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Article

Determination of Combined Effects of Organic and Mineral Fertilizer on Forage Yield and Quality of Annual Ryegrass

by
Ayşe Genç Lermi
1,*,
Halil İbrahim Erkovan
2 and
Ali Koç
2
1
Bartın Vocational Training School, Bartın University, 74100 Bartın, Turkey
2
Department of Field Crops, Faculty of Agriculture, Eskisehir Osmangazi University, 26040 Eskisehir, Turkey
*
Author to whom correspondence should be addressed.
Agronomy 2023, 13(12), 2935; https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13122935
Submission received: 5 November 2023 / Revised: 24 November 2023 / Accepted: 25 November 2023 / Published: 28 November 2023
(This article belongs to the Special Issue Approaches to Promote Wider Emergence of Sustainable Agricultural Production)
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Abstract

:
The widespread practice of using high doses of nitrogen to increase unit area yield in annual ryegrass introduces ecological and economic problems. This research was carried out over two years and aimed to determine the potential forage yield and quality of annual ryegrass by applying manure, humic acid, and low doses of nitrogen fertilizer, within the framework of sustainable forage crop cultivation. The study was carried out from 2020 to 2022 with three replications according to the randomized block split plots experimental design. According to the study results, the highest values were achieved with combinations that included manure application, and even higher values were observed when manure was applied along with low doses of humic acid and nitrogen. The M20 + H20 + N100 treatment yielded the highest fresh yield, dry matter, and crude protein. The treatments with manure, humic acid, and nitrogen fertilizer had varying effects on the ADF and NDF content of annual ryegrass, resulting in fluctuating values. In conclusion, 20 t manure, 20 L humic acid, and 100 kg ha−1 N application can be suggested for sustainable and higher dry matter production with good quality for annual ryegrass cultivation under semi-humid climatic conditions. The results obtained from this research hold promise for sustainable agricultural practices.

1. Introduction

Annual ryegrass, which exhibits tolerance to various climatic and soil conditions [1], is a valuable forage crop known for its abundant leaves, richness in protein, minerals, and water-soluble carbohydrates. Unlike some other plants, its stems do not harden quickly [2,3]. It possesses a high growth rate, nitrogen absorption capacity [2], and offers high-quality hay yield [1,4]. Annual ryegrass can ensure significant forage production when provided with appropriate fertilizer doses. Fertilization plays a crucial role in enhancing forage quality, promoting animal health, and increasing overall forage yield.
The strong response of annual ryegrass to nitrogen, coupled with the fact that nitrogen content in the plant is a critical nutritional factor influencing its growth and development [5], underscores the significance of nitrogen fertilization. However, excessive nitrogen application can lead to intense competition and reduced annual grass yield [5]. The positive effects of nitrogen fertilization peak at a certain level and then diminish [2]. Excessive application of nitrogen can result in the plant’s overabsorption of nitrogen, potentially leading to environmental issues, such as imbalanced plant nutrition and water and soil pollution. Additionally, it can contribute to wasteful nitrogen use in annual ryegrass pastures, potentially posing health risks to animals due to excess nitrogen. Overfertilizing annual ryegrass is a common mistake [6].
Conventional farming systems can enhance yields by reducing nutrient inputs [7]. The use of natural fertilizer sources has become essential for sustainable crop production due to the high cost of chemical fertilizers [8]. Organic fertilizers can reduce long-term dependency on chemical fertilizers by improving soil nutrient efficiency [9], water-holding capacity [10], microbial biomass, and mineralizable nitrogen [11]. On the other hand, when chemical and organic fertilizers are combined, the amount of chemical fertilizer used decreases and higher yields are achieved [12].
Humic substances are released during the decomposition of organic materials and hold great potential as a low-cost natural fertilizer for sustaining soil fertility in high-input agricultural production systems using inorganic fertilizers [13]. Humic acid increases soil organic matter content [14], pH buffering, cation exchange capacity, and nutrient retention capacity, enhancing nutrient availability [15], particularly for immobile elements like phosphorus, iron, and zinc, while reducing heavy metal toxicity. It contributes significantly to improving soil biological properties, aggregation, and structure, promoting plant and root growth, especially under environmental stress conditions, and enhancing plant nitrogen and phosphorus utilization efficiency [16,17]. Additionally, it has been reported that humic acid can partially mitigate the adverse effects of excessive nitrogen application. Organic inputs compensate for the intensive tillage-dependent loss in soil organic matter [8]. However, nitrogen deficiency remains a limiting factor in organic crop cultivation. Still, some researchers [18] have emphasized that, in annual ryegrass cultivation, lower nitrogen fertilization led to increased hay yield in fertile soils.
More than 45 years ago, a review [19] reported that both organic and synthetic fertilizers have their roles in agriculture, and their positive aspects should be recognized. In this context, numerous studies have demonstrated that, by combining organic and chemical fertilizers, more cost-effective crop production can be achieved without sacrificing yield, thereby promoting sustainability [11,12].
The objective of this study was to investigate the effects of manure, humic acid, and low-dose nitrogen fertilization, either individually or in combination, on annual ryegrass forage yield and quality. The study aimed to identify the most suitable fertilizer combination and dose for sustainable forage production.

