Yield Performance of Spring Oats Varieties as a Response to Fertilization and Sowing Distance

: The main objective of this paper is to evaluate the yield potential of 25 different varieties of oat as a reaction to seeding distance and fertilization for improvement of crop technology and identification of the most adapted varieties. Based ANOVA test, the main influence on yield is due to climate, followed by the amount of fertilizers. The sowing distance reveals its influence when combined with the fertilization, this aspect pointing out the differences between studied varieties. The triple interactions gradually reduce the influence of the factors, their combination being very significant in the case year X sowing distance X variety. The spatial comparative analysis of the three experimental years presents an overlap in the median area of the PCA ordering of the 12.5 cm sowing distance, fertilized with N 50 P 50 with the 25 cm sowing distance fertilized with N 100 P 50 . There are differences between the oat varieties regarding the reaction to the nitrogen fertilization, highlighting especially the Mure ş ana variety where comparable yields are obtained on both levels of fertilization: 5.18 t ha − 1 (N 50 P 50 ) and 5.59 t ha − 1 (N 100 P 50 ).


Introduction
Oat plants are cultivated up to an altitude of 1100 m and can reach mountainous, relatively humid, and cool areas located in the countries and the southern areas of Europe, USA, and Canada. Oat was cultivated in 2019 over a global area of 9.42 million hectares, with greater surfaces in the Russian Federation (2.43 million hectares), Canada (1.17 million hectares), Poland (495,000 hectares), Spain (453,000 hectares), Brazil (448,000 hectares), USA (334,000 hectares), etc. [1]. In Romania, spring oats are cultivated on an area that exceeds 160,000 hectares every year and sometimes even exceed 200,000 hectares, as it was the case in 2007-2009. Oat is found mostly between 45-65° latitude N and 20-46° latitude S [2]. The autumn oats crop is sensitive during winter and the warm dry weather before the kernel formation. Because autumn oats crop is sensitive during winter conditions, spring oat is preferable. However, oat performs better than other cereals on clay (400-600). The maximum water usage is when the straw is elongated and during efflorescence-flowering. Soil requirements for oats are low because of its deep root system and the great power of roots to solubilize nutrients. It prefers chernozem and brown soils. It does not give a good yield on compact, non-aerated soils, and on sands from the dry area it suffers from lack of moisture. It succeeds better than wheat, rye, or barley on acid soils.
In some varieties, nitrogen fertilization caused a much greater increase in production compared to the number of seeded seeds m −1 , ranging between 0.36 and 1.48 t ha −1 [9][10][11][12]. Moreover, additional fertilization with nitrogen determines an increase in oat production similar to other small grain cereals [13][14][15].
The main research objective is to improve the technology for cultivating spring oats in the Transylvanian Plain, an area that is very favorable for this crop. This objective will be achieved by accumulating new knowledge aimed at providing a scientific and practice basis for using the best varieties in cultures and as this is correlated with the sowing distance and a rational fertilization it would lead to improved yields, taking into account the economic efficiency and the protection of the environment.

Materials and Methods
The production capacity of 25 varieties and lines of spring oats, of local and foreign origins, were studied (Table 1). The experiment was conducted on a chernozem argic soil [16] from ARDS Turda (46°34′57.5538″ N and 23°47′15.7158″ E), Cluj county, Romania. Based on their origin, the varieties were divided in 4 categories: 7 varieties and lines created at ARDS Turda (RoTd), 6 lines created at ARDS Lovrin (RoLo), 7 varieties from Western Europe (WEu) and 5 varieties from Central and Eastern Europe (CEEu). As presented in the literature, knowledge of genotype-environment interaction is very important for the application of appropriate technology [17][18][19][20]. All varieties belong to the oat collection from ARDS Turda, and they are used for research and plant breeding programs.
The experiment is a four-factor type [21], organized according to the method of subdivided plots, in 3 repetitions. The factors that were considered are: year with 3 graduations-2015, 2016, and 2017; sowing distance with 2 graduations-12.5 (D1) and 25.0 (D2) cm between rows, fertilization with 2 graduations-N100P50 (F1) and N50P50 (F20), respectively 25 spring oat varieties. The sowing was done every year with the Wintersteiger plot machine, around 15th of March; the sown plot had 9 m 2 and the harvested 7.5 m 2 . Fertilization was carried out in two phases, one in autumn with fertilizer 20:20:0, using a quantity of 250 kg ha −1 to provide 50 kg ha −1 nitrogen and phosphorus active substance (a.s.), and second in the spring with fertilizers based only on nitrogen for ensure 50 kg ha −1 nitrogen a.s.
