Response of Forage Quality Characters of Oats (Avena sativa L.) to Nitrogen Spraying, Cutting Stages and Cultivars

A field experiment was conducted during winter season of 2020-2021 in the Al-Hamdhyia research station, College of Agriculture, Anbar Univercity to study the response of forage quality characters of oats (Avena sativa L.) to nitrogen spraying, cutting stages and cultivars. A split-split plots arrangement according to the RCBD at three replications was used. The main plots included spraying of four concentrations of nitrogen (0, 2, 4 and 6 g N L-1), while the sub-split plots included three cutting stages (40, 50 and 60 days after planting, whereas the sub plots included three oats cultivars ((Shifaa, Carlop and Hamel). The results showed that the spraying of nitrogen at a 6 g N L-1 was significantly superiority and gave the highest percentages of protein, ash and fat (12.99, 26.56, 22.45 and 3.12%) respectively. The cutting stages also significantly affected the studied characters, the cutting after 40 days of planting achieved the highest percentages of protein, ash and fat (13.02, 23.59 and 3.24 %) respectively, while the cutting after 60 days of planting achieved the highest percentages of carbohydrates and fiber (27.71 and 30.39%) respectively. Also, the oats cultivars was significantly differed in the most of the studied characters, as the Carlop cultivar excelled in the percentages of fiber (29.23%), whereas the Shifaa cultivar excelled in the carbohydrates percentage of (26.30%), while the Hamel cultivar excelled in the ash percentage (21.23%). The di and triple interactions between studied factors had significant effects on the studied traits.


Introduction
Green forages plays an important and essential role in feeding of animals, as it is considered an essential pillar of agricultural production in the world, as any stable agricultural system must include green forage crops, which are provided to animals directly after cutting or as hay or silage.The deterioration of the livestock sector in Iraq has increased the problem of production, and due to the importance of this sector as it is an essential part of the agricultural sector, it also suffers from a lack of better quality forages, especially in the winter season, and reliance on the meals of maize, cotton seed and soybeans after the end of its growing season or on weeds that lack their content of nutritional compounds, which negatively reflects on the quality of forage and the quality of animal products, which means a significant shortage of animal protein that doesn't parallels the population increase and the growing needs of the population.Therefore, it is necessary to search for crops with high productivity and quality that can tolerant the low temperatures such as oats.Despite the success of its 1259 (2023) 012115 IOP Publishing doi:10.1088/1755-1315/1259/1/012115 2 cultivation in Iraq, it is still grown on a small scale to obtain green forages and grains, although it contains a good percentage of protein (9-12%) of dry matter [1].Oats (Avena sativa L.) is one of the winter cereal crops, which is characterized by the intensity of its vegetative growth and the large number of its leaves, which gives it a high fodder nutritional value, also, it is characterized by the length of its growing season and giving it several mowings during the season.It tolerates low temperatures in the autumn, so it is considered more suitable for cultivation than many forage crops [2].Oats are widely used in the world as livestock feed due to its good forage quality as well as high yield.However, oats in Iraq is a secondary crop, as it is grown either alone or mixed with forage crops such as alfalfa and clover, despite some cultivars proved successful in terms of green forage yield and good quality [3].The efficiency of the forage can be raised through many agricultural operations, among these operations is the use of nitrogen fertilizers using the foliar nutrition method, which is highly efficient as it allows for rapid absorption (50% within 6 hours) and effective transfer to all parts of the plant as well as reducing losses as a result of volatilization and leaching, reducing environmental pollution with chemical compounds and reducing the cost production [4].The importance of nitrogen comes through its role in many vital activities in the plant, its involvement in the synthesis of amino acids, which are the basic structure for proteins building, as well as its involvement in the synthesis of nucleic acids, energy compounds (NADPH 2 and ATP), enzymes, hormones and vitamins, including vitamin B, and its involvement in the formation of cellular membranes, mitochondria and chloroplasts [5].Also, the period of cutting are among the factors affecting the quality of forage crops, through which the appropriate date for cutting is determined to obtain the best quality of forage.Therefore, this research was carried out to study the response of forage quality characters of oats to nitrogen spraying, cutting stages and cultivars.

