THE INFLUENCE OF FOLIAR FERTILIZATION ON THE YIELD AND QUALITY OF SOYBEAN

. This experiment investigated the effect of foliar fertilization on yield components, yield and protein content of 75 soybean genotypes from four maturity groups. The experiment took place within the Soybean Breeding Laboratory at Research and Development Station for Agriculture Turda (RDSA Turda) over the course of two years (2020, 2021). The experimental design was a complete randomized block with three replications in which three variants of fertilization were analyzed, and the application of foliar fertilizers was carried out in different stages of soybean vegetation. In general, if we refer to the yield, it is observed that most of the genotypes that reacted favorably to the application of foliar fertilization are with the Ff 1 variant, on the other hand, for the protein content, it seems that the Ff 2 foliar fertilization variant causes an increase in protein in most of the genotypes that they had a favorable reaction to foliar fertilization. Regarding the component elements of yield, the application of foliar fertilization variants does not greatly contribute to increasing their number, being directly related to the genotype but also the interaction between environment x genotype.


INTRODUCTION
Soybean, being a valuable protein plant, is the main supplier of vegetable protein and has been cultivated on the European continent since the 18th century (Popovic et el., 2012).Also, it is cultivated in different climates such as tropical, subtropical and temperate (Malik et al., 2007).The soybean crop provides a crucial source of protein and edible oil (Leamy et al., 2017).Taking into account the genotype and environmental conditions, soybean contains on average 38% protein, 19% oil and 26% carbohydrates (Popovic et el., 2012).
Soybean (Glycine max L. Merr.) is a food that presents a high variety of nutritional content, therefore, products obtained from soybean are recommended for human consumption (Kurnianto et al., 2020).As well a contribution in alleviation some chronic diseases, soybean grains, due to their protein, oil and mineral content, are beneficial in human and animal nutrition (Kahraman, 2017).
According to Di Mauro et al. (2023) considering the genetic and agronomic advances worldwide, soybean yield will continue to grow over time.Patil et al. (2017) stated that in fact, protein is a key factor that determines the nutritional and economic value of soybeans.
Genetic factors, climatic conditions as well as agro technical measures affect the yield and quality of soybeans (Szostak et al., 2020).Climate changes (irregular precipitation, prolonged heat, drought, large temperature fluctuations, etc.) cause significant reductions in yield (Lesk et al., 2016).Randelovic (2009) mentioned that the absorption of mineral nutrients from the soil and the degree of their use by soybean plants, depends on the climatic conditions during the vegetative growth phase.
Soybeans help to improve soil fertility through symbiotic nitrogen fixation (Sharifi et al., 2018), being less dependent on chemical nitrogen fertilizers according to Pratap et al. (2011), thus it helps to improve the soil structure and is recommended in establishing crop rotations for a sustainable agriculture (Hooker et al., 2023).
Potassium, a macro element vital in plants, has physiological and metabolic functions that can reduce stress conditions caused by biotic and abiotic factors (Cotrim et al., 2023).
Boron is one of the important nutrients for plant development, having multiple roles such as: cell fission, pollination, fruit formation, translocation, sugar and core, synthesis amino acids, and to control metabolism carbohydrate (Timotiwu et al., 2018).
According to Nunes et al. (2023), the deficiency of micronutrients in the soil can be observed globally, the symptoms appearing on the leaves can be different depending on the deficient element, and also the annual loss of micronutrients in the soil can be between 0.01-4.9kg ha -1 depending on the culture.Although most crops have low requirements regarding micronutrients, according to Nunes et al. (2023), most soils cannot provide the quantities needed for crops, being fertilization necessary.Timotiwu et al. (2018) specifies that foliar fertilization is a way to increase the quality of the grains because it brings an additional supply of nutrients that the plants need in the critical phases of development.The same author mentions that foliar fertilization has a faster effect compared to that applied to the soil because nutrients are absorbed directly into the plant with the help of vegetative organs.
An important point of view affirmed by Nunes et al. (2023) is that, application of micronutrients does not have a direct influence on the increase in yield, but it contributes to the reduction of biotic and abiotic stresses of plants.