2. Materials and Methods

2.1. Experimental Site

The study was conducted in Bartin Province, located in an oceanic climate zone in Turkey. Bartin Province is situated at 41°37′54.2″ northern latitude and 32°20′35.5″ eastern longitude, with an altitude of 33 m above sea level. During the growing season (October to July), the long-term average annual precipitation in Bartin Province is 886.8 mm, with 239.9 mm in the first planting year (2021) and 1227.5 mm in 2021, and 1186.7 mm in 2022 [20]. Monthly average precipitation data for 2021 were generally higher during the growing season compared to 2022 and long-term averages, with the exception of June (Figure 1). Similarly, the monthly average temperatures for 2021 and 2022 were 12.81 °C and 12.32 °C, respectively, compared to the long-term average of 11.40 °C. Monthly average relative humidity for 2021 and 2022 was 81.46% and 81.34%, respectively, while the long-term average was 79.32%. The research years experienced higher monthly average temperatures and relative humidity compared to the long-term averages.
The physical and chemical analysis of soil samples, collected from a depth of 0–30 cm in the experimental area, is presented in Table 1. The soil in the research area is characterized as clayey, with a neutral pH. It has high lime content, calcium, iron, copper, and potassium levels, while organic matter, P2O5, and nitrogen content are relatively low.
The manure used in the study is certified and consists of organic matter (50%), total nitrogen (2%), total P2O5 (2%), water-soluble K2O (2%), and total (Humic + Fulvic) acid (15%). Its electrical conductivity (EC) is 6.8 dS/m, and the pH range is 6.5–8.5. The liquid commercial humic acid utilized contains 5% organic matter, 12% total (Humic + Fulvic) acid, 3% water-soluble potassium oxide, and has a pH ranging between 11 and 13 based on weight. Humic acid used in the experiment was provided by Türkiye Coal Company (Ankara, Turkey), and the company confirmed that it was extracted from leonarid and its water-soluble content is organic matte of 5%, humic + fulvic acid of 12, K2O of 1.8%, and pH of 10.5–12.5. Urea (46% N) used as commercial nitrogen resource, and First Steep cultivar of annual ryegrass (Lolium multiflorum L.) is used as plant material in the experiment.

