Regional Weather Variations and Yields Achieved in Soybean Crops

Monitoring weather conditions during soybean cultivation is essential in agricultural planning. The variation of these conditions, such as temperature, precipitation, relative humidity and soil moisture directly influence the productive performance of crop.With this, the objective of the work was to verify the effects of weather conditions on the soybean yield, carrying out the survey of the minimum, maximum and average temperature and the total precipitation during the cultivation of the soybean and collecting the data of productivity reached in the agricultural harvests of 2017/2018, 2018/2019 and 2019/2020 of soybeans in a commercial area with 15.5 ha, located in the Céu Azul City, Paraná State, Brazil. Regarding the results for the three soybean harvests, the air temperature remained adequate for the development of the crop in most of the cycle. And the values observed for precipitation indicated the occurrence of well-distributed rainfall in the 2019/2020 harvest, and in the 2017/2018 harvest there was irregular rainfall distribution, however there were no periods without precipitation. However, the large precipitation deficit occurred in the 2018/2019 harvest, where the lack of rain occurred in 28 days, between 12/03/2018 and 12/30/2018, indicating a drought in this period. The soybean yield obtained in the area in the 2019/2020 harvest was 3.727 t ha -1 , higher than the other two soybean harvests, being that 2018/2019 harvest reaching the lowest value, 2.394 t ha -1 , indicating the influence of the weather in the soyben yield achieved.


Introduction
Agricultural crops still encounter obstacles to achieving high yields due to weather variations.Being that the weather is the main determining factor of yield in agricultural crops (Carmelo, 2018).According to Kurukulasuriya and Rosenthal (2013), agriculture is the sector most vulnerable to climate impacts.Thus, monitoring the main weather parameters is of fundamental importance to measure the impact of weather on agricultural crops.
The weather is extremely important, as it provides support and conditions for the growth and development of plants.Being that the changes in weather system patterns influence agricultural yields, including annual and subannual changes in temperature and precipitation (Snyder, Waldhoff, Ollenberger, & Zhang, 2021).Precipitation associated with water deficit is the main limiting factor for soybean yield in Brazil, but other atmospheric variables, such as air temperature, photoperiod and solar radiation, can both intensify and attenuate the effects of water deficit on soybean yield (Sentelhas et al., 2015).
The soybean crop is able to tolerate, in some cases, water deficit in short periods, but it can present a significant reduction in productivity in long periods without rain.Being that, the drop in performance resulting from the water deficit is of great importance, since the development of the crop is significantly affected by low precipitation and poorly distributed rainfall (Anda, Soós, Menyhárt, Kucserka, & Simon 2020).And, soybeans are more sensitive to water deficit in the reproductive stage (Montoya, García, Pintos, & Otero, 2017).Ferrari, Paz, and Silva (2013) also report that excessive rainfall can lead to a reduction in soybean yield due to the decrease in leaf water potential and, consequently, stomatal closure, impairing photosynthesis, reducing soil aeration, development roots and nitrogen fixation in the soil.

The exper cultivation
The area h of 25°06′3 a humid c 2016).The 1890 mm.The work used the climatological data contained in the periods with soybean cultivation in the experimental area in the 2017/2018, 2018/2019 and 2019/2020 harvests.The data used were: precipitation and minimum, maximum and average air temperatures.
In order to identify the weather parameters that may affect productivity and that are unsuitable for soybean cultivation, climatological data were grouped in periods of fourteen days, within each harvest, obtaining the minimum, maximum and average temperatures reached and precipitation total.

Planting, Harvesting and Yield
In soybean planting in the agricultural years 2017/2018, 2018/2019 and 2019/2020, the soybean cultivar used was Syngenta 1359, soybean cultivar super early cycle, and spacing between rows of 0.70 m was used to facilitate the traffic of machines, as the harvester and sprayer are adjusted for this spacing.
Harvesting was performed with a harvester equipped with GPS and a harvest monitor with a sensor attached to the top of the grain elevator.In the work, yield data were collected for the three soybean harvests and later relating the yield achieved with the weather data obtained.Thus, weather conditions, precipitation and minimum, maximum and average air temperatures during the seedling cultivation period were recorded, aiming to identify improper conditions for cultivation associated with deficits in the yields achieved.

