Contribution of weather conditions and anthropogenic activity to the variation of grain yields in the North-West of Russia

. Current trends in climate change associated with the growth of heat supply contribute to the growth of bioclimatic potential and the increase in productivity of grain crops in the North-West of Russia. In such conditions, research is relevant aimed at clarifying the contribution of weather conditions and anthropogenic activity in the formation of the crop. The research was conducted on the crops of winter rye, spring barley, winter wheat, and spring wheat of the experimental landfill of the Menkovsky branch of the Agrophysical Research Institute. We studied various factors of anthropogenic activity, such as the level of mineral or nitrogen nutrition, an integrated plant protection system, seeding rates, and the size of seed material. Variance analysis was used in statistical processing. According to the results obtained, weather conditions were the most significant factor of productivity for winter cereals, and mineral nutrition was crucial for spring crops. The integrated protection system was less important than both the weather conditions of the growing season and the background of mineral nutrition of cultivated plants. This factor appeared to be the least significant for winter rye, which often has a favorable phytosanitary situation. The novelty of the data obtained lies in determining the predominant value in varying the yield of nitrogen fertilizers and herbicide treatment for spring wheat. A little less critical were the seeding rate and the size of the seed material.


Introduction
Climatic and weather conditions have a significant impact on agricultural production since they largely determine the level of crop yields, product quality, production costs, and features of agrotechnical and technological measures [1,2].The main factors of crop productivity also include the application of fertilizers, the use of plant protection products, and the implementation of appropriate tillage practices [3].These are anthropogenic factors that can be used in a controlled manner.For example, the share of the influence of tillage and doses of nitrogen fertilizers in combination with plant protection products on the yield of winter barley in the Republic of Adygea of the Russian Federation was 44 and 42%, the weather conditions of the growing season of the crop were only 4.3% [4].According to other researchers, the contribution of meteorological conditions to the formation of crop yields was much higher, reaching 24%-55%.At the same time, the strong influence of the weather extends, among other things, to the main indicators of the quality of the resulting crop, such as protein and gluten content in grain, flour strength [5].
According to foreign researchers, the variety accounts for 25%, and in some cases 35%-40% of the yield increase [6].This is due to the peculiarities of varieties to show resistance to biotic environmental factors and different needs for mineral nutrients.
The value of the bioclimatic potential of the North-Western region of Russia is characterized by solid variability (0.48-2.2) with a tendency to increase from north to south.The climatically secured productivity of grain crops varies from 13.9 c/ha (Murmansk Region, Arkhangelsk Region) to 58.0-63.8c/ha (Pskov Region, Kaliningrad Region).Taking into account current trends in climate change, one can predict an increase in heat supply and the duration of the growing season in the North-Western region, leading to an increase in the bioclimatic potential and the productivity of grain crops.The paper is devoted to a comparative assessment of the contribution of weather conditions and anthropogenic activity in the formation of grain crops in the North-West of Russia.Despite the steady interest in such studies, it is necessary to clarify the information available in the literature.

Materials and Methods
The research was conducted in 2012-2020 at the experimental base of the Menkovsky branch of the Agrophysical Research Institute located in the Leningrad Region of the North-Western Region of Russia.The influence of abiotic (weather conditions) and anthropogenic factors (mineral nutrition, integrated plant protection system) on the formation of winter rye (Slavia variety) and spring barley (Leningradsky variety) was studied in the fields of the agroecological hospital, a 7-pole grain-grass-row crop rotation.The levels of mineral nutrition (lowwithout fertilizers, medium -N65P50K50, and high -N100P75K75) are supported by the annual pre-sowing application of azofoska and ammonium nitrate-based on the planned crop yield.In the variant with an integrated plant protection system, protective measures against harmful organisms were introduced, given that the economic threshold of harmfulness was exceeded, involving the etching of seed material and treatment with herbicides, fungicides, and insecticides.
We studied the effect of increasing doses of nitrogen fertilizers (N0, 30, 60, 90, 120, 150) on the phytosanitary condition of crops and crop yields in similar experiments with winter and spring wheat.Moskovskaya 56 and Darya varieties, zoned in the North-Western region, were cultivated.
A micro-field experiment with spring wheat was conducted in 2016-2018.This process involved the study of the influence of seeding rates (5 and 6 million viable seeds/ha), the size of the seed material (the mass of 1,000 grains was 25-30 g and 40-45 g), doses of nitrogen fertilizers (0, 60 and 120 kg d.v./ ha), and the use of herbicide (with and without treatment) on the yield of spring wheat.
Statistical processing of the data obtained, aimed at determining the influence of each of the factors on the formation of grain yields, implied a variance analysis carried out in the Statistica 6.0 program.

