THE EFFECT OF RAINFALL DEFICIENCY ON THE STRUCTURE OF THE HIGH-GROWING TOMATO YIELD GROWN IN THE FIELD

Janusz Suszyna
State Higher Vocational School in Sandomierz, Poland

ABSTRACT

The experiment conducted in the upland part of the Sandomierz region studied the effect of the rainfall deficiency on total, commercial and non-commercial yields of the fruits of high-growing tomato cultivated in the field. Low rainfalls, below the perennial means, occurred in the years 2002–2006 and the obtained results were compared with the values from 2001, which year reflected the average conditions of many years. No effect of low rainfalls on total and commercial yields was observed. In the years deficient in rainfalls, a significantly higher non-commercial yield was obtained where fruits with wrinkled peel dominated. The highest total yield was obtained in the years which were characterized by the highest mean temperature of July.

Key words: tomato, rainfalls, critical conditions, fruit wrinkling.

INTRODUCTION

The possibilities of tomato cultivation follow from climatic conditions and in this respect, tomato is included within thermophilic plants [2,4]. It is said that its cultivation is possible where the mean temperature during vegetation is over 18°C, and the no-frost period is not shorter than 4 months with the July isotherm of 18–19°C [5]. Such conditions are fulfilled in the area of Sandomierz, where a considerable part in the structure of vegetables is made up by high growing tomatoes cultivated in the field on pickets. Tomatoes, especially high growing ones, are included among the vegetables of the smallest sensitivity to drought [6]. However, water availability is a factor decisive of the size and stability of the yielding and the quality features. In the years of extreme values of climatic factors which have been observed lately their remarkable effect on the size of non-commercial yield has been found. This affects profitability and can be also seen in one of the more favourable regions for tomato cultivation, which is the area of Sandomierz [9].

Recent years have been characterized by exceptional deficiency of atmospheric precipitation, with more than average temperature of the vegetation period, which allowed to observe tomatoes in extreme climatic conditions (Table 1). According to Kaniszewski [6], the required rainfalls in the period of tomato vegetation amount to 350–400 mm, and the highest needs occur at anthesis and fruit setting. The moisture of the soil, whose deficit should not exceed -45 kPa, should be ensured to the depth of 40 cm. The years under observation were characterized by considerable deviations from those requirements and they reflect the tendency to climatic changes [7].

The purpose of the paper was to present the reaction of high growing tomato in field cultivation, without irrigation, in the years characterized by deficient atmospheric precipitation to the yield structure and differentiation of the non-commercial yield the weight of which can be considerable from the economic point of view.

MATERIAL AND METHODS

The studies were conducted in the years 2002–2006, when the mean sum of rainfalls of the vegetation period of tomatoes was 254.5 mm and it was considerably lower than the mean value of many years (332.0 mm). A similar deficit was observed in relation to the annual sum of rainfalls. The mean temperature of the vegetation period (17.1°C) was also higher than the many-years' mean value (16.2°C). Therefore, those years were considered as a period of deficient atmospheric precipitation, which was exceptional in the scale of many years (Table 1). The year 2004, despite deficient rainfalls (269.7 mm), was characterized by low temperatures of the vegetation period (15.8°C), which made it difficult to observe the typical effects in the non-commercial yield characteristic of the other studied years. Tomato yielding was related to 2001, when the values of climatic factors were similar to the means of many years.

The studied material was composed of three cultivars of high growing tomato, commonly cultivated in the region of Sandomierz, namely Faustine₁ and Brooklyn F₁ (grown by Syngenta Seeds Ltd.) and Atut F₁ (grown by PHRO of Krzeszowice), which were grown on pickets to one shoot. The studies were conducted in the upland part of Sandomierz, where the last ground frost occurs around 30 April, the temperature of July is 18.8°C and the period without any frost is 258 days [9]. The experiment was set up using the block method in three repetitions, on grey brown soil formed on a deep loess layer, with the mechanical composition of sandy dust (67.0% dust, 27.1% sand) with the 2.6% content of humus in the plough layer and the level of ground waters of about 15 m. The area of one plot was 8 m², where 20 tomato plants were planted on each in the spacing of 0.9 × 0.45 m.

The analyzed features included the total, commercial and non-commercial yields with special consideration of wrinkled fruits which characterized the years deficient in rainfalls. Red, orange and ripening fruits [1]. The obtained results were converted into 1 ha and they were statistically analyzed using the method of variance analysis and Tukey's confidence intervals at the level of significance α = 0.05.

