VARIABILITY OF POTATO YIELD AND ITS STRUCTURE IN ORGANIC AND INTEGRATED CROP PRODUCTION SYSTEMS

Barbara Sawicka¹, Piotr Barbaś², Jan Kuś^3
1 Department of Plant Production, Agricultural University of Lublin, Poland
² Jadwisin Department of Potato Agronomy, Institute of Plant Breeding and Acclimatization, Radzikow, Poland
³ Department of Systems and Economics of Crop Production, Institute of Soil Science and Plant Cultivation, Puławy, Poland

ABSTRACT

The study was based on a field experiment carried out over 2000-2002 at the Osiny Experiment Station of Puławy Institute of Soil Science and Plant Cultivation (IUNG) on a good rye soil suitability complex. The aim of the study was to estimate the variability of tuber yield and its structure of 5 selected potato cultivars (Baszta, Wolfram, Ania, Salto, Wawrzyn) in integrated and organic production systems. In each system different crop rotations and agronomic technologies were used. In the integrated system (potato spring barley faba bean winter wheat + white mustard as a catch crop) nitrogen, phosphorus and potassium fertilization balancing the intake was applied at an amount of 110 kg N, 60 kg P and 60 kg K per ha. Compost in a dose of 35 t·ha^-1 was applied only once in the rotation – under potato. Chemical plant protection measures were applied using agrophage infestation threshold. In the organic system (potato spring barley clover with grass utilized for 2 years winter wheat + white mustard and spring vetch as a catch crop) no mineral fertilizers and pesticides were used except for Novodor and Permasect preparations against Colorado potato beetle. Only 2-year old compost (straw + red clover + addition of stable manure) at an amount of 35 t·ha^-1 was applied under potato. Weed control in this system involved harrowing with a weeding harrow till emergence, 3-fold hilling and a single manual weeding shortly before the last hilling. Cultivation systems had the strongest effect on the share of commercial tubers and tubers of a diameter of 4-6 cm in the total yield, cultivar features – on the share of commercial tubers in the yield, and habitat conditions – on the total tuber yield. The stable cultivars proved to be as follows: Wawrzyn – in respect of total yield, Salto – regarding the share of commercial tubers in the total yield, Ania – in terms of the share of the smallest tubers in the total yield and the commercial yield.

Key words: potato, crop production systems, cultivars, yield and its structure.

INTRODUCTION

Numerous quantitative and qualitative features of potato are conditioned not only genetically, but also environmentally. Most important causes of that variability are seed-potato quality (health, size, storage method) [13,17,22,24,29], unevenness of soil environment (soil variability, pH) [3,4,16,18,19], diversity influence of weather conditions such as precipitation, air humidity, temperature and light (wavelength, intensity and duration) [1,2,3,18]. Diversification of the environment where potato is grown results in modification of inner regulation processes, both within a plant and the stems of potato. According to Sawicka [20] the usefulness of plant products depends mainly on the genetic potential of the cultivars, the environment conditions where they are produced and stored as well as the processing methods. The products should also be free of metabolites of pathogens and pests so as to be useful in food production. This requirement is regulated by the act on health conditions of food and nutrition of 2003, in accordance with the UE 93/43 Directive.

Depending on the amount of industrial means of production used, particularly fertilizers and crop protection preparations, three farming systems are currently distinguished in agriculture: conventional, integrated and organic (ecological) [21]. Integrated agriculture, according to Kus [8], is a system using biological and technological progress in cultivation, fertilization and plant protection in a harmonious way; so it combines economic purposes with ecological ones. Organic farming is a crop production system in which the application of synthetic mineral fertilizers, pesticides, growth regulators and synthetic fodder additives is excluded. It is characterized by a closed production cycle: soil plant animal, retaining high self-sufficiency. Ecological purposes predominate here over economic purposes [7,8].

The current task of breeding is to introduce cultivars suitable for a given production system. To orient the breeding of a given species properly, it is essential to get to know the range of variability and interactions between features both in a given year and among different years. Features that are economically important should be subject to such investigation. That is why the aim of the study was to estimate the variability of tuber yield and its structure in selected potato cultivars in integrated and organic cultivation systems, which will facilitate the selection of cultivars with the highest stability of a desired feature, especially for organic system.

