Wheat, Barley, and Triticale Response to Nitrogen Fertilization in Pannonian Environment

Abstract

Small-grain producers in the southern Pannonian Plain prefer winter barley production in poor soils and drought-prone areas, assuming higher resource use efficiency in barley than in wheat. Similarly, triticale is known to perform well in low-fertility soils and dry environments. However, information about the comparative performance of these crops within the same trials is less available for the Pannonian environment. Therefore, this study aimed to compare the grain yield and nitrogen use efficiency traits of winter wheat, triticale, and two-rowed and six-rowed barley cultivars across different N applications in different growing seasons and locations in the Pannonian Plain. The study was conducted over two seasons at three locations (Novi Sad, Sremska Mitrovica, and Sombor) using a split-plot design. Treatments consisted of winter wheat, triticale, and two-rowed and six-rowed barley under three nitrogen fertilization levels of low, moderate, and high. Averaged across species, the reduction in grain yield in 0 N compared to 100 N was 1218 kg ha⁻¹ (15.7%) in wheat, 1037 kg ha⁻¹ (11.6%) in triticale, 1128 kg ha⁻¹ (13.7) in two-rowed barley, and 1340 kg ha⁻¹ (17.1%) in six-rowed barley. Grain yield was closely related to nitrogen uptake, showing a relationship (R²) from 0.652 in triticale to 0.956 in six-rowed barley. Nitrogen use efficiency showed a positive relationship with nitrogen uptake efficiency, while the relationship with nitrogen utilization efficiency was insignificant. There was a notable difference between crops in terms of grain yield and nitrogen use efficiency traits. Notably, two-rowed barley outperformed wheat in terms of grain yield and nitrogen use efficiency, while wheat outperformed six-rowed barley. Triticale showed the highest yield among all the studied cereal crops, attributed to increased nitrogen use efficiency and uptake, especially under low fertilization conditions.

1. Introduction

Small-grain production is often constrained by the availability and efficient utilization of resources. In significant European crop production areas, such as the Pannonian plain, major crops are predominantly cultivated under rainfed conditions. Therefore, crop yield relies heavily on the timing and amount of seasonal rainfall, which can differ significantly both between and within growing seasons. Unlike nearby regions characterized by a continental climate, the southern part of the Pannonian Plain is characterized by warmer summers and reduced rainfall from March to September, showing a semi-arid climate [1]. Predicted patterns point towards a trend of even warmer and drier climate conditions [2,3]. Given these circumstances, winter small grain cereals offer a valuable alternative to spring crops like maize, soybeans, or sunflowers. Small grain cereals, such as wheat, barley, and triticale, play a crucial role in European and global agriculture due to their adaptability to diverse climatic conditions and their importance as staple food crops. Wheat, for instance, is a primary source of carbohydrates and protein in human diets, while barley is widely used for animal feed and brewing, and triticale serves as a versatile crop for both food and feed purposes. These crops are particularly significant in regions like the Pannonian Plain, where their ability to develop under rainfed conditions and withstand semi-arid climates makes them essential for ensuring food security and sustainable agricultural practices.

Among different mineral nutrients, nitrogen (N) is the most essential in crop production and the improvement of N use efficiency (NUE) may play a critical role in low-input and sustainable agriculture [4]. Simultaneously, genetic improvements and advances in agronomic practices have been major drivers of grain yield increases in different small grain cereal crops [5,6]. During the past century, plant height reduction in wheat and other cereals improved crop lodging resistance, resulting in higher applications of N fertilizer rates, and a significant grain yield (GY) increase [7,8]. Consequently, during the past 50 years the rate of N fertilization in wheat has increased by more than 60 kg ha⁻¹ [9]. Similarly, in Europe, agriculture extensively relies on significant quantities of synthetic N applications [10]. Unfortunately, small grain crops have limited ability to recover applied N and approximately only 33% of applied N is removed by grain [11]. The excess N is lost from the soil by leaching, surface runoff, denitrification, and volatilization, indicating that the intensification of crop production and an increase in N applications during the past decades has resulted in serious environmental problems [12]. NUE and its components are complex traits, characterized by significant variation due to the influence of genotype, environment, management practices, and their interaction [13,14]. In accordance with Liebig’s law of the minimum, NUE tends to decrease as the amount of available N increases, since under conditions of the Pannonian Plain N availability is not the only GY limiting factor and crops respond only to the most limiting factor such as limited rainfall. Also, there are significant variations in NUE among different small grain cereal crops under conditions of the Pannonian Plain [15,16], complicating a proper NUE estimation.

