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Article

Forage and Seed Production of Field Bean Respond Differently to Nitrogen Fertilization and Sowing Rate

by
Silvia Pampana
1,*,
Francesco G. S. Angeletti
2,
Marco Mariotti
2,
Dayana N. Esnarriaga
3 and
Iduna Arduini
1
1
Department of Agriculture, Food and Environment, University of Pisa, Via del Borghetto, 80, 56124 Pisa, Italy
2
Department of Veterinary Science, University of Pisa, Viale delle Piagge, 2, 56124 Pisa, Italy
3
Forschungsinstitut für Biologischen Landbau—FiBL, Ackerstrasse 113, 5070 Frick, Switzerland
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(7), 1660; https://doi.org/10.3390/agronomy15071660
Submission received: 25 April 2025 / Revised: 6 July 2025 / Accepted: 7 July 2025 / Published: 9 July 2025
(This article belongs to the Section Grassland and Pasture Science)
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Abstract

The rising demand for plant proteins and climate change highligth the need for adaptable legume crops. A three-year field experiment examined forage and seed production, as well as nitrogen (N) and phosphorus (P) accumulation in an indeterminate field bean (Vicia faba L. var. minor Beck) variety, as affected by two fertilization rates (0 and 120 kg N ha−1, i.e., N0 and N120) and two sowing rates (60 and 100 seeds m−2, i.e., S60 and S100), along with their interaction with climatic variability. Forage yield ranged from 11.1 Mg ha−1 in Year I (S100) to 6.8 Mg ha−1 in Year III (S60 and S100), and seed yield dropped from 4.1 Mg ha−1 in Year II to 1.9 Mg ha−1 in Year III, due to fewer seeds per pod and lower seed weight unaffected by fertilization and sowing rate. Nitrogen fertilization increased forage by 20% but had no effect on seed production. Field bean showed good adaptability to variable climatic conditions, compensating for lower stem number with more pods per stem. The possibility to obtain either forage or seed yield makes field bean a valuable source of plant proteins in a changing environment, contributing to the sustainability of cropping systems.

1. Introduction

Vicia faba L., of the Fabaceae family, is one of the earliest domesticated crops, going back to early Neolithic times [1]. Nowadays, V. faba is widely cultivated throughout the northern hemisphere, and in the European Union (EU) it ranks third among the most cultivated grain legumes, after soybean (Glycine max L.) and pea (Pisum sativum L.) [2]. Based on seed size, V. faba is roughly distinguished as V. faba L. var. major (faba bean), which produces larger seeds, and is mainly grown for human consumption, and V. faba L. var. minor (field bean, also referred to as pigeon bean, broad bean, or tick bean), which produces smaller seeds and is grown for feeding animals because of greater vegetative biomass [3]. Field bean is a key crop for dietary protein in animal husbandry due to the protein accumulation of its seeds, i.e., 300 g kg−1, essential nutrients (Ca, Mg, K, Fe, and Zn), and bioactive compounds like polyphenols and carotenoids [4]. Additionally, field bean can provide green manure, forage, and silage and further research is needed for fine-tuned cultivation [5,6,7,8,9,10].
The increasing demand for plant proteins in Europe and the USA, along with the impacts of climate change (CC), is leading to the cultivation of grain legumes in new regions, exposing these crops to a variety of environmental conditions [11,12]. Higher year-round temperatures, heavy rainfall, and prolonged summer droughts recently seen in Europe may necessitate changes in crop management techniques [13]. In this scenario, summer crops like soybean may extend into northern regions but are likely to need irrigation during summer. Additionally, soybean was recently proven to be narrowly economic with late sowings [14], while cool season crops such as faba beans, lupins (Lupinus albus L.), and field pea (Lathyrus oleraceus Lam.), which are generally rainfed grown in temperate to semi-arid regions, might increasingly be included into cropping systems of Central and Northern Europe [2,12,15].
Because of the high versatility in terms of sowing time and deserved products, field bean can be integrated into various crop rotations, as sole crop, cover crop, and intercrop, and could be a suitable alternative to soybean for increasing the nutritive value of feed in Europe [7,8,9]. However, to reduce the risk of crop failure and to best exploit the good adaptation and plasticity of field bean crops, appropriate agronomic techniques, in terms of fertilization rate and planting density, should be adopted for the diverse environmental conditions and sowing times [2,16]. Sowing before the autumn rains start can be an agronomic strategy to advance harvest and thus escape from drought during the late part of the crop cycle. However, it may also increase the risk of waterlogging during early growth stages, and even if field bean demonstrated greater resistance compared to other pulses [17,18], it may be damaged by waterlogging during early growth stages when the plants are more susceptible [7,19].
In Mediterranean Europe, the best time to sow field beans is October to November, but unpredictable and heavy autumn rains often prevent the soil from drying enough for mechanical operations. In this case, field bean sowing can be delayed up to the first 10 days of February [20], but late sowings typically reduce the seed-filling phase, resulting in approximately a 26% decrease in seed yield [8,21].
Though the final number of plants per unit surface is a key component of seed yield, the optimal sowing rate of field bean is highly variable, ranging from 10 to 100 seeds per square meter, depending on genotypes and environmental conditions [22]. Helios and collaborators [23] found that rising plant density from 45 to 75 plants m−2 increased seed yield by less than 10%, and Pilbeam et al. [24] reported a 30% increase when rising plant population eightfold, from 10 to 80 plants m−2. The optimal sowing rate is also related to the sowing date, and in general, higher sowing rates are mandatory to achieve high yield with delayed sowings [25]. In turn, this drives an increase in the demand for nutrients by the crop. The accumulation of nitrogen (N) and phosphorus (P) of field bean is high in comparison to other grain legumes such as peas, and the biological N2-fixation cannot fulfill the high N requirements during the reproductive phase, especially in Mediterranean soils that are typically poor in organic matter and total nitrogen [7,26,27]. Therefore, fertilization is often necessary to maximize growth and yield, and a nitrogen fertilization rate of 120 kg N ha−1 was found to increase the mean weight of seeds in this environment [28,29].
The performance of field bean crops also differs between determinate and indeterminate morphotypes. In indeterminate morphotypes, vegetative growth and flowering partially overlap with seed filling, thus prompting intra-plant competition between reproductive and vegetative structures, and within the reproductive structures, between flowers and developing pods [30]. Accordingly, intra-plant competition is expected to increase with early sowings and warmer winter temperatures, as these conditions favor vegetative growth. On the other hand, indeterminate morphotypes show greater ability to adjust to plant density and environmental conditions, and their longer flowering favors seed yield in late sowings [16,22].
Despite the wide cultivation of field bean in the Mediterranean region, data is still inadequate for both forage and seed production of indeterminate morphotypes in response to the combination of fertilization and sowing rate and their interaction with climatic variability. Enhancing this knowledge will help farmers adjust cultivation methods and change target productions based on weather conditions.
To fill this gap, the present study investigated the differential response of forage and seed yield of an indeterminate field bean (Vicia faba L. var. minor Beck) variety to N fertilization and sowing rate, grown for three consecutive years in rainfed Mediterranean conditions (i.e., Central Italy). The evaluated parameters were forage and seed production, N and P accumulation, and the partitioning of biomass, N, and P within aboveground plant parts, at full flowering (i.e., forage production) and plant maturity (i.e., seed production). To give insight into the effects of N fertilizer and sowing rate on the determination of yield components, and to reveal compensation mechanisms, stem traits and the patterns of flower and pod production were also determined.