Statistical Analysis
Statistical analysis was performed using a completely randomized design (CRD), with treatments represented by soybean yields and harvest monitor measurements considered as replicates.Tukey's test, at a 5% probability level, was used to compare the yields achieved in the harvests.

Analysis of Soil Chemical Attributes
The analyzes of the chemical attributes of the soil were carried out in 2017 and 2019 according to Table 1, following the history of soil management in the area and the criterion of the producer, there was no need for chemical analysis of the soil in 2018, as the producer adopts carrying out chemical analyzes of the soil at intervals of 2 years.The results presented for Ca, Mg, P, K, pH in the 2017 and 2019 in soil chemical analyzes are included in the very high interpretation class; and, CTC, V as high in the interpretation table of soil chemical parameters for the Paraná State by the authors Pauletti and Motta (2019), thus being considered suitable for soybean cultivation.
The Al element was the only that presented a low amount in the years 2017 and 2019, but it is not an element considered essential in soybean cultivation.
However, due to the high demand for nutrients N, P and K in soybean cultivation, mineral fertilizer NPK 8-40-00 was used for fertilization, being applied throughout the area in the amount of 125 kg ha -1 made directly with the planting in the three soybean agricultural years.
Regarding precipitation in the 2017/2018 soybean crop, there was excessive precipitation and irregular rainfall distribution, but without periods with no precipitation.In turn, in the 2018/2019 cultivation, the averages of the fourteen-day intervals also indicate a large variation in the amount of rainfall, including the presence of drought in the period between December 3, 2018 and December 30, 2018.In line with this result, in the 2011/2012 crop year there was a deficit of precipitation, in relation to that recommended for the soybean cycle, with the occurrence of the "La Niña" phenomenon, causing a reduction in soybean yield of 44, 29 and 10% respectively, in the states of Rio Grande do Sul, Paraná and Mato Grosso do Sul (CONAB, 2013).
On the other hand, during the 2018/2019 soybean crop, there was a better distribution of precipitation, with rain occurring in all periods in the soybean cycle.Result obtained that is in agreement with the results of Carmelo (2018)  Comparing the 2019/2020 crop: in the 2018/2019 crop there was a decrease of 380.2 mm of precipitation during the soybean cycle, compromising 1.333 t of production; and in 2017/2018 there was an excess of 695 mm of precipitation during the soybean cycle, reducing the final production achieved by 0.743 t.

Conclusions
Keeping the temperature within limits considered ideal for the development and production of soybeans has no influence on the variation in soybean yield.On a regional scale, in an area without irrigation technology, where a monoculture agricultural environment predominates, a microclimate can be generated that is directly dependent on the variability and amount of rainfall in the soybean cycle.
The deficit or excess in precipitation and the incidence of poorly distributed rainfall during the soybean cycle influence the development of the crop, generating negative results in soybean yield.
The occurrence of drought during soybean cultivation can lead to a deficit of available water for soybean plants, influencing their development and, consequently, influencing the final yield achieved by the crop.
Precipitation in excess of the recommended amount during the soybean cycle causes excess water and reduced aeration in the soil, causing, as a consequence, a decrease in soybean yield.

Table 1 .
The results of the analysis of soil chemical attributes

Table 2 .
Precipitation and temperature data for the 2017/2018, 2018/2019 and 2019/2020 soybean crops Precipitation and temperature data from the climatological station located in Cascavel CityThe averages of the fourteen-day temperature intervals over the entire period of the 2017/2018, 2018/2019 and 2019/2020 crops remained between 20 °C and 30 °C, with the minimum temperatures being above 10 °C and the maximum temperatures that occurred in the crops were below 40 °C, remaining according to MAPA (2017) within the appropriate conditions for soybean cultivation, results that indicate that temperature was not a determining factor for the variation in soybean productivity.In agreement with this result, in the Roncador and Boa Esperança Cities, in the Paraná State, in Brazil, during the soybean crops of2008/2009, 2009/2010 and  2010/2011, temperatures remained between 20 °C and 30 °C, not compromising the final productivity achieved Farias (2011)anting in southern Brazil.Since,Farias (2011)express that the water availability during the