Although different winter cereal crops have similar requirements for cultivation and resources, there are many notable physiological and agronomical differences among them [17]. For example, local farmers recognize winter barley as the most stable small grain cereal crop under the rainfed conditions of the southern Pannonian Plain or Mediterranean region [18], favoring barley production in drought-prone environments. Also, there is a general assumption among farmers that winter barley has higher resource use efficiency than other winter cereals, promoting barley production on soils with decreased fertility and limited application of fertilizers, especially N, during the growing season. In regions with higher precipitation or improved soil fertility, farmers prefer wheat production, suggesting that wheat outperforms barley in those conditions. On the other hand, many farmers alternate wheat and barley with triticale due to its higher productivity both in biomass and grain. However, there are not many experimental data on the differences in resource use efficiency from same field trials of winter small grains crops under rainfed conditions, especially in the Pannonian Plain [17] to confirm the belief that winter barley has lower requirements for resources and higher GY stability compared to wheat and triticale. Therefore, a comparative study of GY physiology and NUE among winter bread wheat, triticale, and two-rowed and six-rowed barley could identify the advantages of specific crops under different soil fertility conditions, securing higher and stable GY production.

Record-high prices of N fertilizers, as well as the limited quantity of the fertilizers on the market, represent a notable pressure for small grains producers in Southeastern Europe, as well as globally. Many farmers are forced to apply less N than usual during the growing season. Therefore, the improvement of NUE could represent the most promising strategy to increase the small grains GY under conditions of limited fertilizer application. Other strategies, for instance, the production of less-utilized cereal crops, such as triticale, could be one of the scenarios to increase GY under limited N application and soil fertility. Assuming that winter triticale and barley (both two-rowed and six-rowed) will demonstrate higher GY and NUE compared to winter bread wheat under limited N application, the aim of this study was to compare GY and NUE of winter wheat, triticale, and two-rowed and six-rowed barley cultivars across different N applications, growing seasons, and locations in the Pannonian Plain.

2. Materials and Methods

2.1. Experimental Site

The field trials were carried out at three locations within the region of the Vojvodina province (southern Panonnian Plain, Serbia) during two consecutive growing seasons, 2019–2020 and 2020–2021. The trials were conducted in research fields of the Agricultural Extension Service in Sombor (SO) and Sremska Mitrovica (SM), and research field of the Institute of Field and Vegetable Crops, Novi Sad (NS). The experimental site and environmental conditions are described in

Table 1. Basic description of experimental locations in the southern Pannonian Plain.

Location	Novi Sad			Sombor			Sremska Mitrovica
Coordinate	45°20′ N, 19°51′ E			45°48′ N, 19°07′ E			44°56′ N, 19°49′ E
Growing season	2019/20	2020/21	Long-term average (1991–2021)	2019/20	2020/21	Long-term average (1991–2021)	2019/20	2020/21	Long-term average (1991–2021)
Sowing date	14 Oct	18 Oct		21 Oct	15 Oct		9 Oct	23 Oct
Some properties of the soil
CaCO3, %	5.17	5.09		5.45	6.12		4.30	4.45
P2O5 (Egner-Riehm), mg/100 g	24.5	23.1		19.8	17.4		22.5	24.2
K2O (Egner-Riehm), mg/100 g	18.4	23.5		30.1	28.7		23.9	21.8
N (N-min method), kg ha−1	85	77		75	83		70	90
Humus (Turin)	2.75	2.92		2.35	2.40		2.48	2.56
pH (KCl)	7.26	7.41		7.75	7.88		7.35	7.42
Applied P (kg ha−1)	70	60		80	80		70	60
Applied K (kg ha−1)	50	40		40	40		40	40
Temperature and rainfall during sowing-anthesis period
Rainfall mm	225	289	302	210	152	306	202	234	320
Tmean *, °C	7.9	7.1	6.2	7.3	6.5	6.1	8.0	7.4	6.1
Temperature and rainfall during anthesis-harvest period
Rainfall mm	136	72.7	145	212	108	144	158	98	170
Tmean, °C	21.1	23.5	19.1	20.4	23.1	19.0	20.6	22.1	19.1

* Tmean—average mean daily temperature.