2.2. Field Studies

The study occurred for two years in 2020–2021 and 2021–2022 to determine the effects of manure (farmyard manure), humic acid, and nitrogen fertilizer applications on the forage yield and quality of annual ryegrass. Fertilizer applications were arranged as manure M0: Without manure, M20: 20 t ha−1, liquid humic acid H0: Without humic acid, H20: 20 L ha−1, H40: 40 L ha−1, H60: 60 L ha−1, nitrogen N0: Without nitrogen fertilizer, N50: 50, N100: 100, N150: 150 kg ha−1. The research was conducted in three replications following a randomized block design with split–split arrangement. The experimental plots were sized at 1.2 × 5 m with a 50 cm gap between individual plots and a 1.5 m gap between blocks.
Organic fertilizers (M0 and M1) were applied to the main plots, liquid humic acid doses (H0, H20, H40, and H60) were applied to sub-plots, and nitrogen fertilizer doses (N0, N50, N100, N150) were applied to sub-sub plots (Figure 2). The years were considered as random factors. Manure was applied and thoroughly mixed before planting. Liquid humic acid was mixed with 2 L of water in the seedbed before sowing, randomly sprayed in the relevant plots, and incorporated to a depth of 10–15 cm. Control plots were sprayed with water only [21]. Urea (containing 46% N) was used due to its rapid effect and lower nitrogen loss compared to other nitrogen fertilizers [2]. Half of the nitrogen fertilizer doses were applied at sowing, and the remaining half in early spring [22]. Annual ryegrass was sown on 29 October 2020, in the first year, and on 4 November 2021 in the second year, with a row spacing of 20 cm and a sowing density of 30 kg ha−1 [23]. No supplemental irrigation was applied in either year during the experiment.
Annual ryegrass plants were harvested at two times in both years. Annual ryegrass was harvested at the beginning of flowering. The first mowing took place in the last week of May, and the second mowing was conducted in the third week of July in both years. To determine fresh yield, the entire plot was mowed after excluding one row each side and 0.5 m from each end of the plot. Dry matter yield was calculated by drying 500 g samples of fresh grass from each plot at 70 °C until a constant weight was achieved [24]. The dried and weighed samples were ground through a 1 mm sieve and prepared for chemical analysis. Nitrogen analysis was conducted on the ground samples using the Kjeldahl method, and crude protein percentages were determined by multiplying the obtained ratios by a factor of 6.25. Crude protein yields were calculated by multiplying the crude protein percentages obtained for each plot by the dry matter yields [25]. NDF and ADF ratios in dry matter were determined in accordance with Van Soest et al. [26]. The relative feed value (RFV) of the hay was calculated based on estimates of dry matter digestibility (DDM) and dry matter intake (DMI) [27]. ADF values were used to determine the %DDM value, while NDF values were used to determine the %DMI ratio. The RFV value of the hay was then calculated using the formula
Digestible Dry Matter (%DDM) = 88.9 − (0.779 × %ADF)
Dry Matter Intake (%DMI) = 120/(%NDF)
Relative Feed Value = (%DDM × %DMI)/1.29
In accordance with the Quality Standard established by the Straw Marketing Task Force of the American Forage and Grassland Council, RFV was assessed for roughages based on the following categories: <75 (5)—scraps, 75–86 (4)—poor, 87–102 (3)—fair, 103–124 (2)—good, and 125–151 (1)—first class, while first-class was defined as >151.

2.3. Statical Analyses

All data (year, manure, humic acid, nitrogen fertilizers) were subjected to variance analysis. Data that followed a normal distribution were analyzed using SAS [28] to determine the effects and interactions of these factors. The means were compared using Tukey Multiple Comparison Test.

3. Results

3.1. Plant Height

With the exception of the second-order interactions, M × H and M × N, all the main effects and other second-order interactions were statistically significant (p < 0.01) for plant height (Table 2). Application of manure, humic acid, and nitrogen resulted in increased plant height compared to the control. In the first year, the plants reached a height of 109.0 cm, exceeding the second year’s growth of 94.3 cm (Table 2).
The interactions Y × M (Figure 3A), Y × H (Figure 3B), Y × N (Figure 3C), and H × N (Figure 3D) had significant effects on plant height. Plant height was greater in the first year compared to the second year with manure, humic acid, and nitrogen application. In the second year, there was no significant difference in plant height, but notable differences were observed between the effects of humic acid and nitrogen application (Figure 3A–D).

3.2. Fresh Forage Yield

All the main effects and two-order interactions, as well as the M × H × N (p < 0.01) and Y × H × N interactions (p < 0.05) between years and treatments, were found to be statistically significant in terms of fresh forage yield. Manure, humic acid, and nitrogen treatments resulted in higher fresh forage yields compared to untreated plots (Table 2). While the first year yielded 55.5 t ha−1 of fresh forage production, the second year’s yield was 49.4 t ha−1. Manure application significantly increased fresh forage yield (Table 2). Additionally, both humic acid and nitrogen application led to a significant increase in fresh forage yield (Table 2).
Fresh forage yield showed an increase with higher doses of humic acid and nitrogen in both years. However, the highest fresh forage yield was achieved with the application of 20 L ha−1 of humic acid (H20) and 100 kg ha−1 of nitrogen (N100) (Figure 4A). In cases where manure was not applied, fresh forage yield increased with higher nitrogen doses, except for the H40 application. Furthermore, a less stable condition was observed in the presence of manure (M20) compared to M0, except when H60 was applied (Figure 4B).

