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УДК631.53.04:635
РЕЗУЛЬТАТЫ ЭКСПЕРИМЕНТАЛЬНЫХ ИССЛЕДОВАНИЙ ПРОЦЕССА
ОДНОЗЕРНОВОГО ВЫСЕВА СЕМЯН ОВОЩНЫХ КУЛЬТУР В КАССЕТЫ БАРАБАННО-ВАКУУМНЫМ ВЫСЕВАЮЩИМ АППАРАТОМ
М. Б. ГАРБА, А. А. ШУПИЛОВ
УО «Белорусский государственный аграрный технический университет», г. Минск, Беларусь, e-mail: engrbello@bsatu.by
(Поступила в редакцию 21.06.2017)
Разработана установка для точного высева семян овощных культур в кассеты для производства овощной рассады. Проведены эксперименты по оптимизации эксплуатационных параметров установки для обеспечения качества агротехнических показателей однозернового высева. Основные влияющие факторы: разрежение, создаваемое в высевающем барабане, и диаметр присасывающего отверстия исследованы на семенах томата (сорт halay) и перец (сорт figaro) с использованием пластиковых кассет с 64 ячейкамипри ортогональном центральном композиционном плане регрессионного эксперимента. Определены оптимальные значения параметров: разрежение в высевающем барабане - 2.1 и 2,2 кПа и диаметр присасывающих отверстий- 1,0 и 1,0 мм для получения более 90% однозернового высева семян томата и перца, которые могут служить основой для разработки и повышения эффективности работы установок для высева семян овощных культур в кассеты.
Ключевые слова: установка точного высева в кассеты, овощные культуры, эффективность однозернового высева, ортогональный центральный композиционный план
A vegetable seeds precise sowing device in cell trays was developed for vegetable seedlings production. Experiments were conducted to optimize the working parameters of the vegetable seeds cell tray precision seeder for ensuring effective seed singulation. Major factors; the vacuum pressure in the seeding drum and suction hole diameter were tested on tomato (halay cultivar) and ball pepper (figaro cultivar) seeds and plastic tray with 64 cells using the orthogonal central composite design regression experiment. Optimal parameters of vacuum pressure 2.1 and 2.2 kPa and suction hole diameter of 1.0 and 1.0mm to achieve more than 90% single-seeding in the case of tomato and pepper respectivelywere determined. These parameters provided the basis for design and performance improvement of the cell tray vegetable seeds precision seeder.
Keywords: cell tray precision seeder, vegetable seeds, single-seeding performance, orthogonal central composite experimental design.
Introduction
Vegetableshave important functions, including promoting good health, providing satiety and weight maintenance and supplying a variety of colors, textures and tastes. The majority of vegetable transplants (seedlings) are from three main crops namely, cabbage, tomatoes and pepper. In view of high cost of such seeds, it is necessary to achieve maximum germination and disease-free seedlings for transplanting in open fields. The raising of seedlings in cell trays is one of such technology that provides this agrotechnical requirement. The technology is fast emerging due to its obvious advantages for both vegetable farmers and agricultural enterprises in Belarus. This process involves filling of cell tray with substrate, indenting cells and single seed is manually placed in each cell. However, sowing one seed in each cell is the most tedious and labour-intensive operation, and thus limits the capacities of most Belarusian vegetable farming enterprises. In the peak season, manual labour hardly meets the short period requirement for raising vegetable seedlings. Automation and mechanization of the seeding operation of cell trays is therefore necessary to increase the capacity of the rapidly expanding demand in nursery seedlings in the country.
Precision seeding in cell trays requires single seeds to be picked from the hopper and individually placed in each cell. Singulation of seeds has been investigated extensively by many researchers across the globe and quite largenumbers of precision seeding systems (drum, plate, needle types, etc. precision seeders) were developed for different vegetable crops.
Hanacek et al [1] developed a singulating seeder for high-density plug trays which singulates ellipsoid-shaped seeds, but could not singulate irregular shaped seeds. Marr [2] developed a plate that uses vacuum for plating in plug trays which consisted of two sheets of acrylic plastic cut into rectangular dimensions of the seed flat and holes drilled over it to pick seeds. Chen et al [3] developed a multipurpose vacuum seed planter suitable for flat and spherical vegetable seeds which was thirty six times faster than manual seeding. Another novelty by Zigmanov [4] who investigated the factors that affect the efficiency of sowing as the shape of the seed as well as the degree of seed finishing (cleanliness, size, surface polishing and prilling), nozzle diameter, level of vacuum and the method of inserting nozzle into the vessel holding the seed.
Kim et al [5] also developed a vacuum nozzle seeder for an automatic sowing of large seeds of fruit, vegetables and rootstocks. In their work, it was established that nozzle diameter and extraction vacuum pressure are most important factors that influence seeding rates. Hu et al [6] developed a magnetic precision seeder for plug seedlings, which picked up seeds coated with magnetic powder. The number of seeds picked by magnetic head as well as the seed singulation was controlled by adjusting magnetic field. Rathinakumari et al
[7] developed a tray-type vacuum seeder and dibbler with a capacity of 50-100 plug trays per hour for small vegetable nursery farmers.
