due to its high content of folic acid 5 .The current research aims to know the effect of adding levels of NPK fertilizers and the places of addition on the concentration of these nutrients in the vegetative and fruiting part and the productivity of the okra crop.

Materials and Methods
A field experiment was carried out in the Al-Suwaira district -Wasit governorate by plowing the soil, smoothing it, amending it, opening the waterways and dividing it into sectors and experimental units.Soil samples were taken from the field before planting and prepared for analyses to estimate some of its properties, as mentioned in 6,7 , as shown in Table 1.The experiment treatments included the addition of three levels of NPK macronutrients, the comparison treatment without adding fertilizer C0, the first level C1 (120,80,60) and the second level C2 (180,120,90) kg NPK ha-1 sequentially in the form of urea as a source of nitrogen and DAP as a source of phosphorous and potassium sulfate As a source of potassium.Fertilizers were added at two distances from the plant, 10 and 20 cm beside the plant banding and given the symbol D1, D2 sequentially, from these three levels and two distances, the following combinations C2D2, C2D1, C1D2, C1D1, C0D2, and C0D1 have resulted.The number of experimental units reached 18 experimental units.The seeds of the Batra variety were planted on 15/3/2021, and scientific methods were followed in crop management, such as irrigation, weeding and pest control.I took 12 fairies from the okra crop and then finished the experiment.Growth criteria included taking the dry weight of plants, root diameters and NPK concentrations in The vegetative part at the end of the experiment and the concentrations of NPK in the yield in the first and last fairies and taking the cumulative yield.The plant samples were dried at 65°C until the weight was stable.The plant samples were digested by the wet digestion method, and the NPK elements were estimated according to Tandon 8 .

Effect levels of mineral fertilizers and their placement on nitrogen concentration in the vegetative part and okra pods
Table 2 shows that the added mineral fertilizers significantly affected nitrogen concentration in the vegetative part and okra pods.Treatment C2D2 gave the highest concentration in the vegetative part, 5.2% and treatment C0D1, the lowest concentration, 3.7%.The second level of mineral fertilization, C2D1, gave the highest concentration in the first fairy, 4.6%, and 4.5% in the last fairy, respectively.In contrast, the control treatment C0D2 gave the lowest concentration in the first and last fairy, 1.4% and 2.2%, respectively.3. Effect levels of mineral fertilizers and their placement on phosphorous concentration in the vegetative part and okra pods (%).

Effect levels of mineral fertilizers and their placement on potassium concentration in the vegetative part and okra pods.
Table 4 shows no significant effect of the mineral fertilizers added on potassium concentration levels in the vegetative part and okra pods.However, its concentration in the fertilized treatments was higher than the two comparison treatments.The potassium concentration in the pods was close in the first and last fairies.

Table 4. Effect levels of mineral fertilizers and their placement on potassium concentration in vegetative parts and okra pods (%).
Effect levels of mineral fertilizers and their placement on the vegetative dry weight of okra g plant -1 and root diameter (cm) Table 5 shows that the C2D2 treatment showed a significant difference in the average dry weight of the okra plant from the rest of the treatments, 175.0 g plant -1 .
In contrast, the differences were insignificant between the rest of the treatments, especially with the two comparison treatments.The effect of fertilizer levels on okra's average root diameter was insignificant except for one of the two control treatments, C0D1.The most significant root diameter was in treatment C2D2, 75.0 cm, and the lowest was in the control treatment C0D1, 56.67 cm.

Treatments Dry weight of okra plant g plant -1
The root diameter of the okra plant

Effect levels of mineral fertilizers and the placement of their addition on okra yield kg experimental unit -1
Table 6 shows that fertilizer levels have a significant effect on okra yield.The order of treatments was C0D2˂C0D1˂ C1D1˂C1D2˂C2D1˂C2D2. Treatment C2D2 gave the highest yield of 1.024 kg experimental unit-1, i.e., 1.138 Mg ha-1, while treatment C0D2 gave the lowest yield of 0.675 kg experimental unit-1, i.e., 0.750 Mg ha-1, and the percentage increase in the yield was 51.7%.The significant differences were different between the treatments.6.Effect fertilizer levels and their addition placement on the yield of okra, kg experimental unit -1.

