Sustainable practices impact and planting date on yield of sorghum (Sorghum bicolor L. Moench)

Environmental stress affects the yield of sorghum. This impact can be reduced by seed stimulation technique and determining the appropriate planting date. An experiment was conducted in the spring and fall seasons of 2022. Randomized complete block design with split-plot arrangement in four replications was used. Planting dates (spring season: February 15th, March 1st, 15th, April 1st, 15th; fall season: June 15th, July 1st, 15th, August 1st, 15th) were assigned to the main plots. Seed stimulation treatments (banana peel extract 35% + citric acid 100 mg L−1 and soaking in distilled water only) were applied to the subplots. The interaction treatment of soaking with banana peel extract + citric acid and the planting date of April 15th showed superiority in traits of head grain number (1743) and total grain yield (6.135 tons ha−1) during the spring season. Seed stimulation treatment with banana peel extract + citric acid on July 1st planting date outperformed in traits of plant dry weight (398.8 g), head grain number (4582), total grain yield (10.82 tons ha−1), and biological yield (67.8 tons ha−1) during the fall season. It can be concluded that seed stimulation with banana peel extract + citric acid improved yield characteristics. Early planting date in the spring season (February 15th, March 1st, or March 15th) or the delay in the fall season (August 1st or August 15th) resulted in less efficient plant performance. This is closely related to the nature of the climatic conditions accompanying crop growth from planting to harvesting. Also, using of agricultural applications related to the use of natural materials could helping hand sustainable agriculture. It can be recommended to soak seeds with banana peel extract + citric acid and adopt the planting date of April 15th for the spring season and July 1st for the fall season to enhance grain yield.


Introduction
The yield and quality of sorghum grains decrease under unfavorable environmental conditions due to the impact on various plant growth stages, ultimately affecting the yield [1,2].The appropriate temperature 1325 (2024) 012013 IOP Publishing doi:10.1088/1755-1315/1325/1/012013 2 during the period of grain formation and filling means an increase in the accumulation of dry matter, the number, and weight of the grains, and total yield [3].
Seed stimulation improved plant performance such as plant height, leaf area, seedling dry weight, ratio of chlorophyll, proline, and reduced sodium to potassium ratio [4].Osmotic potential of activator solution, temperature and soaking duration are the key for improving germination percentage [5].Soaking or coating seeds to withstand herbicide, disease, and high or low temperatures during the spring and fall seasons, which affect carbon assimilation efficiency and yield [6,7,8,9].Temperatures effect on potential performance and ability of seeds, germination, field emergence and growth [10].Seed priming enhances crop seeds performance, especially under environmental stresses like soil salinity or unfavorable temperatures [11,12,13].Sorghum seed priming technology before planting increased the seed vitality and vigour through improving germination ratio, seedling growth and performance to tolerate drought stress compared to the unprimed [14,15,16].Maize cultivars had the ability to tolerate drought stress somewhat after priming their seed, especially when planting in fall season [17].Soaking of deteriorated seed with GA 3 led to improve germination ratio and seedling growth in oat [18].Soaking seed of maize with GA 3 improved characteristics of germination, emergence properties and seedling growth [19,20].
Seed priming led to favorable results through good field establishment reaching to yield [21,22]. Seed priming led to accelerate physiological maturity and increasing grain yield through promoting grain growth rate, and grain filling period [23,24].Seed soaking improved growth, and grain yield of bread wheat, especially seed soaking with GA 3 [25].Seed stimulation in nutritional elements or various substances and compounds was suitable solution to unlock the potential energy in many crop seeds under a wide range of environmental conditions [26,27,28,29,30].Cold test and first count in sorghum and accelerated aging test in maize were closer to predict the field emergence [31,32].Seed stimulation reduced negative effect of soil temperature and microorganism and led to increase germination rate in the accelerated age test and the cold test through [33].
Banana peels contain a high percentage of vitamins A and C, tryptophan, carbohydrates, proteins, essential amino acids, natural phenolic compounds, flavonoids, natural antioxidants, and growthpromoting substances, especially nitrogen, and potassium [34,35].Citric acid is highly water-soluble organic acid, non-enzymatic antioxidants, and had significant role in alleviating and tolerating both biotic and abiotic stresses in plants [36,37].Citric acid contributed to the formation of plant cells and the synthesis of compounds like fats, proteins, and various carbohydrates that the plant produced during growth stages [38].
Adapting to climatic changes is essential in light of the new environmental impact.Winter has become shorter and warmer, and spring arrives earlier than usual.These changes can be addressed by determining the planting date and utilizing seed stimulation technique to achieve suitable synchronization between plant growth stages and appropriate temperature, light, and moisture conditions.This synchronization will lead to an increase in yield by finding the optimum match between the planting date, plant growth, and yield which was the aim of this study, in addition to use sustainable agricultural practices to support good ecosystem.

