AGROECOLOGICAL IMPACT OF DEFICIENT AND EXCESSIVE ATMOSPHERIC PRECIPITATION IN POLAND (1971-2000)

Tadeusz Zawora, Agnieszka Ziernicka-Wojtaszek
Department of Agricultural Meteorology and Climatology, University of Agriculture in Cracow, Poland

ABSTRACT

The paper has been aimed at assessing agroecological impact of precipitation observed in years anomalous with regard to its amount, in particular the impact of precipitation deficiency and excess. The analysis performed on the ecological and economic impact data reported by agricultural correspondents proved that months can be divided into month of deficient, adequate (optimal), and excessive precipitation. Regardless the differences between individual months and diversity of the territory it was shown that according to agricultural and ecological criteria the optimal precipitation varies within the limits 79-125% of the standard. The upper limit for optimal precipitation, i.e. 125% of the standard is the same as the upper limit for average precipitation by Kaczorowska [1]. The observed increase in air temperature of about 0.5 °C over the studied period resulted in optimal monthly precipitation increased of about 3 mm on average.

Key words: precipitation, effects of precipitation deficiency and excess, Poland.

INTRODUCTION

Due to significant variability in total atmospheric precipitation in different years, neither vegetation of cultivated plants nor field works do not always can take advantage of favourable weather conditions. Both deficient and excessive precipitation over a specific period have distinct impacts on grassy agro-ecosystems or ecosystems, i.e. meadows and pastures, depending how precipitation coincides with sowing or planting, maintenance works or other cultivation practices, as well as harvesting cultivated plants. Thus, unfavourable weather conditions produce in consequence specific economic results, depending on the phenomenon intensity.

To facilitate analysis of the presented problem, a register of agro-ecological after-effects of deficient and excessive atmospheric precipitation in Poland over the following months of a year was established. It allowed to determine the number of months with deficient, adequate and excessive precipitation over the studied 3 decades, and thus by confronting it with monthly totals, to find the range for optimal precipitation, i.e. to set the respective values at which deficiency and excess start. It was then possible to compare typical precipitation values by Kaczorowska [1] within the conventional limits 76-125% of the standard against the values of optimal precipitation defined as such precipitation that causes no negative effects to be detected in agroecosystems. Comparing the optimal precipitation values for two subsequent 1.5 decades let assess the impact of the observed increase in the air temperature over the studied period upon the increased level of optimal precipitation.

MATERIALS AND METHODOLOGY

Monthly totals of atmospheric precipitation and reports on the conditions of crops and weather conditions for field works published in Monthly Agrometeorological Reports over the period 1971-2000, and later since April 1999 in Decade Agrometeorological Reports, provided the base data for the research.

Characteristics for the plants vegetation and wintering conditions, crops status and field works related successively by agricultural correspondents were applied to present an agroecological impact for both deficient and excessive precipitation. Considering plants reaction to changeable meteorological conditions, and to various precipitation totals in particular, months could be classified as deficient, adequate, and excessive with regards to precipitation magnitude. Relevant monthly totals of atmospheric precipitation were allocated to months of deficient and excessive precipitation.

RESULTS

In January over 12 years, namely: 1974, 1975, 1977, 1981, 1982, 1984, 1985, 1988, 1995 and 1998-2000, precipitation varied within the optimal limits of 27-44 mm, which corresponded to 84-138% of the standard. In February, there were 15 such years: 1971, 1974, 1980, 1981, 1983, 1985, 1987, 1989, 1990, 1991, 1992, 1993, 1996, 1998, 1999 with precipitation raging within 21-37 mm, i.e. 78-137% of the standard. Lower rate precipitation, which occurred in January in 12 years: 1971-1973 1978, 1980, 1987, 1989-1992, 1996 and 1997, and February over 9 years – 1972, 1975, 1976, 1978, 1979, 1982, 1984, 1986 and 1994, were the source of such a negative impact as frost damage to plants, thaw and freezing of soil surface layer, weakened plant root system, marginal lakes occurrences, ice layer and plants mechanical damage, plants scorching, and sporadically, at high temperatures, too early pre-vegetation of plants (see Table 1).

– insufficient precipitation – optimal precipitation – excessive precipitation

Excessive precipitation, recorded in 6 years for January – 1976, 1979, 1983, 1986, 1993, 1994 and February as well – 1973, 1977, 1988, 1995, 1997 and 2000, were found to have been the cause for such detrimental impact as asphyxiation of winter crops, occurrence of snow mould in years with thick snow cover, ice covering, thaws and freezing of soil at big temperature differences, weakening and de-hardening of plants in years with higher air temperatures, and sporadically swollen rivers and floods (Table 1).