Discussion
Table (1) shows that the nitrogen concentration in the vegetative part is higher than in the pods, consistent with Al-Zubaidi 9 obtained.It was found that the nitrogen concentration in the vegetative part was 5.0% and in the pods 4.8%.This can be explained by the entry of nitrogen into the formation of the chlorophyll molecule 3 .The same table shows that the concentration of nitrogen in the pods is close in the first and the last fairies, especially in the fertilized treatments, with an increase in the concentration in the two comparison treatments.The results show that plants suffer from nitrogen deficiency in the two comparison treatments, as the values were less than 3%.At the same time, Barker and Pilbeam 1 mentioned that the ideal nitrogen level in plants is higher than 3%.The location of the fertilizer addition did not affect the nitrogen concentration in the plant due to the expansion and spread of the roots to far distances from the addition distances.Concerning the effect levels of mineral fertilizers and their placement on phosphorous concentration in the vegetative part and okra pods, the result indicated that phosphorous concentration in the vegetative part is less than in pods.This can be explained by phosphorous being stored in the fruit parts as faytin 10 .The table shows that the concentration of phosphorous in the pods is close in the first and last fairies and that the plants suffer from a lack of phosphorus in the two comparison treatments, as the values were less than 0.3%.At the same time, Barker and Pilbeam 1 mentioned that the sufficient level of phosphorus in almost all plants when it is higher than 0.3%.The location of the fertilizer application did not affect the phosphorous concentration in the plant, as mentioned previously.The table shows that the potassium concentration in the vegetative part is higher than in the pods.This can be explained by the fact that potassium maintains the swelling pressure of the plant and is necessary in the process of photosynthesis and metabolic processes and can affect the rate of transpiration and water absorption by regulating the process of opening the stomata, so it is more present in the vegetative part than the fruit.The location of the fertilizer addition did not have a significant effect on the potassium concentration in the plant due to the expansion and spread of the roots far beyond the distances of addition, in addition to the fact that the soils of dry and semi-dry areas are characterized by their high content of potassium Total and non-exchanged potassium, which is likely to supplement the soil solution and exchange surfaces with potassium 3 or that this soil has a high buffering capacity for potassium and a high ability to release potassium 11 .Similarly, the potassium concentration in the vegetative part is higher than in the pods.This can be explained by the fact that potassium maintains the swelling pressure of the plant, is necessary for photosynthesis and metabolic processes, and can affect the rate of transpiration and water absorption by regulating the process of opening the stomata.Thus, it is more present in the vegetative part than in the fruit.The location of the fertilizer addition did not significantly affect the potassium concentration for the same reason mentioned above, in addition to the fact that the soils of dry and semi-dry areas are characterized by their high content of potassium Total and non-exchanged potassium, which is likely to supplement the soil solution and exchange surfaces with potassium 3 or that this soil has a high buffering capacity for potassium and a high ability to release potassium 11,12,13,14 .

Conclusions
It can be concluded from table (5) that the position of adding fertilizer did not have a significant effect on the vegetative dry weight of okra because the diameter of the plant roots is greater than the distances of the place where fertilizers were added.This means that the roots of plants can reach the places where fertilizers are added, even if the nutrient ion is immobile Or with little movement in the soil.Notably, the percentage of dry matter in the okra plant is 26%, meaning that the percentage of moisture is 74%.Finally, The location of the fertilizer application did not have a significant effect on the yield due to the considerable dispersal distance of the plant roots, as shown in table (5)

Table 2 . Effect levels of mineral fertilizers and their placement on nitrogen concentration in vegetative part and okra pods (%).
Table 3shows that the levels of added mineral fertilizers significantly affected the phosphorous concentration in the vegetative part and okra pods.Treatment C2D2 gave the highest concentration in the vegetative part, 0.43%, and treatment C0D1 had the lowest concentration, 0.20%.The second level of mineral fertilization, C2, gave the highest concentration in the first and last pounds, 0.47% and 0.46%, respectively, while the two control treatments, C0, gave the lowest concentration in the first and last pounds, 0.21% and 0.23%.