Materials and Methods
A field experiment was conducted for two seasons at the fields of the Directorate of Horticulture, Ministry of Agriculture, in the spring season and the fields of the College of Agricultural Engineering Sciences, University of Baghdad, in the fall season in 2022.A randomized complete block design was used with split-plot arrangement and four replications.The first factor was seed stimulation before planting (100 mg L -1 citric acid + 35% banana peel aqueous extract, in addition to the soaking treatment with distilled water only).The second factor was five planting dates in the spring season (February 15 th , March 1 st and 15 th , April 1 st and 15 th ) and in the fall season (June 15 th , July 1 st and 15 th , August 1 st and 15 th ).Planting date treatments were allocated to the main plots and seed stimulation treatments were in the subplots.The seeds soaking duration was 12 hours [9] at room temperature on filter paper in Petri dishes.Banana peel aqueous extract was prepared by cutting banana peels after washing them well with distilled water into pieces (3x3 cm) soaking 100 g of them in 1 liter of distilled water, and left until the banana peel tissues were completely decomposed for 7 days at room temperature, taking care to open the bottle cap once a day to remove the accumulated gases in the bottle.The clear yellow liquid begins to turn dark as the reaction continues, then it turns into a black opaque liquid, or the banana peels float and the liquid settles at the bottom or the appearance of a sweet and sour smell of the liquid, which is an indicator of the completion of decomposition [39].Then the liquid was filtered using (150 ml) diameter filter paper and buchner funnel.The volume of the aqueous extract reached 900 ml and the volume was completed to 1000 ml with distilled water to obtain a 10% concentration of the extract.The required concentrations were prepared by taking (15, 25, and 35) ml of the aqueous extract and completing the volume to 100 ml with distilled water, and it was kept in the refrigerator at a temperature of 5°C until use.Concentrations of citric acid (C 6 H 8 O 7 with molecular weight 192.12 and purity 99% from Avonchem) were prepared by dissolving the acid in water to prepare the required concentrations.
The field was plowed thoroughly, leveled, and sub-plots (4 m length × 3 m width) were established, with five rows spaced at a distance of 70 cm between them and 10 cm between holes (plants).The distance between main plots was 1 m, and between replicates was 1.5 m.Diammonium phosphate fertilizer DAP (46% N and 18% P) was added at a rate of 436 kg ha -1 in a single application, and urea fertilizer was applied at a rate of 696 kg ha -1 in two doses: the first at planting and the second 40 days after planting [40].The fertilizers were applied as topdressing 10 cm away from the planting line.Seeds of the variety "Inqath" were used.This variety was approved in 2002 by the Agricultural Research Directorate, Ministry of Agriculture.It is suitable for both spring and fall seasons in the central and southern regions of Iraq.Planting was done with three seeds per hole at a depth of 3 cm.Thinning was carried out after emergence when plant height reached 15-20 cm, leaving one plant per hole at a plant density of 142,857 plants ha -1 .Manual weeding was performed whenever necessary.The granular pesticide Diazinon 10% EC, with an active ingredient concentration of 6 kg ha -1 , was used to control the stem borer insect.It was applied twice to the growing tip of the plant: the first as a preventive measure at the stage of 4-5 leaves, and the second 15 days after the first treatment.Traits were studied on ten randomly selected plants from the midlines at the harvest stage, as follows: Number of heads per plant.Number of grains per head.Weight of 1000 grains (g).Total grains yield (ton ha -1 ): It was calculated by multiplying the yield of a single plant by the plant density.Biological yield (ton ha -1 ): It was calculated after drying whole plants in an electric oven at a temperature of 70°C for (2-4) days until the weight was stable.Harvest index (%): It was calculated by equation (1) [38]: Harvest index (%) = ୰ୟ୧୬ ୷୧ୣ୪ୢ ୠ୧୭୪୭୧ୡୟ୪ ୷୧ୣ୪ୢ ‫ݔ‬ 100 (1) Data was statistically analyzed according to the randomized completely block design with a split-plot arrangement with four replications.The simple correlation coefficient between the studied traits was calculated.The means of the treatments were compared by the least significant difference (LSD) test at a probability level of 5% using the Genstat statistical program [41].Note: Only, soaking seeds in distilled water before planting in February 15 th gave no data for all traits.