MATERIAL AND METHODS

The results of the research were based on a field experiment carried out over 2000-2002 at the field experimental station at Osiny on heavy loamy sands of very good rye complex, with a slightly acid reaction (pH 5.5 in KCl). The factors of the experiments were plant cultivation systems, i.e. integrated and organic as well as five potato cultivars: semi-early – Baszta, semi-late: Ania, Salto and Wolfram and late – Wawrzyn.

Different crop rotations and production technologies were used in each system. In the integrated system (potato spring barley faba bean winter wheat + white mustard as a catch crop) nitrogen, phosphorus and potassium fertilization, compensating the intake, was applied at the amount of: 110 kg N, 60 kg P, 60 kg K·ha^-1 and compost – in a dose of 35 t·ha^-1. Control of a number and weight of weeds in the integrated system involved the following mechanical practices till emergence: harrowing with a weeding harrow, single hilling and earthing-up, and shortly before potato emergence Afalon 450 SC was applied at the dose of 2 dm³·ha^-1, while after emergence (at the stage of 15-20 cm plant growth) – Fusilade Super 125 EC (2 dm³·ha^-1). Chemical pesticides were applied using agrophage infestation thresholds. Colorado potato beetle was controlled using the preparations: Buldock 0.25 EC (0.25 dm³·ha^-1) and Bancol 50 WP (0.4 kg·ha^-1), and potato blight – with fungicides, such as: Dithane M-45 80 WP, Acrobat MZ 69 WP, Curzate M 72.5 WP, Tattoo C 750 SC and Brestanid 502 SC. (Table 1). A decision about the need for applying agrochemicals was made on the basis of observation of a threat to the plantation with Colorado potato beetle and potato blight, as well as on the grounds of PIORiN (Plant Health and Seed Inspection) announcements.

In the organic system (potato spring barley clover with grass utilized 2 years winter wheat + white mustard and spring vetch as a catch crop) mineral fertilizers were not used and of pesticides only the preparations Novodor 02 SC and Permasect 250 EC against Colorado potato beetle were applied. The choice of an insecticide, especially in this system, was determined by an intended utilization of protected potato cultivars, a development stage controlled of a pest and ambient temperature. The preparation Novodor is a biological insecticide where the active substance is Bacillus thuringiensis ssp. tenebrionis (H serotype 8a8b, strain NB-176). Permasect (made by Mitchell Cotts Chemicals Ltd, license no. Tox-190/80) is a low-toxic insecticide with contact and nutritive action with permetrine as an active substance. Only 2-year old compost (straw + red clover + addition of stable manure) at the dose of 35 t·ha^-1 was applied under the potato. Control of weed infestation in this production system involved harrowing with a weeding harrow till emergence, 3-fold hilling and a single hand-weeding shortly before the last ridging. The experiment was conducted on all the plots simultaneously. Each plot had an area of about 1 ha. Detailed data concerning cultivation in both farming systems are presented in Table 1.

* potato spring barley faba bean winter wheat stubble crop (white mustard) ** potato spring barley red clover + grasses winter wheat stubble crop (white mustard + spring vetch)

Tuber samples were taken at the harvest time in three replications from each combination to determine the yield and its structure according to fractions: < 4 cm, 4-6 cm and > 6 cm in diameter. Tubers with a diameter > 4 cm were regarded as the commercial fraction.

The results of the study were statistically verified with variance analysis. The significance of variability sources was tested with the “F” Fischer-Snedecor test, and the significance of differences between the means compared was estimated with the Tukey multiple range test. To determine the percentage of particular variability sources and their interactions in the total variability of the features tested, variance components were estimated using the following notations:

• σ_e² – estimation of environmental variability for observation or measurements in time,

• σ_G² – estimation of genotypic (cultivar) variation,

• σ_p² – estimation of phenotypic (total) variation.

Empirical values of mean squares obtained from variance analysis were compared with their expected values. Solving systems of equations allowed to obtaining the estimation of variance components corresponding to particular variability sources. Mutual relationships of the determined estimations of variance components and their structure were the base for the evaluation of the effect of a cultivar factor and years on the variability of tuber yield and yield structure characters. Variation coefficients of each feature were also calculated according to the formula:

V =

where:
S – standard deviation,
x – arithmetic mean.

The course of air temperature and precipitation intensity over vegetation period varied in the years of research. The year 2000 was warm and humid, favorable for the development of Phytophthora infestans; the year 2001 was characterized by a moderate amount of precipitation and air temperature at the level of the multi-year average, while the year 2002 was marked by substantial precipitation shortage during vegetation and air temperature higher than the multi-year average (Table 2).