2. Materials and Methods

The field experiment was carried out during three consecutive cropping seasons, from 2017 to 2020 (i.e., Year I, Year II, and Year III, hereafter), at the experimental station of the Department of Agriculture, Food and Environment, University of Pisa (Italy) (43°40′34″ N, 10°18′41″ E). The climate is Mediterranean (Csa) according to Köppen classification, with an irregular pattern of yearly rainfall distribution together with low temperatures in winter, and a hot and dry summer. The long-term mean annual maximum and minimum daily air temperatures are 20.2 °C and 9.5 °C, and the mean rainfall is 971 mm. Over the research period, daily minimum and maximum temperatures and rainfall were measured by a meteorological station located at the trial site. The soil is Typic Xerofluvents, with loam texture, moderately alkaline reaction, low N and organic matter contents, medium available P, and modest limestone contents. Soil chemical and physical properties measured at the beginning of the experiment (October 2017) were 45.7% sand (∅ 2–0.05 mm), 43.6% silt (∅ 0.05–0.002 mm), 10.8% clay (∅ < 0.002 mm), 2.8% organic matter (Springer and Klee method), 8.3 pH, 1.6 g kg−1 total N (Kjeldahl method), 15.6 mg kg−1 available P (Olsen method), and 234.1 mg kg−1 available K (BaCl2-TEA method).
Each year, two N fertilization rates and two sowing rates were arranged in a split-plot design with four replicates: the N fertilization was allocated in the main plot, and the sowing rate in the subplot (Supplementary Figure S1). Each subplot was 39 m2 (13 × 3 m).
The fertilization treatments were (i) unfertilized control (N0), without any N application, and (ii) N fertilized (N120), each year receiving 120 kg ha−1 of N, split into three distributions: 30 kg ha−1 of N at pre-sowing, as ammonium sulfate, and the remaining top-dressed, as urea, at the stages 8-leaf unfolded (BBCH 18) and flowering (BBCH 63) [31], in two equal rates of 45 kg N ha−1. The 120 kg N ha−1 rate was chosen hypothesizing that it could exert distinct effects on forage and seed production according to [28,29]. Moreover, this is also a common N rate for the cultivation of intercropped field bean [22].
The sowing rate treatments were (i) 60 seeds m−2 (S60) and (ii) 100 seeds m−2 (S100); S60 is the most adopted in the area and S100 is the highest for Mediterranean environments [22]. Immediately before sowing, seeds were inoculated with Rhizobium leguminosarum bv. Viciae and visual assessment of nodule presence and color was periodically carried out by extracting roots from each plot. In all treatments, nodulation and N2-fixation were revealed after the stage three leaves unfolded (BBCH13) and maintained up to flowering (Supplementary Figure S2).
All plots were cultivated uniformly using the practices commonly adopted by local farmers. The field bean crops were grown under rainfed conditions and were rotated yearly with barley (Hordeum vulgare L.). The soil was plowed at a depth of 35 cm in September, then disk and rotating harrows were used for final seedbed preparation. Phosphorus (P) and Potassium (K) fertilizers were applied at plowing both at the rate of 100 kg ha−1 as triple superphosphate and potassium sulfate, respectively. Nitrogen was applied or not as per the experimental design, and no chemical weed control occurred during the experiment or in the previous three years.
The experiment used the field bean variety ‘Vesuvio’, an open-pollinated variety with indeterminate growth, and one of the most cultivated in Central Italy, because of its high productivity and adaptability [20].
Field bean growth stages were assessed when over half the plants reached the given stage following the BBCH scale [31]. The length of each phase was calculated in days and in accumulated Growing Degree Days (GDD), using the formula GDD = (Tmax + Tmin)/2 − Tbase, where Tmax and Tmin are the maximum and minimum temperatures (°C) and Tbase the base temperature. Following Iannucci et al. [32], a Tbase of 2 °C was incorporated into the equation, as if Tmin < Tb then Tmin = Tb.
The crops were harvested at two stages: full flowering (flowers open on five racemes per plant, BBCH 65) and maturity (plant dead and dry, BBCH 97), corresponding to the utilization for forage and seed. The sowing and harvest dates over the three years of the experiment are provided in Table 1.
At both harvests, field bean plants and weeds were manually cut at ground level on a 1 m2 surface in each plot. At full flowering, the plants were partitioned into stems, leaves, and reproductive organs (pods + flowers). Well-developed basal branches were counted as independent stems. The average crop height was determined, and the numbers of stems and pods were counted. For dry weight (d.w.) determination, field bean plant parts and weeds were oven-dried at 65 °C to a constant weight. The partitioning of assimilates among shoot organs was determined by calculating the stem mass fraction (SMF), the leaf mass fraction (LMF), and the reproductive mass fraction (RMF) as a proportion of their mass on the entire shoot mass [33]. The specific stem length (SSL) was calculated by dividing the average crop height by the average unit stem dry weight.
At maturity, the pods were detached, and the stems and pods were counted. After threshing, seeds were weighed, and the pod hulls were combined with stems and leaves and collectively weighed as residues. The average seed weight, number of pods per stem, and seeds per pod were calculated. The harvest index (HI) was calculated as the percentage proportion of the seed weight to the total shoot dry weight.
At both harvests, stem fertility parameters were determined on four replicates per plot, each consisting of five randomly chosen stems. At full flowering, we determined the numbers of basal and terminal sterile nodes, and the number of fertile nodes (i.e., defining ‘sterile’ a node bearing only leaves, and ‘fertile’ a node also bearing either flowers or pods). At maturity, we determined the numbers of ‘fertile’ and ‘reproductive’ nodes, the latter defined as the nodes that produced pods.
Chemical analyses were performed on plant materials of Years I and III. Dry samples of separate plant parts were ground to powder and then wet digested with nitric acid and hydrogen peroxide for the determination of the nitrogen and phosphorus concentrations. Nitrogen was determined by the Kjeldahl method [34] and phosphorus by the ammonium–molybdophosphoric blue color method [35]. The N and P accumulation of separate plant parts was calculated by multiplying the N, or P, concentration by the corresponding dry weight. At maturity, the nitrogen (NHI) and the phosphorus (PHI) harvest indexes were calculated as the percentage proportion of either N or P accumulation in seeds to the total N or P accumulation of the shoot biomass.
To test the effects of year (Y), fertilization (F), sowing rate (S), and their interactions on the measured parameters, data were arranged in a split-split-plot design with four replicates and subjected to Analysis of Variance (ANOVA). Year was the main plot, fertilization treatment the subplot, and sowing rate the sub-subplot. All statistical analyses were performed with JMP ver. 2017 (SAS statistical package) using the fit model function with Y, F, and S set as fixed effects. Models were evaluated to ensure they met the assumptions of independence and normality of residuals and, if necessary, response variables were transformed, and then back transformed to report data means. Post hoc Tukey’s test was used for comparison among treatments and significantly different means were separated at the 0.05 probability level [36]. In addition, correlations between rainfall and GDD and forage and seed production, seed mean weight and N and P accumulation in forage and seeds were assessed by Pearson’s correlation analysis performed with JMP Student Edition 18.2.0.

