The impact of foliar feeding on the yield components of three winter rape morphotypes (Brassica napus L.)

The aim of the study was to determine the impact of foliar fertilizers containing amino acids, sulphur, boron on the number of productive branches, the number of pods per plant, the number of seeds in pods and the length of pods of three winter rape (Brassica napus) varieties (Monolit, PX115, PT248). The research was carried out in 2016-2017, 2017-2018, 2018-2019 at the Zawady Agricultural Experimental Station (52o03’N and 22o33’E) belonging to the University of Natural Sciences and Humanities in Siedlce, Poland. The field experiment was set up in a splitplot layout in triplicate. The area of one plot for harvest was 21 m2. The examined factors were I morphotipe of winter rape: population variety (Monolit), hybrid restored with a semi-dwarf growth type (PX115), hybrid restored with a traditional growth type (PT248). II types of foliar feeding: 1. treatment without biostimulator and foliar feeding, 2. Bioregulator Aminoplant, 3. Foliar fertilizer Siarkomag with foliar fertilizer Bormax, 4. Foliar fertilizer Siarkomag with foliar fertilizer Bormax and Aminoplant. Variable climatic conditions in the years of the experiment affected the studied components of seed yield of three L. morphotypes. In the year 2016-2017 of research, the plants produced the most productive branches, had the longest pods filled with the largest number of seeds. Foliar nutrition with a biostimulator containing amino acids did not significantly affect the increase of the number of productive branches, pods per plant and pod length compared to the variant on which no foliar fertilization was applied. Foliar fertilization with S and B in combination with biostimulators was the most effective in increasing the components of seed yield, while the number of productive branches and length of pods under the influence of foliar fertilizers was the same regardless of the application of the biostimulator. The long-stem variety had longer pods that were filled with more seeds than the others.


Introduction
Fertilization is designed to provide nutrients in the right doses and proportions, the right form and time to create optimal conditions for plant growth and development (Barczak and Majcherczak 2008).
Among environmental stresses, the abiotic stress caused by nutrient deficiency is one of the most severe stresses limiting the plant growth and development, as well as crop yield (Bray et  Foliar nutrition is an effective way to supply macro and microelements, especially in conditions that are not favourable for the proper supply of plants with nutrients through the root system. Foliar fertilization of plants is part of the agricultural technology of many arable crops. Foliar feeding results in faster delivery of deficient nutrients (macro and microelements), high efficiency of small amounts of substances in comparison with soil fertilization, their even distribution, as well as reduction of environmental pollution and avoidance of chemical and biological sorption (Tobiasz-Salach et al. 2018). Foliar fertilization with quickly available forms of nutrients improves the condition of plants, and thus increases their yields and their quality (Wierzbowska et al. 2015).
In agrotechnics of winter rapeseed, foliar nutrition is considered as a basic treatment providing micronutrients to plants, and partially supplementing them with macronutrients. Beneficial 2011) after applying biostimulants observed a significant increase in raw fat in winter rapeseed seeds. According to Gugała et al. (2019b), after the application of natural plant preparations, an increase in crude fibre content in winter rapeseeds was found on average from 0.15 to 0.84 g/kg of d.m.
The research hypothesis was assumed in the work that biostimulators combined with foliar nutrition might have a positive impact on the yield components of three winter rapeseed varieties. The aim of the research was to determine the impact of foliar fertilizers containing amino acids, sulphur, boron on the number of productive branches, the number of pods per plant, the number of seeds in pods and the length of pods of three winter rapeseed varieties (Monolit, PX115, PT248).