It can be observed that freeze damage caused by freezing and defrosting soil top layer, as well as occurring marginal lakes, are found at both low and high precipitation totals, and can be attributed to air temperature oscillating frequently near 0 °C.

In 16 out of 30 years precipitation within the optimal range between 25-44 mm, i.e. 74-129% of the standard, were observed in March, namely in years: 1971-1973, 1975, 1977, 1978, 1982, 1983, 1985, 1987, 1989, 1990, 1993, 1995, 1997 and 1999. In dry months, which occurred in years 1974, 1976, 1980, 1984, 1986, 1991 and 1996, depending on the winter character, with insufficient snow cover frost damage in plants occurred, as well as soil frost adjustment in the root layers and plants scorching, whereas in years with earlier spring – sprouts were delayed and field works impeded. For 7 years, namely 1979, 1981, 1988, 1992, 1994, 1998, 2000 excessive precipitation was recorded and phenomena related to it such as excessive soil dampness, marginal lakes, retarded growth and development of winter crops, asphyxiation of winter crops and crop destruction by wet weather, impeded field works, and prolonged sowing and sprouting periods, particularly in years 1979, 1998 and 2000, as well as floods (Table 1).

For April optimal precipitation ranging within the limits 30-48 mm, respective standard range 75-120%, were recorded for 16 years over the study, namely in 1971, 1973, 1975, 1978, 1982, 1983, 1985-1987, 1989-1992 and 1995-1997. Lower values, as insufficient resulted in soil dampness deficiency, delayed sprouting, blocked growth and development of winter crops, meadows and pastures quality deterioration, adverse conditions for fruit trees blooming, as well as impeded field works. Deficiency of precipitation was remarkable in 6 years: 1974, 1976, 1981, 1984, 1988 and 1993, whereas excessive in 8 years: 1972, 1977, 1979, 1980, 1994, 1998, 1999 and 2000. It resulted in excessive soil dampness, retarded growth and development of plants, widely occurring marginal lakes and crop destruction by wet weather, damaged orchards, prolonged sowing and sprouting periods, impeded field works, while in years 1979, 1998 and 2000 floods (Table 1).

For May optimal precipitation was found to vary from 49 to 69 mm, which corresponds to 86-121% of the standard over 1971-2000. They occurred in 18 year, namely in 1971, 1973-1978, 1981, 1982, 1985-1987, 1991, 1994, 1995 and 1998-2000. Lower precipitation, as insufficient, made an atmospheric drought regress into a soil one, crops to deteriorate, particularly spring crops, root crops plants to wither, fruit-setting and growth condition for potato tubers to deteriorate, rape silique to fill insufficiently, meadow and pasture vegetation regrowth to be impeded, and current fields works to be slowed down. Insufficient precipitation was detected for 7 years, namely 1979, 1980, 1988, 1989, 1990, 1992, 1993. For the remaining 5 damp years: 1972, 1983, 1984, 1996 and 1997 excessive dampness in soil was observed, crops laying, damaged corn seedling, excessive weeds development, impeded hay harvest, while in orchards damaged fruit blastema in and immoderate development of detected diseases and pests (Table 1).

Over the studied 3 decades, similarly to May, in June the highest number of 18 optimal cases was registered in years: 1972, 1973, 1975, 1977, 1978, 1981, 1982, 1984, 1986-1991, 1993 and 1995-1997. The optimal precipitation ranged within the limits 61-92 mm, which corresponds to a range 80-121% of the standard. Lower precipitation, recorded for 6 years, namely 1976, 1979, 1983, 1992, 1994 and 2000, in most cases caused atmospheric drought to turn into a soil drought, overall deterioration of permanent grasslands, impeded grass regrowth at meadows and pastures, at times even terminated cattle grazing, deterioration in spring and root crops observed as their withering, as well as deteriorated conditions for fruit-setting and development of potato tubers and disadvantageous conditions for cultivation maintenance practice. Excessive precipitation occurred in 6 years - 1971, 1974, 1980, 1985, 1998 and 1999. It resulted in excessive soil dampness, degraded plant development rate, flooding over or partly flooding of arable lands, development of weeds, crops to lay, potato to root, disturbances in potato ridging as well as in other field activities and haysel (Table 1).