MATERIAL AND METHODS
The experiment took place within the Soybean Breeding Laboratory at Research and Development Station for Agriculture Turda (RDSA Turda) over the course of two years (2020, 2021).In this experiment, a number of 75 soybean genotypes from four maturity groups were analyzed.Thus, in order to draw clear conclusions regarding the effect of foliar fertilization, we analyzed 15 genotypes from the maturity groups; very early (000), semi-early (0), semi-late (I) and 30 from the early (00) maturity group.
The experimental design was a complete randomized block with three replications, and in both experimental years, the genotypes were sown in two rows, at a distance between rows of 50 cm and a number of 55 germinating seeds m -1 , the harvestable plot being ten square meter.The soil had a humus content of 3.5%, mobile phosphorus 4.5 mg P2O5/100 g soil (AL), mobile potassium 30 mg K2O/100g soil (AL) and the soil reaction is characterized neutral (the soil type is faeozem).
The data on temperatures and rainfall recorded during the experiment period (2020, 2021) were obtained from the RDSA Turda meteorological station.During the experiment, the thermal regime of the spring months recorded negative deviations compared to the multi-year average, with the exception of April of 2020, when positive deviations were recorded (Figure 1).The spring of 2021 was characterized by a cold April month followed by a normal May month.In all the summer months, there were positive deviations compared to the multi-year average, variations that were between 0.4°C and 3°C.Also, in the autumn months, the monthly thermal regime registers positive deviations in most years.In both experimental years, the spring months were characterized by poor rainfall, with the exception of 2021, when in May there was a positive deviation from the multi-year average of 12 mm (Figure 2).With the exception of August, the summers of the two years differ significantly, thus June and July of 2020 are rainy or even excessively rainy, while the same lines of 2021 are very droughty or excessively rainy.Also, the autumn months of the two years differed quite a lot, so that in 2020 the excess rainfall regime made harvesting quite difficult.In this sense, due to the fact that the climatic conditions are more and more different from year to year and have a high influence on the yield and quality of the harvest, it is necessary to pay more attention to the cultivation technology, which involves an important link, namely fertilization.
According to Fehr and Caviness, (1977), the soybean vegetation period is divided into two stages, the vegetative (V) growth stage and the reproductive (R) development stage.The application of the foliar fertilization variants was carried out respecting this noting scale and producer recommendation (Figure 3).