3. Results

3.1. Weather Conditions and Crop Phenology

Temperatures from October to June varied by approximately 1 °C among the three growing seasons, with means ranging from 12.2 to 13.2 °C, minima from 6.6 to 8 °C, and maxima from 17.4 to 18.4 °C (Figure 1). The lowest maximum temperatures were recorded in Year I, the lowest minima in Year II, whereas both the maximum and minimum temperatures were the highest in Year III.
Cumulative rainfall from October to June differed greatly among the three growing seasons, and in Year I (841 mm) and in Year III (1015 mm) rainfall was about 38% and 66% higher than in Year II (612 mm), and those of the optimal field bean sowing period (October–November) were 157, 184, and 484 mm, in Years I, II, and III, respectively, highlighting the great difficulty of sowing winter crops at the optimal time in Mediterranean climates. The rainfall averages and ranges of variability calculated over the research years were close to those recorded by the same weather station over the 25-year period preceding the research (1990–2014) and can, therefore, be considered typical of the area (Supplementary Table S1). Conversely, the average of mean temperatures was 1 °C higher in the experimental period (i.e., 2017–2020) compared to the 25-year mean (Supplementary Table S1).
The timing and length of growth phases of field bean were unaffected by fertilization and sowing rates but varied among different years. In Years II and III, the crop cycle was shortened by 14% and 40%, respectively, compared to Year I. The cumulative thermal time to maturity was 2226, 1961, and 1742 GDD in Years I, II, and III, respectively (Supplementary Table S2). Reductions were to be imputed to the shorter period from sowing to full flowering in Year II, and to a shortening of both phases in Year III.
The pairwise correlation graph, showing the correlations between each pair of variables (rainfall and GDD, forage and seed production, seed mean weight and N and P accumulation in forage and seeds) is reported in Supplementary Figure S3. Based on the results shown in the graph, higher positive correlations existed between GDD or rainfall and forage (i.e., 0.90 and 0.91) than with seed production (i.e., 0.30 and 0.34).

3.2. Full Flowering

3.2.1. Forage Production and Biomass Partitioning

The results of ANOVA for the analyzed characters of field bean at the full flowering stage are reported in Supplementary Table S3. Increasing the sowing rate from S60 to S100 improved forage yield by 52% in Year I and by 85% in Year II, while the yield advantage was negligible in Year III (Table 2). The highest forage yield was consistently achieved with S100 in both Year I and Year II, averaging 1113 g m−2 across the two years. Similar responses to treatments were observed for stem and leaf biomass, whereas the biomass of reproductive structures was highest in Year III and was not affected by sowing rate (Table 2).
As a result, the partitioning of biomass among stems, leaves, and reproductive structures varied significantly in response to year (Figure 2). SMF was 0.69, 0.56 and 0.45 g g−1 in Year I, II and III, respectively; RMF was more than two-fold in Year III compared to Year I and II, 0.18 g g−1 vs. 0.08 and 0.06 g g−1, respectively. The reverse was true for LMF, which was 0.24 g g−1 in Year I and approximately 0.37 g g−1 in Year II and III. SMF increased from 0.55 to 0.58 g g−1 with the increase in sowing rate from 60 to 100 seeds m−2, while LMF decreased from 0.34 to 0.31 g g−1 and RMF was 0.11 g g−1 irrespective of sowing rate.
The weight of a single stem was nearly double in Year I compared to Year III (Table 3). Crop height was 50% higher in Year I than Year III, regardless of sowing rate, while in Year II, plants were significantly taller (+26%) with S100. The number of stems per unit surface was positively affected by sowing rate but did not differ significantly among years (Table 3). Because the changes in stem weight were greater than in height, the specific stem length (SSL) was higher in Year III, highlighting a lower investment in stem biomass compared to elongation (Table 3). The highest SSL (35.1 cm g−1), i.e., 48% higher compared to the average values achieved in Year I and II, was obtained in Year III with S100.
The differences in stem elongation recorded in Year I and II did not affect the total number of nodes per stem, and the proportion of sterile and fertile nodes (Table 4). In Year III, the total number of nodes dropped by about 30%, and fertile nodes were reduced by more than a half, decreasing the proportion of fertile nodes per stem from around 33.5% in Years I and II to 23.3% in Year III. Sowing rate affected the number of basal sterile nodes per stem (i.e., 7.4 in S60 and 8.7 in S100).
Fertilization resulted in a 20% increase in the number of stems per unit area, as well as an increase in stem biomass, leaf biomass, and overall forage biomass (Table 5). It did not affect the biomass of reproductive structures, which were approximately 86 g m−2, nor the leaf mass fraction (0.33 g g−1). Consequently, the stem mass fraction increased by 5.5%, while the reproductive mass fraction decreased by 25%.