A suction pressure of 49.03 kPa was reported to be sufficient for singulation of seeds. They also developed a rotary drum seeder with nozzle holes of 0.5 mm diameter and a suction pressure of 49.03kPa.Xia et al
[8] used cabbage seeds for sowing performance test. Their single factor test results showed that with the increase of diameter of suction hole, single-seed rate began to increase and then decreased, multi-seed rate increased, empty-seed rate began to decrease and then increased. Gaikwad and Sirohi [9] developed a predicting plug tray seeder using indigenous materials and off-the-shelf available standard components/ experimental results indicated that the seeder worked satisfactorily at suction pressure of 4.91 and 3.92 kPa and nozzle diameters of 0.46 and 0.49 mm to achieve more than 90% single seed sowing in the case of capsicum and tomato respectively.
Presently, in the republic of Belarus there are no locally produced mechanical seeders for nursery cell tray seeding. Vegetable nursery enterprises have not fully adopted imported seeders (e.g.Urbinati, Mosa, Hamilton, Visser etc.) because of high costs and unconformity to the cell trays produced in the country as well as other uneconomic scale of production.A cell tray vegetable seeder with capacity of 200 -300 trays/h which works with a vacuum seeding drum were designed and developed in Belarusian State Agrarian Technical University, Minsk. The cell tray vegetable precision seeder is made out of local material with a vacuum pump as source of vacuum for seeds suction. The main objective of the study was to investigate the singleseeding performance of the seeder with target of reducing doubles and misses as well as determining the optimal parameters.
Material and methods
Experiments were conducted in a laboratory on the developed cell tray precision seeder as shown in figure 1, which was operated as described in [10]. The seeds used in this test were tomato (halay) and pepper (figaro) cultivarsrespectively obtained from Agro-industrial Complex «Zhdanovichi» in Minsk. The one-thousand kernel weight (TKW) of the seeds was 467 and 888 g and friction angle of 21.22 and 22.320for tomato and pepper respectively, using stainless steel material [11].The study considered the vacuum pressure in the drum (xj) and the suction hole diameter (x2) as the experimental factors. The singles, multiples and misses were taken as indices using quadratic regression experimental design. The three levels were adopted based on the results of a preliminary experiment to obtain a compromise solution.The coding of factor levels is presented in table 1.
Table 1. Code and level of factors
Codevalue Vacuumpressurexi (kPa) Suction hole diameter X2 (mm)
Upperlevel (+1) 1.0 1.0
Zerolevel (0) 2.5 1.4
Lowerlevel (-1) 4.0 1.8
Before the experiment, necessary preliminary checks were conducted and the speed of the conveyor belt was regulated by means of vector frequency converter to 2.4 m/min. while the motor speed became stable. 64 cells tray was then seeded for four replicates as shown in table 2 for the experimental plan of the laboratory study.
Table 2. The experimental plan of the laboratory study
Sr. No Treatments Levels
1 Type of seed 51 = Tomato 52 = pepper
2 Suction hole diameter, d, mm d1 = 1.0, d2 = 1.4, d3 =1.8
3 Vacuum pressure, p, kPa p1 = 1.0, p2 = 2.5, p3 = 4.0
4 Replications 4
The performance study of the seeder was carried out by seeding single seeds of tomato and pepper seeds in the trays with 64 cells. Vacuum pressure and suction hole diameter, optimized in the laboratory study, were maintained for the both tomato and pepper. The conveyor speed was fixed at 2.4 m/min.
Results and discussion
By the initial experimental design, results of quadratic orthogonal regression experiment were presented in tables 3 and 4. The recorded values are the average from four observations. The numbers of seeds placed in each cell were counted to calculate % singles, % multiples and % misses.
Singulation efficiency both tomato and pepper was calculate as the ratio of total cells seeded to the total seeds in a all cells while seeding efficiency is the total % of singles, misses and multiples, seeds sown.