Data analysis was conducted with R Studio [22]. Statistical analysis was elaborated based on the formulas from the "psych" [23] package. The ANOVA tests and the least significant difference (LSD) from the "agricolae" package [24,25] were used. The entire set of observation was transformed using the Euclidean method, the stats package available in R [26], before being analyzed with the cluster method from the "ape" package [27]. In order to completely explore the experimental data, the redundancy analysis (RDA) ordination from the "vegan" package [28] was applied, a method that allows spatial grouping.

Results
The vegetation period of spring oats is, in average, of 135 days and lasts from sowing of the crop in the field (usually sown in the first decade of March) until the harvest (end of July). Tables 2 and 3 show the characteristic of the months: March, April, May, June, and July from the point of view of temperatures and precipitations, and climate data recorded by the Turda weather station.
The year 2015 was characterized by the month of May being more droughty but preceded by the month of February that was balanced from the point of view of precipitations, a fact that led to the emergence of spring oats 10 days after sowing, followed by a lower vegetative development in the first phenophases, given also that the month of April that followed was also dry, with a minus of 12.5 mm compared to the multiannual average. The period of vegetation for spring oats in 2015 happened on a background of higherthan-normal temperatures from the month of March until the month of July, with the exception of April, and an excess of humidity in the month of June, when the phenophases of flowering and, partially, growth and filling grain took place. If we analyze the year 2015 in terms of favorability for spring oats we can say that it was "favorable", the productions being lowered by the drought in April (−12.5 mm of rainfall) and July (−24.5 mm of rainfall). The year 2016 was less favorable for the spring oats culture, although an excess of rain of 160.6 mm was recorded in the vegetation period, thus in the organized experiments the smallest productions in the three experimental years series were recorded. The abundant rains in the months of June and July have caused the plants to lodge, diminishing the production, but the Mureşana variety especially stood out, being less affected by this phenomenon. The year 2017 was the most favorable year for the spring oats, particularly due to the balanced spread of the precipitation during the vegetation period of the oats. The analysis of the data presented in Table 3, regarding the precipitation, corroborated with the 2017 yield, allows us to elaborate an important conclusion, namely that for the vegetation period of the spring oats (March-July), given the conditions from the Transylvanian plain, approximately 300 mm of rain are needed. An ideal distribution of rainfall for the spring oat culture would mean: 8% (24 mm) in March, 16% (48 mm) in April, 23% (69 mm) in May, 28% (84 mm) in June, and 25% (75 mm) in July. With regards to this distribution of rainfall during the spring oat's vegetation period, 2017 almost achieved this, with the exception of June that was excessively dry but followed a balanced month from this point of view.
The production of spring oats is subject to both the singular impact of experimental factors as well as that of their combined influence (Table 4). At the singular level, weather conditions of the crop year (Y) has the greatest influence, followed by fertilization and sowing distance. All the experimental factors that were studied have a very significant influence over production and the value of the Fisher test for the variety factor (V) shows that there are genetic differences in between them with regards to the production capacity. The two factor interactions point out the very significant impact of the crop year combine with sowing distance, fertilization X variety. The sowing distance reveals its influence when combined with the fertilization and the variety, this aspect pointing out the differences between studied varieties. The triple interactions gradually reduce the influence of the factors, their combination being very significant in the case year X sowing distance X variety. The year and the fertilization have a significant impact in combination with the sowing distance or the variety. This aspect supports the idea of the necessity of optimizing the technologic resources separately for each variety. The origin of the oat spring varieties that were tested is visible in reducing the significance of the ternary combinations (DxFxV) and quaternary (YxDxFxV), in both cases test F was insignificant.