** ecological crop production systems *** integrated crop production system

RESULTS

The total average tuber yield amounted to 32.7 t·ha^-1 and ranged from 26.8 t·ha^-1 – in the organic system, to 38.6 t·ha^-1 – in the integrated system (Table 3). The potato grown in the organic system proved to be more stable in yielding than those in the integrated system, which indicates the higher water requirements of plants in the integrated system. A significant difference in the total yield occurred between the late cultivar Wawrzyn and the semi-early cultivars: Baszta and Wolfram, as well as the semi-late cultivar Ania, while Salto and Wawrzyn as well as Ania, Wolfram and Baszta, proved to be homologous groups. Wawrzyn and Salto found themselves in the group of cultivars with high yield, while the other cultivars were characterized by average yield. The cultivars Wawrzyn and Salto also turned out to be the most stable in yielding, while the most changeable one was Wolfram, which can indicate higher water and soil requirements of this cultivar.

An approximation of the total yield and the number of shoots per plant showed that the tuber yield was linearly, negatively correlated with a number of stems (Fig. 2).

There was observed the largest share of tubers of a diameter 4-6 cm, and the smallest one – of diameter < 4 cm in the total tubers yield (Table 4). Farming systems modified the share of tubers all size fractions. The share of tubers < 4 cm in diameter in both cultivation systems was similar. A significant difference among the cultivation systems occurred within the fraction 4-6 and > 6 cm. In the organic system predominated fraction of tubers with a diameter of 4-6 cm, while in the integrated system – the fraction of the largest tubers.

Within the fraction of tubers with a diameter < 4 cm, the semi-early cultivar Baszta was distinguished by a remarkably largest share in yield and the semi-late Salto – by smallest. The variation coefficient of this tuber size fraction was highest of the estimated elements of yield structure and it was on average 57.3%. According to the smallest tubers in the yield, the most stable cultivar turned out to be the semi-late Ania, and the least stable – the semi-early Baszta As regards the share of the smallest tubers in yield, the semi-late Ania proved to be most stable, while the semi-early Baszta – the least stable one (Table 5). Tuber fraction 4-6 cm in diameter made a rather homogenous group. Small differences occurred among more and less early-ripening cultivar groups, as well as within them. The cultivars Ania and Baszta, where the share of the tubers of this fraction was almost 55.0% in both of them, proved to be homologous group. Also Wawrzyn (48.6%) and Wolfram (50.1%) turned out to be homologous as regards this feature. Salto cultivar was marked by the smallest share of tubers 4-6 cm in diameter (45.4%). Variation coefficient of this fraction was on average 30.7%. Its highest value was noted for Wolfram (32.5%), while the lowest – for Salto (24.9%) cultivars, which means that Salto was the most stable in respect of the percentage of tuber weight of the above diameter. Large tubers, with a diameter more than 6 cm, constituted on average 41.6% yield weight. They differed both among cultivar groups, and within the groups of early and late-ripening cultivars. Semi-late and late cultivars were marked by a higher share of tubers of that fraction than semi-early ones. The cultivar with the highest share of these tubers in the yield was Salto (50.6%), while Baszta was marked by their lowest share (31.7%). The most stable cultivar in respect of the share of large tubers in the total yield, turned out to be the Salto (V = 24.7%), and the most changeable – Ania (V = 59.7%).

The share of commercial tuber weight in total yield was 92%, and depending on weather conditions in the years ranged from 88.4% to 96.4% (Table 6). The cultivation system did not affect significantly this feature values. Only in 2001 the share of commercial tubers was significantly higher in the integrated system than in the organic system. This feature was formed significantly by a cultivar factor. Salto turned out to be the cultivar with the largest share of commercial tubers, while Baszta – with smallest. Within the tested cultivars two homologous groups can be distinguished: Baszta and Ania, as well as Wolfram, Salto and Wawrzyn. Salto was the most stable cultivar in the share of commercial tubers (V = 24.8%), while Ania was the most changeable (V = 44.3%). Not all the cultivars showed a significant reaction to the cultivation systems. Only in Wolfram and Baszta the increase in the share of commercial tubers weight was observed in the integrated cultivation system.