Results
Spring barley is the main forage grain crop in the North-West of Russia, occupying about 40% of the sown area structure, with changes in the regions ranging from 15% to 60%.
Over the years of research, spring barley yield varied from 23.9 to 41.4 c/ha.The main contribution to the variability of barley yield was achieved through the use of mineral fertilizers.This factor had the highest influence: 37.5%, in some years -52.0%-70.8%.The influence of the weather conditions of the growing season was expressed by 17.9% of the yield variation and the integrated plant protection system -5.6% (Table 1).Depending on the prevailing phytosanitary situation, protective measures determined the value of the formed barley yield by 0.1%-21.9%.Note: * -differences are significant at Р≥0.95.Source: Compiled by the authors.
Along with spring barley, one of the main grain crops in the North-West of Russia is spring wheat.In the structure of grain crops, this crop accounts for 11%-65%, and the average for the region is about 40%.According to the results obtained, spring wheat yield was determined by 33.9% by the level of nitrogen nutrition and by 22.4% by the weather conditions of the growing season.The interaction between the two productivity factors was significant, confirming the significance of weather conditions for the effectiveness of fertilizers (Table 2).
Statistical processing of experimental data from the micro-field experiment showed that the main factor affecting the yield of spring wheat was the use of nitrogen fertilizers (29.1%).The second most important factor was herbicide treatment (14.9%).The effect on the wheat yield of the spring seeding rate and the size of the seed material was less than 1%.
In recent years, the structure of sown areas has changed dramatically due to an increase in the share of winter wheat, the yields of which can be compared with the Southern and North Caucasus regions.
In our experiments, winter wheat yield varied widely (21.9-55.8c/ha).Given the importance of overwintering for this crop, weather conditions appeared to be the main factor limiting the yield (Table 2).Spring fertilizing with nitrogen fertilizers had little effect on the formation of the winter wheat crop, including due to negative phenomena such as strong lodging of plants at high doses.
Traditionally, winter rye is considered the main grain crop of the North-Western region of Russia.Compared to the last century, the presence of this crop in the structure of sown areas decreased to the level of 1% over the past two decades.Note: * -differences are significant at Р≥0.95.Source: Compiled by the authors.
The variation in the yield of winter rye over the years ranged from 40.3 to 72.1 c/ha.The strong degree of variation was equally determined by weather conditions and the level of mineral nutrition.The share of the influence of these factors accounted for 30.1% and 31.3%, respectively.Based on the identified interactions, the influence of weather conditions extended to the effects associated with the improvement of mineral nutrition and phytosanitary conditions in winter rye crops (Table 3).Besides, the integrated plant protection system has a weak effect on the formation of the rye crop (0.4%).Even in the years with the least favorable phytosanitary conditions, the contribution of plant protection did not exceed 7.1%.Note: * -differences are significant at Р≥0.95.Source: Compiled by the authors.

Discussion
According to the data available, spring barley and winter rye cultivated in the natural and climatic conditions of the North-West of Russia are characterized by the prevalence of weather conditions of the growing season over anthropogenic factors in the formation of the crop.The influence of the "weather" factor was 43% and 59%, "fertilizer system" -24% and 21%, "plant protection system" -11% and 2%.The research results confirm the secondary role of phytosanitary measures to protect crops from a complex of harmful organisms.At the same time, there was a stronger influence on the yield of these crops of the background of fertilization due to the shortage of the main elements of mineral nutrition in the sod-podzolic soils of the North-West of Russia.
The research conducted for the first time revealed a different value of the weather factor and fertilization for winter and spring wheat for this region.For winter wheat, the conditions of overwintering (i.e., the weather) are decisive in the formation of the harvest, whereas, for spring wheat, nitrogen nutrition is crucial.The interaction of these factors appeared to be strongly pronounced and equally manifested in both winter and spring wheat.New data were obtained on the correlation of the roles of anthropogenic factors in varying the yield of spring wheat, namely, the predominant importance of nitrogen fertilizers and herbicidal treatment, secondary -seeding rates and seed size.

Conclusion
The results obtained clarify the contribution of weather conditions and anthropogenic activity to the variation of grain yields in the North-West of Russia.For winter grain crops, weather conditions were more significant than the introduction of mineral fertilizers and protective measures.The reverse situation was observed for spring grain crops, where the most significant productivity factor was the level of mineral nutrition.The integrated protection system was less important than the weather conditions of the growing season and the background of mineral nutrition of cultivated plants.This factor turned out to be the least significant for winter rye, in which cases with a complex phytosanitary situation are less often recorded.
Against the background of the studied productivity factors, the seeding rate and the size of the seed material were the least significant for spring wheat.

Table 1 .
The contribution of weather conditions and anthropogenic activity to the variation of spring barley yield in the North-West of Russia.

Table 2 .
The contribution of weather conditions and anthropogenic activity to the variation of winter and spring wheat yields in the North-West of Russia.

Table 3 .
The contribution of weather conditions and anthropogenic activity to the variation of winter rye yield in the North-West of Russia.