The Influence of the Year on the Production Capacity of Spring Oats
The production capacity of spring oats is closely connected with the origin of the varieties (Figure 1), this leading to significant differences between the tested genotypes. The best performing variety is Mureșana, created at ARDS Turda (approved in 2012) and adapted to the climate conditions of this area. Compared to the production potential of this variety, only the lines T. 38-81 M and LV. 4363-86 have registered insignificant differences. This group of three genotypes significantly surpass the majority of the other varieties that were tested. From the foreign varieties only Rumak (Poland) is present in the top of the fourth place, but with small differences when compared to the other varieties. Two local varieties (Mureș and T. 44-81 M) have productions similar to Skakum (Russia) and Fucs (Latvia) proving that they have similar climate needs. A group of eight varieties: V1, V5, V9, V15, V17, V18, V19, V25, on the graph (c d e f g) have close productions in the experimental conditions, which suggests an identical reaction to the environmental conditions. Two varieties from Germany (Romulus and Gramena), one from France (Integrale) and the variety from Belarus (Bug) record productions close to 5 t ha −1 and surpass insignificantly LV. 4362-86, a variety of Romanian origin. Variant 3 Mureşana is on the first place, clearly detaching from the others.
For the year 2015 ( Figure 2a), the variation explained by principal component analysis (PCA) is 95.38%, with a greater importance of the first principal component (PC) (88.44%). At a sowing distance of 25 cm, one starts seeing the differences in performance between the studied varieties with regards to the production capacity. The greatest dispersions are recorded at the variants fertilized with N100P50 (F1), that strongly separates the varieties along PC 2 (variance = 6.95%). In the case of fertilization with equal doses of nitrogen and phosphorous (F2), the dispersion of the production values is homogenous, grouping the data in different quadrants of the PCA graph. The variations in production that were recorded in 2015 group the varieties in five well-defined clusters (Figure 2b), independent of their origin. The production average in cluster 1 is 5.31 t ha −1 , with similar margins, the Mureș variety (5.38 t ha −1 ), respectively Bug with 5.35 t ha −1 . The second and third clusters have a reduced number of variants, but show great differences when it comes to the average production. The heterogeneity of cluster two sets the average production at a level of 5.14 t ha −1 , with identical margins as production of 5.12 t ha −1 . In cluster 3 there are only lines of oats created at Lovrin and varieties from Western Europe. The average of this cluster is the highest for 2015, respectively 5.88 t ha −1 . Cluster 4 brings together six genotypes, with a production average of 5.60 t ha −1 , but with two variation directions in the production of marginal varieties being from CEE Rumak (5.55 t ha −1 ) and Fucs (5.65 t ha −1 ). In the last cluster an increase of the productions can be observed, from 5.37 t ha −1 (Someșan) up to 5.61 t ha −1 (Cory).  Table 1. For the second experimental year (2016), the placement of the variants in the PCA plan has an impact on explaining the major variance on PC 1 (96.42%) and of only 2.06% on PC 2 ( Figure 2c). A very large dispersion of the variants due to the fertilizations applied at the distance of 12.5 cm in between rows can be noticed. The best combination of technological variables is at a distance of 25 cm between rows and a moderate fertilization (N50P50). The fertilization N100P50 overlapped over a distance of 12.5 cm has a standard deviation that is almost circular and a median position on the graphic, an aspect indicating the variation potential of the varieties production due to this combination of technological factors. The harvest obtained in this experimental year groups the oat genotypes in six clusters, with large differences between the registered average values (Figure 2d). Clusters 1, 2, and 3 have average productions below 4 t ha −1 , with a minimum of 3.10 t ha −1 for cluster 3. This group include varieties from WEu, CEEu, respectively an autochthonous variety. Cluster 4 contains 2 varieties from WEu and CEEu, respectively one from the Romanian research stations. Line LV. 4324-86 records productions of 4.18 t ha −1 , while the performer of the Solidor group attains 4.42 t ha −1 . Cluster 5 surpasses the average value of 4.5 t ha −1 , while the final cluster has the highest production, 5.28 t ha −1 including two Romanian varieties: T. 90-81 with 5.53 t ha −1 , respectively LV. 8644-82 with 5.63 t ha −1 .