3.2.2. Nitrogen and Phosphorus Concentration and Accumulation

ANOVA results for the N and P variables at the full flowering stage are reported in Supplementary Table S4.
At full flowering, the N concentration in leaves and reproductive structures was lower in Year III than in Year I, whereas that of stems was not affected (Table 6). Nevertheless, because of the differences in biomass partitioning and N concentrations among plant parts, the average N concentration of the forage was markedly higher in Year III. The P concentration, conversely, did not vary between years, being approximately 2.1, 3.1, and 4.7 mg g−1, respectively, in stems, leaves and reproductive structures, and 2.7 mg g−1 in the forage.
The distribution of N fertilizers improved the N concentration of leaves and reproductive structures, but not that of stems (Table 6). Conversely, the P concentration increased only in the reproductive structures in response to N fertilization, from 5.1 to 6 mg g−1, and the increase in sowing rate reduced slightly and not significantly the N and P concentration of all plant parts (data not reported).
In addition, the concentrations of N and P in the forage were affected by the interaction fertilization x sowing rate, in that the forage of unfertilized S100 had a significantly lower N (Figure 3a) and P (Figure 3b) concentrations compared to the other treatments. Fertilization increased both N and P accumulation in stems and leaves, while reproductive structures remained unaffected (Table 7). This led to approximately a 30% rise in the N and P accumulation in the total forage.
The year x sowing rate interaction affected N and P accumulation by stems and forage (Figure 4) which were strictly correlated with GDD and rainfall (Supplementary Figure S3). In Year I, S100 field beans accumulated more nitrogen and phosphorus in stems (Figure 4a,c), resulting in 46% more nitrogen and 62% more phosphorus in forage compared to S60 (Figure 4b,d). Moreover, S100 had higher accumulations in Year I than in Year III, while the N and P accumulated by S60 forage were similar in the two years.

3.3. Maturity

3.3.1. Seed Production and Yield Components

The ANOVA results for variables on seed production and yield components of field beans at the maturity stage are documented in Supplementary Table S5.
Seed yield, residue biomass, and total shoot biomass varied only by year and were the highest in Year II, with an increase compared to Year I of approximately 20% for seed and 30% for residues, while compared to Year III, the increase was 120% and 170%, respectively (Table 8). The harvest index remained consistent (Supplementary Table S5) at approximately 22% each year. Variations in seed yield and residue biomass over the years were mainly due to differences in mean seed weight (Table 8) and residue biomass per stem (Table 9). Conversely, the numbers of both stems per unit surface and pods per stem did not vary across years but were affected by sowing rate (Supplementary Table S5). As expected, the number of stems per unit surface was 41% higher with S100, whereas the number of pods per stem was 26% higher with S60 (Table 9). Sowing rate did not significantly impact seed yield or residue biomass.
The percentage of fertile nodes that developed at least one pod containing seeds, was approximately double in Year III and 10 percentage points higher with S60 (Table 9).
The higher seed yield obtained in Year II compared to Year I depended on the 21% increase in mean seed weight, whereas the lower seed yield obtained in Year III was associated with a marked decrease in both mean seed weight (Table 8), and in the number of seeds per pod which was significantly affected by year x fertilization and year x sowing rate interactions (Figure 5). In Year I, adding N fertilizer increased seeds per pod by 35% (Figure 5a), and S60 had 24% more seeds compared to S100 (Figure 5b), whereas the responses to both treatments showed no differences in later years.

3.3.2. Nitrogen and Phosphorus Concentration and Accumulation

Supplementary Table S6 provides the results of ANOVA for variables related to the N and P concentrations and accumulations of field bean determined at the maturity stage.
The year was the only variable that significantly affected specific concentration levels. N concentration was higher in all plant parts in Year III. Conversely, P concentration in seeds was elevated in Year I but no significant differences were observed between years in the residues or the entire shoot (Table 10).
Consequently, due to variations in concentration and dry weight dynamics, the N and P accumulations were consistently greater in Year I compared to Year III (Table 10). N and P accumulation by seeds in Year I were approximately 72% and 165% higher than in Year III, while P accumulation by the shoots was approximately 57% higher.
The N accumulation in the entire shoot, changed with a significant interaction year x fertilization (Figure 6). In Year I, the N accumulation was 39% higher than in Year III without fertilization, and 88% higher when N fertilizer was added. N and P accumulation were correlated to GDD and rainfall (Supplementary Figure S3).
The N and P harvest indexes were not affected by year, fertilization, and sowing rate and measured, on average, 41.5% (NHI) and 43.1% (PHI).

3.4. Weed Development

The dry biomass of weeds varied greatly among years, and in Year I, it was markedly higher with the lower sowing rate both at full flowering and at maturity (Figure 7).
At full flowering, weed biomass was 143 g m−2 with S60 in Year I, and about 37 g m−2 with other treatments (Figure 7a). At maturity, weed biomass reached 432 and 235 g m−2 in Year I with S60 and S100, respectively, and averaged 43 g m−2 in Years II and III across all sowing rates (Figure 7b). Adding N fertilizer boosted weed growth, more at full flowering (+68) than at maturity (+22%) (Figure 8).