. The soil at the locations is a Haplic Chernozem Aric [19]. In this experiment we directly compared the performance of different small grains cereal species under a wide range of environmental conditions determined by the combination of two growing seasons, three locations, and three levels of N fertilization.

Weather data were obtained from meteorological stations near the field trials and compared to long-term averages. During 2019/20, rainfall from sowing to anthesis was below average in all locations—Novi Sad, Sombor, and Sremska Mitrovica. Temperatures were higher than average, with Novi Sad being the warmest location. From anthesis to harvest, rainfall in Novi Sad and Sremska Mitrovica was close to the long-term average, while Sombor exceeded it. Temperatures remained above average throughout the season. In 2020/21, sowing-to-anthesis rainfall was highest in Novi Sad (289 mm) but lower in Sombor (152 mm) and Sremska Mitrovica (234 mm). Temperatures were again above average. The anthesis-to-harvest period was significantly drier across all locations, with Novi Sad recording only 72.7 mm. Temperatures were notably higher, peaking at 23.5 °C in Novi Sad. Overall, 2020/21 was drier and warmer than 2019/20, particularly during anthesis to harvest, highlighting significant weather variability across locations and seasons.

2.2. Experimental Design

Treatments within each location consisted of the factorial combinations of (a) winter bread wheat, triticale, and two-rowed and six-rowed barley cultivars, and (b) three levels of N fertilization, low (0 kg N ha⁻¹), moderate (50 kg N ha⁻¹), and high (100 kg N ha⁻¹). Treatments were arranged in a split-plot design with four replicates, where the main plots were the N levels while the sub-plots were the cultivars. In order to minimize possible N losses, N was applied in two doses after emergence (GS11-12) (25 kg N ha⁻¹ for the moderate level and 50 kg N ha⁻¹ for the high level) [20] and prior to the start of the stem elongation period (GS30) (25 kg N ha⁻¹ for the moderate level and 50 kg N ha⁻¹ for the high level), as ammonium nitrate (34%). Each N fertilizer application was conducted on the same day for all cultivars.

The eight winter small grain cultivars were evaluated in the experiment: two bread wheat (Triticum aestivum L.), two triticale (× Triticosecale spp. Wittmack), and two two-rowed (Hordeum vulgare subsp. distichum L.) and two six-rowed barley (Hordeum vulgare subsp. hexastichon L.). Although two-rowed and six-rowed barley cultivars are the same species, due to significant variation in grain yield determination, they were analyzed separately. Cultivars of winter bread wheat (cv. Simonida and NS 40 S), triticale (cv. Odisej and NS Paun), two-rowed barley (cv. Novosadski 525 and 565), and six-rowed barley (cv. Nonius and Rudnik) were chosen to represent widely grown and well-adapted modern cultivars in the Vojvodina province of the Republic of Serbia. Moreover, NS 40 S, Odisej, Novosadski 565, and Rudnik are used as standard controls in national small grains registration trials in Serbia. Although there is a significant genotypic variation within each species, to efficiently manage different locations and N fertilization combinations during the crop growth cycle the two most representative cultivars for each species were selected.

The size of each experimental plot was 5 m long and 1 m wide, with 10 rows per plot, with a target density of 450 plants per square meter for all species and cultivars. In each year, soil samples were taken prior to plowing at depths of 0−60 cm, and soil mineral N [21], phosphorus (P), and potassium (K) (Egner-Riehm) data are shown in Table 1. P and K were applied prior to sowing to avoid P and K deficit and the applied doses per location are presented in Table 1. Where necessary, weeds (tribenuron-methyl), pests (deltamethrin), and diseases (tebuconazole and protioconazole) were controlled by appropriate chemical applications in the spring.

