Weather impact and winter grains condition in Ukraine in January 2020 — NAAS

The high temperature figures became the absolute feature of the current calendar winter, which according to the meteorological indicators, can be considered as rather unique feature. In most oblasts, there were no snow cover on the fields. Of course, in many previous years there was observed some deficit of precipitations, but the event did not have such complex and protracted nature. It is clear that such weather conditions during the winter period caused some concern for grain producers, since in terms of sharp decrease of the temperature indicators, in the future there is a real risk of damaging and frost-killing of crops, and the deficit of moisture in the fields can lead to negative consequences in the first half of the spring-summer vegetation processes of winter crops. Such weather conditions are especially adverse for the regions, where in the autumn period it was not possible to get timely sprouts of winter crops, due to the longtime drought, and plants began the wintering period in the weakened state.

At the same time, it should be noted that the general hydrothermal conditions were quite favourable, since for most time the plants did not feel any negative impact of low temperatures, they fairly received the moisture reserves, and had the opportunity to revive the life processes in the daytime. It was especially beneficial for winter crops of late planting periods, because the significant share of such plants already reached the tillering stage.

For the first two months of the calendar winter, there were no strong reasons for damages, and even losses of crops, because December and January demonstrated the high air temperatures, which exceeded the average long-term standards by 3-5°C, and the insufficient level of precipitation, which negatively affected the reserves of productive moisture in the soil.

The largest share of precipitation was observed in the third ten-day period of December 2019, and reached nearly 28 mm, up 12 mm compared with the average long-term standard. In the same period, the average air temperature totaled +3.7°C, an increase of 6.7°C compared with the average long-term indicators. At the end of the ten-day period, snow covering in the fields was largely absent, and the depth of soil freezing did not exceed 3-7 cm. The soil temperature at the tillering zone depth of winter wheat was not lower than -0.5…-1°C, and it was significantly higher than the critical frost-killing temperature, which varied at the level of -14°C.

Generally, in December 2019 the average air temperature totaled +2.5°C, up 4.8°C above the climate standard. The average precipitation depth totaled 34.7 mm, down almost 30% compared with the average long-term rates.

In the first ten-day period of January, in terms of morning heavy fogs and minor precipitations, the increased temperature regime continued keeping in the country. Thus, the average air temperature totaled -0.7°C, up 3.6°C compared with the average long-term standard. On some days, the temperature figures rose to +2.9°C, and the soil surface warmed up to +7°C, and on the contrary, at nighttime the temperature reduced to -7°C, and the soil surface cooled to -9.7°C. The precipitation in the form of rains and sleet totaled 5.2 mm only, down 11.8 mm compared with the average long-term standard.  Relative humidity of the air was quite high, and varied within 66-95%.

The average depth of soil freezing was insignificant, and varied within the range of 4-8 cm. Snow cover in the fields was almost absent, only in some raions its depth did not exceed 1-1.5 cm. The minimum soil temperature at the tillering zone depth of winter wheat decreased to -1.3°C only, and did not constitute any threat to the plants.

Taking into account the hydrothermal indices of the first ten-day period of January, it is certain that their values and duration of their action almost matched the beginning of the second phase of crops hardening. In fact, winter crops developed in such condition for a relatively long time, starting from the last days of December and until the end of January 2020.

In the second ten-day period of January, the weather was abnormally warm for the reporting time of year, with minor precipitations. In the first half of the reporting period, the average daily air temperature varied within +0.4…1.4°C, in the second — within -0.4…-3.2°C. In daytime, the maximum air temperature increased to +4.5°C, the soil surface warmed up to +9.6°C, and at night the temperature indicators decreased to -4.7°C and -6°C, respectively.

In the reporting ten-day period, the average air temperature totaled -0.5°C, up 6.3°C compared with the average long-term standard. The precipitation depth was insignificant — 3.4 mm, or 28% of the average long-term standard. At the same time, relative humidity of the air varied within the range of 70-98%, due to fogs, drizzle and glaze ice.

On the last days of the ten-day period, there was formed a slight snow cover with the depth of nearly 0.5-1 cm, but it quickly melted. The average depth of soil freezing totaled 4-8 cm. The minimum soil temperature at the tillering zone depth of winter wheat did not reduce below -1°C, which was significantly higher than the critical temperature of frost-killing, which varied at the level -14°C.

Generally, the weather conditions of the second ten-day period of January were favourable for winter crops, but the analysis of the content of productive moisture in the soil demonstrated that its level under winter wheat crops although significantly increased for two months of the winter period, but it was extremely insufficient after several preceding crops. The moisture reserves under winter grain crops after sunflower seed gave rise to most concern, where in the tilth top and meter layers of the soil its level totaled 37 and 101 mm respectively, down 9 and 61 mm compared with the average long-term standard (table. 1).

Table 1. Reserves of productive moisture content in the soil (mm) under winter wheat areas during the winter period -2019/20.

In addition, most part of January was extremely dry, which in most cases caused the unsatisfactory accumulation of agronomically valuable moisture in the soil. Thus, the average air temperature for two ten-day periods of January 2020 totaled -0.6°C, up 5°C compared with the average long-term standard, which was the abnormal phenomenon for the coldest month of winter.

Fig. 1. Average values of hydrothermal indicators for the first and second ten-day periods of January, 2011-2020

Also, for the first two ten-day periods of January the average precipitation depth totaled 4.3 mm, down 10.2 mm compared with the average long-term figures, or 30% of the climate standard only. Such small level of atmospheric precipitation during the calendar period was observed for the first time during 2011-2020, which can certainly affect the moisture content of the soil, the general condition of plants in the future, and the level of productivity.

Most part of the third ten-day period of January, there was observed the high air temperature and low precipitation level.

The average daily air temperature varied within -0.4…+1.5°C. On some days, the air temperature and soil surface warmed up to +4.9°C and +8.8°C respectively, and at night they cooled to -1.8°C and -10°C respectively. The first half of the ten-day period was drought-burdened, and in the second half there were uneven precipitations. At the same time, there were no dangerous weather events for winter crops development.

The analysis of the condition of winter grains and rapeseed, and the hydrothermal indicators for most part of the current winter period (November-January), indicated that there was no any significant negative impact on the overwintering period of the plants.

Taking into account the average temperature regime of November, when the plants stopped active vegetation processes, and the two winter months — December and January — it should be noted that the current calendar period in terms of its indicators was the warmest for seven recent years. The average air temperature totaled nearly +2.2°C, up 4.2°C compared with the average long-term standard (fig. 2).

Fig. 2. Average values of hydrothermal indicators during November-January period, 2013/14-2019/20 MYs

The general depth of precipitation for November-January reached 83.4 mm, which was significantly lower than the average long-term standard, which totals 131 mm. For several recent years, it is one of the worst results, because only in 2013/14 MY there were the lower results (61.7 mm).

Of course, it is clear that the overwintering period has not completed yet. February and March 2020 can present an undesirable surprise to grain producers in the form of short-term frosts in terms of the absence of snow cover in the fields, which can somewhat damage crops.

Taking into account the current development of winter crops, and the weather forecasts for the nearest future, it is certain that there is not expected any significant threat for crops at the final stages of the winter period. At the same time, there is a high probability of resuming of active vegetation of winter crops at the relatively early dates, which can provide rather significant harvest volumes, at least not worse than in previous years.