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True Potato Seed Production and Its Economic Analysis as Influenced by Supplemental Nitrogen and Planting Density

Tuhin Suvra Roy
Faculty of Agriculture, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh

Takashi Nishizawa
Faculty of Agriculture, Yamagata University, Tsuruoka 997-8555, Japan

Mohammed Hazrat Ali
Faculty of Agriculture, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh

Abstract/ Executive Summary:

A field experiment was carried out to evaluate True Potato Seed (TPS) production and its relative economic return as influenced by supplemental nitrogen (N) at a range of 0-250 kg ha^-1 and planting density at a range of 8-16 haulms m^-2 in potato mother plants (Solanum tuberosum L.) using a cross of MF-II) and TPS-67. The single effect of supplemental N application and planting density on the yield of berries and TPS was significant. Number of berries plant^-1, mean berry weight, number of TPS berry^-1 and yield of TPS showed maximum values when 0-150 kg N ha^-1 was applied, but the values decreased thereafter as supplemental N application increased, irrespective of the size of the harvested berries. Although only the weight of 100-TPS showed a maximum value at 250 kg N ha^-1 application, the value was similar to that at 200 kg N ha^-1 application. Mean berry weight, number of seeds berry^-1 and weight of 100-TPS showed the maximum values at the lowest (8 haulms m^-2) planting density and the values decreased thereafter as the planting density increased, irrespective of the size of harvested berries. A positive effect of higher planting density was detected only in the number of berries plant^-1 and yield of TPS. The combination effect of supplemental N application and planting density on the yield of berries and TPS was also significant. Although the total yield of TPS was the highest at the combination of 150 N kg ha^-1 and 16 stems m^-2, the yield of large size TPS, which is regarded as high quality TPS, was the highest at the combination of 200 N kg ha^-1 and 12 stems m^-2. This was also true for the other characteristics of harvested TPS under different supplemental N applications and planting densities; i.e., number of berries plant^-1, number of TPS berry-1 and weight of 100-TPS showed the maximum values at the combinations of 0-150 N kg ha^-1 and 8-16 stems m^-2 or 200 kg N ha^-1 and 8 stems m^-2, but not at 200 N kg ha^-1and 12 stems m^-2. The benefit cost ratio, which was estimated from total cost of production and gross return also showed that the combination of 200 kg N ha^-1 and 12 stems m^-2 were the optimal growth conditions to harvest high quality TPS from the potato mother plants.

Keywords: Berry, Supplemental nitrogen, Planting density, Seed quality, TPS

Location: Tuber Crops Research Center (TCRC), Bangladesh Agricultural Research Institute, Gazipur, Bangladesh

Start Date: 00-00-2006

End Date: 00-00-2007

Program Area: Crop-Soil-Water Management

Commodity: Potato

Objectives:

To evaluate how supplemental N fertilizer and PD (Planting Density) affect the yield and quality of TPS (True Potato Seed).

Methodology:

The experiment was conducted at the experimental field of the Tuber Crops Research Center (TCRC), Bangladesh Agricultural Research Institute, Gazipur, Bangladesh, during 2006-2007. The soil characteristics were pH 6.8 (Jackson, 1962) with 1.65% organic matter, 0.096% N, 0.001% available P, 0.131 me% exchangeable K and 0.00123% available S. On 19 October 2006, sprouted tubers (50-60 g) of the female parent (MF-II) were planted in the experimental plots of TCRC at a depth of 5 cm. In contrast to the standard procedures for growing potato mother plants (Roy et al., 2007a), the experimental plots were not hilled to prevent tuberization. The above ground stolons were pruned soon after emergence for better growth of the main shoots. Two to four haulms per tuber were allowed to grow to obtain small, medium and high PD (8, 12 and 16 potato haulms m^-2, respectively and hereafter described as PD⁸, PD¹² and PD¹⁶, respectively). Each haulm was supported on trellises. Considering the findings of our previous studies (Roy et al., 2007a, b), N:P:K:Gypsum:ZnSO₄:Borax (150:120:125:120:12:6 kg ha^-1) and farmyard manure (10 t ha^-1) were applied 3 days before planting as a basal fertilizer. Four different levels of N (0, 21.4, 28.6 and 35.7 kg ha^-1, respectively) were applied supplementary at a depth of 3-5 and 10-15 cm apart from the mother plants, when the first flower bud commenced (27 DAP). This supplemental N application was conducted 7 times at 7 day intervals as described above. Therefore, the total amount of supplemental N application was 0, 150, 200 and 250 kg N ha^-1 for each treatment (hereafter described as N₀, N₁₅₀, N₂₀₀ and N₂₅₀ kg N ha^-1, respectively). The experiment was conducted in a split-plot design with 3 replications. Supplemental N was assigned to main-plots and PD to sub-plots. The distance between two rows was 1 m and each seed potato was planted at a distance of 0.25 m apart in a row. The sub-plot was a single row 3 m long and each consisted of 12 plants. On 12 October 2006, the male parent (TPS-67) was planted in separate plots to harmonize their flowering with the female parent. Only the first and second inflorescence on a stem was allowed to develop for pollination and each inflorescence was pruned to 6 flower buds of similar maturity to equalize the date of anthesis. Berries were harvested when they became soft (approximately 6-7 weeks after pollination) and classified into large- (> 10 g) and small-(<10 g) berries. Ten berries from each weight class were selected per replication. All other practices and procedures of production, extraction and drying of TPS were same as those described in the previous report (Roy et al., 2007a). After proper drying, TPS were separated into three sizes of small-(<1.18 mm), medium-(1.18-1.4 mm) and large-(>1.4 mm) seeds using testing sieves (Tokyo Screen, Japan). The Benefit Cost Ratio (BCR) of TPS production under different combinations of supplemental N and PD was estimated from the cost of production, gross return and net return according to standard labor/material costs of Bangladesh (BADC, 2006). The analysis of variance was carried out using MSTAT-C statistical software (MSTAT, 1991). Means were compared using the Least Significant Differences (LSD) test at a 5% probability level.

Source of Information: Asian Journal of Plant Sciences, 7: 73-78; ISSN 1682-3974

Article Link (Online Journal): DOI: 10.3923/ajps.2008.73.78 and URL: http://scialert.net/abstract/?doi=ajps.2008.73.78

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The result of combination effect of supplemental N application and PD revealed that N_0-150 PD_8-16 and N₂₅₀ PD₈ were the best combinations when the objective of TPS production was focused on number of berries plant^-1or number of TPS berry^-1 and weight of 100-TPS, respectively, irrespective of the size of harvested TPS. However, from the economic point of view, the combination of N₂₀₀ PD₁₂ was found to be most profitable compared to other treatment combinations in respect of gross returns, net returns and BCR values. This combination was also produced the maximum yield of marketable TPS (> 1.18 mm size). The price of hybrid TPS is still high (US $ 228.6 kg^-1) and not within the reach of majority farmers. It would be reduced either by increasing the yield of quality TPS or by applying appropriate crop management practices. Therefore, in the commercial aspect 200 kg N ha^-1 of supplemental N application in 7 separate installments at 7 day intervals starting from 27 DAP and 3 stems tuber^-1 (12 stems m^-2) is the most suitable combination to produce high quality TPS from MF-II x TPS-67.

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