2.3. Crop Measurements and Data Analysis

Crop growth was regularly monitored during growing seasons following the decimal code of Zadoks [20]. The anthesis date (GS65) and physiological maturity (GS89, 50% peduncle yellowing) were recorded for each cultivar and sampling was adjusted to the cultivar/species phenology. Biomass sampling was performed at anthesis and maturity by harvesting two 1 m long samples from two central rows (to avoid the border effects) at ground level, where samples from maturity were separated into grains and the rest of the canopy. The plant material was oven-dried at 60 °C for 48 h before being weighed. The N concentration in grains and the rest of the canopy was determined by the Kjeldahl method [22]. After biomass sampling, each plot was harvested by a combine. The weight of grain from the previously cut 1 m rows was added to the weight of grain from the combine-harvested plot, and grain yield (GY) in kg ha⁻¹ was corrected at 13% moisture. The NUE was calculated by dividing the grain yield by the amount of N available to the crop from the soil and the fertilizer N (kg_grain kg _{available N}⁻¹ in soil ha⁻¹) according to [23]. The nitrogen uptake efficiency (NUpE; kg N_{in biomass} kg N_{available in soil}⁻¹) was calculated by dividing the above-ground N at harvest (N uptake; kg N ha⁻¹) by the amount of N available to the crop from the soil and the fertilizer N. The nitrogen utilization efficiency (NUtE) was calculated by dividing the grain yield by above-ground N at harvest (kg_grain kg N_{in biomass}⁻¹). The following shows the equations used:

$$NUE={\displaystyle \frac{GY }{Naviable in soil}}$$

$$NUpE={\displaystyle \frac{\mathrm{N} \mathrm{u}\mathrm{p}\mathrm{t}\mathrm{a}\mathrm{k}\mathrm{e}}{Navailable in soil}}$$

$$NUtE={\displaystyle \frac{\mathrm{G}\mathrm{Y}}{\mathrm{N} \mathrm{u}\mathrm{p}\mathrm{t}\mathrm{a}\mathrm{k}\mathrm{e}}}$$

Analysis of variance for the three factors (location, nitrogen, and crop species) were performed for each year independently. A Tukey test at a 0.05 probability level was used to compare the mean difference between treatment groups. Regression analysis was used to identify the relationship between the species and the nitrogen used by them.

3. Results

3.1. Grain Yield and Nitrogen Uptake

The results show significant variation in grain yield, nitrogen uptake, and nitrogen use efficiency across growing seasons and locations, reflecting the influence of climatic and site-specific conditions on crop performance (Supplementary Table S1). The 2019–2020 growing season achieved higher GY (8200.1 kg ha⁻¹) and N uptake (189.4 kg N ha⁻¹) due to favorable conditions, but with lower NUtE (44.59 kg_grain kg N_{in biomass}⁻¹). In contrast, the warmer and drier 2020–2021 season resulted in lower GY (7030.5 kg ha⁻¹) and N uptake (143.3 kg N ha⁻¹), but higher NUtE (49.63 kg_grain kg N_{in biomass}⁻¹). The location of Novi Sad achieved the highest GY (8855.3 kg ha⁻¹) and N uptake (206.1 kg N ha⁻¹), likely due to more favorable soil or climatic conditions, but with an NUtE of 43.98 kg_grain kg N_{in biomass}⁻¹. Sremska Mitrovica and Sombor showed a GY of 6910.6 kg ha⁻¹ and 7080.0 kg ha⁻¹, respectively, and a N uptake of 150.7 kg N ha⁻¹ and 142.3 kg N ha⁻¹, but a higher NUtE of 49.27 kg_grain kg N_{in biomass}⁻¹ and 48.08 kg_grain kg N_{in biomass}⁻¹.

Results from our study showed that GY varied significantly among studied crops across treatments (Figure 1). Averaged across species, the reduction in GY in 0 N compared to 50 N and 100 N was 925 (12.4%) and 1218 (15.7) kg ha⁻¹ in wheat, 413 (5%) and 1037 (11.6) kg ha⁻¹ in triticale, 563 (7.4%) and 1128 (13.7) kg ha⁻¹ in two-rowed barley, and 687 (9.7%) and 1340 (17.1%) kg ha⁻¹ in six-rowed barley. On average, the proportional loss under 0 N conditions compared to 50 N was less for triticale in NS in the second season, as well as six-rowed barley and wheat in SO.