The commercial tuber yield was on average 30.4 t·ha^-1 and depending on weather conditions during vegetation ranged from 26.6 to 34.8 t·ha^-1 (Table 7). The integrated crop production system, using organic and mineral fertilization, based on soil fertility and also plant protection, increased commercial tuber yield by 11 t·ha^-1, as compared with the organic system. Genetic features of the cultivars tested, irrespective of the cultivation system, modified also the commercial yield. The late cultivar Wawrzyn gave the highest commercial yield, and the semi-early Baszta – the lowest. The cultivars Wolfram, Ania as well as Wawrzyn and Salto turned out to be homogenous group. The cultivar yielding varied in the successive years of the research. In the year when the total precipitation was sufficient for potato, the most productive was Salto, while both in the humid year and the dry one – it was the late Wawrzyn which could still use September and October rainfall. The most yield-stable cultivar was Ania, and the most changeable – Salto.

The analysis of variance components showed that the tuber yield obtained in the experiment was to the highest degree dependent on the interaction between cultivars and cultivation systems (33.8%) as well as the weather conditions in particular years of the research (32.1%), and to a considerably less degree on: cultivation systems (10.3%), the interaction between cultivars and years (7.3%), between cultivars, years and systems (6%) and the interaction between systems and research years (5.2%) (Table 8). The share of the tuber weight of size < 4 cm in total yield variability was to the highest degree dependent on the interaction between systems and years (50.5%), and to a lesser degree on systems (19.3%) and cultivars (15.8%). The percentage of years in the total variability amounted to 6.2% and the interaction between cultivars and cultivation systems – 6.3%. The interaction between cultivars and years as well as cultivars, years and systems were within the 1.6-0.3% range and it had no major influence on the total variability of the fraction of tubers < 4 cm. The fraction of tubers with a diameter of 4-6 cm in total variability was similarly dependent on cultivars (21.1%), cultivation systems (21.3%) and the interaction between cultivars and years (22.5%). The interaction between cultivars, years and systems made 11.4% of total variability, and the interaction between systems and years had the least effect on the share of tubers with a diameter of 4-6 cm (1.1%). As for the largest tubers in the yield, the share of variance components in the total variability was dependent to the largest degree on the interaction of systems and years (58.7%), and later on the cultivars (13.5%) and years (11.6%). Interaction of cultivars and systems as well as of cultivars, years and systems was not of a great importance to shaping the total variability of tubers of this size. The cultivation systems were distinguished by the largest share of the total variability of this feature (40.1%). The share of genotypic variation in the total variability of commercial tuber participation amounted to 31.3%. The interaction of cultivation systems and years diversified this feature in 18.2%, while the other variance components did not have a substantial part in the total variability. Determination of the variance components allowed to establish that tuber commercial yield was to the highest degree dependent on the interaction of cultivation systems and years (47.7%), and to a lesser degree on systems (21.0%) and cultivars (14.3%), while the other variance components did not have a major effect on this feature.

DISCUSSION

Most analyzed features, being significant for plant productivity, are subject to a large phenotypic variation depending on the effect of various habitat and genotypic factors [5,11,12,18,19,25,23,27,30]. Although potato yield in Poland cannot be compared with those in West Europe countries, mainly due to different climatic conditions, certainly could be much higher. According to Mazurczyk [10] potential potato yield in Poland amounts to 74 t·ha^-1. Michałek et al. [12], evaluated the potential yield of very early potato cultivars in the eastern part of Poland at 52 t·ha^-1. In the present studies the yield of semi-late cultivars was little lower than the potential one obtained in this part of Poland. In the study by Michałek et al. [12], semi-late and late potato cultivars registered obtained a mean Y_A/Y_P value (the ratio of mean potential yield to mean current yield) of 0.78, which is a little lower than that obtained in Dutch agriculture [28]. As far as yield stability is concerned, the tested cultivars can be arranged in order as follows: Wawrzyn > Wolfram > Ania > Baszta > Salto. For the tuber total yield, the value of variation coefficient varied, depending on the cultivar, from 12.2 to 16.8%. A relatively low variation coefficient of these cultivars indicates their high yielding stability and thus their high usefulness for organic production. There have been few such studies in Poland that is why the results are essential for organic farms growing potato for consumption.

The share of genotypic variation in the total variability ranged from 1.3 to 31.3%, depending on the feature analyzed. The cultivars had the largest effect on the share of commercial tubers. A big effect of genetic factors on this feature is supported by the research by Wurr and Allen [26], Yildirm and Cliscan [27], Sawicka [19], as well as Zimnoch-Guzowska [30]. Environmental factors had a decisive influence on the total tuber yield as well as the share of tuber weight of all size fractions. A significant influence of the environment on these features of yield and its structure was confirmed by Wurr and Allen [26], Keller and Baumgartner [5], Yildrim and Caliscan [27], Sawicka [19], Sawicka and Pszczółkowski [22].