The evaluation of the production in the third experimental year (2017) indicates a clear separation between the technological factors that were studied: fertilization and sowing distance (Figure 2e). This detail is underlined also by a drop in the variation explained by PC 1 (69.28%), concomitantly with increasing the value of PC 2 (19.97%). The location of the centroid of each data group is in diagonally opposite quadrants, with an overlap of the N50P50 fertilization center on the edge of the N100P50 fertilization area. The dispersion of the data in the ordering plane is similar at the data grouped by the same sowing distance, for each variety there are two parallel vectors. The cluster analysis presents a strong separation of the varieties in seven unequal clusters (Figure 2f). Cluster 1 has an average production potential of 6.31 t ha −1 and is composed of three varieties created at ARDS Turda and two west-European varieties. The cluster's marginal production potential is in the Avalanche (6.35 t ha −1 ) and Integrale (6.42 t ha −1 ) varieties, both with great differences in between repetitions. The second cluster had the highest average production (6.64 t ha −1 ) and it includes two varieties created at ARDS Lovrin and one each from Turda, respectively, CEEu. The maximum production value in this cluster is encountered at the Lv. 7878-82 variety (6.77 t ha −1 ). The two West-European varieties and the variety LV. 4324-86 from cluster 3 have an average production of 5.75 t ha −1 , surpassed by the varieties from clusters 4 and 5 with 5.93 t ha −1 , respectively, 5.99 t ha −1 . These three clusters comprise autochthonous varieties (ARDS Turda and ARDS Lovin), four varieties from WEu and the Rumak variety (6.05 t ha −1 ) from CEEu. Clusters 6 and 7 are made up of two varieties, both with an average production potential of over 6 t ha −1 .
The spatial comparative analysis of the three experimental years (Figure 2g) presents an overlap in the median area of the PCA ordering of the 12.5 cm sowing distance, fertilized with N50P50 (AF2) with the 25 cm sowing distance fertilized with N100P50 (BF1). Both groups of values present an orientation of the dispersion on the diagonal axis (--++) of the ordination. PCA explain a total variance of 82.05% (PC 1 64.81%, respectively PC 2 17.24%), an aspect indicating the graphical correction due to axis 2. The N50P50 fertilization and the sowing at a distance of 12.5 cm in between rows positions the center of the AF1 group in the upper left quadrant of the ordination (-+), opposed to BF2. The clustering shows an interaction annual normalization of the productions, with a strong reduction in the production potential and a reorganization of the varieties in groups (Figure 2h). Clusters 2 and 4 have an average production potential below 5 t ha −1 and include in majority Romanian varieties. One can observe at the level of cluster 1 a great gap between the autochthonous varieties and those from WEu and CEEu, all with productions of over 5 t ha −1 , while the Romulus variety (WEu) registers a production of just 4.92 t ha −1 . The fifth cluster records average productions of 5.35 t ha −1 , this group includes only the line LV. 4363-86, with an average production of 5.34 t ha −1 . The varieties with the highest productivity are included in cluster 3, with an average of 5.61 t ha −1 . The edges of this cluster have productions of 5.51 t ha −1 (LV. 4325-86), respectively 6.02 t ha −1 (LV. 864-82). The central area of cluster 6 is occupied by the Bug variety from Belarus, with an average production of 5.38 t ha −1 , also characterized by a strong fluctuation in the annual production.

The Influence of the Sowing Distance and of the Fertilization on the Production Performance of the Spring Oat
The analysis of the multiannual response of the spring oat genotypes to each experimental factor indicates significant differences specific for the fertilization or the sowing distance (Table 5). At a distance of 12.5 cm between rows, two autochthonous varieties have recorded the highest productions: Mureșana (RoTd, 6.30 t ha −1 ), respectively, LV. 4363-86 (RoLo, 6.15 t ha −1 ), with considerable difference compared to the other varieties. At the opposite end, the varieties Gramena (WEu, 5.10 t ha −1 ), respectively LV. 4363-86 (RoLo, 5.02 t ha −1 ), remain at a production of just 5 t ha −1 . Favorable climate conditions for the oat do not determine an increase in production by increasing the sowing distance in between rows to 25 cm. The classification of the varieties indicates once more the genotypes Mureșana and LV. 4363-86, as having the greatest production potential. Significant difference for the varieties considered in the study have been observes on the fertilization level N50P50. The two autochthonous varieties (Mureșana and LV. 4363-86) have productions of over 6 t ha −1 , with significant differences compared to the WEu varieties (Integrale and Gramena), respectively LV. 4362-86, and between the Bug (5.20 t ha −1 ) and the T.44-81 M (5.89 t ha −1 ) variety the difference is of 0.69 t ha −1 . The increase of the sowing distance and the increase of the nitrogen fertilizer dosage (N100P50) means that a group of nine varieties stands out, recording values of over 5 t ha −1 , with a maximum of 5.86 t ha −1 for the Mureșana variety and a minimum of 5.03 t ha −1 for the LV. 4325-86 variety, the difference in this group reaching 0.83 t ha −1 . In the group comprising the other varieties the production difference is just 0.35 t ha −1 , with a maximum for the Jumbo variety (4.95 t ha −1 ), respectively a minimum for LV. 4362-86 (4.60 t ha −1 ).   Table 1.

