RESEARCH ON THE OPTIMUMSHAPE AND SIZE OF POTATO RIDGES

Transcription

1 UNIVERSITY OF AGRICULTURAL SCIENCES AND VETERINARY MEDICINE CLUJ-NAPOCA DOCTORAL SCHOOL OF ENGINEERING AGRICULTURAL SCIENCES Eng. VITOS Iván Zoltán RESEARCH ON THE OPTIMUMSHAPE AND SIZE OF POTATO RIDGES (SUMMARY OF PhD THESIS) Scientific Coordinator: Univ. Prof. dr. eng. Gavrilă MORAR Cluj Napoca 2015

2 Contents INTRODUCTION... 2 CHAPTER I THE IMPORTANCE AND USE OF THE POTATO CROP... 2 CHAPTER II GENERAL REQUIREMENTS OF POTATO FACTORS IN RELATION TO VEGETATION FACTORS... 3 CHAPTER III CURRENT STAGE OF THE RESEARCH ON THE OPTIMUM SHAPE AND SIZE OF THE POTATO RIDGE... 4 CHAPTER IV RESEARCH OBJECTIVES AND METHODS... 5 CHAPTER V PEDOCLIMATIC CONDITIONS OF THE RESEARCH PERIOD... 7 CHAPTER VI RESULTS AND DISCUSSION TRIAL RESULTS ON THE RIDGE SHAPE THROUGHOUT THE EXPERIMENTAL CYCLE TRIAL RESULTS ON THE RIDGE SIZE THROUGHOUT THE EXPERIMENTAL CYCLE TRIAL RESULTS FOR THE EXPERIMENTAL CYCLE ON THE INFLUENCE OF PLANTING DENSITY ON TWO POTATO VARIETIES PLANTED IN RIDGES IN A SINGLE ROW AND A DOUBLE ROW CHAPTER VII CONCLUSIONS AND RECOMMENDATIONS SELECTED BIBLIOGRAPHY

3 INTRODUCTION Potato production, according to statistics recently published by FAO (2011), is of global significance, being the 4 th most important food crop according to total production values. Nowadays potato is grown in different production systems in over 140 countries on an area over 19 million hectares, with a total annual production of 368 million tonnes and an average yield of approximately 19 t /ha. Potato will remain a strategically important crop in Romania as well due to being able to ensure food security. Although in recent years there has been a slight increase in the average potato yield produced in our country, there still exist significant reserves to harvest qualitatively and quantitatively superior potato crops in the future. To improve potato cultivation technology, the research aimed to optimize the nutrition space by forming the shape and size of potato ridges, to study planting densities in ridges of different types and conducted on different varieties to obtain the desired tubers used for consumption, industrial purposes or as seed tubers. CHAPTER I. THE IMPORTANCE AND USE OF THE POTATO CROP The first chapter presents the importance and uses of potatoes, the chemical composition of the potato tuber but also the food products obtained through processing. More than 1000 varieties are cultivated worldwide which are used for the following purposes: - consumed fresh and after various processing methods: peeled (fresh or frozen), dehydrated (flakes, flour, slices), par-fried and frozen (pommes frites/ fries) and deep-fried (chips, extruded); - Food and non-food uses (starch, alcohol etc.) - Animal feed (DRAICA et al., 2004 cited by GÖNCZ, 2011). The industrial uses of potato include the production of alcohol, starch, glucose. From 1000 kg of potato liters of alcohol, 140 kg of starch, kg chips, or kg pommes frites can be obtained. (DRAICA, 1995 quoted by GÖNCZ, 2011). 2

4 CHAPTER II. GENERAL REQUIREMENTS OF POTATO FACTORS IN RELATION TO VEGETATION FACTORS This chapter addresses the general requirements of potatoes relating to the major vegetation factors: temperature, moisture, light and soil. Budding in the growth stage happens at 5 C (BERINDEI, 1977), the optimum temperatures for sprouting under sufficient aeration conditions are of 15 C - 16 C and the maximum is 31 C (BROUWER et al., 1976 cited by MORAR et al., 2004). The minimum temperature for vine growing is about 7 C, the optimal values are between 19 and 21 C and 42 C is the maximum. The optimum temperatures for tuber growth are from 16 to 17 C, the lowest being 2 C and the highest 29 C (BROUWER et al cited by MORAR et al., 2004). Potato crops demand a continuous supply of water. Soil moisture requirements are different in each growth stage. According to NEVISKI et al., (1958) cited by MORAR (2008), potato plants have the greatest need for water at flowering when soil moisture has to be 85% of the active humidity interval and 75% before and after this stage. It is considered that for a high tuber yield at least 250 mm of water is required in the areas favorable for potato cultivation during the summer months. The decrease in light intensity from 67% to 33% leads to a 38% decrease in dry matter content for the whole plant and an 80% decrease in tuber weight. However, there is a dry matter accumulation of 80% in the buds. Light intensity influences not only the production but also the distribution of assimilates and foliage development. At low light intensities (2000 lux) stem elongation is more pronounced than at higher intensities ( lux), leaf weight is bigger at light intensities between 8,000 and 16,000 lux. Low light intensity results in decreased leaf surface while high light intensity increases leaf surface but it reduces their thickness. High light intensities stimulate flowering (MORAR, 2008). The potato crop is sensitive to the physico-chemical properties of the soil. It requires light, deep and loose soils with good drainage and aeration, rich in organic matter and with suitable water holding capacity. In terms of texture, the most suitable soil types for potato cultivation are sandy loams, loamy sands and loam soils, which are well structured with no tendency to form clods and with hydro stable aggregates (MORAR, 2008). 3