In the majority of treatment combinations, growing seasons, and fertilization changes, triticale could be highlighted as the most yielding crop. On the other hand, in about half of the treatment combinations, six-rowed barley cultivars were lowest yielding crops. The increase in fertilizer applications was followed by GY improvement in all studied crops.

The nitrogen uptake (NUp) varied among studied crops between treatments (91–268 kg N ha⁻¹ in wheat, 123–251 kg N ha⁻¹ in triticale, 102–247 kg N ha⁻¹ in two-rowed barley, and 91–252 kg N ha⁻¹ in six-rowed barley; Figure 2). Triticale tends to have higher NUp than other crops under most N fertilization treatments, with average NUp values 19.8%, 29.7%, and 16.4% higher than those of two-rowed barley, six-rowed barley, and wheat, respectively. On the other hand, in most cases six-rowed winter barley showed the lowest NUp compared to other crops. Although there was a significant influence of the location and growing seasons, NUp significantly varied across fertilization treatments, and NUp significantly increased as a result of N fertilizer application. Also, across all sources of variation (location, growing season, and fertilization treatments) GY was linearly related to NUp increase in all studied crops.

3.2. Nitrogen Use Efficiency

There were significant differences between winter wheat, triticale, and two-rowed and six-rowed barley in the NUE across different locations and fertilization levels (Figure 3). The N fertilization resulted in a NUE decrease in all of the studied cereal crops. Comparing the two-rowed and six-rowed barley, two-rowed barley had higher NUE (9.35%) under 0 N conditions (Figure 3a). Under moderate fertilization levels, in most cases two-rowed barley had higher NUE than six-rowed (except NS during the second growing season), while under 100 N treatment the higher of the two NUE values was also mostly recorded in two-rowed winter barley. In most cases, two-rowed winter barley had a higher NUE under conditions of 0 N (7.53%) than wheat (Figure 3b). Under 50 N treatments, winter wheat tended to have a higher NUE at location SM, while under 100 N, wheat had a higher NUE in only one growing season in SM compared to two-rowed barley.

Winter triticale tends to have a higher NUE than two-rowed winter barley under 0 N fertilization (11.5%), and a similar or higher NUE at 50 N and 100 N treatment in most combinations (Figure 3c). There were no clear differences in NUE between winter wheat and six-rowed barley (Figure 3d). Compared to six-rowed barley, triticale showed higher NUE values under 100 N, and in most treatments at 0 N and 50 N fertilization conditions (Figure 3e). In most combinations of location and growing seasons, triticale had a higher NUE than wheat (Figure 3f).

3.3. Nitrogen Uptake and Utilization Efficiency

The nitrogen uptake efficiency (NUpE) varied among studied crops between treatments. The NUpE ranged from 1.33 to 2.28 kg N_{in biomass} kg N_{available in soil}⁻¹ under 0 N, from 0.84 to 1.77 kg N_{in biomass} kg N_{available in soil}⁻¹ under 50 N, and from 0.76 to 1.41 kg N_{in biomass} kg N_{available in soil}⁻¹ under 100 N in two-rowed winter barley. In six-rowed winter barley, the NUpE varied from 1.21 to 2.12 kg N_{in biomass} kg N_{available in soil}⁻¹ under 0 N, from 0.76 to 1. kg N_{in biomass} kg N_{available in soil}⁻¹ under 50 N, and from 0.62 to 1.40 kg N_{in biomass} kg N_{available in soil}⁻¹ under 100 N (Figure 4). In wheat, the NUpE variation was from 1.29 to 2.14 kg N_{in biomass} kg N_{available in soil}⁻¹ under 0 N, from 0.82 to 1.82 kg N_{in biomass} kg N_{available in soil}⁻¹ under 50 N, and from 0.68 to 1. kg N_{in biomass} kg N_{available in soil}⁻¹ under 100 N. On average, triticale tends to have a higher NUpE (1.59 kg N_{in biomass} kg N_{available in soil}⁻¹) than other crops, ranging from 1.75 to 2.62 kg N_{in biomass} kg N_{available in soil}⁻¹ under 0 N, from 1.21 to 1.64 kg N_{in biomass} kg N_{available in soil}⁻¹ under 50 N, and from 0.91 to 1.32 kg Nin biomass kg N_{in biomass} kg N_{available in soil}⁻¹ under 100 N. As result of fertilizer application, the NUpE decreased in all crops. There was a significant positive relationship between NUE and NUpE (R², from 0.772 to 0.915) in different cereal crops. On average, triticale exhibited 20.7%, 31.6%, and 17.9% higher NUpE than two-rowed barley, six-rowed barley, and wheat, respectively.

