THE INFLUENCE OF THE ACTIVITY OF THE EUROPEAN MOLE TALPA EUROPAEA L. ON THE DENSITY

Ewa Żurawska-Seta
Department of Zoology, University of Technology and Life Sciences in Bydgoszcz, Poland

ABSTRACT

The main aim of this study is to assess the influence of digging activity of the European mole Talpa europaea L. on the density of winter triticale, winter barely, spring oat and winter rape. Research was carried out in 2005–2007. Study plots were located on three arable fields – up to 60 microplots about area of 1m², in 30 investigative pairs on each field. The study has shown that digging activity of the mole affected the density of plants in winter rape crops. However, there were not significant effects of the mole's activity on the density of seedlings in winter cereal crops and spring oat crops.

Key words: the European mole Talpa europaea, cereal crops, winter rape crops, density of crop plants.

INTRODUCTION

The European mole Talpa europaea L. is one of the most common mammals inhabiting arable fields, meadows, pastures, gardens, parks and forests, especially mixed and deciduous forests and is rarely presents in the coniferous forests.

It is often regarded as a pest, therefore many scientific studies were devoted to issues of the possible control of the number of population of this species or the reduction of its activity [1,2,5,6,8,21,23,26].

The most visible effect of the mole's presence and activity on a given area is the occurrence of molehills which can bury cultivated plants. The most sensitive for burying are cereal seedlings in stage 1–3 leaves. But it is worth remembering that the winter surviving by cereal crops depends on the development and condition of winter crops in autumn. The winter rape is less cold-long-lasting than winter cereal crops. The wintering of the winter rape is also directly connected with a strong rosette of leaves and well developed root system created by plants during autumn.

The main aim of this study is to evaluate the impact of the digging activity of the European mole, recognized as molehills disposing on the ground surface, on the density of chosen crop plants on an early stages of development.

STUDY AREA

Fieldwork was carried out in 2005-2007, within cereal crops like: winter barley (Hordeum vulgare L.), winter triticale (Triticosecale Wittm.), spring oat (named also common oat Avena sativa L.); and within winter rape (Brassica napus L.) crops.

The investigative plots (so-called microplots) were located on three arable fields (P1, P2 and P3) which were situated in the vicinity of a round about small village called Warcino, in the commune Kępice, (pomorskie voivodship), on the soil classified as the rye good soil complex. According to the natural-forest regionalization, this area is located in The First Baltic Land (I Kraina Bałtycka), in The Fifth Drawsko-Kaszubski Lake District (Dzielnica 5 Pojezierza Drawsko-Kaszubskiego), in the range of mezo-region Wysoczyzna Polanowska, which is included in a Lake District of Zachodnio-Pomorskie (Pojezierze Zachodnio-Pomorskie). It is situated in the river basin of Wieprza River [15,22].

Considering climatic conditions, the study sites are located in the range of the type of the lake district climate, in the Bytowski District, with moderate temperature during summers and mild winters with an impermanent and quicklyy disappearing snow cover. The average annual temperature of air ranges from +6.8°C to +7.4°C. The vegetation season goes on for about 200 days per year, and temperature below 0°C lasts about 97 days every year. The annual amount of fall is about 543 mm [19,20].

Crop rotation in an individual farmlands in 2005–2007 was as follows:

• P1: winter rape (Brassica napus L.) – winter barley (Hordeum vulgare L.) – winter triticale (Triticosecale Wittm.);

• P2: common oat (Avena sativa L.) – winter triticale (Triticosecale Wittm.) – winter rape (Brassica napus L.);

• P3: winter triticale (Triticosecale Wittm.) – winter rape (Brassica napus L.) – winter triticale (Triticosecale Wittm.)

MATERIAL AND METHODS

60 microplots were chosen in 30 investigative pairs on each field, an area of about 1 m² every microplot. The microplots were selected in a way that in the centre of one microplot from every investigative couple was one molehill of average size with the diameter of about 240 mm and about 150 mm length [12,13,27,29]. In contrast, the second microplot in investigative couple was without molehills. Microplots in pairs bordered each other.

The density of molehills in the study area ranged from about 6 to 10 molehills per 1 ha, but it is worth pointing out, that molehills were concentrated mainly in the neighbourhood of fields' boundaries – especially up to 10 m from the edges to the centres of every farmland. Although, it would be possible to find two or even three molehills on 1 m², the situation was very rare. Therefore, it was decided to choose microplots with one molehill only, because this situation was much more popular [29].

The estimation of number of plants was based on the direct counting of undamaged seedlings. In the case of winter cereal crops the counting of plants number was made in 3 – leaves stage during the autumn vegetation period and in the cultivation of the spring oat it was made in spring. In cultivations of the winter rape the estimation was held in autumn, when the plants were in phase 4–6 leaves.

Gathered data was statistically analysed using Statistica 6.0. Standard techniques of data analysis and methods of statistical concluding were used. Firstly, it was checked if the samples are normally distributed by using Shapiro-Wilk test. Then, comparisons of series of results concerning plants number between microplots in pairs were made using t-Studnet's test for tied pairs. Significance of statistical tests was assessed at α = 0.05 [14,17,24,25].

RESULTS

The number of plants in cultivations of winter barley ranged from 286 to 320 seedling per 1 m² (±SD = 8.44) within microplots with one molehill and from 286 to 315 seedling per 1 m² (±SD = 7.97) within microplots without molehills (Fig. 1). In cultivations of winter triticale it was from 291 (Fig. 3) to 354 (Fig. 5) plants per 1 m² in microplots without molehills and from 285 (Fig. 3) to 340 (Fig. 2 i 4) seedling per 1 m² in microplots with one molehill. There were not statistically significant differences (t-Student's test; p > 0.05) in the number of seedlings between microplots with one molehill and microplots without molehills in cultivations of winter triticale and winter barley (Table 1).