5 CHAPTER III. CURRENT STAGE OF THE RESEARCH ON THE OPTIMUM SHAPE AND SIZE OF THE POTATO RIDGE This chapter presents the conducted research and the obtained results for the different trials that experimented with the shape and size of potato ridges, production systems, the correlation between vegetation factors and types of ridges, planting densities. Growing potatoes in ridges appeared for the first time in the eighteenth century (LINDEMANS, 1952 quoted by KOUWENHOVEN, 1970) in order to increase production, to protect the tubers against water excess in wet periods, to implement more effective weed control, to reduce the number of green tubers because of insufficient soil cover (SHOTTOON, 1964 STEPHENS, 1966, quoted by KOUWENHOVEN, 1970), to reduce the damage caused by the wheels of different machinery, and to optimize the amount of soil mobilized during harvest. It is a known fact that when increasing the distance between rows higher ridges can be formed and thus their sides are less compacted due to tractor wheels, having a greater amount of soil. Also during harvest, the higher volume of soil protects tubers from mechanical damage (BOUMAN, 1998; VAN der ZAAG 1992 quoted by BERNIK et al., 2009). The results of the research conducted in Slovenia by Bernik et al., in the years show an increase in production with values between 3.2 to 8.1 t of potato / ha when the distance between rows was 90 cm as opposed to the production obtained in the case of rows with a distance of 75 cm between them, noting that this period presented higher rainfall values compared to the multiannual average. Increasing inter-row width to 90 cm led consequently to a larger cross-sectional area of the ridges which resulted in the disappearance of green tubers. Therefore, prior to harvesting, the cross-sectional area of ridges exceeded 1000 cm 2 at 90 cm inter-row width and at 75 cm it was about 750 cm 2. So, while increasing the distance between rows the extent of soil coverage improves. Regarding the choice for the optimal shape of the ridge-top, KOUWENHOVEN (2003) emphasizes the need to consider the potato variety and the climate. Ridges with pointed tops do not retain water excess, thus their use is recommended in areas where rainfall is frequent and quantitatively significant. Ridge sizes are defined by the width of the ridge top and its internal height. Internal height depends largely on the depth of the seedbed. Lately ridges are shaped with ridging machines, so their size is no longer reduced to a significant extent during the growing season. The research carried out by KOUWENHOVEN et al. (2000) shows that the size of unshaped ridges decreased by 7.6% during the growing season, while the size of the shaped ones decreased by only 3%. On average, at the inter-row width value of 90 cm ridges were 24% larger than the ones at 75 cm inter-row width value, but the total production was nearly identical, but with fewer tubers per plant, and with 20% fewer green tubers (KOUWENHOVEN et al., 2000). Since the 1960 s ridge sizes and inter-row spacings have been doubled, they changed from 400 cm 2 and 67 cm to 800 cm 2 and 75 cm, and with an inter-row width of 4

6 90 cm a 1000 cm 2 cross-sectional area has been reached. Cluster width in the ridge is an important dimension and is largely dependent upon the cultivar and the length of the stolons and is influenced by the growing conditions in the ridge and general weather conditions. The highest percentage of green tubers (60%) was positioned at the ridge top while the smallest percentage (10%) occurred on the ridge side, thus the internal height of ridges constitutes the criteria for preventing the occurrence of green tubers (KOUWENHOVEN et al., 2003). The research carried out in our country by BERINDEI et al. (1979) demonstrated that increasing planting density from 30,000 to 70,000 plants per hectare increased the production of tubers from tonnes per hectare to tonnes per hectare. In cases when the planting density did not exceed 60,000 plants per hectare and intra-row distances did not exceed cm, even if the inter-row widths were of cm, there was a significant increase in production. As a result, irrigated potato crops with planting densities of 60,000 plants per hectare can provide a yield of over 50 tonnes/ ha when applying cm inter-row spacing. Seed tubers of smaller sizes (30 mm) can be planted at a density of 75,000 plants per ha, and medium sized tubers (45 mm) at densities up to 60,000 plants per hectare (BERINDEI et al., 1979). CHAPTER IV. RESEARCH OBJECTIVES AND METHODS Chapter IV.presents the arguments for choosing this research theme and its objectives and describes the three trials that were carried out, research methods, the experimental technique that was used and the biological material. For studying the optimum ridge shape and size we proposed the following objectives: the ridge shape which ensures thorough soil cover for seedbeds and the highest yield; the ridge shape which produces the highest number of tubers per plant; the ridge shape which produces the highest average tuber weight; the ridge shape which ensures the lowest number of green tubers; the ridge size achieved by the usage of different machinery to ensure the highest yield; the ridge size which produces the highest number of tubers per plant; the ridge size which produces the highest average tuber weight; the ridge shape which ensures the lowest number of green tubers; the influence of planting density on two potato varieties planted in ridges in a single row and in two rows; 5