3.3. Dry Matter Yield

All the main effects were found to have statistically significant effects on dry matter yield (p < 0.01), except for the year–treatment interaction, the Y × H × N third-order interaction, and the Y × M × H × N four-way interaction (Table 2). Dry matter yield increased in all treatments compared to the untreated plots. However, an increase in humic acid doses did not lead to an increase in dry matter yield, whereas nitrogen doses did result in an increase in dry matter yield (Table 2).
In 2021, dry matter yield increased as the humic acid dose increased in plots without manure application, while H0 and H20 treatments and H40 and H60 treatments yielded similar results in 2022 (Figure 5A). In both years, dry matter yield increased with the increase in humic acid doses with manure application, except for H20 (Figure 5A).
In 2021, dry matter yield increased with an increasing nitrogen dose, except for the H20 application, while the highest yield was obtained with N100 in the H20 application (Figure 5B). When manure was not applied, there was no statistical difference between humic acid application and nitrogen doses (N50, N100, and N150). Additionally, the dry matter yields were similar in H40 and H60 applications without nitrogen application, N50, and N100 applications, but the yield was higher in N150 applications (Figure 5C). In the first year, when manure was applied, there was a linear increase with increasing nitrogen doses, except for H40, while, in the second year, differences were observed between the treatments (Figure 5C).

3.4. Crude Protein Ratio and Crude Protein Yield

Manure, humic acid, and nitrogen applications, as well as Y × M, M × H, H × H, H × N two-way interactions, and the M × H × N interaction, significantly affected the crude protein ratio. An increase in humic acid and nitrogen doses resulted in an increased crude protein ratio compared to untreated plots (Table 2). However, when manure was applied, the increase in nitrogen and protein was not statistically significant in H40 and H60 treatments (Figure 6).
The effects of year, manure, humic acid, and nitrogen as the main factors, as well as the two- and three-way interactions of these treatments, were found to be statistically significant (p < 0.01) in terms of crude protein yield. Manure, humic acid, and nitrogen treatments increased crude protein yield with increasing doses, except for H20 and H40 (Table 2). Similar to dry matter yield, crude protein yield increased with an increasing humic acid dose in plots without manure application in 2021, while, in 2022, the yields were similar in H0 and H20 treatments, as well as H40 and H60 treatments (Figure 7A). In both years, crude protein yield did not increase directly with the humic acid doses when manure was applied. However, there was a difference in the H20 application in 2021 (Figure 7B). In the absence of manure, an increase in both humic acid and nitrogen doses led to an increase in crude protein yield, while an unstable situation was observed when manure was applied (Figure 7C).

3.5. Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF)

All the main effects and interactions, with the exception of the Y × M, Y × M × H interactions, affected the NDF ratio. Similarly, the treatments and their combinations, except for the Y × M and Y × N two-way interactions, as well as the M × H × N three-way interactions, had statistically significant effects on the ADF ratio. Similarly, in both 2021 and 2022, the NDF and ADF values exhibited wide variations among treatments and between years. In 2021, the ADF and NDF ratios were higher in untreated plots in some treatments, whereas, in 2022, they were higher in treated plots (Figure 8 and Figure 9).

3.6. Relative Feed Value

The relative feed value (RFV) was statistically significant, except for the year, manure, humic acid, nitrogen, and the second- and third-order interactions, Y × M and Y × M × N. When manure was applied, the highest feed quality was obtained from the H40, H60, N50, and N100 treatments (see Table 2). In 2021 and 2022, the RFV values among the treatments exhibited instability concerning the years and treatments and displayed wide variation.
In 2021, it was observed that the feed values were higher with low doses of nitrogen and high doses of manure and humic acid. In 2022, it was determined that manure application increased the RFV values, while the effects of humic acid and nitrogen doses varied (Figure 10).

