Weather impact and agricultural crops condition in Ukraine in May 2020 — NAAS

The weather conditions of April-May played the crucially important role in forming of the yield figures of most varieties of winter grain crops, since in the reporting period of calendar year the main elements of plant productivity are formed and start developing, including the number of spiciferous stalks, spikelets and kernels in the ear. The moderate temperature conditions and good soil moisture content usually contribute to the process development, as well as the cool and hot weather in terms of the absence of precipitation, negatively affect the organogenesis of plant bodies. It is commonly known that winter wheat and other winter grains spend the maximum moisture content and nutrients during the interphase period, starting from the beginning of stem elongation until the stage of earing, which mainly develops in the second half of the calendar spring.

The current spring became rather lengthy for the majority of Ukrainian farmers, as well as complex, and demonstrated various weather conditions, although in most oblasts the weather conditions were relatively favourable for winter crops development. Despite the significant deficit of precipitation, mainly in the central and southern regions, the major amplitude fluctuations in temperature indicators (from intense night frosts to high daytime temperature), and the dry hotwind weather events, at the end of the spring period winter wheat throughout most planted areas demonstrated relatively good and satisfactory condition. First of all, it is a case of the planted areas, where farmers observed the technologies of growing of the main grain crops. Although, there are some annoying exceptions, in particular in southern oblasts of the country, where the long-term drought caused the losses of winter crops throughout rather significant areas, which share in some farms even reached 50%.

The significant deficit of precipitation became the specific feature of the spring months of 2020, which had a negative impact on the soil moisture content and the general condition of plants, especially if they are grown after non-fallow forecrops, in terms of low soil preparation. Thus, in March 2020 the precipitation depth reached 72% only of the average long-term precipitation rate, in April — 27%, and in May — nearly 53%.

In the third ten-day period of April, the weather conditions were quite difficult, when in terms of the long absence of productive precipitation, there were observed some air and soil surface frosts of varying intensity, which had a negative impact on the growth and development of plants of winter grains. During the reporting period, the average daily air temperature varied within +5.7…13.9°C. In daytime, the maximum air temperature increased to +21.5°C, and the soil surface warmed up to +41.6°C. At night, the air temperature cooled to -1.4°C, and the soil surface — to -3.5°C. The average ten-day air temperature totaled 10.1°C, down 1.2°C compared with the average long-term standard.

The depth of precipitation totaled 0.6 mm only, or nearly 5% of the climate standard. The average relative humidity of the air totaled 35-72%, while for eight days the minimum values of the indicator varied below 30%, which indicated the presence of the air and soil drought. It was evident by the results of determination of the reserves of productive moisture content in the soil, which at the end of April in the meter soil layer under winter wheat crops planted after sunflower seed, did not exceed 67 mm, down 84 mm compared with the average long-term standard. During two recent ten-day periods of the month, the consumption rates of moisture from the soil significantly increased, due to the dry weather, and totaled nearly 3 mm per day.

Generally, in April 2020 the average air temperature totaled +8.5°C, down 0.7°C compared with the average long-term standard. The precipitation depth totaled 9.4 mm, or 27% of the average long-term standard. The average relative humidity of the air totaled 49%, down 17% compared with the climate standard.

For 10 recent years, such reduced temperature regime and small depth of precipitation in April period developed for the first time. At the same time, in relatively recent history in the reporting calendar period the less precipitation depth was observed in 2007 and 2009 only, and totaled 2.7 and 0.3 mm, respectively.

Average values of the hydrothermal indices in April period, 2011-2020

At the end of the reporting period, the analysis of the condition of winter grain crops showed that winter wheat plants of early, optimum and reasonably late planting dates (September 5 - October 5), which are grown after the best forecrops, were at the final stages of stem elongation — they reached the flag leaf stage. The winter plants, which had relatively early planting periods after non-fallow forecrops, reached the stage of flag leaf, while the optimum and reasonably late planting dates — the very beginning of such stage.

In winter barley plants of all recommended planting periods, there was observed formation of flag leaf, and in some varieties — beginning of the earing stage.

The early spring and drought-burdened weather conditions in April contributed to the enhanced growth rates and maturing of the main stages of winter grains development. In the beginning of May, the outrunning of their development varied within 10-14 days, compared with the average long-time period.

In some raions of Odessa, Zaporizhia, Kherson and Mykolaiv oblasts, there was observed the most difficult situation with soil moisture provision under winter crops, where not only in April, but also in March 2020, the fields almost did not receive any effective precipitation.

In the first ten-day of May, the air temperature figures were moderate, with frequent rains of varying intensity. In such terms, the average air temperature totaled +14.4°C, up 0.5°C compared with the average long-term standard. The average daily air temperature varied within +10.3…17.6°C. On some days, the maximum air temperature increased to +24.6…25.7°C, and the minimum temperature decreased to +3.6…6.5°C. At the same time, in daytime the soil surface warmed up to +46.6…49.5°C, and cooled to +1.7…6°C at night. In some raions, there were the frosts at the level of nearly +2°C.

For most part of the ten-day period, the average precipitation depth totaled nearly 10.5 mm, although in some raions the figures were quite significant, and varied within 50-80 mm. The average relative humidity of the air in the country totaled 66%, while the minimum humidity level dropped to 29%.

At the end of the ten-day period, the sum of effective air temperatures (above +5°C) accumulated by plants since resumption of the spring vegetation processes totaled 302°C, in terms of the average long-term standard of 240°C.

After the rains, the reserves of productive moisture in the soil under winter grains after various forecrops somewhat increased, and at the end of the reporting period in the meter soil layer the figures were mostly satisfactory and sufficient, and totaled 80-117 mm, while in southern oblasts the figures were insufficient — 48-57 mm.