7 the correlation between optimum planting densities, potato varieties (fewer and larger tubers or many smaller ones) and ridge types for producing higher yields, higher number of tubers per plant, with diameters under and over 40 mm, for producing tubers with the highest average tuber weight; the optimal planting density depending on the size and shape of the ridges, within the range of thousand plants / ha. For these objectives we have proposed three different trials carried out in the span of three years. The first trial experimented with the optimal shape of ridges, the second trial with the optimum size of ridges and the third trial aimed to observe the influence of planting density of two types of potato varieties planted in ridges in a single row and in two rows. For the study of the optimum ridge shape 3 different shapes of the same size of 1200 cm 2 in cross-sectional area have been designed, the variants being: - V1 - triangular shape - V2 - trapezoidal in one row - V3 - trapezoidal in two rows To study the optimum size of the potato ridge, trapezoidal shaped ridges were made of three different sizes: - v1 cross-sectional area of 800 cm 2 - v2 cross-sectional area of 1200 cm 2 - v3 cross-sectional area of 1600 cm 2 The trial observing the influence of planting density on two types of potato varieties in ridges in one row and in two rows: 1. Factor (A): The potato variety: - a1 cultivar with fewer but larger tubers - Bellarosa; - a2 cultivar with many smaller tubers - Gared. 2. Factor (B): planting density: - b1-40,000 plants / ha; - b2-60,000 plants / ha; - b3-80,000 plants / ha. 3. Factor (C): type of ridge: - c1 - simple ridge (in a single row); - c2 double ridge (in two rows). 6

8 All three trials were carried out on the fields for experimental planting belonging to the Potato Research and Development Station in Tg. Secuiesc, Covasna county. For all variants four rows were planted in four randomized repetitions in the years 2012, 2013 and The common technology of ridge ploughing was used and mechanically performed phytosanitary treatments were executed with the usual products. An analysis of variance was carried out for completely randomized plots in the uni- and multifactorial trials and the data processing was accomplished by using average values, the t-test at 5%, 1%, 0,1% significant difference levels and the Duncan Multiple Range Test. While experimenting in the unifactorial trials regarding the optimal size and shape of potato ridges the Bellarosa variety was used in all three years of research and for the experiments on the influence of planting density on two types of potato varieties in ridges in a row and in two rows two types of potato varieties were studied. Thus, in addition to the import Bellarosa variety which forms fewer but larger tubers another local variety was also experimented on, namely the Gared varity which forms many but smaller tubers. CHAPTER V. PEDOCLIMATIC CONDITIONS OF THE RESEARCH PERIOD Chapter V describes the climate conditions of the trial years (2012, 2013, 2014) and the characteristics of the soil on which the potatoes were grown. In the year 2012 the recorded temperatures were above the multiannual average throughout the growing season, the measured differences being +1.5 C in April, +1.1 in May, +3.1 in June, +5.5 C in July, +2.3 C in August and +2.9 C in September. The trial year of 2012 was affected by lower levels of precipitation, the rainfall total of mm was below the multiannual average, and in the growing season this value became mm thus making the year 2012 unfavorable for potato production due to the drought. In 2013 the recorded temperature values in the basin of TârguSecuiesc were close to the multiannual average values thus favoring potato cultivation. Each month throughout the growing season produced a higher average temperature value when compared to the multiannual average, with the exception of September. However, these differences were not significant. The mean annual amount of precipitation was 42,8 mm higher than the multiannual average and the Meteorological Station of TârguSecuiesc measured a 460,7 mm rainfall amount throughout the growing season. Despite the surplus of 73,2 mm of water in comparison to the long-term average during the growing season the crop was not affected due to the drought conditions of the previous year. In 2014 as well the recorded temperature values were above the multiannual average throughout the whole growing season, the differences being C in April, +0,8 C in July and +1,0 C in August. These temperature values did not affect the development of potato crops, although values above the multiannual average in June and July favored the development of the phytopathogenphytophthorainfestans that manifested very aggressively throughout the whole area for potato cultivation. In 2014 the recorded rainfall total during the growing season (373.7 mm) was almost equal to the multiannual average of the growing period registered in TârguSecuiesc (380 mm), the difference being of mm. While in April and May rainfall values were above the 7