Materials and Methods
A field experiment was conducted during winter season of 2020-2021 in the Al-Hamdhyia research station, College of Agriculture, Anbar Univercity to study the response of forage quality characters of oats (Avena sativa L.) to nitrogen spraying, cutting stages and cultivars.A split-split plots arrangement according to the RCBD at three replications was used.The main plots included spraying of four concentrations of nitrogen (0, 2, 4 and 6 g N L -1 ), while the sub-split plots included three cutting stages (40, 50 and 60 days after planting, whereas the sub plots included three oats cultivars (Shifaa, Carlop and Hamel).The required soil service operations were carried out, then the experimental land was divided into 108 experimental units.The area of each experimental unit was 6 m 2 (2 m × 3 m).The seeds were sown in 15/10/2020 at a seeding rate of 140 Kg ha -1 .Phosphate fertilizer was added as a triple superphosphate (45% P 2 O 5 ) at a level of 100 Kg P ha -1 at one dose before planting [6], while the nitrogen fertilizer was spraying as a urea (46% N) according to used concentrations at three doses, the first after two weeks of emergence, while the second and third were added after each cutting for all experimental units to ensure the restoration of growth after mowing [7].Crop service operations were conducted as needed.

Studied Traits
 Protein percentage (%): The nitrogen percentage was estimated using the Micro kjeldahl device, then the protein percentage was calculated from the following equation [8]: Protein percentage (%) = Nitrogen percentage (%) × 6.25  Carbohydrates percentage (%): It was estimated according to the method used in [8]. Ash percentage (%): It was estimated using the Muffle Furnace device according to the method followed in [8]. Oil percentage (%): It was estimated according to the method used in A.O.A.C [8]. Fibers percentage (%): It was estimated using the Tecator Fibertic System according to the method used in A.O.A.C. [8]. 3 The data were statistically analyzed using Genstat program and least significant difference (Lsd) test at 0.05 probability level was used to compare between averages.

Protein Percentage (%)
The results in Table (1) show that the spraying of nitrogen at a 6 g N L -1 was significantly superiority and gave a highest protein percentage 12.99% with non-significant difference with spraying of nitrogen at a 2 and 4 g N L -1 which gave 12.36 and 12.90% respectively compared to control treatment (0 g N L -1 ) which gave a lowest (12.09%).The reason of increase the protein percentage when increasing the nitrogen concentrations may be attributed to the role of nitrogen in the formation of amino acids and their accumulation in the leaves.This result agrees with the results of [7].According to the shown percentages, the results in Table (1) reveal that the cutting after 40 days of planting was significantly superiority and achieved a highest protein percentage 13.02% with non-significant difference with cutting after 50 days of planting (12.48%) compared to cutting after 60 days of planting which achieved a lowest (12.35%).The reason of decrease of protein percentage when progression of the growth stages could be due to an increase the fiber percentage in the forage.This result is in line with the findings of [9].The results in Table (1) indicate that there was non-significant difference between oats cultivars in the protein percentage.The interaction between nitrogen spraying concentrations and cutting stages had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 × the cutting after 40 days of planting recorded a highest value (13.62%), whereas the spraying of distilled water (0 g N L -1 ) × the cutting after 60 days of planting recorded a lowest value (11.80%).The interaction between nitrogen spraying concentrations and oats cultivars had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 on the Carlop cultivar plants gave a highest value (13.34%), while the spraying of distilled water (0 g N L -1 ) on the Shifaa cultivar plants gave a lowest value (11.25%).The interaction between cutting stages and oats cultivars had significant effect on this character, the cutting of Carlop cultivar plants after 40 days of planting achieved a highest value (13.73%), whereas the cutting of Shifaa cultivar plants after 50 days of planting achieved a lowest value (12.07%).The interaction between three studied factors had significant effect on this character, the spraying of Carlop cultivar plants with nitrogen at a 4 g N L -1 and cutting after 40 days of planting gave a highest value (14.47%), while the spraying of Shifaa cultivar plants with distilled water and cutting after 60 days of planting gave a lowest value (11.00%).