4. Discussion

The rainfall variability throughout both the crop cycle (October–June) and the optimal sowing period (October–November) of field bean observed over the three consecutive experimental years reflected the typical Mediterranean climate conditions, which may become more common due to climate change [37]. However, our research indicates that forage production at full flowering was significantly influenced by N fertilization and sowing rates, which outdid the variations observed across different years. Overall, N fertilization enhanced the forage biomass, whilst increasing the sowing rate from S60 to S100 resulted in higher forage production only during the longer growth cycle seasons (Year I and Year II) and was ineffective with a short growth cycle (Year III).
The forage yield obtained without nitrogen fertilization (N0) and with a lower seeding rate (S60) remained consistent at 5.7–7.6 Mg ha−1 across years, a reference value reported for field bean in Mediterranean conditions [8].
Moreover, the forage of field bean sowed at the higher sowing rates (S100) was 30% lower in Year III compared to the previous years (6.9 vs 11.1 Mg ha−1), but there were no significant changes with S60. This result goes against the usual farming practice of increasing sowing rate for late plantings.
In Year III, we noted an increased allocation of biomass to leaves and reproductive structures, which elevated the nitrogen and phosphorus concentrations of the forage, potentially enhancing its nutritional value [9]. Late sowing (Year III) led to fewer basal sterile nodes, indicating an earlier transition to the reproductive phase and a longer overlap with the vegetative phase, thereby reducing stem biomass accumulation.
This year-to-year stability of forage biomass was associated with the stability of the most prominent biomass component, i.e., the number of stems per unit surface, which did not change across years, but was always higher with N120 and with S100. We impute the lack of year effect on stem number to the fact that the higher branching, that is generally associated with longer vegetative periods, was counterbalanced by higher seedling mortality due to winterkill in Year I and II [2,25]. Branching was probably also impaired by weed development, which was more pronounced in Year I and II, and especially with S60, so that the lower plant density (i.e., sowing rate, S60) could never be compensated by a greater number of stems per plant [25,38]. Conversely, the sowing rate affected the number of basal sterile nodes per stem, likely due to earlier shading near the soil surface at higher plant densities [39].
On the other hand, in all years and with all sowing rates, N fertilization increased forage biomass by improving stem number, which we essentially attributed to improved plant survival, thus confirming the importance of sufficient mineral N availability for field bean at early growth stages [26]. Moreover, the lower N and P concentrations recorded in the forage of S100 clearly demonstrated that fertilization is necessary to fulfill the requirements of field bean crops sown at high density, which is in line with the higher mineral of this crop compared to other grain legumes [7,40].
The higher forage biomass achieved with the higher sowing rate in Years I and II was associated with both higher stem number and height [16]. Consistent with the findings of Loss et al. [38], the higher crop height was only attributed to increased internode elongation, as the number of nodes per stem was not modified by sowing rate. In Year I and II, the increased internode elongation did not affect the specific stem length, highlighting that the environmental resources were adequate to support photosynthesis and plant growth at both sowing densities [41]. Our results indicate that late winter sowing (Year III) resulted in fewer resources being allocated to stem biomass, leading to a reduced stem mass fraction and a significant increase in stem-specific length, suggesting inadequate resources for rapid stem elongation.
Unlike forage, seed production was influenced solely by the year treatment, highlighting that annual variability influences Vicia faba seed yield in Mediterranean regions. Indeed, seed yield showed only a low correlation with GDD and rainfall, suggesting that these factors play an indirect role, and that climate exerts a stronger effect on plant growth and phenology rather than on seed filling.
For example, Barilli et al. (2025) [42] reported that rainfall increased yield, while high temperatures reduced it, with no damage from cold temperatures even during winter sowing. Sufar and collaborators [43] found that weather conditions significantly affected faba bean performance, including seed yield, over seven growing seasons in Northern Europe.
In our research, seed yields over the entire research were comprised between 1.9 Mg ha−1 in Year III and 4.2 Mg ha−1 in Year II, thus matching with those obtained in Austria by Neugschwandtner et al. [44] (1.7–4.5 Mg ha−1), and in Spain by Barilli et al. [42] (2.2–4.1 Mg ha−1), and close to the potential yield of 4.5 Mg ha−1 estimated for Mediterranean conditions by Manschadi et al. [45]. Our data were also comparable to those reported for soybean in Europe by Karges et al. [46] (1.3–2.7 Mg ha−1) and by Nendel et al. [12] (0.7–5.4 Mg ha−1), recognizing field bean a valuable alternative source of proteins. Moreover, the seeds produced in Year III displayed a higher N concentration, thus compensating for a lower yield with higher quality (i.e., protein concentration). The phosphorus concentration of seeds was lower in Year III, likely due to the shorter seed-filling period. Phosphorus is primarily derived from remobilization [47] and its concentration in the forage at flowering did not differ between years.
The low seed yield obtained in Year III had to be imputed primarily to the shorter reproductive phase in terms of days and accumulated thermal time, which reduced the duration of seed filling, thus leading to lower mean seed weight [30]. Increased weed competition because of earlier sowing also contributed to the lower average seed weight [48]. Sufar et al. [43] showed that rigorous weed control significantly increases seed and straw yields in faba bean. The lower seed yield in Year I compared to Year II was due to decreased mean seed weight, fewer pods per stem, and reduced podding nodes. The decline in mean seed weight was also partly due to heavy rainfall and lower temperatures during flowering, which extended the vegetative phase and likely increased flower abortion [22]. During vegetative phase, conversely, low temperature was found to be the strongest positive driver for seed and straw yield of faba bean, as confirmed by the high correlation between GDD and rainfall with biomass produced at flowering [43]. Similar results were reported in Spain, where winter sowing showed no damage from cold temperatures but high temperatures negatively affected seed yield [42]. It is significant to note that seed yield reached its peak during the driest year, which corroborates the hypothesis proposed by Khan et al. [49] that field beans demonstrate robust drought resistance through the development of an extensive root system. Contrary to our findings, Barilli et al. [42] indicated that seed yield was improved due to increased rainfall. Moreover, though stems accounted for the greatest mass fraction at full flowering [38], we observed a marked shift to reproductive structures in Year III, which further highlights that indeterminate field bean has a good plasticity in partitioning resources to seeds.
In field beans, stem number is the sole yield component determined prior to flowering, which may influence both forage and seed yield. The remaining, number of pods per stem, number of seeds per pod, and mean seed weight are sequentially set during the reproductive phase. In our research, only mean seed weight (i.e., the last determined yield component) varied yearly in line with seed yield. In Year III, the number of pods per stem barely decreased, despite fewer nodes setting flowers, due to the significant increase in flowering nodes setting pods. Furthermore, we observed an increased number of pods per podding node. Consistent with the findings of Manning et al. [50], our results for Year III indicated that flower set commenced one node lower on the stem, thus confirming an earlier transition to the reproductive phase.
The imposed treatments, i.e., N fertilization and sowing rate, affected yield components, but not the final seed yield, thus demonstrating that indeterminate field bean compensated among components in response to growth conditions [22]. Different from the findings of Serafin-Andrzejewska et al. [51], and consistent with Acay and Bicer [39], the lower stem number per unit surface obtained with the lower sowing rate was, indeed, compensated by a higher number of pods per stem, leaving seed yield unchanged. The positive impact of fertilization and sowing rate on the number of seeds per pod was observed only in Year I. This may be due to the earlier cessation of seed set when field beans were sown later, as in Years II and IIII [52].
Higher plant density moved the flowering nodes upwards without changing the number of flowering nodes per stem or the reproductive potential per stem unit.