9 multiannual average, in June the total amount of rainfall was below it registering a value of mm which negatively affected potato crops, these being in the phenophases of budding - flowering. The soil classes within the area of S.C.D.C. Tg. Secuiesc where the experiments were conducted are phaeozems, which occur in cooler environmental conditions and are sometimes wetter than "ordinary" chernozems. Those formed on medium clay have excellent air and water conditions thus being the most suitable soil group of the area and the most favorable for potato production. CHAPTER VI. RESULTS AND DISCUSSION In the trial years of 2012, 2013 and 2014 in all three experiments several research elements were observed like potato yield (kg / ha), tuber number per plant, average tuber weight. The trial that focused on the influence of planting density on two types of potato varieties planted in ridges in a single row and in two rows in 2013 and 2014 also studied the number of tubers in a seedbed that were smaller than 40 mm and the number of green tubers (2014). In this chapter the research results, the influence of the studied factors and in some cases the interaction among these factors are presented. Of the three experimental years , 2013 and the first year can be defined disadvantageous for potato production because of the unfavourable rainfall and temperature values that characterized the growing period. Consequently, the experimental results of 2012 were highly compromised due to factors like the lack of water and high temperatures, which is why the result analysis included mean values recorded only in the years 2013 and The last two trial years can be considered normal agricultural years with suitable meteorological parameters but, in some instances, when the results of the first trial year were still considered relevant, they were taken into account TRIAL RESULTS ON THE RIDGE SHAPE THROUGHOUT THE EXPERIMENTAL CYCLE Table 1. The influence of ridge shape upon the average tuber weight in the trial years of 2013 and 2014 Year Shape of the ridge Average % Difference (g) Signif. Duncan s test weight (g) 2013 Triangular 143,75 100,0 0 Ctr. b Trapezoidal 165,50 115,1 21,75 ** c Double- 165,50 114,4 20,75 ** c Trapezoidal 2014 Triangular 114,75 100,0 0,00 Ctr. a Trapezoidal 131,50 114,6 16,75 * b Double- 83,00 94,1-6,75 - a Trapezoidal DL (p 5%) 13,36 DL (p 1%) 18,76 DL (p 0,1%) 26,48 DS (teor.) 13,35 8

10 In both trial years of 2013 and 2014 potatoes harvested from trapezoidal shaped ridges showed higher average tuber weight values than the ones harvested from triangular shaped ridges with significantly positive difference and significant difference respectively (Table 1.). In 2013 potatoes harvested from double-trapezoidal shaped ridges showed significantly higher tuber weight values when compared to the control variant (average tuber weight of potatoes harvested from trapezoidal ridges) but in 2014 the analysis of variance did not show significant differences considering the average tuber weight produced in triangular shaped ridges (Ctr.), respectively in double-trapezoidal ones. Table 2. The influence of ridge shape upon the number of tubers under the hill the in trial years of 2013 and 2014 Year Shape of the No./ % Difference Signific. Duncan s test ridge hill (no.) 2013 Triangular 3,48 100,0 0 Ctr. a Trapezoidal 3,09 88,9-0,39 - a Double- 3,53 101,5 0,05 - a Trapezoidal 2014 Triangular 5,37 100,0 0 Ctr. c Trapezoidal 4,78 89,0-0,59 0 b Double- Trapezoidal 3,51 65,4-1, a DL (p 5%) 0,43 DL (p 1%) 0,61 DL (p 0,1%) 0,86 DS (teor.) 0,43 The number of tubers per plant in the experimental years of 2013 and 2014 was lower in the trapezoidal shaped ridges than in the triangular shaped ones, the difference being insignificant in 2013 and significantly negative in The Duncan test highlights the nearly identical tuber numbers recorded per plant in 2013 for all three ridge shapes and the number of tubers per plant in 2014 harvested from double trapezoidal shaped ridges (Table 2.). 9

11 Table 3. The influence of ridge shape upon the average tuber weight in the trial years of 2013 and 2014 Year Shape of the ridge Average weight (g) % Difference (g) Signif. Duncan s test 2013 Triangular 143,75 100, 0 Ctr. b 0 Trapezoidal 165,50 115, 21,75 ** c 1 Double- 165,50 114, 20,75 ** c Trapezoidal Triangular 114,75 100, 0,00 Ctr. a 0 Trapezoidal 131,50 114, 16,75 * b 6 Double- Trapezoidal 83,00 94,1-6,75 - a DL (p 5%) 13,36 DL (p 1%) 18,76 DL (p 0,1%) 26,48 DS (teor.) 13,35 In both trial years of 2013 and 2014 potatoes harvested from trapezoidal shaped ridges showed higher average tuber weight values than the ones harvested from triangular shaped ridges with significantly positive difference and significant difference respectively (Table 3.). In 2013 potatoes harvested from double-trapezoidal shaped ridges showed significantly higher tuber weight values when compared to the control variant (average tuber weight of potatoes harvested from trapezoidal ridges) but in 2014 the analysis of variance did not show significant differences considering the average tuber weight produced in triangular shaped ridges (Ctr.), respectively in double-trapezoidal ones. The Duncan test showed similar average tuber weight values recorded for triangular shaped ridges in 2013 and trapezoidal shaped ridges in 2014 (Table 3.). 10