In July the range for optimal precipitation varied between 62-102 mm, which corresponds to 76-124% of the standard (1971-2000). The values within this range were recorded for 14 years: 1972, 1973, 1976, 1979, 1984-1990, 1993, 1998, 1999. Precipitation lower occurred in 8 years: 1971, 1978, 1982, 1983, 1991, 1992, 1994 and 1995 and contributed to the following ecological and economical results in agriculture: atmospheric drought turned into a soil one – in years 1992 and 1994 reaching the level of catastrophic soil drought, deteriorated maize and cultivated root crops visible as beetroot withering and drying potato herbage, poor regrowth and bad state of pastures that quite frequently led to terminating cattle grazing, damage in orchards, disadvantageous field works, delayed sowing and sprouting after crops. Precipitation higher than the values from the optimal range were noted on years 8: 1974, 1975, 1977, 1980, 1981, 1996, 1997 and 2000 and the month was found excessively wet. It resulted in soil over-dampness, crop destruction by wet weather, crops layering, weeds development, delayed rape and crops ripening, impeded mechanical cultivation and protection practices for root crops plants cultivation, potato rooting, damage to orchards, terminated cattle grazing and floods, especially in years 1980, 1981 and 1997 and 2000 (Table 1).

In August the values for optimal precipitation over the area of Poland tend to vary within the limits 58-89 mm, i.e. 87-133% of the standard (1971-2000). Such values were recorded in 14 successive years: 1974, 1976, 1979-1981, 1986, 1987, 1990, 1991, 1993, 1995, 1997, 1998, 2000. Lower precipitation was recorded in 11 years: 1971, 1973, 1975, 1982-1984, 1988, 1989, 1992, 1994 and 1999, which as dry years caused the following: potato herbage and sugar beet leaves withering, impeded processes of forming potato tubers and roots growth of sugar beet, shortening of potato vegetation period, restrained regrowth and termination of cattle grazing, reduced growth of maize green mass, disadvantageous skimming, poor after crops, delayed sowing and sprouting of rape. In years: 1972, 1977, 1978, 1985 and 1996 precipitation in August overdid the needs of the major cultivated crops. It led to crops laying, grain sprouting in ears, prolonged period for crops harvesting and hindrance for applying harvesting machines, necessity to dry wet crops, potato blight outbreak, potato putrefaction, pastures softening and flooding, hindered or even terminated field works and floods, especially in 1977 and 1985 (Table 1).

In September in 16 years out of the studied 30, namely in 1971, 1973, 1974, 1976, 1977, 1979, 1980, 1983, 1986-1988, 1993, 1994, 1997, 1998 and 2000, the recorded precipitation fell within the optimal precipitation range, so negative results due to neither deficiency nor excess were recorded. The optimal precipitation varies within 44-67 mm, which contributes to 77-118% of the standard (1971-2000). In 6 dry years: 1975, 1981, 1982, 1989, 1991, 1999 with precipitation lower then the optimal the ecosystems suffered their negative results such as: an atmospheric drought turned into the soil one, reduced plant rate development, especially in grasslands, rape and after crops, shortened vegetation period for maize, adverse conditions for harvesting root and fodder plants, impeded field works, winter crops sowing and their delayed sprouting. The remaining 8 years were the wet ones: 1972, 1978, 1984, 1985, 1990, 1992, 1995, 1996 and the following excessive-precipitation-related negative results were reported: over-dampness of soil, impeded plants rate development, disadvantageous finishing of the delayed harvest, grain sprouting and seed shattering, necessity to dry the crops, delayed maize ripening, impeded process of sugar accommodation in sugar beet, potato tuber putrefaction, hindrances in root crops harvest, hay harvest, impeded field works, especially sowing winter crops (Table 1).

In October the optimal precipitation varies within the limits 31-60 mm, which corresponds 70-136% of the standard. The values from this range were recorded only for 12 years: 1971, 1973, 1976, 1977, 1983, 1986, 1987, 1989, 1991, 1992, 1996 and 1999. Insufficient precipitation, below these values, were recorded in: 1972, 1979, 1982, 1984, 1985, 1988, 1990, 1993, 1995, and 2000, and resulted in reduced water resources in soil, deteriorated pastures, disadvantageous conditions for field works, delayed winter crops sowing and sprouting, as well as harvesting root crops. Precipitation higher than the optimal ones occurred in 8 years, namely 1974, 1975, 1978, 1980, 1981, 1994, 1997 and 1998 and apart from over-excessive soil dampness, they caused hindrances in field works, especially in harvesting root and fodder plants, potato rotting, delayed winter crops sowing and sprouting, terminated cattle grazing at pastures, over-growth of winter crops. Moreover, it created also adverse conditions for plants hardening (Table 1).