5. Conclusions

Under rainfed Mediterranean conditions, year-to-year variability played a key role in determining the forage and seed yield of indeterminate field bean, affecting the time of sowing and the relative duration of the vegetative and seed-filling phases, as well as the development of weeds.
The forage production of field bean sown at 60 seeds m−2 showed great stability across years, despite the rather different rainfall patterns and sowing dates. Our results highlight that forage production can be improved by approximately 70% rising the sowing rate to 100 seeds m−2, but only when sowing can be performed in early or late autumn (as in Year I and II); in addition, 120 kg N ha−1 increased forage yield by 20% and proved to be necessary to sustain the high-density crop.
The seed production was on European average when the crop was sown in early or late autumn but was reduced by about half when sown at the end of winter (Year III); thus, growing field bean for seed production is not recommended with late sowings. Neither N fertilizer nor a higher sowing rate improved seed yield in our research, indicating that a common sowing rate of 60 seeds m−2 without N fertilization is the most rational strategy in Central Italy when field bean is cultivated for seed production.
In conclusion, field bean consistently provided adequate forage, and seed productions across multiple years, demonstrating adaptability to varying environmental conditions.
The ability to produce either forage or seed makes this crop a viable source of protein in Mediterranean and temperate climates, provided that the product objectives are fine-tuned to management techniques.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy15071660/s1. Table S1: Cumulative rainfall and average temperatures (mean, maximum, minimum) of the whole year (1 October–30 September) and of the field bean growing season (1 October–30 June) during the research period, as well as for the previous 25 years (1990–2014). Rainfall data for the optimal sowing period (1 October–30 November) is also included. Table S2: Duration of the growth phases of field bean crop, given in number of days and thermal time (GDD), in Central Italy over the three years of the study. Table S3: Analysis of Variance (ANOVA) for variables on biomass and plant traits of field bean at the full flowering stage with source of variation, effect type, degrees of freedom (df), and p values > F for the main effects and the interactions. Sources of variations are year (Y), N fertilization (F), and sowing rate (S). Table S4: Analysis of Variance (ANOVA) for N and P concentrations and accumulation of field bean determined at the full flowering stage with source of variation, effect type, degrees of freedom (df), and p values > F for the main effects and the interactions. Sources of variations are year (Y), N fertilization (F), and sowing rate (S). Table S5: Analysis of Variance (ANOVA) for variables on seed yield and yield components determined on field bean at the maturity stage with source of variation, effect type, degrees of freedom, and p values > F for the main effects and the interactions. Source of variations are year (Y), NP fertilization (F), and sowing rate (S). Table S6: Analysis of Variance (ANOVA) for variables on N and P concentration and accumulation determined on field bean at the maturity stage with source of variation, effect type, degrees of freedom, and p values > F for the main effects and the interactions. Source of variations are year (Y), NP fertilization (F), and sowing rate (S). Table S7: Values of field bean characters at full flowering averaged over the three sources of variations: year (Y), N fertilization (F), and sowing rate (S). Table S8: Values of field bean characters at maturity averaged over the three sources of variations: year (Y), N fertilization (F), and sowing rate (S). Figure S1: Field bean plants at the beginning of stem elongation (BBCH30) in Year I: (a) N0 S60 and (b) N0 S100. Figure S2: Roots of field beans with nodules. A cross-section reveals the red center, indicating effective nitrogen fixation. Figure S3: Pairwise correlations between variables (rainfall, GDD, forage and seed production, mean seed weight, N and P in forage and seeds). Red indicates a positive correlation, blue a negative correlation; darker shades represent stronger correlations.

Author Contributions

Conceptualization, I.A. and S.P.; methodology, I.A. and D.N.E.; software, I.A.; validation, S.P. and I.A.; formal analysis, I.A., and S.P.; investigation, D.N.E., F.G.S.A., M.M. and I.A.; resources, I.A.; data curation, S.P. and I.A., writing—original draft preparation, S.P. and I.A.; writing—review and editing, S.P. and I.A.; visualization, S.P.; supervision, M.M.; project administration, I.A.; funding acquisition, I.A. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data presented in this study are available on request from the corresponding author.

Acknowledgments

During the preparation of this manuscript, the authors used Copilot for the purposes of improving the language. The authors have reviewed and edited the output and take full responsibility for the content of this publication.

Conflicts of Interest

The authors declare no conflicts of interest.

Abbreviations

The following abbreviations are used in this manuscript: LMF: leaf mass fraction; NHI: Nitrogen Harvest Index; PHI: Phosphorus Harvest Index; RMF: reproductive mass fraction; SMF: stem mass fraction; SSL: stem specific length.