Arrangement of the experiment and research location
The Monolit is a population variety, characterized by low soil requirements and good frost resistance. PT248 is a restored hybrid with a traditional growth type, while PX115 is a restored morphotype with a semi-dwarf growth type.
In the first year of research, spring wheat was the forecrop for winter rape, in the second and last year of research, it was winter triticale. The experiment was carried out on soil classified according to the World Reference Base for Soil Resources, (2014) in the Haplic Luvisol group, sanded, belonging to the very good rye soil complex, of the IVa class. In the years of research, the pH (pH in 1n KCl) of the soil was slightly acidic and ranged from 5.68 to 5.75. Soil was characterized by low availability of absorbable phosphorus forms and average absorption of potassium and magnesium.
After forecrop harvest, a set of post-harvest procedures was carried out using the ploughing aggregate and open cage roller. Then two weeks after the first procedure, pre-sow ploughing at the depth of 20.0 cm was carried out, using a ring roller at the same time. Before sowing. phosphorus-potassium fertilization (40 kg P·ha -1 , 110 kg K·ha -1 and 40 kg N·ha -1 (the first dose). Applied in the form of Lubofos at the dose of 600 kg. Fertilizing doses were supplemented with 55.9 kg·ha -1 of ammonium nitrate, 29.6 kg·ha -1 triple superphosphate and 29 kg·ha -1 potassium salt. The second dose of nitrogen (100 kg·ha -1 ) in the amount of was applied in spring, before vegetation started (BBCH [28][29][30] applying ammonium nitrate at the dose of 255.5 kg·ha -1 and ammonium sulphate at the dose of 62.5 kg·ha -1 . The third dose of ammonium (60 kg·ha -1 ) was applied at the inflorescence emergence, by applying ammonium nitrate at the dose of 176.5 kg·ha -1 .
Sowing of winter rapeseed was performed with a row spacing of 22.5 cm, assuming a sowing of 60 pcs·m -2 . Sowing was done at the optimal time recommended for this region (in 2016 on August 12, in 2017 -August 14, and in 2018 -August 13).
Chemical protection against weeds, diseases and pests was used in accordance with the recommendations of good agricultural practice. Rapeseed was harvested in two stages in the first and second decade of July.
Immediately before harvest (BBCH 86-87), on a sample mean of 20 plants from each plot, the components of seed yield were determined: -number of productive branches (pcs.), -number of pods per plant (pcs.), -length of pods (cm), -number of seeds in pods (pcs.) (taken from the central part of the main shoot and lateral branches).

Statistical analysis
The results of the study were statistically analysed with the use of the Analysis of Variance (ANOVA). The significance of variation sources was tested with the "F" Fischer-Snedecor test and the assessment of significance at the significance level of p=0.05 between compared means -with Tukey's range test. Statistical calculations were made on the basis of own algorithm written in Excel in accordance with the above mathematical model:

Results and discussion
In the years 2016-2019, different weather conditions prevailed ( Figure 1-4, Table 1). In the first year of research, the annual rainfall was 389.2 mm and was lower by an average of 9% compared to the average for many years. Based on the calculated Sielianinov hydrothermal coefficient, the first and second years of the studies were optimal. In the 2017-2018 growing season, the annual rainfall was only 13 mm lower compared to the 1996-2010 average, while the average annual temperature was higher by 1.1°C. The year 2018-2019 of studies was the driest and the warmest. Precipitation in this season was lower by an average of 40.8% than the average for many years, while the average value of the hydrothermal index was the lowest and amounted to 0.75. This research has shown that climatic conditions significantly affected the components of seed yield of three winter rape morphotypes (Table 2). In the 2016-2017 growing season, the sum of rainfall much higher than the multiannual average in the period from March to April caused the plants to produce the largest number of productive branches, pods, seeds in pods and plants had the largest length of pods. The smallest number of productive branches was obtained in the last year of the study, in which very little rainfall was recorded in April, while the number of pods per plant, length of pods and number of seeds in pods in the second year of the study with a sum of rainfall lower by an average of 53.2% in May.
Interactions of varieties and research years were found in relations to the number of productive branches, which indicates the individual response of varieties to climatic conditions prevailing in individual study years ( Table 2). The highest number of productive branches in all varieties was recorded in the first year of research, and the smallest in the 2018-2019 growing season, while in the case of a restored PX115, the value of this parameter was the same in the last two years of research and amounted to 5.5 pieces, on average. The Monolit population variety and PX115 restored hybrid, in the first year of the studies, had Based on the conducted research, it was found that the number of productive branches depended significantly on the types of foliar fertilization (Table 3). Only after using a biostimulator containing amino acids, the value of this parameter was the same as on the control treatment. Sikorska et al. (2018b), obtained different results, who showed the largest increase in this parameter by an average of 18.3%, under the impact of the Asahi SL bioregulator. Similarly, after the application of the preparation based on amino acids of plant origin and extracts from sea brown algae, Wenda-Piesik et al. (2017), found that the plants produced more productive branches on average from 36 to 72% compared to the variant without using foliar feeding and amino acids biostimulator. In our research, the most productive branches were noted after the application of the Siarkomag with Bormax and Aminoplant (treatment 4). This means that the biostimulator in connection with foliar fertilizers containing S and B stimulated the number of productive branches. Different results were obtained by Jarecki and Bobrecka-Jamro (2008), who did not prove the significant impact of this  factor on the value of this parameter. Of the compared varieties, the largest number of productive branches was found in PT248 (on average 6.1 pcs.). This is in line with the results of Sikorska et al. (2018b). In contrary, Jarecki and Bobrecka-Jamro (2008) did not find any significant differences in the number of productive branches of the evaluated varieties (Lirajet, Marita, Lisek). The effect of foliar nutrition on the number of productive branches depended on the genetic factor ( Table  3). As a result of using the Aminoplant biostimulator in the studied morphotypes, the same number of productive branches was found. All varieties had the highest value of this parameter on the fourth treatment, where the Aminoplant biostimulator was used with foliar fertilizers containing S and B. In addition, it was shown that the differences between the Monolit and the semi-dwarf hybrid on the control treatment and with the Aminoplant biostimulator (treatment 2) were statistically insignificant. On treatment 3, where foliar nutrition was sulphur and boron was applied, the value of this parameter in the Monolit and PT248 was the same. A similar tendency was observed on treatment 4 in restored hybrids PT248 and PX115.
Our data showed that the application of the Aminoplant biostimulator (treatment 2) did not affect the significant increase in the number of pods per plant compared to the control treatment, while after the application of foliar nutrition with sulphur and boron, this number increased on average by 16.3 pcs. (treatment 3), while the differences between treatments 2 and 3 were statistically insignificant (Table 3)    This study showed that under the influence of a biostimulator containing amino acids, the length of the pods was the same as on the treatment 1 ( Table 3). The largest significant increase in this parameter was noted after the use of foliar fertilization with S, B and amino acids (treatment 4), while the additional use of a biostimulator in combination with foliar feeding did not significantly increase the length of the pods. Similar results were obtained by Kaur et al. (2019). Of the compared morphotypes, restored hybrids with traditional and semi-dwarf growth types were characterized by the largest length of pods, while the differences between the population and semi-dwarf varieties were not statistically significant.
The foliar fertilization used in the experiment significantly increased the number of seeds in pods ( Table  3). As a result of using preparations Siarkomag, Bormax and Bioregulator (amino acids), this number increased on average by 3.9 pcs. This is in line with the results of Of the compared varieties, the largest number of seeds in pods was recorded in a restored hybrid with a traditional type of growth. This is in line with the results of Interactions of foliar nutrition types and varieties were observed in relations to the number of seeds in pods, which indicates the individual response of the varieties studied to foliar fertilization (Table 3). In the studied morphotypes, the highest value of this parameter was recorded on treatment 4, where foliar nutrition Siarkomag, Bormax and Bioregulator (amino acids) was applied. The number of seeds in pods was the same for the population variety and semi-dwarf hybrid on variant 1 and 2, while for restored hybrids PT248 and PX115 on treatment 4, after the application of preparations Siarkomag with Bormax and bioregulator Aminoplant.

Conclusions
1. Variable climatic conditions in the years of the experiment affected the studied components of seed yield of three winter rape morphotypes. In the first year of research, the plants produced the most productive branches, had the longest pods filled with the largest number of seeds.
2. Foliar nutrition with a biostimulator containing amino acids did not significantly affect the increase of the number of productive branches, pods per plant and pod length compared to the variant on which no foliar fertilization was applied.
3. Foliar fertilization with S and B in combination with biostimulators was the most effective treatment in increasing the components of seed yield, while the number of productive branches and length of pods under the influence of foliar fertilizers was the same regardless of the application of the biostimulator.
4. The long-stem variety had longer pods that were filled with more seeds than the others.