Carbohydrates Percentage (%)
The results in Table (2) clarify that the spraying of nitrogen at a 6 g N L -1 was significantly superiority and gave a highest carbohydrates percentage 56.26%with non-significant difference with spraying of nitrogen at a 4 g N L -1 which gave 25.98% compared to control treatment (0 g N L -1 ) which gave a lowest (24.12%).The reason of increase the protein percentage when increasing the nitrogen concentrations may be due to the role of nitrogen in improving the vegetative growth and the accumulation of nutrients in the leaves, which increases the photosynthesis process and then increase the building of carbohydrates [10].The results in Table (2) show that the cutting after 60 days of planting was significantly superiority and achieved a highest carbohydrates percentage 27.71%compared to cutting after 50 days of planting which achieved a lowest 24.53% with non-significant difference with cutting after 40 days of planting (24.61%).The reason of increase the percentage of carbohydrates when progression of growth stages may be due to the increased accumulation of carbohydrates in the last stages of growth.Regarding of oats cultivars, the results in Table (2) reveal that the Shifaa cultivar was significantly superiority and gave a highest carbohydrate percentage 26.30%compared to Carlop cultivar which gave a lowest 24.54%.The reason of difference between oats cultivars may be due to their different in the genetic structure.These results are in line with the findings of [10].The interaction between nitrogen spraying concentrations and cutting stages had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 × the cutting after 60 days of planting recorded a highest value (29.37%), whereas the spraying of distilled water (0 g N L -1 ) × the cutting after 40 days of planting recorded a lowest value (23.06%).The interaction between nitrogen spraying concentrations and oats cultivars had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 on the Shifaa cultivar plants gave a highest value (27.83%), while the spraying of distilled water (0 g N L -1 ) on the Carlop cultivar plants gave a lowest value (20.23%).The interaction between cutting stages and oats cultivars had significant effect on this character, the cutting of Shifaa cultivar plants after 60 days of planting achieved a highest value (28.62%), whereas the cutting of Carlop cultivar plants after 50 days of planting achieved a lowest value (22.93%).The interaction between three studied factors had significant effect on this character, the spraying of Shifaa cultivar plants with nitrogen at a 6 g N L -1 and cutting after 60 days of planting gave a highest value (31.27%), while the spraying of Carlop cultivar plants with distilled water and cutting after 50 days of planting gave a lowest value (19.43%).

Ash Percentage (%)
The results in Table (3) reveal that the spraying of nitrogen at a 6 g N L -1 was significantly superiority and gave a highest ash percentage 22.5% compared to control treatment (0 g N L -1 ) which gave a lowest (17.9%).The reason of increase may be attributed to the role of nitrogen in stimulating growth and increasing the absorption and accumulation of nutrients in the plant.This result is in agreement with the results of [7].According to the shown percentages, the results in Table (3) reveal that the cutting after 40 days of planting was significantly superiority and achieved a highest ash percentage 23.6%compared to cutting after 60 days of planting which achieved a lowest (17.3%).The reason of increase the ash percentage could be due to an increase the accumulation of nutrients in the leaves and plant tissues, which increased their concentrations a the early stages of growth.This result is in line with the findings of [11].The results in Table (3) indicate that the Hamel cultivar was significantly superiority and gave a highest ash percentage 21.2% with non-significant difference with Carlop cultivar (20.8%) compared to Shifaa cultivar which gave a lowest 19.6%.The reason of difference of oats cultivars may be due to their different in the genetic structure (Kim et al., 2006).These results are in agreement with the results of [12].The interaction between nitrogen spraying concentrations and cutting stages had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 × the cutting after 40 days of planting recorded a highest value (25.4%), whereas the spraying of distilled water (0 g N L -1 ) × the cutting after 60 days of planting recorded a lowest value (14.2%).The interaction between nitrogen spraying concentrations and oats cultivars had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 on the Hamel cultivar plants gave a highest value (24.1%), while the spraying of distilled water (0 g N L -1 ) on the Carlop cultivar plants gave a lowest value (17.0%).The interaction between cutting stages and oats cultivars had significant effect on this character, the cutting of Carlop cultivar plants after 40 days of planting achieved a highest value (24.3%), whereas the cutting of same cultivar plants after 60 days of planting achieved a lowest value (17.0%).The interaction between three studied factors had significant effect on this character, the spraying of Hamel cultivar plants with nitrogen at a 6 g N L -1 and cutting after 40 days of planting gave a highest value (27.0%), while the spraying of Carlop cultivar plants with distilled water and cutting after 60 days of planting gave a lowest value (13.0%).