Number of heads in the plant
The treatment involving soaking with a solution of banana peels extract + citric acid outperformed, with an average of 1.2 heads plant -1 , compared to soaking with distilled water which yielded 0.9 heads plant -1 for the spring season.However, contrasting results were observed for the fall season (Table 1).
Planting dates of March 1 st and March 15 th exhibited superiority with an average of 1.3 heads plant -1 , while the lowest average was recorded for the planting dates of April 1 st and April 15 th , with a mean of 1.0 heads plant -1 .Several factors caused variations and influenced cell growth in plants, such as external (environmental) and internal factors.One of the most important internal factors is plant growth hormones.Some studies showed that low temperatures and high relative humidity affected the levels of plant hormones that are responsible for growth and increased number of branches, and inflorescences.These conditions enhanced the production or inhibition of certain hormones, such as auxin and cytokinin, which led to increase plant heads number.Many plant hormones, such as auxins, gibberellins, brassinosteroids, ethylene, and cytokinins, accelerated or enhanced cell growth.Plant hormones reduced abiotic stress (salinity, temperature, drought, etc.), and led to improve growth, and yield under severe conditions [42].
The interaction treatment of soaking with banana peel extract + citric acid and the planting date of March 15 th outperformed, with an average of 1.5 heads plant -1 , and only, soaking seeds in distilled water before planting in February 15 th gave no data for all traits.

Number of grains per head
The seeds that were soaked in banana peel extract + citric acid outperformed the distilled water soaking treatment in both seasons (Table 3).Banana peels contain amino acids, vitamin A, vitamin C, tryptophan, and a carbohydrate [43].Amino acids, especially tryptophan, are the building blocks for the formation of auxins in plant tissue, which are active in cell division and play a major role in the polarization of carbohydrates synthesized in the leaves and transferred to the seeds [44].Soaking in citric acid stimulated roots growth, lateral roots, and uptake nutrient in soil.[45].
Citric acid acts as a catalyst for metabolic processes in seeds and emerging plants.Citric acid increased enzymes activity which responsible on availability and transport of necessary nutrients for the growth and development of seeds.Citric acid promoted growth of roots, leaf and formation other plant organs.Also, had role in enhancing plant tolerance to abiotic stresses such as drought, salinity, and temperature [46].
The planting date of April 15 th outperformed the date of March 15 th , with the highest number of grains per head (1497) compared to the date of March 15 th , which gave the lowest average (914 grains head -1 ).The seeds soaked in banana peel extract + citric acid planted in April 15 th gave (1743 grains head -1 ).The treatment of soaking in banana peel extract + citric acid and suitable planting date, led to the photosynthetic efficiency through converted light energy into chemical energy, increase the accumulation of dry matter, and grains number.The date of July 1 st outperformed the date of August 15 th , with the highest average of 3688 grains per head, while the date of August 15 th gave the lowest average of 1940 grains head -1 , which did not differ significantly from the date of June 15 th , which gave 1941grains head -1 .Suitable temperature, humidity, and length of the light period during the flowering period led to raise fertility rate through pollination process success, number of pollinated florets up to increase number of grains per head.The seeds soaked in banana peel extract + citric acid planted on July 1 st outperformed, with the highest average (4582 grains head -1 ), while the seeds soaked in distilled water and planted on August 15 th gave the lowest average of 1766 grains head -1 .

Weight of 1000 grains (g)
The seeds soaked in banana peel extract + citric acid gave the highest average for this trait compared to the distilled water soaking treatment in the spring season (Table 4).The date of April 1 st outperformed, with the highest average of 33.87 g compared to the date of March 15 th , which gave the lowest average (22.57g).Environmental conditions contributed nutrients transfer from source into sink in seeds.The average temperature was (30.46°C) (Table 2).The suitability of the temperature during the grain formation and filling period led to increase in production and accumulation of dry matter, and grain weight [47].The interaction results showed the superiority of stimulating the seeds with banana peel extract + citric acid planted on April 1 st with an average of (37.98 g).
The distilled water soaking treatment had the highest average weight of 26.04 g, outperforming the banana peel extract + citric acid soaking treatment in the fall season (Table 4).

Total grain yield (ton ha -1 )
In both seasons, the seeds soaked in banana peel extract + citric acid outperformed the soaking treatment with distilled water (Table 5).The date of April 1 st had the highest average yield of 5.61 tons ha -1 , which was not significantly different from the date of April 15 th at 5.48 tons ha -1 .The lowest average yield was at the date of March 15 th (2.952 tons ha -1 ).This is because the same date also had the highest average weight of 1000 seeds (Table 4).The seeds soaked in banana peel extract + citric acid and planted on April 15 th had the highest average yield of 6.135 tons ha -1 .The reason for the superiority is due to the soaking treatment with banana peel extract + citric acid planted in April 15 th , which had the highest results in the number of grains per head trait (Table 3).This is supported by the significant positive correlation between the total grain yield and the number of grains per head, with a correlation coefficient of 0.777 (Table 6).It is also possible that the suitability of environmental conditions during this period helped to increase the number of grains, which in turn led to an increase in the total grain yield.The average temperature during this period was 25.37 o C (Table 2).The highest average yield of 8.86 ton ha -1 was observed for the July 1 st planting date, which was not significantly different from the July 15 th planting date with an average of 7.93 ton ha -1 .The highest average yield of 10.82 ton ha -1 was observed for the banana peel extract + citric acid soaked seeds planted on July 1 st , compared to the distilled water-soaked seeds planted on August 15 th with an average of 5.01 ton ha -1 .This is because the same interaction treatment showed superiority in the number of grains per head trait, which is further, supported by the correlation coefficient value between the traits, which reached 0.759 Table 5.Effect of seed stimulation with banana peel extract and citric acid, planting date and their interaction on total grains yield (ton ha