4. Discussion

The plant height of annual ryegrass increased in response to manure, humic acid, nitrogen fertilizer, and their combinations when compared to plots without fertilizer application. In 2021, the precipitation, especially monthly distribution, was higher than in the second year and the long-term average. This situation extended the plant growth period, consequently leading to increased use of fertilizer, which caused an increase in plant height. Among the treatments, manure application had the most significant effect on plant height.
Many researchers have demonstrated that using organic manure promotes plant growth by increasing nutrient efficiency and soil water-holding capacity [29]. Additionally, Bauddh and Singh [30] reported that manure application increases organic matter content and enhances microbial activity, leading to more pronounced effects on plant biomass. In contrast, Liu et al. [31] reported that organic manure sometimes promotes plant growth more efficiently than inorganic fertilizer. When humic acid was used alone, plant height increased compared to the control, but there was no significant difference among the treatments. Khan et al. [13] reported the highest plant height in a combination of low-chemical fertilizer (30:20 NP) and humic acid (3 kg/ha). Our research results are consistent with this finding. Available soil moisture changes depending on precipitation pattern; these situations also affect fertilizers’ efficiency [13,30]. The differences in precipitation pattern between the years resulted in an interaction effect on plant height (Figure 3A–C).
The higher and better distributions of precipitation in the first year, compared to the second year during the growing season, led to a higher fresh herbage yield. All fertilizer treatments increased fresh forage yield compared to untreated plots, with the most significant increase observed in manure application. Verlinden [21] reported an additional 1–1.7 t ha−1 of fresh forage yield for annual ryegrass when organic fertilizers were applied compared to the control. Similarly, Demiray and Parlak [32] reported the highest fresh yield (3.4 ha−1) from manure application, with 2.6 t ha−1 of fresh forage yield obtained with 100 kg ha−1 of nitrogen application. These results are consistent with those of other researchers [31], who emphasized that, when organic and chemical fertilizers (NPK) were applied to grass, the positive effects of organic fertilizer were more significant, leading to a significant increase in forage yield when applied alongside chemical fertilizer.
Rose et al. [10] reported that the growth response of humic acid from black coal at low rates is non-linear but can enhance nutrient uptake when co-applied with inorganic fertilizers, reducing input costs. Researchers have shown that using inorganic fertilizers alongside humic acid in various plants increases yield [8,13]. Additionally, Nikbakht et al. [33] reported that humic acid application to perennial ryegrass enhances nutrient uptake, root development, and leads to reduced fertilizer requirements and increased drought resistance.
Consistent with previous research, our study found that lower nitrogen doses, when combined with manure, humic acid, and chemical fertilizer, yielded higher results compared to high nitrogen doses. When nitrogen was applied alone, increasing nitrogen doses led to higher fresh forage yield, but the yield was significantly higher at lower N doses when applied with organic-based fertilizers. Similar findings have been reported by other researchers [31] regarding the promotion of biomass production by both inorganic and organic fertilizers. Due to differences in the amount and distribution pattern of precipitation between years, plant growth and availability of fertilizers changed, and this situation caused interactions regarding years and fertilizer resources on fresh herbage yield.
Manure, humic acid, and nitrogen fertilizer applications increased dry matter yield compared to untreated plots. Similar to fresh forage yield, manure application significantly increased dry matter yield. Demiray and Parlak [32] investigated the effect of organic matter and different nitrogen sources on annual ryegrass yield, reporting that the highest yield was obtained from manure application.
Researchers have obtained different results in studies on the effects of humic acid on plant growth and yield. Some researchers have reported that humic acid increases plant growth and, consequently, yield [21,34], while others have reported that, when humic acid and organic fertilizers are applied together, the outcome varies according to the source of the humic substance, and high doses sometimes reduce nutrient uptake by competing in the roots [17,35]. In the study, a higher dry matter yield was achieved with low humic acid application in conjunction with manure application. The obtained results are in line with the findings of the researchers.