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Agronomy 15 01660 g001
Figure 1. Air minimum (white dots) and maximum (black dots) temperatures and rainfall (bars) during field bean crop cycle (October–June) in Central Italy in (a) Year I, (b) Year II, and (c) Year III. Values of temperature are 10-day averages and values of rainfall are 10-day sums.
Figure 1. Air minimum (white dots) and maximum (black dots) temperatures and rainfall (bars) during field bean crop cycle (October–June) in Central Italy in (a) Year I, (b) Year II, and (c) Year III. Values of temperature are 10-day averages and values of rainfall are 10-day sums.
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Figure 2. Stem (SMF), leaf (LMF), and reproductive (RMF) mass fractions of field bean, as affected by the year mean effect, at full flowering. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). SMF: stem mass fraction; LMF: leaf mass fraction; RMF: reproductive mass fraction.
Figure 2. Stem (SMF), leaf (LMF), and reproductive (RMF) mass fractions of field bean, as affected by the year mean effect, at full flowering. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). SMF: stem mass fraction; LMF: leaf mass fraction; RMF: reproductive mass fraction.
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Figure 3. Concentration of (a) nitrogen and (b) phosphorus of field bean forage, as affected by the fertilization x sowing rate interaction, at full flowering. Values are means of two years, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. 0: unfertilized crop; NP: crop fertilized with 120 kg ha−1 of N. S60: sowing rate of 60 seeds m−2; S100: sowing rate of 100 seeds m−2.
Figure 3. Concentration of (a) nitrogen and (b) phosphorus of field bean forage, as affected by the fertilization x sowing rate interaction, at full flowering. Values are means of two years, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. 0: unfertilized crop; NP: crop fertilized with 120 kg ha−1 of N. S60: sowing rate of 60 seeds m−2; S100: sowing rate of 100 seeds m−2.
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Figure 4. Nitrogen accumulation of (a) stems, and (b) forage and phosphorus accumulation of (c) stems, and (d) forage of field bean, as affected by the year x sowing rate interaction, at full flowering. Values are means of two fertilizer treatments, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
Figure 4. Nitrogen accumulation of (a) stems, and (b) forage and phosphorus accumulation of (c) stems, and (d) forage of field bean, as affected by the year x sowing rate interaction, at full flowering. Values are means of two fertilizer treatments, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
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Figure 5. Number of seeds per pod, as affected by (a) the year x fertilization and (b) year x sowing rate interactions, at maturity. Values are means of either two sowing rates (a) or two fertilizer treatments (b), and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N. S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
Figure 5. Number of seeds per pod, as affected by (a) the year x fertilization and (b) year x sowing rate interactions, at maturity. Values are means of either two sowing rates (a) or two fertilizer treatments (b), and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N. S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
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Figure 6. Nitrogen accumulation of shoots of field bean, as affected by the year x fertilization treatment interaction, at maturity. Values are means of two sowing rates, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N.
Figure 6. Nitrogen accumulation of shoots of field bean, as affected by the year x fertilization treatment interaction, at maturity. Values are means of two sowing rates, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05, Tukey test. N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N.
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Figure 7. Dry weight of weed biomass as affected by the year x sowing rate interaction, at (a) full flowering and (b) maturity. Values are means of two fertilization treatments, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05. S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
Figure 7. Dry weight of weed biomass as affected by the year x sowing rate interaction, at (a) full flowering and (b) maturity. Values are means of two fertilization treatments, and four replicates (n = 8). Bars represent HSD for p ≤ 0.05. S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
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Figure 8. Dry biomass of weed biomass as affected by the fertilization mean effect, at full flowering and maturity. Values are means of three years, two sowing rates, and four replicates (n = 24). Bars represent HSD for p ≤ 0.05. N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N.
Figure 8. Dry biomass of weed biomass as affected by the fertilization mean effect, at full flowering and maturity. Values are means of three years, two sowing rates, and four replicates (n = 24). Bars represent HSD for p ≤ 0.05. N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N.
Agronomy 15 01660 g008
Table 1. Sowing and harvesting dates (i.e., full flowering and maturity) along with the corresponding BBCH code for stages of field bean during the three years of the experiment in Central Italy.
Table 1. Sowing and harvesting dates (i.e., full flowering and maturity) along with the corresponding BBCH code for stages of field bean during the three years of the experiment in Central Italy.
StageBBCH CodeYear IYear IIYear III
Sowing026 October 201711 December 201812 February 2020
Full flowering6519 April 201826 April 201914 May 2020
Maturity9715 June 201829 June 201930 June 2020
Table 2. Dry biomass of field bean forage, stems, leaves, and reproductive structures, as affected by the year x sowing rate interaction, at full flowering. Values are means of two fertilizer treatments and four replicates (n = 8). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 2. Dry biomass of field bean forage, stems, leaves, and reproductive structures, as affected by the year x sowing rate interaction, at full flowering. Values are means of two fertilizer treatments and four replicates (n = 8). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
YearSowing RateDry Biomass
ForageStemsLeavesReproductive
Structures
g m−2
IS60764.5 bc522.8 b184.6 ab57.1 ab
S1001164.3 a795.1 a270.5 a98.7 ab
IIS60572.5 c307.7 c229.1 b35.7 b
S1001061.1 ab629.1 ab366.0 a66.0 ab
IIIS60624.3 c277.3 c236.3 b110.7 a
S100659.3 c287.2 c248.1 b124.0 a
S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
Table 3. Crop height, weight of single stem, number of stems per unit area, and specific stem length, as affected by the year x sowing rate interaction, at full flowering. Values are means of two fertilizer treatments and four replicates (n = 8). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 3. Crop height, weight of single stem, number of stems per unit area, and specific stem length, as affected by the year x sowing rate interaction, at full flowering. Values are means of two fertilizer treatments and four replicates (n = 8). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
YearSowing RateCrop
Height		Weight of Single StemNumber of StemsSpecific Stem Length
cmg stem−1n m−2cm g−1
IS60142.7 ab6.2 a89.4 ab23.1 b
S100156.4 a7.0 a114.3 a22.4 b
IIS60107.4 c4.2 bc72.8 b25.4 b
S100135.0 b5.7 ab112.5 a23.9 b
IIIS60110.8 c3.9 c83.3 b29.3 ab
S100100.1 c2.9 c112.5 a35.1 a
S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
Table 4. Number of total, sterile (basal and terminal), and fertile nodes, and percentage of fertile nodes, as affected by the year mean effect, at full flowering. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 4. Number of total, sterile (basal and terminal), and fertile nodes, and percentage of fertile nodes, as affected by the year mean effect, at full flowering. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
YearTotal
Nodes		Sterile NodesFertile
Nodes
BasalTerminal
n stem−1% of Total
I30.7 a8.6 a12.0 a10.1 a33.0 a
II28.0 a8.2 a10.3 a9.5 a34.0 a
III20.1 b7.6 b7.8 b4.7 b23.3 b
Table 5. Number of stems per unit area, dry biomass of forage, stems, and leaves, and mass fractions of stems, leaves, and reproductive structures, as affected by N fertilization treatment mean effect, at full flowering. Values are means of three years, two sowing rates, and four replicates (n = 24). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 5. Number of stems per unit area, dry biomass of forage, stems, and leaves, and mass fractions of stems, leaves, and reproductive structures, as affected by N fertilization treatment mean effect, at full flowering. Values are means of three years, two sowing rates, and four replicates (n = 24). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
FertilizationNumber Dry BiomassMass Fraction
StemsForageStemsLeavesReproductive StructuresStemsLeavesReproductive Structures
n m−2g m−2g g−1
N086.9 b743.0 b428.1 b233.4 b88.5 a0.55 b0.33 a0.12 a
N120104.9 a882.8 a511.6 a278.1 a83.7 a0.58 a0.33 a0.09 b
N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N.
Table 6. Nitrogen concentration of forage, stems, leaves, and reproductive structures, as affected by the year and fertilization mean effects, at full flowering. For the year effect, values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16); for the fertilization effect, data are means of three years, two sowing rates, and four replicates (n = 24). For each effect, different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 6. Nitrogen concentration of forage, stems, leaves, and reproductive structures, as affected by the year and fertilization mean effects, at full flowering. For the year effect, values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16); for the fertilization effect, data are means of three years, two sowing rates, and four replicates (n = 24). For each effect, different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
EffectNitrogen Concentration
ForageStemsLeavesReproductive Structures
Year
I22.8 b12.6 a44.5 a45.0 a
III29.0 a12.9 a41.9 b40.9 b
Fertilization
N0n.r.12.3 a37.0 b49.2 b
N120n.r.13.1 a41.8 a52.1 a
N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N. n.r.: not reported (because affected by fertilization x sowing rate interaction (Figure 3)).
Table 7. Nitrogen and phosphorus accumulation by forage, stems, leaves, and reproductive structures, as affected by the fertilization mean effect, at full flowering. Values are means of two years, two sowing rates, and four replicates (n = 16). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 7. Nitrogen and phosphorus accumulation by forage, stems, leaves, and reproductive structures, as affected by the fertilization mean effect, at full flowering. Values are means of two years, two sowing rates, and four replicates (n = 16). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
FertilizationNitrogen AccumulationPhosphorus Accumulation
ForageStemsLeavesReproductive StructuresForageStemsLeavesReproductive Structures
g m−2
N017.9 b5.3 b8.6 b4.0 a1.9 b0.9 b0.6 b0.4 a
N12022.6 a6.7 a11.6 a4.3 a2.5 a1.2 a0.8 a0.5 a
N0: unfertilized crop; N120: crop fertilized with 120 kg ha−1 of N.
Table 8. Drybiomass of seeds, residues, and shoots and mean seed weight of field bean, as affected by the year mean effect, at maturity. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 8. Drybiomass of seeds, residues, and shoots and mean seed weight of field bean, as affected by the year mean effect, at maturity. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). Different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
YearDry BiomassMean Seed Weight
SeedsResiduesShoots
g m−2 mg
I346.6 b1240.1 b1586.7 b283.7 b
II415.0 a1618.5 a2033.5 a343.5 a
III188.7 c599.9 c788.6 c238.0 c
Table 9. Number of stems per unit area, residues biomass per stem, number of pods per stem, and percentage of fertile nodes effectively bearing pods, as affected by the year, and sowing rate mean effects, at maturity. For the year effect, values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16); for the sowing rate effect, data are means of three years, two fertilization treatments, and four replicates (n = 24). For each effect, different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 9. Number of stems per unit area, residues biomass per stem, number of pods per stem, and percentage of fertile nodes effectively bearing pods, as affected by the year, and sowing rate mean effects, at maturity. For the year effect, values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16); for the sowing rate effect, data are means of three years, two fertilization treatments, and four replicates (n = 24). For each effect, different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
EffectNumber of StemsResidues per StemNumber of PodsPodding Nodes
n m−2g stem−1n stem−1% of Fertile
Year
Year I106.0 a11.7 b4.2 a41.2 b
Year II99.2 a16.3 a4.8 a48.5 b
Year III104.7 a5.7 c4.0 a90.8 a
Sowing rate
S6085.7 b12.6 a4.8 a58.3 a
S100120.8 a9.9 b3.8 b48.8 b
S60: sowing rate 60 seeds m−2; S100: sowing rate 100 seeds m−2.
Table 10. Nitrogen and phosphorus concentration and accumulation of seeds, residues, and shoots of field bean, as affected by the year mean effect, at maturity. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). For each parameter, different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Table 10. Nitrogen and phosphorus concentration and accumulation of seeds, residues, and shoots of field bean, as affected by the year mean effect, at maturity. Values are means of two fertilization treatments, two sowing rates, and four replicates (n = 16). For each parameter, different letters within a column indicate statistical difference at p ≤ 0.05, Tukey test.
Nitrogen ConcentrationPhosphorus ConcentrationNitrogen AccumulationPhosphorus Accumulation
YearSeedsResiduesShootsSeedsResiduesShootsSeedsResiduesShootsSeedsResiduesShoots
mg g−1g N m−2g P m−2
I40.7 b15.4 b20.9 b5.9 a1.9 a2.8 a14.1 a19.1 a33.2 a2.0 a2.4 a4.4 a
III43.4 a20.2 a25.8 a4.1 b1.9 a2.4 a8.2 b12.1 b20.3 b0.8 b1.1 b1.9 b
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MDPI and ACS Style