12 6.2. TRIAL RESULTS ON THE RIDGE SIZE THROUGHOUT THE EXPERIMENTAL CYCLE Table 4. The influence of ridge size upon the tuber yield in the trial years of 2013 and 2014 Year Size of the ridge Kg/ ha % Difference (kg) Signific. Duncan s test cm ,63 100,0 0 Ctr. c 1200 cm ,70 85,5-5261, b 1600 cm ,70 92,4-2761,92 0 b cm ,75 100,0 0 Ctr. a 1200 cm ,55 96,5-1035,20 - a 1600 cm ,67 99,0-297,08 - a DL (p 5%) 2317,42 DL (p 1%) 3252,89 DL (p 0,1%) 4592,32 DS (teor.) 2315,18 Considering the results of the two trial years it can be stated that in both years the highest tuber yield was obtained in the case of ridges with the cross-sectional area of 800 cm 2, considered to be the control variant. Thus, in 2013 there was a significant decrease in yield regarding ridges with the cross-sectional area of 1200 cm 2 whereas regarding ridges with the cross-sectional area of 1600 cm 2 there was also a decrease in yield (Table 4.). Table 5. The influence of ridge size upon the number of tubers under the hill in the trial years of 2013 and 2014 Year Size of the ridge No./ hill % Difference Signif. Duncan s test cm 2 4, Ctr. c 1200 cm 2 3,52 84,9-0,63 00 a 1600 cm 2 3,63 87,6-0,51 00 ab cm 2 3, Ctr. bc 1200 cm 2 3,88 97,4-0,10 - abc 1600 cm 2 3,83 96,2-0,15 - c DL (p 5%) 0,34 DL (p 1%) 0,47 DL (p 0,1%) 0,67 DS (teor.) 0,34 11

13 Regarding the influence of the ridge size on the number of tubers per plant in the two trial years (2013, 2014) it can be stated that this number is inversely proportional to the size of the ridges. In 2013 ridges with the cross-sectional area of 1200 cm 2 and 1600 cm 2 produced a significantly lower number of tubers per plant when compared to the control variant (800 cm 2 ), the differences being distinctly significant (Table 5). The year 2014 also produced fewer tubers per plant in bigger sized ridges, but the differences were not statistically confirmed (Table 5.). The Duncan test highlights the similarity between the tuber number produced in ridges of 800 cm 2 cross-sectional area in 2013 and the tuber numbers produced in all three sizes of ridges in 2014 (Table 5.). Table 6. The influence of ridge size upon the average tuber weight in the trial years of 2013 and 2014 Year Size of the ridge Average weight (g) % Difference (g) Signific. Duncan s test cm 2 157,25 100,0 0 Ctr. b 1200 cm 2 158,00 100,5 0,75 - b 1600 cm 2 165,50 105,2 8,25 - b cm 2 134,25 100,0 0 Ctr. a 1200 cm 2 132,00 98,3-2,25 - a 1600 cm 2 137,25 102,2 3,00 - a DL (p 5%) 8,65 DL (p 1%) 12,14 DL (p 0,1%) 17,14 DS (teor.) 8,64 After analyzing the influence of ridge size on the average tuber weight it was found that among the three ridge sizes of the same trial year there were no significant differences according to the t test. The Duncan test revealed higher average tuber weight values in 2013 for all three ridge sizes when compared to the average tuber weight values obtained for the three ridge sizes in 2014, so the average tuber weight can be significantly influenced by vegetation conditions (Table 6.). 12