In both years, increased yield was achieved with higher humic acid doses in plots without manure application. However, the increase was more significant when it was applied together with manure. Regarding the manure x humic acid interaction, no significant differences were observed in yield values when manure was applied. Nonetheless, differences in precipitation between years may explain this situation, with plants treated with humic substances showing higher water efficiency, enabling them to produce more biomass for the same water consumption [34]. On the other hand, the interaction of humic acid, nitrogen fertilizer, and year indicates that the difference between years affects the effectiveness of humic acid and chemical fertilizer. Numerous studies on annual ryegrass and other crops have shown that combinations of manure, humic acid, and chemical fertilizers increase yields, and these applications are more effective than using them alone [15,21]. In addition, researchers have found that both soil properties improve and high yields are obtained with low doses of chemical fertilizers when organic-based fertilizers and chemical fertilizers are used together [13]. The obtained results are consistent with those of the researchers.
Humic acid and nitrogen applications increased the crude protein ratio, but no difference was observed at high doses of humic acid. Some studies determined that humic acid application increased the N content in plants [36]. In contrast, Verlinden et al. [21] reported that humic substances had little effect on the crude protein ratio.
Nitrogen fertilizers applied in appropriate amounts increase the protein ratio of grasses [37], but excessive nitrogen use also leads to nitrate accumulation and increased alkaloid ratios in plants [38]. Thus, high-dose nitrogen fertilization should be avoided to increase the protein ratio and crude protein yield in grasses with high nitrogen requirements. In sustainable agricultural practices, it is essential to include organic-origin fertilizers as a nitrogen source in fertilizer planning. Researchers have determined that the combined use of organic and chemical fertilizers in annual ryegrass and different crops increases nitrogen content, crude protein content, and yield [39].
Crude protein yield and dry matter yield showed similar interactions due to the more stable crude protein ratio in the dry matter against increasing fertilizer applications. In both years, manure application significantly increased crude protein yield. Yolcu et al. [40] reported that increasing doses of organic-based fertilizers increased the crude protein ratio and yield compared to the control.
Regarding crude protein yield, the results obtained from the combinations of organic and chemical fertilizers (at nitrogen doses similar to our research) were similar to some reports [2,22,40].
In plots where manure and humic acid were applied, the NDF and ADF ratios were lower than in plots where humic acid was not applied. Researchers obtained different results regarding the fiber content of annual ryegrass. Pavinato et al. [41] reported that nitrogen levels in annual ryegrass cannot promote forage NDF content. Similar results were obtained by Valk et al. [42]. On the other hand, Turk et al. [22] and Bıçakcı et al. [43] reported that NDF and ADF ratios decreased with increasing nitrogen doses. The results we obtained in terms of NDF and ADF ratios (for manure and humic acid treatments) are similar to the results obtained by the researchers [21,42]. However, NDF and ADF ratios varied in manure, humic acid, and nitrogen fertilizer, and their combinations. Similar to our research results, Demiray and Parlak [32] reported that fertilizer applications affected NDF and ADF ratios at different rates, and this situation was closely related to climatic factors in the study in which he investigated the effects of organic matter and different nitrogen sources applied to annual ryegrass.
The variation in fiber ratio between years may be related to climate differences, particularly higher warmth and lower humidity, causing lignification in plants [44]. As a result, the first year’s NDF and ADF values were higher than the second year’s because it was warmer than the second year.
Relative feed value, which determines feed quality and is calculated using ADF and NDF ratios [45], was within the ‘good’ range (101–120) in all plots where manure was applied. There was wide variation among the treatments, but the RFV values were high in plots where manure, humic acid, and low nitrogen doses were applied. Casler [46] reported that ryegrass differed in RVF values in the study in which RVF values of forage crops were analyzed, and the genotype–environment interactions of the differences were species-specific.
Except for June, the monthly total precipitation was lower than both the long-term average and first year during the growing period of the second year; hence, moisture deficiency triggered plant maturity and plants had shorter height. On the other hand, fertilizer treatments’ effects changed depending on the differences in precipitation regime. Consequently, there are so many interactions related to years and fertilizers. Similar results were also reported by various researchers [22,32,40]. When the interactions related to dry matter yield were evaluated overall, it was clear that the combined usage of the fertilizers was more effective than their single application. Especially, humic acid alleviated the negative effect of drought stress on dry matter yield in the second year (Figure 5B). This situation mainly resulted from the increasing water-holding capacity of the soil-originated organic fertilizer, and, additionally, humic acid application physiologically promoted drought resistance in the plants [47]. As a result of these aspects, a general conclusion can be drawn regarding yield and quality parameters considering the interactions.