Fat Percentage (%)
The results in Table (4) clarify that the spraying of nitrogen at a 6 g N L -1 was significantly superiority and gave a highest fat percentage 3.12% with non-significant difference with spraying of nitrogen at a 2 g N L -1 which gave 2.98% compared to control treatment (0 g N L -1 ) which gave a lowest (2.42%).The reason of increase the fat percentage when increasing nitrogen concentration may be attributed to the important role of nitrogen in accelerating the process of respiration, through which most carbohydrates are converted into crude fat.These results are in line with the results of [13].The results in Table (4) show that the cutting after 40 days of planting was significantly superiority and achieved a highest fat percentage 3.24% compared to cutting after 50 days of planting which achieved a lowest 2.66% with non-significant difference with cutting after 60 days of planting (2.70%).The reason of decrease could be attributed to decrease of ether extract with the progression of the cutting stages as result of delay the plants growth stage or the consumption of part of it in energy production [5].The results in Table (4) indicate that there was non-significant difference between oats cultivars in the fat percentage.The interaction between nitrogen spraying concentrations and cutting stages had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 × the cutting after 40 days of planting recorded a highest value (3.64%), whereas the spraying of nitrogen at a 2 g N L -1 × the cutting after 60 days of planting recorded a lowest value (2.10%).The interaction between nitrogen spraying concentrations and oats cultivars had significant effect on this character, the spraying of nitrogen at a 6 g N L -1 on the Hamel cultivar plants gave a highest value (3.47%), while the spraying of distilled water (0 g N L -1 ) on the Shifaa cultivar plants gave a lowest value (2.27%).The interaction between cutting stages and oats cultivars had significant effect on this character, the cutting of Shifaa cultivar plants after 40 days of planting achieved a highest value (3.27%), whereas the cutting of same cultivar plants after 60 days of planting achieved a lowest value (2.24%).The interaction between three studied factors had significant effect on this character, the spraying of Shifaa cultivar plants with nitrogen at a 6 g N L -1 and cutting after 40 days of planting gave a highest value (4.03%), while the spraying of same cultivar plants with distilled water and cutting after 60 days of planting gave a lowest value (1.70%).

Fiber Percentage (%)
The results in Table (5) reveal that the spraying of nitrogen led to a significant decrease of fiber percentage, as the spraying of distilled water gave a highest percentage of this character 29.22% compared with spraying of nitrogen at a 6 g N L -1 which gave a lowest 25.81%.This result is agrees with the results of [7].According to the shown percentages, the results in Table (5) reveal that the cutting after 60 days of planting was significantly superiority and achieved a highest fiber percentage 30.39%compared to cutting after 40 days of planting which achieved a lowest (25.60%).The reason of decrease the fiber percentage at the early stages of growth may be due to the lack of materials that enter into the fiber formation, as there is an inverse relationship between the cutting stages and fiber percentage, as the delay of cutting date lead to an increase the percentage of cellulose, hemicellulose and lignin [14], or the reason of decrease may be due to the increase the protein percentage (Table 1).This result is in line with the findings of [11].The results in Table (5) indicate that the Carlop cultivar was significantly superiority and gave a highest fiber percentage 29.23%compared to Hamel cultivar which gave a lowest 27.57% with non-significant difference with Shifaa cultivar (27.80%).The reason of difference of oats cultivars may be due to their different in the genetic structure.These results are in agreement with the results of [14].The interaction between nitrogen spraying concentrations and cutting stages had significant effect on this character, the spraying of nitrogen at a 4 g N L -1 × the cutting after 60 days of planting recorded a highest value (31.89%), whereas the spraying of spraying of nitrogen at a 4 g N L -1 × the cutting after 40 days of planting recorded a lowest value (23.14%).The interaction between nitrogen spraying concentrations and oats cultivars had significant effect on this character, the spraying distilled water on the Carlop cultivar plants gave a highest value (34.29%), while the spraying of nitrogen at a 6 g N L -1 on the Shifaa cultivar plants gave a lowest value (24.74%).The interaction between cutting stages and oats cultivars had significant effect on this character, the cutting of Shifaa cultivar plants after 60 days of planting achieved a highest value (30.92%), whereas the cutting of Hamel cultivar plants after 40 days of planting achieved a lowest value (24.84%).The interaction between three studied factors had significant effect on this character, the spraying of Shifaa cultivar plants with nitrogen at a 2 g N L -1 and cutting after 60 days of planting gave a highest value (38.40%), while the spraying of Hamel cultivar plants with nitrogen at a 6 g N L -1 and cutting after 40 days of planting gave a lowest value (22.63%).

Table 1 .
Effect of nitrogen spraying and cutting stage on protein percentage (%) in forage of oats cultivars.

Table 2 .
Effect of nitrogen spraying and cutting stage on carbohydrates percentage (%) in forage of oats cultivars.

Table 3 .
Effect of nitrogen spraying and cutting stage on ash percentage (%) in forage of oats cultivars.

Table 4 .
Effect of nitrogen spraying and cutting stage on fat percentage (%) in forage of oats cultivars.

Table 5 .
Effect of nitrogen spraying and cutting stage on fiber percentage (%) in forage of oats cultivars.