14 6.3. TRIAL RESULTS FOR THE EXPERIMENTAL CYCLE ON THE INFLUENCE OF PLANTING DENSITY ON TWO POTATO VARIETIES PLANTED IN RIDGES IN A SINGLE ROW AND A DOUBLE ROW Table 7. Tuber yield obtained in the interaction of trial year X planting density considering the ridge types Year Density Yield (kg/ % Difference Signifiance Duncan s test (pl/ ha) ha) (kg) ,31 100,0 0 Ctr. b ,01 102,1 538,71 - b ,34 100,0-5,96 - b ,14 100,0 0 Ctr. a ,59 99,9-25,54 - a ,25 99,5-100,89 - a DL (p 5%) 1455,13 DL (p 1%) 1977,84 DL (p 0,1%) 2648,90 DS (teor.) 1458,48 Considering the tuber production of the three planting densities with different cultivars and ridge shapes on average, there are no significant differences in any of the experimental years according to the analysis of variance. The Duncan test confirmed the results of the t- test analysis, and revealed higher yields for all three planting densities in 2013 when compared to the ones in 2014 (Table 7). Table 8. Number of tubers obtained in variety type X trial years interaction Year Variety No./ hill % Difference (no.) Signific. Duncan s test 2012 Gared 7,24 100,0 0 Ctr. d Bellarosa 3,18 43,9-4, a 2013 Gared 5,42 100,0 0 Ctr. b Bellarosa 3,16 58,3-2, a 2014 Gared 6,52 100,0 0 Ctr. c Bellarosa 3,05 46,8-3, a DL (p 5%) 0,50 DL (p 1%) 0,73 DL (p 0,1%) 1,07 DS (teor.) 0,51 According to the statistical calculations using the "t-test" and the Duncan test in all three trial years the numbers of tubers per plant were lower for the Bellarosa variety (with fewer but larger tubers) than the numbers of tubers for the Gared variety (many and small tubers), the difference being significantly negative (Table 8.). This trait is genetically determined and is unaffected by growing conditions. 13

15 Table 9. Number of tubers obtained in planting densities and trial years interaction Year Density (pl/ No./ hill % Difference Signif. Duncan s test ha) (no.) ,56 100,0 0 Ctr. e ,14 78,3-1, d ,93 59,8-2, ab ,02 100,0 0 Ctr. d ,17 83,1-0, bc ,67 73,0-1, a ,14 100,0 0 Ctr. e ,40 71,7-1, c ,81 62,1-2, ab DL (p 5%) 0,44 DL (p 1%) 0,59 DL (p 0,1%) 0,78 DS (teor.) 0,44 In all three trial years with different cultivars and ridge types on average, densities of 60,000 and 80,000 plants/ha resulted in fewer tubers per plant when compared to the number of tubers produced per plant by the density of plants/ ha, the difference being significantly negative (table 9). The number of tubers per plant obtained is inversely proportional to the planting density, a fact that was confirmed by the Duncan test as well. Table 10. Number of tubers obtained in the interaction of density X trial years X type of the variety Year Variety Density No./ hill % Diff. Signif. Duncan s test (pl./ ha) (no.) 2012 GARED ,49 100,0 0 Ctr. i ,11 75,0-2, g BELLA ROSA ,12 54,0-4, d ,64 100,0 0 Ctr. bc ,17 87,0-0,47 - abc ,73 75,1-0,91 00 a 2013 GARED ,21 100,0 0 Ctr. f ,23 84,1-0,99 00 de ,81 77,4-1, d 2014 BELLA ROSA GARED BELLA ROSA ,82 100,0 0 Ctr. c ,12 81,6-0,70 0 ab ,52 66,0-1, a ,73 100,0 0 Ctr. h ,80 66,4-2, ef ,04 57,8-3, d ,55 100,0 0 Ctr. bc ,01 84,8-0,54 - ab ,58 72,7-0,97 00 a DL (p 5%) 0,63 DL (p 1%) 0,84 DL (p 0,1%) 1,11 DS (teor.) 0,63 14

16 Regarding the interaction between planting densities, the experimental year and type of varieties in different ridge types the analysis of variance revealed the decreasing tendency that characterizes the tuber number per plant when increasing planting density, differences ranging from insignificant to significantly negative (Table 10.). The Duncan test shows the number of tubers obtained were fairly alike in all three experimental years for the Bellarosa variety, at the planting density of 80,000 plants per ha. Table 11. Average tuber weight recorded in the interaction of cultivar type X trial years Year Variety Average weight (g) % Difference (g) Signif. Duncan s test 2013 Gared 75,72 100,0 0,00 Ctr. b Bella 150,56 198,8 74,84 *** d rosa 2014 Gared 63,63 100,0 0,00 Ctr. a Bella 110,95 174,4 47,32 *** c rosa DL (p 5%) 7,81 DL (p 1%) 11,83 DL (p 0,1%) 19,01 DS (teor.) 7,80 Taking into consideration the interrelationship between the different varieties planted in different types of ridges and with different planting densities in the trial years, the analysis of variance revealed that the average tuber weight value was bigger in the case of the Bellarosa variety (potato variety with fewer and larger tubers) than in the case of the Gared variety (many but smaller tubers), the difference being significantly positive (Table 11.). Both varieties produced smaller average tuber weight values in 2014 as opposed to Table 12. Average tuber weight recorded in the interaction of planting density X trial years Year Denstiy (pl/ ha) Average weight (g) % Difference (g) Signif. Duncan s test ,41 100,0 0 Ctr. e ,74 81,6-24, d ,28 70,9-39, c ,61 100,0 0 Ctr. c ,69 88,8-10, b ,58 79,5-20, a DL (p 5%) 3,79 DL (p 1%) 5,15 DL (p 0,1%) 6,89 DS (teor.) 3,80 15