RESULTS AND DISCUSSIONS
Thus in this experiment, among the components element of yield where the application of foliar fertilization variants had a positive effect with statistically ensured values are the number of grains/plant and the weight of 1000 grains.
Although in this case we analyzed the effect of fertilization on the genotypes within each maturity group on average, it seems that in the genotypes from the semi-early maturity group the Ff1 fertilization variant determined a distinctly significant increase in the number of grains/plant (Figure 4).In general, a reduction in the number of grains/plant can be observed in the analyzed maturity groups, although the values are not statistically insured except in the case of very early and semi-late maturity groups when applying the Ff2 fertilization variant.According to Silva et al. (2015), the most important components of yields are the number of pods/plant, the number of grains/plant and the mass of 1000 grains that directly influence yield and are influenced not only by genotype but also by climatic conditions.
In the case of the mass of 1000 grains, only for the very early maturity group, the application of the Ff1 fertilization variant determined a distinctly significant increase of this character (Figure 5).There is no influence on the mass of 1000 grains in the genotypes from the semi-late maturity group, but in the early and semi-early maturity groups, a decrease in the weight of the grains is observed, ensured and statistically when applying the foliar fertilization variants compared to the control variant (fertilization mineral).As stated by Silva et al. (2015) the number of grains/plant is closely related to the number of pods/plant being a genetic characteristic influenced by the environment, and the mass of 1000 grains is determined genetically and is affected especially by the lack of rainfall in the phase of filling the grains.In order to have broader view of the yield, but especially of the genotypes that reacted favorably to the application of foliar fertilization variants, we analyzed the genotypes within each maturity group, being represented only those that reacted positively with statistically ensured values.Thus, within the very early and early maturity groups, most genotypes reacted favorably to the application of the Ff1 fertilization variant (Figure 6, 7).However, is remarkable one genotype from each maturity groups: Lissabon (000) and Christine (00) reacted favorably to both variants of foliar fertilization.In the case of genotypes from the semi-early and semi-late maturity groups, a smaller number of genotypes reacted positively to foliar fertilization (Figure 8, 9).However, the most of them reacted positively to both variants of foliar fertilization, but there are also genotypes that reacted to one of the two variants.Di Mauro et al. (2023) highlighted that fertilization practices options modify soybean yield and seed quality, also foliar fertilization efficiency depended on the region climatic conditions where soybean was cultivated.Since the protein content is of high interest not only for animal feed but especially in the food industry for supplementing the world's need for protein, we followed the effect of foliar fertilization on this important qualitative index.Thus, we wanted to identify the genotypes within each maturity group that reacted favorably by increasing the protein content to the application of foliar fertilizers.
Both for the genotypes from the very early maturity group and for the early ones, only the application of the Ff2 fertilization variant determined an increase in the protein content (Figure 10,11).Within these maturity groups, among the genotypes that reacted positively to foliar fertilization, genotypes with a protein content of more than 40% can be identified (Fortuna, Sigalia, ES Mentor, Proteix, Amphor), however, there are genotypes in which the application of Ff2 fertilization led to an increase of more than 40% at the protein content (CH 22/174, ES Senator, Yakari, Atacama, Christine, Josefine).For the genotypes from the later maturity groups (0, I), there are also genotypes that reacted favorably to the application of both foliar fertilization variants, such as: Aires, Daciana, Columna and Ika (Figure 12, 13).However, there are also genotypes that reacted positively to one of the two foliar fertilization variants.As it is known that the yield is negatively correlated with the quality and the genotypes with a longer vegetation period have higher yields compared to the early ones, within these groups of maturity there is only one genotype (Ana) with a percentage of over 41% protein.Also, according to Hooker et al. (2023) protein and oil content are quantitatively inherited complex traits, influenced by genotype and environment but also by the interaction between them.
We can state that for a low number of these genotypes, the application of foliar fertilization determined an increase in the protein content of over or 1%.

CONCLUSIONS
Food demand is increasing due to population growth, requiring the creation of more productive and qualitative genotypes that can ensure food needs worldwide.Besides these, after to many researches, the implementation of new technological measures designed to ensure a good development of plants are also related to the fertilization of crops.Ensuring the specific nutritional requirements for each crop also gives plants good resistance to biotic and abiotic stress factors.
Depending on the genotype, a technological measure to increase yield and quality is fertilization.The application phase of foliar products seems to have an influence in this sense on the reaction of the genotype.The identification of the genotypes that reacted favorably to the application of foliar fertilization (supplementary) can also contribute to the choice of the genotype according to the maturity group if yield or quality is being followed.
It seems that the genotype has the greatest influence on yield and quality, however environmental conditions and fertilization can considerably influence the expression of these quantitative characters.Regarding the component elements of yield, the application of foliar fertilization variants does not greatly contribute to increasing their number, being directly related to the genotype but also the interaction between environment x genotype.

Figure 3 .
Figure 3. Application model of fertilization variants Data interpretation and analysis was carried out with the help of the Anova PoliFact Soft program and the Excel function of the Microsoft Office program.Analysis of quality parameters was performed at RDSA Turda with NIR Tango spectrophotometer (Bruker Optik Gmbh, Ettingen, Germany).

Figure 10 .
Figure 10.Interaction between fertilization and genotype Figure 11.Interaction between fertilization and genotype (FxG) regarding protein content on the very early (FxG) regarding protein content on the very early maturity group (Turda 2020, 2021) maturity group (Turda 2020, 2021)