In November the precipitation within the optimal range, i.e. 35-46 mm, which corresponds to the standard range of 85-112%, were recorded in 16 years: 1971, 1972, 1974, 1976, 1983, 1988-1992, 1995-2000. Reduced soil dampness in years: 1975, 1982, 1984, 1985, 1986, 1993 caused deterioration in winter crops and constraints for winter tillage. Precipitation higher than the standard value was recorded 8 times in years: 1973, 1977-1981, 1987 and 1994. They caused excessive soil dampness, ice to create whenever temperature fell below zero, over-growth of rape. It prevented maize and sugar beet from being harvested in full, created adverse conditions for winter crops hardening, caused potato to rot, hindrances for late winter tillage and floods (Table 1).

In December the range for optimal precipitation can be drafted between 32-49 mm, i.e. 76-117% of the standard. Such precipitation was recorded for 18 years: 1971, 1973, 1975, 1976, 1978, 1980, 1983, 1986-1992, and 1997-2000. Lower precipitation, observed for 5 years: 1972, 1982, 1984, 1995 and 1996 caused not only soil dampness deficiency, under-growth and under-develop in plants, but foremost frost-damage and plants scorching. Excessive precipitation was recorded for 7 years: 1974, 1977, 1979, 1981, 1985, 1993 and 1994, and resulted in creating marginal lakes, crop destruction by wet weather, and with no snow cover or frequent temperature drops – freezing the top soil layer and thus ice cover forming, reduced plants winter hardiness, and with occurrences of rain a and temperature drop below 0 °C – also frost damage to plants (Table 1).

Over the studied period a systematic raise in air temperature was recorded [2]. To check that due to increased evapotranspiration and reduced soil dampness, it has already caused over the studied 3-decade period the optimal precipitation range to increase, the optimal precipitation values for the 2 subsequent 1.5-decades, 1971-1985 and 1986-2000, were compared (Table 2). To widen the data scope the values compared originated actually form periods 1971-1990 and 1981-2000. It was assumed, following Kożuchowski and Żmudzka [2], that the air temperature within the area of Poland, between the two compared 15-yers periods increased by 0.5 °C. The performed research allowed to conclude that regardless the monthly variations, the optimal precipitation values increased on average by 3 mm. With the assumed scenario for temperature raise by 1 °C, the optimal precipitation over an average month of a vegetation period (April to October) will thus rise by 6 mm, which is in full correspondence with calculations performed while applying other methods, as well as the research performed by others [3,4].

DISCUSSION AND CONCLUSIONS

The performed analysis have revealed that the reports on ecological and economical results delivered by agricultural agencies allow to determine months of insufficient, standard (optimal) and excessive precipitation. Thus, it made possible to compare the average precipitation range within the percentage of the standard between 76-125% [1] to the rains of optimal precipitation which causes no negative effects in agroecosystems. Summarising, it can be noted that over the concerned periods the optimal precipitation fall, by agricultural and ecological standards, within the limits 79-125%. If minor differences between particular months are disregarded, the precipitation deficiency starts a bit quicker since at precipitation totals below 79% of the standard, instead of 75%. The upper limit of the optimal precipitation, i.e. 125% of the standard, overlaps the upper limit of the standard precipitation by Kaczorowska (1962). Differences in optimal precipitation range for particular months have been reported above while providing the characteristics for each month, as well as in Table 1.

The performed research has led to the following conclusions:

1. The effects of deficient and excessive precipitation are manifested not only in extreme years, but also in years when the deviation from the standard precipitation is not that significant, on average with monthly total precipitation lower and higher than the standard by 21% and 25%, respectively. The precipitation deficiency is quickly noticeable for May, the month at which negative results of insufficient precipitation start to be demonstrated at precipitation lower than the standard one by 14%. Regional dependencies of the studied phenomena requires further detailed research.

2. With the assumed scenario for the temperature rise by o 1 °C, the increase in the value of optimal precipitation can be estimated for the vegetation period to the order of magnitude of 6 mm over the month.

REFERENCES

1. Kaczorowska Z.; 1962. Opady w Polsce w przekroju wieloletnim. [Precipitation in Poland over long term profile]. Pr. Geogr., IG PAN; 33; 1-102 [in Polish].

2. Kożuchowski K., Żmudzka E.; 2001. Ocieplenie w Polsce: Skala i rozkład sezonowy zmian temperatury powietrza w drugiej połowie XX wieku. [Warming in Poland: scale and seasonal distribution of changes in air temperature over the 2^nd half of the 20^th century]. Prz. Geof.; XLVI; 1-2; 81-90 [in Polish].

3. Press H.; 1963. Praktika selskochozjajstwiennoj melioracji. [Practical melioration at farmsteads]. Moscow [in Russian].

4. Ziernicka A.; 2004. Globalne ocieplenie a efektywnosc opadów atmosferycznych. [Global warming versus precipitation efficiency]. Acta Agroph.; 3 (2); 293-397 [in Polish].

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