At the end of the first ten-day period of May, winter wheat plants of the recommended planting dates reached the stage of flag leaf, while winter barley plants of short-season varieties were in the earing stage.

Generally, in the reporting ten-day period the weather conditions were quite favourable for the growth and development of winter grains.

In the beginning of the second ten-day of May, the weather conditions were rather changeable in temperature, they were relatively cool, with light precipitation. The average daily air temperature varied within +9.9…17.4°C. On certain days, the air temperature somewhat increased and dropped to +25.4°C and +2.9°C, respectively, and the soil surface warmed and cooled to +46.2°C and +1.3°C. The average air temperature totaled +13.6°C, down 2.5°C compared with the average long-term standard. For 10 recent years, only the same ten-day period in 2017 demonstrated the colder conditions (+12.1°C).

Average values of the hydrothermal indices in the second ten-day period of May, 2011-2020

The precipitation depth totaled 8.1 mm, down 9.9 mm compared with the average long-term values. In the reporting period, the less precipitation depth was observed in 2011 (1.5 mm), 2012 (4.9 mm), and 2019 (1.3 mm) only. At the same time, it should be noted that for 5-6 days, uneven precipitations developed throughout whole territory of the country, and demonstrated nonregular results even at the territory of one administrative region. The average relative humidity of the air totaled 60%, while the minimum humidity level dropped to 30%.

Due to relatively dry weather conditions, and sudden increase of consumptive water use and transpiration of plants, at the end of the reporting ten-day period the reserves of productive moisture in the soil under wheat after various forecrops declined to nearly 60-110 mm, and were much lower compared with the average long-term indicators, and generally characterized as satisfactory and insufficient. At the same time, in some raions of central and southern oblasts the productive moisture reserves in the meter soil layer under well developed crops after the black fallow decreased to 19 mm, down almost seven times compared with the standard rates, regulated for the earing stages of the major grain crops. For the first time for six recent years, such small level of productive moisture content in the soil was observed, and caused the significant reduction in the efficiency of applied fertilizers, especially for the crops after non-fallow forecrops, poor turgor in leaf blades, stoppage of the growth processes, weakening of the rates of photosynthesis and metabolic processes in the plants, which can definitely lead to lowering of the crops capacities (see the table).

Productive moisture reserves in the soil under winter wheat in the earing stage, mm

Inspection of winter wheat crops at the end of the second ten-day period of May showed that most varieties of the optimum and late planting dates reached the stages of earning on the last days of the reporting period. The plants of short-season varieties (Kohanka, Mudrost odesskaya, Manera odesskaya, Fortetsya, Smuglyanka, Slavna, Mariya, Konka, Krasa laniv), which were planted at the early dates, reached the flowering stage, which was 8-12 days earlier compared with the average long-term dates.

Winter wheat after the best and fertilized forecrops demonstrated the average plant height of 85-115 cm, and after non-fallow forecrops — 65-90 cm.

The plants of most winter barley varieties reached the flowering stage — beginning of the grain formation.

Most of the third ten-day period of May 2020 was characterized by the cool weather conditions with little precipitation. The average daily air temperature varied within +9.4…14.6°C. On certain days, the maximum air temperature rose to +20.5°C, and the minimum temperature dropped to +1.9°C; the soil surface warmed to +41.5°C and cooled to -0.3°C. On the first days of the ten-day period, there were observed air frosts throughout whole territory of the country at +2°C. The depth of precipitation totaled nearly 4 mm. The average relative humidity of the air varied within 51-76%, and in the beginning of the reporting period the figures even decreased to 22-28%.

At the end of the spring vegetation period of winter grains, it should be noted that to date, winter wheat was in the best condition, because the grain was planted at the reasonable time for the black fallow and after peas, which provided the sufficient terms of plant nutrition. In such areas, the number of productive stems varies at the level of 518-663 pcs/m², and the kernel weight per ear can total 1 g or even more. Taking into account the figures, we can make a preliminary forecast that the yield of winter wheat after the best forecrops can reach nearly 6.5-7 t/ha. At the same time, winter crops that are grown after non-fallow forecrops with rather low level of mineral nutrition, especially late planting periods, can provide the grain yield of no more than 3.2-5 t/ha.

The phytosanitary condition of winter wheat crops was satisfactory, although most farms continue treating the crops with fungicides and insecticides, which mainly have the preventive nature.

In winter wheat crops after non-fallow forecrops, namely after sunflower seed, there was observed the deficit of nutrients, including nitrogen, which was expressed in the light green color of leaf blades and premature decline of leaves of the bottom circle, and is the consequence of rather cool and relatively dry weather, which slows down development of microbiological processes in the soil.

Inspection of the crops to determine the condition of plants of spring cereals and pulses, provided at the end of May, showed that their degree of development is generally satisfactory. Thus, in the planted areas of spring cereals (barley, spring wheat and triticale, as well as oats), there was observed the stage of the flag leaf, and the plant height totaled 48.9-53 cm, and pulses (peas, lentils, chickpeas) — 24.7-27.4 cm.

In May 2020, the weather conditions in Ukraine were satisfactory for the growth and development of agricultural crops. Their further performance will depend on the weather conditions and timely provision of technological measures to care for crops in the following stages of vegetation. The long-term absence of productive precipitation in April and May 2020, which in some regions contributed to formation of the air and soil drought events, will undoubtedly affect the level of agricultural crop yields and production volumes of grain products. However, in terms of keeping of the dry weather conditions during the grain filling period, especially in terms of the high air temperature, the share of secondary crop can vary within 10-15%, due to the production of fine and shrunken grain. Also, in the current year farmers will start the harvesting campaign of winter grains in nearly 8-10 days earlier than usual, taking into account the development rates of plants and the weather conditions.