In cultivations of spring oat the minimum number of plants per 1 m² was 354 seedlings (±SD = 13.65) within microplots without molehills and 360 seedlings (±SD = 11.64) within microplots with one molehill. The maximum number of seedlings was 405 plants/m² in microplots without molehills and 400 plants/m² in microplots with one molehill (Fig. 6). There were not statistically significant differences (t-Student's test; p > 0.05) in the number of seedlings between microplots with one molehill and microplots without molehills in cultivations of spring oat (Table 1).

In cultivations of winter rape the plants number ranged from 80 to 102 seedlings/m² (±SD = 6.26) in microplots without molehills and from 75 to 100 seedlings/m² (±SD = 6.72) in microplots with one molehill in arable fields P1 (Fig. 7); from 87 to 107 plants/m² (±SD = 4.70) in microplots without molehills and from 85 to 102 plants/m² (±SD = 4.69) in microplots with one molehill in arable fields P2 (Fig. 8); from 49 to 70 plants/m² (±SD = 6.73) in microplots without molehills and from 44 to 66 plants/m² (±SD = 4.69) in microplots with one molehill in arable fields P3 (Fig. 9).

There were statistically significant differences (t-Student's test; p ≤ 0.05) in the number of seedlings between microplots with one molehill and microplots without molehills in cultivations of winter rape in all three cases – in arable fields P1, P2 and P3 (Table 1). The differences in means of the number of seedlings between individual ploughlands (P1, P2 P3) are connected with the different density of sowing.

DISCUSSION

In cultivations of winter cereal crops like winter triticale and winter barley, but also in cultivations of spring oat there were not statistically significant differences in the number of seedlings between microplots with and without molehill. Thus, it seems that the digging activity of the mole did not have a significant impact on the number of seedlings of cereal crops. And it is worthwhile to underline that this research was conducted during the highest seasonal activity of moles – in autumn and spring. The counting of plants number was made in 3 – leaves phase and in this stage in which the seedlings of cereal crops have the greatest sensitivity on bury. The adequate number of plants is crucial for appropriate growing apace, for the number of grains from the plant and from the ear – therefore, it has an impact for the entire future crop. It has also a great effect on the plant resistance to lodging, diseases and pests [7,10,11,16].

The correct number of seedlings in the cultivation of winter barley should amount to about 300–400 plants/m². Too high density of plants causes an increase in the susceptibility to upfreezing and diseases vulnerability [7,10,16]. The results obtained in this study showed that the density of winter barley seedlings on investigative plots was perfect in both microplots with and without molehills and this density guarantees good condition of plans and abundant harvest.

Similarly, the average density of seedlings per 1 m², in the cultivations of winter triticale and spring oat, was optimum, for used by farmers the density and the date of sowing, in microplots with one molehill and in microplots without molehills as well [10,11,7].

Winter rape, planted in the right date, creates strong rosette of leaves and well developed roots, which have the considerable influence on the proper growing of plants before the winter, their good wintering, and in consequence – on the crop of seeds. The Very important is the density of sowing. The most favourable density of seedlings, recommended by specialists, should ranged from 60 to 120 plants/m², depending on the crop variety and the date of sowing. It is said that in intense technologies it should be about 70 plants per 1 m². It is achieved if there is about 4 kg seeds per 1 ha in use, put in distance of 80–150 mm. In economical technologies, that do not use so many fertilizers and crop protection chemicals, the winter rape has better competitiveness in density such as 100 plants per 1 m². It is achieved if there is about 5 kg seeds per 1 ha. The hybrid varieties sown in the right date, in average soil conditions and with moderate climate conditions, there should be about 60–80 plants per 1 m². However, in better conditions the number of plants per  1 m² should range from 50 to 60, and in less favourable conditions – from 90 to 120. The rarer sowing is recommended at the spot seeding. The thicker sowing has a negative impact on wintering of winter rape. Too high density of winter rape results also in the decrease in the plant resistance to lodging and causes diseases and pests [3,4,18,28].

The density of winter rape in investigative plots was: 91, 99 and 66 plants/m² in microplots without molehills and consequently: 86, 96 and 55 plants/m² in microplots with one molehill (Figs. 7, 8, 9). Even though the differences turned out to be statistically significant (Table 1), the densities, in both microplots with one molehill and without molehills, are located within the limits of the recommended densities. Only in the case of rare sowing, got by the spot seeding of covered seeds, where the average density was about 66 plants per 1 m², the density in microplots with one molehill was lower than optimum. However, the state of the winter rape cultivation still can be judged as good, even at such density. A field is recognised a little bit thinned out when there is about 40 plants per 1 m², although even in those cases the cultivation can be still growing, because the winter rape has great compensating abilities. The winter rape belongs to strongly spreading plants. Low densities allow for bigger spreading of plants and by this the plants can create more shucks. If the winter rape wintering well, the density ranging from 40 to 50 seeldlings/m² can provide a good harvest. The crop depends on the density as well as on the number of branches, the number of shucks and the number and the size of seeds [9,18,28].

Moreover, the mole occupied only 2.4–5 % areas of farmlands [29], thus the influence of moles' activity on the decrease of the winter rape density would concern only a limited area.

CONCLUSIONS

Obtained results showed that the activity of the mole, manifesting itself in disposing of molehills on the surface of the earth did not have a significant influence on the number of seedlings of cereal crops.

In the cultivation of the winter rape there was observed a low number of plants per 1 m² in microplots with one molehill in comparison to microplots without molehills. However, the number of winter rape seedlings was enough to continue the cultivation.

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Accepted for print: 17.11.2010

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