Pampana, S.; Angeletti, F.G.S.; Mariotti, M.; Esnarriaga, D.N.; Arduini, I. Forage and Seed Production of Field Bean Respond Differently to Nitrogen Fertilization and Sowing Rate. Agronomy 2025, 15, 1660. https://doi.org/10.3390/agronomy15071660

AMA Style

Pampana S, Angeletti FGS, Mariotti M, Esnarriaga DN, Arduini I. Forage and Seed Production of Field Bean Respond Differently to Nitrogen Fertilization and Sowing Rate. Agronomy. 2025; 15(7):1660. https://doi.org/10.3390/agronomy15071660

Chicago/Turabian Style

Pampana, Silvia, Francesco G. S. Angeletti, Marco Mariotti, Dayana N. Esnarriaga, and Iduna Arduini. 2025. "Forage and Seed Production of Field Bean Respond Differently to Nitrogen Fertilization and Sowing Rate" Agronomy 15, no. 7: 1660. https://doi.org/10.3390/agronomy15071660

APA Style

Pampana, S., Angeletti, F. G. S., Mariotti, M., Esnarriaga, D. N., & Arduini, I. (2025). Forage and Seed Production of Field Bean Respond Differently to Nitrogen Fertilization and Sowing Rate. Agronomy, 15(7), 1660. https://doi.org/10.3390/agronomy15071660

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