The Influence of the Source on the Production Stability of the Varieties Given Different Sowing and Fertilization Conditions
The realization of the bi-factorial experimental design for testing the spring oat genotypes allowed the evaluation of the response of each to the technological factors, fertilization and distance between rows (Figure 3a-d). In the sowing condition of 12.5 cm in between rows and a fertilization with N50P50 (Figure 3a The increase of the fertilizer dosage at the same sowing distance in between rows (AF2- Figure 3b), leads to a strong dispersion of the tested genotypes. The variation explained by PC 1 is 66.71%, completed by PC 2 with 13.58%, which normalizes the dimension of the ordination quadrants. The varieties LV. 4362-86, Gramena, Integrale, and Fucs, generally give productions below 6 t ha −1 , with strong drops until 3 t ha −1 in the second experimental year (2016). In the upper ordination quadrant, the varieties T. 44-81 M, LV. 4324-86 and Romulus present a greater stability of the productions, no matter the year, not dropping below 4 t ha −1 but also not reaching production over 6 t ha −1 . The varieties Mureșana and LV. 4363-86 record the highest productions and do not drop in any year below 5 t ha −1 , similar to the LV. 4325-86 variety, but where one can notice a drop in production to 4 t ha −1 given the conditions of the second experimental year.
The PCA evaluation for the 25 cm distance in between rows and the fertilization with N50P50 (Figure 3c), indicates a positioning of the centroids from the origin groups in the median area of the ordination. The variance explained by PC 1 is 74.52%, with an increase weight for PC 2 (17.75%). The varieties Mureșana and LV. 4363-86 are located in the same quadrant, because of their increased production potential. The varieties LV. 8644-82 and Romulus show the lowest production fluctuations in all the years that the experiment was conducted, their potential production being 5 t ha −1 . The difference in the production potential between the Gramena and Integrale varieties is 0.5 t ha −1 , in favor of Gramena for the first year of the experiment (2015), respectively in favor of Integrale in the third (2017). It is only in the second year of the experiment, 2016, a year that was less favorable for the spring oats culture, that both varieties had similar yields.
A clear separation between the Mureșana and Gramena as compared to the other varieties is easy to observe in the PCA ordination plan given a distance of 25 cm in between rows and a fertilization with N100P50 (Figure 3d). Both varieties register productions over 5.5 t ha −1 in the first year of the experiment, but the Mureșana variety takes the lead with 2 t ha −1 in the second year, respectively 1 t ha −1 in the third year, when compared to Gramena. The varieties LV. 4325-86 and Integrale suffer from a sharp reduction in production in the second experimental year, both recording productions below 3 t ha −1 . Two varieties of oat, LV. 4363-86 and Rumak, maintain their production potential in the limits of 4-5 t ha −1 in the first two experimental years and register over 6 t ha −1 in the third. LV. 4362-86 has a special position in the right upper quadrant, because of the production fluctuations of 1.5 t ha −1 in the three experimental years.   Table 1.

Discussion
This paper presents the results of a complex study conducted in 2015, 2016, and 2017 on a batch of 25 spring oat varieties and lines, all from the Avena sativa L. species, all with yellow hull grains.
A clear observation that can be exposed without statistical analyses could be observed by comparing of the productions obtained in the three experimental years in Romania [25,29,30], with those registered in the conditions from Turda in the same period. We can state that there exists a positive relation between yields and sum of precipitations from the month of June and July that coincide with the growth and the filling of the grain phenophases. This observation might be contradicted by the period 1st of June-31 of July 2016 when an excess of rain with a deviation of +91.8 mm, as compared to the normal (156.3 mm) was observed, and the harvests were the lowest obtained given the conditions from Turda, due to the fact that the spread was not equal and there was no rain in the third decade of June and the first two days of July. In fact, the last rainfalls from June 2016 had a torrential character (28.8 mm) and as it is well-known this rain infiltrates slower, evaporating on the surface of the soil. In a study concerning the year 2005 [29], showed that the partitioning of the variance components of the environment factors is predictable for locations and unpredictable for the year and that they were an important source of variation.