17 Regarding the interrelationship between planting densities for the varieties planted in different types of ridges in the studied trial years, a decrease in the average tuber weight values can be observed when increasing planting density. Thus, in both trial years of 2013 and 2014, in the case of plants/ha and plants/ha planting densities the average tuber weight values were lower in comparison to the average tuber weight values of the control variant, the plants/ha planting density, the differences being significantly negative (table 12.). The Duncan test confirmed the results of the analysis of variance and emphasized the higher average tuber weight values obtained in 2014 as opposed to the year 2013 (Table 12.). Table 13. Recorded average tuber weight in planting density X trial year X variety type interaction Year Variety Density (pl./ ha) Average weight (g) % Diff. (g) Signif. Duncan s test ,69 100,0 0 Ctr. d GARED ,23 84,1-14, c ,25 66,4-30, b BELLA ,13 100,0 0 Ctr. j ROSA ,25 89,9-34, i ,30 73,2-47, h ,54 100,0 0 Ctr. c GARED ,18 89,9-7,36 00 b ,19 73,3-19, a BELLA ROSA ,69 100,0 0 Ctr. g ,21 88,2-14, f ,96 83,1-20, e DL (p 5%) 5,36 DL (p 1%) 7,28 DL (p 0,1%) 9,75 DS (teor.) 5,37 Through statistical analysis of the experimental data using the "t-test" and the Duncan test and considering the interrelationship between planting densities, varieties in different ridge types and experimental year, distinctly significant differences appear and the significantly negative ones for the average tuber weight values appear for both varieties of potato in both trial years in the case of the 60,000 and 80,000 plants per ha planting densities as opposed to the planting density of 40,000 plants per ha, considered to be the control variant. As a result it can be pointed out that planting densities significantly affect the obtained tuber sizes (Table 13.). 16

18 Table 14. The influence of ridge shape X trial years X planting density interaction upon the number of tubers under 40 mm per hill Year Density Type of the ridge No. tubers under 40 mm/ hill 17 % Diff. (no.) Trapez simplu Trapez dublu Trapez simplu Trapez dublu Trapez simplu Trapez dublu 2014 Trapez simplu Trapez dublu Trapez simplu Trapez dublu Trapez simplu Trapez dublu DL (p 5%) 0,30 DL (p 1%) 0,41 DL (p 0,1%) 0,54 DS (teor.) 0,31 Sign. Duncan s test 2,34 100,0 0 Ctr. b 2,01 85,9-0,33 0 ab 1,97 100,0 0 Ctr. a 2,06 105,0 0,10 - ab 1,85 100,0 0 Ctr. a 2,12 114,5 0,27 - ab 4,24 100,0 0 Ctr. f 4,58 108,0 0,34 * g 2,98 100,0 0 Ctr. cd 3,45 116, ** e 2,82 100,0 0 Ctr. c 3,20 113,3 0,37 * de Considering the interrelationship between planting density, the two varieties planted in different ridge shapes and the trial years, it appears that in most cases the number of small tubers per nest is higher in the case of the double-trapezoidal shaped ridges as opposed to simple trapezoidal shaped ones. In 2013, the planting density of 40,000 plants/ha produced fewer smaller tubers per nest in the case of the double-trapezoidal shaped ridges as opposed to the simpletrapezoidal shaped ones, the difference being significantly negative, whereas the planting densities of 60,000 and 80,000 plants/ha produced a higher number of small tubers per plant in the case of the double-trapezoidal ridges, though the differences were not

19 confirmed statistically (Table 14.). In 2014, all three planting densities produced higher numbers of small tubers per hill in the case of the double-trapezoidal shaped ridges as opposed to the simpletrapezoidal shaped ones, the differences ranging from significant to significantly positive (Table 14). In this case the Duncan test confirmed the results obtained from the analysis of variance. CHAPTER VII. CONCLUSIONS AND RECOMMENDATIONS CONCLUSIONS AND RECOMMENDATIONS REGARDING THE OPTIMAL SHAPE OF POTATO RIDGES - The trapezoidal shaped ridges formed on a single row produced higher tuber yields than the triangular shaped ridges; - If normal weather conditions are dominant in the growing season and the large and loose double-trapezoidal ridges are prepared on time, a higher tuber yield can be achieved in those than in the simple-trapezoidal shaped ones; - The number of tubers per plant produced in the case of triangular shaped ridges is higher or very close to the number of tubers per plant obtained in the case of trapezoidal and double-trapezoidal shaped ridges respectively; - The average tuber weight values are higher for both the simple and double-trapezoidal shaped ridges when compared to the average tuber weight values of the triangular shaped ones; CONCLUSIONS AND RECOMMENDATIONS REGARDING THE OPTIMAL SIZE OF POTATO RIDGES - The highest yield was obtained in the case of ridges with the cross-sectional area of 800 cm 2, and the lowest in the case of ridges with the cross-sectional area of 1200 cm 2 ; - The number of tubers per plant decreases if the ridge size is increased; the highest number of tubers per plant was obtained in the case of ridges with the cross-sectional area of 800 cm 2, the lowest number of tubers per plant was produced by ridges with the crosssectional area of 1600 cm 2 ; - Regarding the influence of the ridge size on the number of green tubers per nest it was revealed that that the number of these unwanted tubers is inversely proportional to the ridge size. - Ridge sizes do not influence average tuber weight values. 18