Biological Yield (ton ha -1 )
Seeds soaked in banana peel extract + citric acid had a higher biomass yield than the seeds treated with distilled water, except for the stimulation treatment and planting dates in the fall season, which were not statistically significant (Table 7).April 15 th had the highest average yield of 34.84 ton ha -1 , while the lowest average yield was in March 1 st and March 15 th (29.84 and 29.86 ton ha -1 , respectively).The interaction of soaking seeds with distilled water and planting them on April 15 th (35.77 ton ha -1 ) had a higher yield.Seeds treated with banana peel extract + citric acid and planted on July 1 st had the highest average of 67.8 ton ha -1 , compared to the seeds soaked in distilled water and planted on July 1 st , which gave the lowest average of 42.0 ton ha -1 .The superiority of the stimulation treatments and planting dates may be since the same combination treatment gave the best results in the number of grains per head, which was positively correlated with the trait, with a correlation coefficient value of (0.568) (Table 6).

Harvest index (%)
There is a significant effect between the study factors and their interaction on the harvest index in the spring season.Conversely, the results in the fall season were not significantly different between the study factors and their interaction (Table 8).
The banana peel extract + citric acid soaking treatment had a significantly higher average harvest index of 11.22% than the control treatment of distilled water soaking (9.88%).The date of April 1 st also had a high average harvest index of 14.56%, which was not significantly different from the date of April 15 th (14.16%).The lowest average harvest index was recorded on March 15 th , with 9.08%.The seeds soaked in distilled water and planted on April 15 th had the highest rate of 15.54%, which was significantly higher than other which had the lowest average for the trait.This may be because these treatments are the same treatments that gave the highest values for the average total grain yield and biological yield (Tables 4 and  5).This is reinforced by the positive significant correlation between the harvest index and the total grain yield and biological yield (0.977 and 0.826) respectively (Table 6).

Conclusions
It can be concluded that Seed stimulation improves plant performance, especially under environmental stress.Seeds stimulated with banana peel extract and citric acid respond better to planting date than distilled water only.Response of plants varies depending on the planting date within the same season, from the temperature and humidity of the soil during the germination stage to the temperature and humidity at harvest time.The results of this study boost sustainable agriculture as a result of the use of agricultural applications related to the use of natural materials to stimulate seeds to increase their ability to withstand adverse conditions and reveal their potential energy.It can be recommended to treat sorghum seeds before planting with a concentration of 35% banana peel extract + 100 mg L -1 citric acid as an alternative to growth regulators to improve plant growth and yield.Also, planting sorghum seeds in the April 15 th and July 1 st is recommended.

Table 1 .
Effect of seed stimulation with banana peel extract and citric acid, planting date and their interaction on number of heads per plant in sorghum.
LSD 0.05 , Least significant difference test at a probability level of 0.05; N.S: Non-significant at P≤0.05

Table 2 .
Meteorological data in the spring and fall of 2022.

Table 3 .
Effect of seed stimulation with banana peel extract and citric acid, planting date and their interaction on the number of grains per head in sorghum.

Table 4 .
Effect of seed stimulation with banana peel extract and citric acid, planting date and their interaction on weight of 1000 grain (g) in sorghum.
LSD 0.05 , Least significant difference test at a probability level of 0.05; N.S: Non-significant at P≤0.05

Table 6 .
Simple correlation coefficient between traits studied in the spring and fall of 2022 in sorghum.: significant at 0.05, the upper and lower values represent the spring and the fall seasons, respectively. *

Table 7 .
Effect of seed stimulation with banana peel extract and citric acid, planting date and their interaction on biological yield (ton ha -1 ) in sorghum.

Table 8 .
Effect of seed stimulation with banana peel extract and citric acid, planting date and their interaction on harvest index (%) in sorghum.
LSD 0.05 , Least significant difference test at a probability level of 0.05; N.S: Non-significant at P≤0.05