The yields that were obtained for the spring oat genotypes, in the conditions of the Transylvanian Plain (Romania), are similar or even higher in the years with favorable climatic conditions. The average production in the 3 years of the experiment for the spring oat varieties was 5.  [32] showed that the sowing date had a great effect on hay yield and quality potential of oat genotypes.
Irfan et al. [33] determined the production of dry substance for autumn oat for fodder being greater at a distance of 12 cm; they are 18.4 t ha −1 in the season 2011-2012 and 23.4 t ha −1 in the season 2012/2013. The production of dry substance was with 20%, respectively 35% lower given a sowing distance of 24, respectively, 46 cm. Determining the forage potential for cultivation requires not only the dry matter yield, but also the nutritional value for animals [8,34]. Henson et al. [35] conducted a study following the influence of the seed norm on the production of oat grains, using for sowing 0.75, 1 and 1.25 million seeds acre −1 , corresponding to 1.85, 2.47, and 3.09 mill. grains ha −1 ; the highest yield was obtained in the variant with the largest norm, of 3.31 t ha −1 . Gao et al. [12] revealed that increasing the planting density is an important factor for increasing the crop yield for oats. The increase in the seeded acreage of oats, yield potential with newer varieties and practices, causes an increase in demand on markets for these oats.
The consumption of nutrients for oat, per 100 kg of grains + returning straw (about 150 kg), is on average 2.72 kg N; 1.34 kg P2O5; 2.74 kg K2O; and 0.65 kg CaO. The absorption rhythm of these elements increases until the flowering. Oat reacts well to organic and chemical fertilizers on all the types of soil [36][37][38]. As noticed, the consumption of nitrogen in oats is twice as high as the consumption of phosphorous, thus researchers have studied more the influence that this element has on the production. Maral et al. [39] has studied the response that 6 varieties of autumn oats have on three graduations of the nitrogen doze (N0, N10, and N20), noting that the highest yield was obtained with the highest nitrogen concentration. In the study conducted at ARDS Turda, it was shown that an increase in the dose of nitrogen by 50 kg ha −1 a.s. on the level of fertilization N100P50 had led to an increase in the production of spring oats by 514 kg ha −1 . The study conducted by [40] led to results showing that an increase in the dose of nitrogen from 60 to 120 kg ha −1 a.s. causes an increase in the production of dry matter for oats with 70% in 2011-2012 and 53% in 2012-2013. Moreover, the data on the green fodder yield (t ha −1 ) has showed that the green fodder yield varied significantly among the varieties [41]. Knowing the particularities of the reactions of spring oat varieties, Romanian and foreign, to the environmental conditions and to the technological inputs is important for their correct zoning in the territory but also for mentioning the place that they need to occupy in the structure of the varieties for each area [42]. The increase in the yield per surface unit can be achieved in two ways: by improving agronomic practices and by cultivating improved varieties with a superior genetic production potential, with an improved resistance to diseases and an increased tolerance to the poor environmental conditions. The introduction of the new breeds has led in many cases to reducing the vulnerability of the crops, by increasing biological diversity but also to improving the quality of the raw material for the manufacturing industry. The development of high yielding varieties of oats therefore, has assumed greater importance for the human consumption and the animal health and also Kashmir valley is ideally suitable for oats cultivation because of its temperate climate [43].
The results confirmed that there are genetic differences between varieties in terms of production capacity. It seems that newer cultivars are more responsive to environmental changes than their predecessors and this can also be explained with the help of the Mureşana variety (registered in 2012 in Romania), which is originally a more adapted selection from Mureş variety (realized in 1993). However, the yield potential seems positively associated with responsiveness to the environmental enhancement so that future increases for avoidance of losses in the yield stability would remain dependent upon management improvements like a better choice of the cultivated varieties, the rational use of nitrogen for fertilization, a more suitable sowing distance between rows. However, the decrease in production may also be due to climatic conditions, such as heavy rains in the last part of the oat vegetation period, which can cause the plants to lodging. Redaelli et al. [44] evaluate the genetic progress of oats in Italy over the past 40 years using 14 cultivars from three different group. Genetic gain was estimated to 3.6 g m −2 y −1 . They found also that the yield increase is negatively correlated with the plant height and positively correlated with the test weight and the seed weight. It can be observed that most cereals have exhibited a trend for relatively low yield increases during much of the first half of the 20th century followed by a rapid rate of yield gains, due to both genetic and management improvement, during the second half.