Serialnumber Vacuumpressurexi (kPa) Suction hole diameter x2 (mm) Singles, (%) Misses, (%) Multiples, (%)
i 1.0 1.0 94.5 3.9 1.6
2 4.0 1.0 94.5 1.2 4.4
3 1.0 1.8 93.4 5.5 1.3
4 4.0 1.8 89.8 1.6 8.6
5 2.5 1.4 95.0 2.3 2.8
6 1.0 1.4 95.3 4.7 0.0
7 4.0 1.4 94.5 0.8 4.7
8 2.5 1.0 95.3 2.0 2.8
9 2.5 1.8 88.8 3.9 7.5
Table 4. CCD experimental results for pepper (figaro cultivar)
Serialnumber Vacuumpressurex (kPa) Suction hole diameter X2 (mm) Singles, (%) Misses, (%) Multiples, (%)
1 1.0 1.0 89.1 1.6 1.6
2 4.0 1.0 94.2 0.8 5.2
3 1.0 1.8 89.5 9.4 1.3
4 4.0 1.8 96.6 0.8 2.8
5 2.5 1.4 92.2 3.1 4.7
6 1.0 1.4 88.3 8.3 3.6
7 4.0 1.4 93.0 2.8 4.4
8 2.5 1.0 93.8 2.8 3.6
9 2.5 1.8 95.8 2.0 2.3
The experimental data were analyzed using Microsoft Excel. The regression equations were determined between each experimental factor and performance index for both tomato and pepper seeds as shown below: Tomato:
Y1 = 59.81 - Q.46X1 - 1.33X2 - 0.56X^2 - 1.42Xf (1)
Y2 = 1.33 - 1.13Ai + 0A2X2 (2)
Y3 = 2.36 + 156A'! + 0.92X2 + OJSX^ - 1.17Jf| (3)
Pepper:
Y1 = 59.17 + U79X1 + 0.50^ - 1.37J£? + 125X% (4)
Y2 = 2.73 - 2.42X1 + 1.67X* * (5)
Y3 = 2.06 + 0.63^ - 0A2X2 - 0.31X^2 - G.9Qjf (6)
Where, Y1 is singles, %; Y2 is misses, %; Y3 is multiples, %; X] is vacuum pressure, kPa and X2 is suction hole diameter, mm.
In order to verify the significance of regression equation, the Ftest was used for equations (1) - (6). The calculated F-values were compared with the table values at a 5% level of significance and are given in table 5 below.
Table 5. F- values for % singles, %misses and % doubles fortomato and pepper seeds
Dependent parameters Seed Source of variation (F-values)
Calculated Fisher F-values, Fcalc Fisher Table F-values,
% Singles Tomato Pepper 2.357 1.184 2.728 2.728
% Misses Tomato Pepper 1.418 1.464 3.823 2.459
% Multiples Tomato Pepper 2.640 1.821 2.728 2.728
Significant at 5% level of significance (Fcalc. <Ftab)
The test of the regression equation coefficients of equations (4) - (6) indicated that the primary and secondary order of the factors affecting the single-seeding performance and misseswere the vacuum pressure in the seeding drum and the suction hole diameter while the factor affecting multiples was vacuum pressure.
The suction pressure and suction hole diameter affected % singles, misses and multiples seeding. The suction pressure influenced singles most, then followed by suction hole diameter for both tomato and pepper seeds as evident from regression equations (1) - (6). Thus, in order to obtain maximum singulation of both seeds, it is necessary to adjust the suction pressure precisely during seeding. The % of missing was influenced most by suction pressure, followed by suction hole diameter for tomato seeds. In case of pepper seeds, % of misses was significantly influenced only by the suction pressure. The % of multiples was significantly influenced by both suction pressure and suction hole diameter for tomato and pepper seeds respectively.
According to precision cell tray seeder performance requirement, three regression equations for the performance index of single-seeding, empty-seeding and multiple-seeding are taken as the index. A solver main
objective method was used with Microsoft Excel to optimize the solution, achieving the improved parameter combination scheme under different objective functions.
The optimum parameter combinations are presented in table 6.
Table 6. Optimum parameters for single-seeding performance
Factors Optimized values
tomato pepper
Vacuum pressure, kPa 2.1 2.2
Suction hole diameter, mm 1.0 1.0
To achieve maximum singulation performance of more than 90% with minimum misses/multiples, the optimum parameters are: the vacuum pressure is 2.1 and 2.2 kPa; the suction hole diameter is 1.0 and 1.0 mm for tomato and pepper seeds respectively.
Conclusions
An orthogonal central composite design (CCD) was used to establish a nonlinear regression model that illustrates the relationship between the vacuum pressure in the seeding drum, suction hole diameter and singles, misses and multiples seeding of tomato and pepper seeds. This enables a theoretical foundation for parameters improvement of the vegetable seeds cell tray precision seeder.
Vacuum pressure and suction hole diameter are the main factors affecting singulation andmisses, while the only factor affecting multiples is vacuum pressure. The optimal seeding mechanism parameters of the vegetable cell tray precision seeder in the study are the vacuum pressure in the seeding drum of 2.1and 2.2 kPa and suction hole diameter of 1.0 and 1.0 mm for tomato and pepper seeds respectively.
The performance indices verified experimentally are the singulation of 96.0%, misses of 1.4% and multiples of 2.7% which all meet the agrotechnical requirements. Single-seed vegetable cell tray seeding techniques are important for reducing seeds wastage, ensuring germination rate and improving vegetable production, which is conducive to the promotion of rational use of human and material resources to achieve quality seedlings for vegetable-growing enterprises in Belarus.
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