The nitrogen utilization efficiency (NUtE) differs among small grain cereal crops (Figure 4b). On average, the highest NUpE values were recorded in six-rowed winter barley (49.7 kg_grain kg N_{in biomass}⁻¹), followed by two-rowed barley (48.9 kg_grain kg N_{in biomass}⁻¹). On the other hand, wheat (45.53 kg_grain kg N_{in biomass}⁻¹) and triticale (44.24 kg_grain kg N_{in biomass}⁻¹) tend to have lower average NUpE values. The relationship between NUtE and NUE, as well as between NUtE and NUpE, were not significant (Figure 4c).

4. Discussion

4.1. Wheat, Barley, and Triticale Difference in Grain Yield

According to the results of this study, factors such as growing season, location, fertilization, and crop type had a significant impact on the yield variability of the studied varieties. Given the variability of weather conditions, particularly rainfall and temperature, the two growing seasons differed significantly in average yield. The first season was more favorable for production, resulting in higher average yields compared to the second season. Additionally, there were differences in yield between locations, with higher yields achieved at the Novi Sad site compared to Sombor and Sremska Mitrovica. Previous research indicates that barley’s early vigor, faster leaf appearance, and higher tillering rates contribute to its potential yield advantage [24]. Additionally, soil type plays a significant role in relative yields, with barley demonstrating a greater advantage on fine-textured soils [25]. Through a comparative analysis of wheat and barley yield performance across temperate environments, barley achieves higher yields compared to early-flowering wheat in low-yielding environments. Conversely, wheat tends to produce higher yields as the yield environment improves [26]. According to the results of this study, we found that when major winter small grain cereal crops were grown comparatively and side by side under broad N fertilization conditions, barley (two-rowed and six-rowed average) did not consistently outperform wheat and triticale under low- and high-fertilization conditions. These results challenge the generally accepted belief that barley is more resilient to low-fertility soil and stress than other cereal crops, favoring barley production in low input and yielding conditions, since triticale outperformed both wheat and barley in terms of yield. However, barley performance in this study was found to depend on the row type, with two-rowed barley demonstrating a higher yield compared to six-rowed barley, while the yield of six-rowed barley was similar to that of wheat. This lack of advantage of six rowed barley compared to wheat under more intensive production conditions (100 N) is in line with previous findings for the Mediterranean conditions [21,27,28]. Although some studies have reported an increased susceptibility of barley to lodging [29], especially under intensive production conditions, lodging occurs very infrequently under rainfed Pannonian conditions. Additionally, the development of new barley cultivars was accompanied by a notable decrease in plant height and improved lodging tolerance [16]. These factors could contribute to the absence of wheat superiority under intensive production conditions.

Looking closer at the performance of the different types of barley (2r versus 6r), a significant difference in their resource use efficiency and yield potential is evident, as previously reported by [17]. Generally, two-rowed winter barley tends to produce higher GY than six-rowed winter barley (approximately 500 kg ha⁻¹) in all conditions of different N fertilizer applications. This contrasts with previously obtained results from high-yielding conditions in Western Europe, such as France [30] or Mediterranean conditions, where six-rowed barley outperformed two-rowed cultivars, especially under low-yielding conditions [31]. This could be explained by the higher tillering capacity of two-rowed cultivars compared to six-rowed barley [32], supporting a higher grain number per unit area and, consequently, an increased grain yield in environments where other environmental factors are less limiting. Nevertheless, two-rowed winter barley showed better performance than wheat in most combinations of fertilizer, location, and growing season treatments. Therefore, this led to the conclusion that farmers should also pay attention to winter barley type when selecting cereals for grain production.