In South Korea, on a mixture of sand and mud soil, the increase in sowing density led to a decrease in plant size and panicle length, due to a decrease in nutrition/plant space. Regarding the number of siblings/area unit, the differences were not significant between the different sowing densities. The effect of progressive nitrogen fertilization on plant height and panicle length was directly proportional to the applied dose, the maximum being 90 kg ha −1 N s.a. [43]. The size of the grains and their number/spike (the number of grains per spike area) has decreased when sowing density was increased [14,45]. Nitrogen fertilization positively influenced the hectoliter mass and mass of 1000 grains (liter and 1000-kernel weight) in oats. The production of kernels has significantly increased along with density. A negative effect of the increased nitrogen fertilizer dose is the increase in the unevenness in the ripe period, meaning a higher percentage in the insufficiently matured kernels. The seeding rate and nitrogen fertilization did not affect the emergence date and degree, and the lodging degree of oats [14,46].
In Romania, oats are the most cultivated spring cereal, but there are few studies on the chemical composition of the grain, although today we see a reversal in its use in human nutrition, especially in advanced countries, where it is used to produce functional foods, so-called nutraceuticals. Moreover, in Brazil oats remained an optional food item that appealed to a small section of the population until more recently, when consumption started to increase [46]. However, for Romania, spring oats are a very efficient crop, because they have a fairly easy cultivation technology and in a short period of up to 135 days (it is usually sown around March 15 and harvested at the latest at the end of July), important productions can be obtained.
Nitrogen fertilization had a greater impact on the oat composition than on milling characteristics and in many cases the effect of nitrogen was dependent on the location. Other results obtained during this research project has showed that the yield in flour is correlated with the hectoliter mass, the tested genotypes having on average 45% yield in flour. At sites where the residual nitrogen was low (less than 36 kg ha −1 ), the fertilization resulted in increased levels of proteins and B-glucans (by as much as 4.4% and 1%, respectively), while oil decreased slightly (less than 1%) [47]. However, determining the forage potential for cultivars requires not only dry matter yield, but also the nutritional value for animals.
In the course of the project, "Avena genetic resources for quality in human consumption" co-funded by the European Commission (AGRI GENRES 061, Council regulation 870/2004), 658 European oat genotypes grown in different environments in 2008 or 2009, it was noticed that "indicated that the genotype had a major effect on the b-glucan content and suggested that the most favorable conditions for its accumulation were found both in Romania, which also presented the widest variation, and in Sweden in 2009, with climatic conditions regarded as normal for these environments and characterized by mild mean temperature and sufficient rainfall amounts during the period of the vegetative growth" [44].

Conclusions
For 2015, we point out especially the behavior of the Mureşana variety, where similar productions were obtained on both nitrogen fertilization levels, this is mostly due to their resistance to lodging due to their low height, as compared to the other genotypes that were tested. In 2016 the diminishing yields for spring oats was due to abundant rainfall in June and July, causing the plants to lodge, the Mureşana variety, that has a lower height, was less affected as compared to the other varieties. The year 2017 had an almost ideal distribution of precipitation during the vegetation period of spring oats in Turda, which is why the largest productions in the series of the three experimental years were obtained.
The resulting productions obtained at Turda show that three different years for the spring oats cultivation were included, the year 2017 was very favorable, the year 2015 was favorable and the year 2016 was less favorable, a fact that allowed the singling out of three genotypes where yields higher that the average yield for the experimental years were obtained and that showed yield stability, respectively: Mureşana, T. 38-81 M and LV.4363-86. The best distance between rows for spring oats is 12.5 cm, a distance where the average production was 5.46 t ha −1 , with 0.47 t ha −1 greater than the one obtained at a 25 cm sowing distance, for which a quantity of seed in between 150 and 180 kg per ha is used, based on the mass of 1000 grains. Given less favorable climatic conditions for the cultivation of spring oats, the increase in production due to the sowing distance is greater for some varieties, Mureşana is included, as compared to the increases determined by the nitrogen dose. There are differences between the oat varieties regarding the reaction to the nitrogen fertilization, highlighting especially the Mureşana variety where comparable yields are obtained on both levels of fertilization.