The structure of tuber yield turned out to be not stable enough, and components of phenotypic (total) variation were different. This resulted from different course of weather conditions, particularly the uneven distribution of precipitation from May to August, deciding about the size and amount of tubers of particular fractions. The interaction of systems and years had a predominant part in the tuber variability of all the size fractions (1.1-58.7%). The share of genotypic variation in the total variability was from 11.6 to 21.1%, and the interaction of cultivars and years – from 1.6 to 22.5%. The effect of the environment on the yield structure was confirmed by MacKerron et al. [9], Sawicka [19] as well as Sawicka and Pszczółkowski [22].

One of the causes diversifying tuber weight of particular fractions in yield is competition among stems on a plant; the competition for photosynthetic products among particular stolons growing from nodes made at different levels of stem underground parts [17]. Pytlarz-Kozicka [15] indicated that the cultivars of longer flowering period are characterized by a larger number of shoots, leaves and tubers per plant and a larger number of shoots per area unit, as well as a larger aboveground part weight and less tuber weight, while at harvest time they have bigger stalk and tuber weight than very early cultivars. Competition among germs and the predominance of the apical germ, the main bud, can influence a number of stems per plant and the competition among them, and this affects tuber size in yield [9,26,27]. Sawicka [18,19] confirms the effect of genotypic characters on the features of yield structures. Cultivation systems (V = 13.8-21.3%) had a substantial share in shaping the yield structure. A large effect of a cultivation technology on this character is supported by MacKerron et al. [9], Mikołajko and Jabłoński [13], Sawicka [19] as well as Sawicka and Pszczółkowski [22] reports.

As for stability of tuber weight share in the yield, size fractions analyzed were put in order as follows: 4-6, > 6, < 6 cm, from which it appears that the share of the largest tubers in the yield was the most changeable feature, and that of commercial fraction tubers was the least changeable. In the research by Sawicka [19], the most stabilized feature of yield structure turned out to be the fraction of tubers 4-5 cm in diameter, and in the research by Wurr and Allen [26] – they were the tubers with a diameter of 3-4 cm.

The commercial tuber yield turned out to be a not very stable character. As regards this feature, the most stable proved to be Ania (semi-late) and Wawrzyn (late) cultivars. According to MacKerron et al. [9] and Sawicka [19] this feature is not very stable and mainly of cultivar character [11]. Kopcewicz and Lewak [6] report that each cultivar produces assimilates in its individual way. With the growth of a leaf blade, a reduction in nutrients supply to tubers occurs, which results in decreasing Fo level (the level of the minimum fluorescence gain). According to Puła et al. [14] the level of Fo depends mainly on the genetic properties of cultivars, and the maximum photosynthetic efficiency occurs when the area of a leaf blade already achieves the minimal size, and then it decreases together with the growth of a leaf blade. Sawicka [19] proved that there is relationship an increase in dry matter content and an increase in the number of sunny hours and the temperature in July and August.

CONCLUSIONS

1. Cultivation systems and cultivar characters enhanced mostly the share of commercial tubers, whereas habitat conditions – the total tuber yield.

2. The genetic factor determined the phenotypic variation of potato characters in the following order: the share of tuber weight of Ø > 6 cm > the share of tuber weight of Ø < 4 cm > commercial tuber yield > the share of commercial tuber weight > total tuber yield > the share of tuber 4-6 cm weight.

3. The interaction of systems and years had the strongest effect on the share of weight of the tubers with a diameter > 6 cm and <4 cm as well as tuber commercial yield, while it had the least effect on the share of tuber weight 4-6 cm in diameter.

4. The interaction of cultivars and farming systems affected mostly the total tuber yield and the percentage of tubers 4-6 cm in diameter, while the interaction of cultivars and weather conditions in the years of study – the share of tuber weight 4-6 cm in diameter.

5. Of the compared potato features, the share of commercial tubers was distinguished as the most stable, while the share of the largest tubers in the yield was the most changeable.

6. The stable cultivars proved to be Wawrzyn – in total yield, Salto – in the share of commercial tubers in the total yield, Ania – in the share of the smallest tubers in the total and commercial yield.

7. In central-eastern Poland, the semi-late cultivar Salto appeared to be the most useful for ecological farming, due to total and market yields as well as a high stability of the yield desirable features.

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Accepted for print: 30.12.2006

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