RESULTS AND DISCUSSION

Results of the studies point to significant differences in the total fruit yield depending on the year of cultivation (Table 2). Significant differences occurred between the years of the greatest deficit in rainfalls in the vegetation period and in the annual scale (2003, 2005). This confirms Kaniszewski's [6] opinions on small sensitivity of high growing tomatoes to drought. The highest total yield was obtained in the years which were characterized by the highest temperature in July (2006, 2005, 2002), confirming the opinions of other authors on the decisive influence on July temperature on the success of tomato cultivation [5].

The value of the total yield significantly depended on the cultivar. No significant differentiation of the total yield was observed between the cultivars of Faustine₁ and Brooklyn F₁, which are closely related from the point of view of growing them.

The analysis of the structure of the total yield points to a high proportion of the commercial yield (98.3–99.8%) with a decreasing tendency in the successive years that were deficient in rainfalls (Fig. 1). The highest proportion of the commercial yield was obtained in 2001, when the values of climatic factors were close to those of many years. The years that were deficient in rainfalls (especially 2005 and 2006), which contributed to dry periods, favoured high total yields, with the highest proportion of the non-commercial yield (1.6–1.7%). In 2001, which reflected the conditions of many years, the lowest weight of the non-commercial yield was obtained (0.2 t·ha^-1), while in 2006 – the highest (2.17 t·ha^-1). That is why the obtained weight of the non-commercial yield in the years of deficient rainfalls was significant and should not be indifferent from the economic point of view (Table 3).

In the non-commercial yield, wrinkled fruits dominated over the broken and deformed ones. The structure of the non-commercial yield had an individual character in particular studied years (Fig. 2). Broken fruits dominated in 2001 and 2002, when July and August were characterized by alternating rainy periods and those of high average diurnal temperature exceeding 20°C. Especially July of 2001 was full of rainfalls caused by a local deluge (Table 1).

The fruits with deformations, which constituted the smallest proportion in the non-commercial yield, occurred in 2001, 2004 and 2006, which was related to low temperatures at anthesis and fruit setting of the first cluster (May, June). Broken (87.3%) and deformed (12.7%) fruits dominated in the structure of the non-commercial yield in the lowest non-commercial yield obtained in 2001, which reflected the average conditions for many years in the studied area (Fig. 2).

The year 2002 was conducive to tomato yielding and it was characterized by more than average temperature of the vegetation period, especially in July and August; however, the low level of rainfalls, which were of irregular nature, especially in August and September, influenced the domination of broken fruits in the non-commercial yield (100%). Fruit wrinkling was characteristic of the last 4 years considered as deficient as regards atmospheric precipitation, and their proportion had an increasing tendency in each following year. In 2005, wrinkled fruits constituted 99% of the non-commercial yield, which was favoured by deficit rainfalls in the yearly scale and in the vegetation period as well as by high temperatures of summer months, especially July (mean 20.2%).

The year 2006, due to a high total yield, should be considered as exceptionally favourable for tomato cultivation despite the highest weight of the non-commercial yield (2.17 ha^-1).

The obtained results are similar to those from other studies which do not find any relation between tomato yielding and the sum of rainfalls or the daily mean rainfall, which is due to the relatively well developed root system [9]. Most frequently, the years with considerable irregular rainfalls causing breaking of the fruits and burdensome development of diseases are considered as unfavourable to tomato cultivation. On the other hand, Korzeniewska et al. [8] in the studies on the quality in the conditions of water deficiency in the soil in July found out a decrease of the unit weight of fruits. The effect of tomato reaction to deficit atmospheric precipitation in the vegetation period and in the yearly scale is discussed in the present paper (Photo 1).

Fruits with wrinkled peel were rarely encountered on commercial plantations due to the increased frequency of the harvest in relation to that used in the experiment.

Results of the studies testify to the necessity of introducing irrigation in the field cultivation of tomato in the face of an increasing number of years with extreme weather conditions, even in such a beneficial region of the cultivation of this species as the Sandomierz area. This confirms the opinions that a rational field cultivation should be irrigated and the climate which is difficult to predict causes that tomato cultivation in Poland is unreliable [3].

It can be concluded that elimination of wrinkled fruits in the present experiment through irrigation would enable to reduce the non-commercial yield to the minimum, and as a consequence, improve the quality and the economic effect of the cultivation.

CONCLUSIONS

1. Deficient atmospheric precipitation in the vegetation period and in the yearly scale cause drought but they did not affect the size of the total and marketable yields of tomato.

2. Rainfalls deficit decisively influenced the size of the non-commercial yield and its structure, where the fruit with wrinkled peel dominated.

3. The proportion of wrinkled fruits indicated increasing tendencies in each successive year with deficit rainfalls.

REFERENCES

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Accepted for print: 4.01.2011

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