Among the studied winter cereal crops, winter triticale stood out as the most yielding cereal, with the highest GY under unfertilized, as well as both fertilized treatments. Under unfertilized treatments, triticale showed 11%, 21%, and 20% higher yields, compared to two-rowed barley, six-rowed barley, and winter wheat, respectively. By applying N fertilizer, the GY difference between triticale and other studied cereals slightly decreased, although triticale tended to achieve higher GY. Therefore, triticale showed higher GY performance under low fertilization conditions, indicating that under low soil fertility conditions farmers should primarily produce triticale cultivars. The superior performance of triticale compared to other cereal crops has also been previously reported under Mediterranean conditions, which has been attributed to higher biomass at both anthesis and maturity [33].

Prior to this study, there was limited information about the comparative performance of triticale compared to wheat, and six-rowed and two-rowed barley under different fertilization regimes. Our results showed that triticale outperformed other studied cereals, especially under lower or unfertilized treatment. Therefore, triticale should be favored as a potential crop for sustainable production conditions, given its higher yield under unfertilized treatment [34]. However, despite its agronomic advantages, its adoption may be limited due to grain quality factors that do not meet the requirements of certain end-use markets. Therefore, future breeding efforts should focus on improving grain quality traits to enhance its competitiveness with wheat and malting barley. Furthermore, the choice of cereal crops for cultivation is heavily influenced by economic factors. In Serbia, wheat dominates small-grain cereal production, covering over 600,000 hectares, while barley is grown on approximately 100,000 hectares and triticale on around 30,000 hectares. Wheat not only has a higher price but also shows greater demand compared to feed barley and triticale. Additionally, a declining trend in livestock production in the region has further reduced interest in triticale and feed barley cultivation as these crops are primarily used for animal feed. These economic and market dynamics highlight the challenges in promoting triticale, despite its agronomic potential.

4.2. Wheat, Barley, and Triticale Difference in NUE

Results from this study showed that N was essential for GY formation in studied winter small grain cereal crops, indicating that unfertilized treatments led to significant yield penalties. Our findings demonstrate a positive response of various small grain cereals to nitrogen fertilization treatments, with the yield response predominantly higher under increased nitrogen levels, while significant differences were observed among crops in terms of NUE and NUE-related traits, such as NUpE and NUtE. Therefore, small grain producers in this part of Europe under rainfed conditions would mostly benefit from intensified nitrogen application, as previously concluded in the Mediterranean Basin [35], Australia [36], and in the US [37].

Changes in N fertilization influenced N uptake, as well as NUpE and NUtE, with the final impact on GY. The higher GY was mostly related to the increase in N uptake, showing a significant positive relationship in all studied crops. These findings confirm the previously reported relationship between nitrogen uptake and grain yield in different grain crops and production systems [38,39], justifying the higher nitrogen management under rainfed conditions in central Europe [40]. Our results also showed that winter cereals differed in N uptake, particularly triticale from six-rowed barley and wheat. A close linear relationship between N uptake and GY, especially in wheat (R² = 0.92) and six-rowed barley (R² = 0.96), indicates that the N uptake is the main GY limiting factor in these crops. On the other hand, a slightly lower relationship between N uptake and GY in triticale (R² = 0.65) suggests that the relationship between these two traits probably does not follow a strict linear pattern and that GY variation could also be limited by other environmental factors, especially under high N fertilization conditions. Therefore, non-linear models should probably be used to more accurately describe the relationship between N uptake and GY in cereal crops [4]. Differences in N uptake between studied cereal crops mostly followed the trend of GY differences. Therefore, triticale was characterized by higher N uptake potential under different treatment conditions, while the lowest values were recorded in six-rowed winter barley.