5. Conclusions

In this study, conducted to assess the potential for forage yield in sustainable agricultural practices as an alternative to high-dose fertilizer applications due to the high responsiveness of annual ryegrass to nitrogen, it was observed that the application of manure significantly increased both yield and quality. Moreover, the application of humic acid and nitrogen fertilizer alone enhanced the studied characteristics when compared to the control group. However, the efficacy of these applications was further enhanced when they were combined with manure. The most favorable results in terms of forage yield and quality were obtained from our studies when a combination of 20 t ha−1 manure, 20 L ha−1 of humic, and 100 kg ha−1 was used. These findings can be suggested for similar ecological conditions (semi-humid) to achieve satisfactory hay production in annual ryegrass stands under sustainable agricultural farming practices.

Author Contributions

A.G.L., writing—original draft preparation; H.İ.E. and A.K., writing—review and editing. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The datasets generated and/or analyzed in the current study are available from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare no conflict of interest.

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Agronomy 13 02935 g001
Figure 1. Average monthly total precipitation for autumn of 2020, 2021, 2022, and long-term average (LTA).
Figure 1. Average monthly total precipitation for autumn of 2020, 2021, 2022, and long-term average (LTA).
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Figure 2. The distribution of manure, humic acid, and nitrogen doses in the main plots, sub-plots, and sub-sub-plots according to a randomized complete block design with a split–split plot arrangement (the figure shows treatment combinations, not field applications. The factors were distributed considering randomized procedure).
Figure 2. The distribution of manure, humic acid, and nitrogen doses in the main plots, sub-plots, and sub-sub-plots according to a randomized complete block design with a split–split plot arrangement (the figure shows treatment combinations, not field applications. The factors were distributed considering randomized procedure).
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Agronomy 13 02935 g003
Figure 3. Plant height as affected by year, manure, humic acid, and nitrogen. (A) = Y × M, (B) = Y × H, (C) = Y × N, and (D) = H × N interactions. Bars indicate ±1 s.e.
Figure 3. Plant height as affected by year, manure, humic acid, and nitrogen. (A) = Y × M, (B) = Y × H, (C) = Y × N, and (D) = H × N interactions. Bars indicate ±1 s.e.
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Agronomy 13 02935 g004
Figure 4. Fresh forage yield as affected by year, manure, humic acid, and nitrogen. (A) = Y × H × N, (B) = M × H × N. Bars indicate ±1 s.e.
Figure 4. Fresh forage yield as affected by year, manure, humic acid, and nitrogen. (A) = Y × H × N, (B) = M × H × N. Bars indicate ±1 s.e.
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Figure 5. Dry matter yield as affected by year, manure, humic acid, and nitrogen. (A) = Y × H × M, (B) = Y × H × N, (C) = M × H × N. Bars indicate ±1 s.e.
Figure 5. Dry matter yield as affected by year, manure, humic acid, and nitrogen. (A) = Y × H × M, (B) = Y × H × N, (C) = M × H × N. Bars indicate ±1 s.e.
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Figure 6. Crude protein ratio as affected by manure, humic acid, and nitrogen. Bars indicate ±1 s.e.
Figure 6. Crude protein ratio as affected by manure, humic acid, and nitrogen. Bars indicate ±1 s.e.
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Figure 7. Crude protein yield as affected by year, manure, humic acid, and nitrogen (A) = Y × H × M, (B) = Y × H × N, (C) = M × H × N. Bars indicate ±1 s.e.