20 CONCLUSIONS AND RECOMMENDATIONS REGARDING THE INFLUENCE OF PLANTING DENSITY ON TWO POTATO VARIETIES PLANTED IN RIDGES IN A SINGLE ROW AND IN TWO ROWS - The Gared variety with many small tubers was more constant in terms of yields, while the Bellarosa variety was more productive in the first year in comparison to the last year; - Planting density did not significantly influence the total potato production values under the conditions of the field trials carried out by our research team, within the range of 40,000-80,000 plants / ha; - Under normal agro-meteorological conditions and in case of suitable ridge preparations performed on time, trapezoidal shaped ridges in two rows produced higher yield than trapezoidal shaped ridges in a single row; - The number of tubers obtained per plant is genetically determined for the studied varieties - The number of tubers obtained per plant is inversely proportional to the planting density. The planting density of 40,000 plants per ha produced the highest tuber yield per plant, and the density of 80,000 plants/ha, on the other hand, the lowest; - In the case of both cultivars the number of tubers obtained per plant decreases if planting density is increased; - In the case of both cultivars the average tuber weight value decreases significantly provided that the planting density is increased; - The number of tubers smaller than 40 mm decreases when planting density is increased; - Based on our research results we recommend planting tubers at higher densities ( plant /ha) in double-trapezoidal ridges for the production of seed potatoes. 19

21 SELECTED BIBLIOGRAPHY 1. AUSERWALD K., G. GERL, M. KAINZ, 2005, Influence of cropping system on harvest erosion under potato, p BERINDEI M., G. MORAR, H. BREDT, D. SCURTU, I. BRETAN, I. SIMIONESCU, MARIA NĂFORNIȚA, I. MĂZĂREANU, I. BORA, IOANA VLĂDUȚIU, LIDIA GEAMĂNU, I. CĂLINOIU, ȘT. HOMORODEANU și GH. PAMFIL, 1978, Rezultatele cercetărilor privind mărirea distanței între rândurile de plante în vederea mecanizării totale a culturii cartofului pentru consum în toamnă-iarnă în condiții de cultură neirigată, Lucrări științifice - Institutul de cercetări pentru cultura cartofului Brașov, vol. IX. p BERINDEI M., G. MORAR, H. BREDT, L. TAMAȘ, A. CREȚU, I. BORA, N. POPA, I. NEGUȚI, R. COȘOVEANU, LUCIA DRAGOMIR, 1979, Rezultatele cercetărilor privind mărirea distanței între rândurile de plante în vederea mecanizării totale a culturii cartofului pentru consum în toamnă-iarnă în condiții de irigare, Lucrări științifice - Institutul de cercetări pentru cultura cartofului Brașov, vol. X, p BERNIK R., T. GODEŠA, P. DOLNIČAR, F. VUČAJNK, 2009, Potato yield and tuber quality in 75 cm and 90 cm wide ridges, Acta agriculturae slovenica, 95-2 july 2010, p BUDUȘAN V., 1976, Densitatea în culturi de sămânță, Cercetări privind desimea de plantare în funcție de mărimea tuberculilor la cultura cartofului pentru sămânță, Lucrări științifice Institutul de cercetări pentru cultura cartofului și sfeclei de zahăr Brașov, Cartoful, volumul VI, 1976, p CHIRU S., V. DONESCU, CARMEN BĂDĂRĂU, GH. OLTEANU, A. GHINEA, 2013, Cartoful în România, Vol. XXII, nr. 1, 2, Ed. Tipotex, Brașov, p. 1, GÁLFI N., 2003, Cercetări privind îmbunătățirea metodicii de apreciere a creațiilor de ameliorare (linii și soiuri) la cartof, Teză de doctorat, p GÖNCZ E., 2011, Perfecționarea tehnologiei de cultivare a cartofului destinat procesării în condițiile județului Covasna, Teză de doctorat, p IANOȘI S., 1992, Importanța bilonului în cultura cartofului, Cartoful în România, Institutul de Cercetare și Producție a Cartofului Brașov, Vol. II, nr. 1, p.18 20

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