The present experiment showed the existence of variability for NUE, NUpE, and NUtE under different fertilization treatments among studied winter small grain cereal crops adapted for cultivation in the southern Pannonian Plain. An increase in N fertilizer application was followed by a N uptake and GY improvement, while the NUE notably decreased. As expected, high N fertilization led to a significant decrease in the NUE, since N is not the only yield limiting factor in cereal production under conditions of the Pannonian Plain [16,41]. Also, a GY increase is often related to a decrease in grain N or protein content [38]. Among the studied cereal crops, grain protein decrease could be acceptable or desirable for two-rowed barley since it is used mostly for the malting industry [42]. On the other hand, triticale and six-rowed barley are mostly used for animal feed, while wheat has a central role in the milling and baking industry, and so grain protein decrease is not desirable trait. Therefore, the GY or NUE increase in these crops cannot be assessed without detailed end-use quality analysis [43,44].

Also, in most cases triticale showed a higher NUE than other studied cereal crops, confirming that it has an increased resource use efficiency. The greater NUE of triticale compared to other cereals was mostly the result of increased nitrogen (N) uptake, indicating higher N soil recovery by triticale. The reputation of triticale as a cereal crop with effective N uptake has also been confirmed in European regions, such as the UK [45] and Denmark [46]. Triticale is characterized by early root growth and increased transpiration efficiency, which contribute to biomass accumulation [45]. Its vigorous early root development helps the crop capture more nitrogen that would otherwise be leached beyond the root zone [47]. Two-rowed barley showed an increased NUE compared to wheat and six-rowed barley. Regarding the NUpE variation, triticale also showed higher values than other cereal crops. Although two-rowed barley had a higher GY than wheat, wheat was characterized by a slightly higher NUpE. This could be explained by a higher grain protein content in wheat, compensating for a lower GY performance compared to two-rowed barley. Moreover, triticale cultivars had lower NUtE values compared to the other crops. A decreased NUtE in triticale is probably due to a higher biomass and lower values of the harvest index compared to the wheat and barley [46,48]. Triticale is produced both for grain and biomass [30,49], and notable plant height and biomass reduction were not among the most important goals during the past century of plant breeding activities. Therefore, in the future we could expect an increase in the triticale harvest index and NUtE, but only if the breeding activities become more focused on the development of cultivars for grain production.

The variation in NUpE accounted for more of the variation in NUE, while the relationship between the NUE and NUtE was not significant. Also, NUpE and NUtE were not related in all of the studied crops. As previously reported by [50], the absence of correlation between NUpE and NUtE indicates that these two components could be improved independently. Although NUE genetic improvement in barley was based on the simultaneous NUpE and NUtE increase with the year of cultivars release [16], further NUtE improvement would represent more challenging task since the harvest index in modern cereal crops has almost reached a theoretical maximum [51].

5. Conclusions

We concluded that there was a positive response of different small grains to N fertilization in diverse agroecosystems characterized by standard low-input farming, driven by unfavorable weather conditions or high fertilizer costs. This response was primarily attributed to the ability of small grain crops to uptake more N from the fertilized soil, irrespective of varying environmental conditions. However, the magnitude of the yield response varied significantly among species, highlighting the importance of species-specific nitrogen management strategies. Two-rowed winter barley showed a higher GY compared to winter wheat, while six-rowed winter barley had the lowest GY and N uptake among studied crops. These findings emphasize the necessity of differentiating between two-rowed and six-rowed barley when selecting cultivars for specific production goals. Although triticale is not widely accepted by farmers in the Pannonian Plain, it outperforms both wheat and barley under all fertilization levels. Triticale’s superior yield performance under low nitrogen conditions reinforces its potential role as a sustainable crop choice for resource-limited environments. Therefore, a better understanding of triticale’s higher N uptake and GY, especially under low N conditions, may provide a valuable insight for further wheat and barley resource use efficiency breeding and production under low-input conditions. Moreover, increased N fertilization and the introduction of triticale into wider production both in low- and high-yielding environments can help small grain producers achieve attainable yields in rainfed systems, mostly by improving nitrogen uptake. However, the economic feasibility of triticale expansion depends on improving its market value and end-use quality. Addressing these factors through breeding and industry collaboration could enhance the acceptance of triticale in commercial grain production.