Figure 7. Crude protein yield as affected by year, manure, humic acid, and nitrogen (A) = Y × H × M, (B) = Y × H × N, (C) = M × H × N. Bars indicate ±1 s.e.
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Figure 8. NDF as affected by year, manure, humic acid, and nitrogen.
Figure 8. NDF as affected by year, manure, humic acid, and nitrogen.
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Figure 9. ADF as affected by year, manure, humic acid, and nitrogen.
Figure 9. ADF as affected by year, manure, humic acid, and nitrogen.
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Figure 10. RVF as affected by year, manure, humic acid, and nitrogen.
Figure 10. RVF as affected by year, manure, humic acid, and nitrogen.
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Table 1. Physical and chemical properties of the soil of the experimental area.
Table 1. Physical and chemical properties of the soil of the experimental area.
Soil Properties
% Nitrogen0.09
P2O5 kg ha−149.3
K2O kg ha−11141.8
% Organic Carbon0.96
pH7.14
EC dSm−11.3
% Lime11.72
Ca (ppm)9708
Mg (ppm)251.3
Na (ppm)156.98
Fe (ppm)15.40
Cu (ppm)2.01
Zn (ppm)0.99
Mg (ppm)3.07
B (ppm)0.11
% Clay 61.30
% Silt21.06
% Sand17.64
Table 2. Results of the effects of treatments on investigated characteristics of annual ryegrass.
Table 2. Results of the effects of treatments on investigated characteristics of annual ryegrass.
Plant Height (cm)Fresh Forage Yield (t ha−1)Dry Matter Yield (t ha−1)CP Yield (t ha−1)CP (%)ADF (%)NDF (%)RFV
Year (Y)
2021109.0 A55.5 A15.9 A2.18 A13.5533.82 A54.53 A106.81 B
202294.3 B49.4 B15.0 B2.06 B13.5433.46 B53.77 B108.80 A
Manure (M)
M092.3 B43.7 B12.6 B1.68 B13.11 B33.94 A54.69 A106.31 B
M20111.0 A61.2 A18.3 A2.57 A13.97 A33.33 B53.61 B109.30 A
Humic acid (H)
H094.52 C48.5 B13.6 B1.80 C13.04 D34.42 A54.84 A105.36 C
H20100.8 B53.7 A16.0 A2.16 B13.35 C33.80 B54.00 B107.86 B
H40103.3 B53.9 A15.8 A2.18 B13.62 B33.16 C53.94 B108.89 A
H60108.0 A53.6 A16.3 A2.35 A14.18 A33.17 C53.81 B109.11 A
Nitrogen (N)
N091.1 B43.2 D12.2 D1.52 D12.27 D33.87 A54.67 A106.51 C
N50103.9 A49.9 C15.0 C1.99 C13.18 C33.22 C53.89 B108.85 A
N100104.9 A56.7 B16.8 B2.36 B13.98 B33.48 BC54.02 B108.24 AB
N150106.7 A59.9 A17.6 A2.61 A14.74 A33.98 A54.01 B107.61 B
Mean101.752.515.52.1213.5533.6454.15107.81
Y********ns******
M****************
H****************
N****************
Y × M**nsnsns*nsnsns
Y × H**nsnsnsns******
Y × N*nsnsnsnsns****
M × Hns**************
M × Nns******ns*****
H × N****************
Y × M × Hnsns****ns*ns*
Y × M × Nnsnsnsnsns**ns
Y × H × Nns*****ns******
M × H × Nns********ns****
Y × M × H × Nnsnsnsnsns******
Different letters indicate statistically significant differences (p < 0.05), ns: non-significant, *: p ≤ 0.05, **: p ≤ 0.01.
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Genç Lermi, A.; Erkovan, H.İ.; Koç, A. Determination of Combined Effects of Organic and Mineral Fertilizer on Forage Yield and Quality of Annual Ryegrass. Agronomy 2023, 13, 2935. https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13122935

AMA Style

Genç Lermi A, Erkovan Hİ, Koç A. Determination of Combined Effects of Organic and Mineral Fertilizer on Forage Yield and Quality of Annual Ryegrass. Agronomy. 2023; 13(12):2935. https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13122935

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Genç Lermi, Ayşe, Halil İbrahim Erkovan, and Ali Koç. 2023. "Determination of Combined Effects of Organic and Mineral Fertilizer on Forage Yield and Quality of Annual Ryegrass" Agronomy 13, no. 12: 2935. https://0-doi-org.brum.beds.ac.uk/10.3390/agronomy13122935

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