Yield and economics of potato in short duration rice-based cropping system in Rangpur district

The potato crop is sensitive to environmental factors as optimum planting time of potato depends on the most favorable temperatures extending over the longest period of the crop season and requires less than maximum and above the minimum temperatures for emergence after planting. To secure good yield, the potato crop should be planted in such a time that all the three growth and development phases pass through favorable environmental conditions. Cognizant the above facts, a field experiment was conducted at RDRS Farm, Rangpur during 2014 and 2015 for cultivating potato in different dates with two popular potato varieties like Diamont and Cardinal to find out the optimum planting time of potato production in Bangladesh under short duration rice-based cropping system as well as assess the economic viability of potato cultivation in November. The cost-benefit analysis indicates that no major variation was observed in the performance of two varieties e.g. Diamont and Cardinal. But significant variation was observed in different planting dates. The 22 November planting of both Diamont and Cardinal produced highest yield (29.2 and 28.8 t/ha1 respectively) compared to other three planting dates like 7 th November (27.8 t/ha and 26.9 t/ha), 7 December (21.1 t/ha and 19.8 t/ha) and 22 December (15.2 t/ha and 14.7 t/ha). The 7 November planting was found economically profitable for both the varieties, where the highest economic return was recorded as TK. 2,06,372/ha for Diamont and TK. 2,08,772/ha for Cardinal. Thus, from the economic point of view, the 7 November planting performed best for both varieties. The cost of production was gradually higher in case of late planting due to use of higher amount of pesticides in the crop field. It may be concluded that potato could be cultivated during 1 half of November month, just after harvesting of short duration aman rice in October that will bring harvesting of potato in 1 half of February which can ensure highest net income from potato cultivation and enables farmers to cultivate next crop like mungbean as additional income.


Introduction
The potato is the fourth leading food crop in the world after rice, wheat and maize because of its great yield potential and high nutritive value. Potato is a rich source of starch and it is consumed for its calorie value. In terms of energy produced per unit area of land, potato exceeds all the cereals. Protein yield per unit area is also superior to the cereal grains and second only to soybean. Bangladesh is the seventh largest potato production countries in the world (AMIS, 2016). After rice, potato is the third most important crop in Bangladesh (Siddique et al. 2015). The area under this crop is increasing rapidly and the farmers are gradually adopting it as a cash crop. Due to cold storage facilities, potato is available in the market throughout the year while almost every family of the country consumes potato round the year. Potato is now the second staple food item In Bangladesh and per person potato consumption rose to ten times more than that were in 1980 (The Prothom Alo, 2015).
Rice is becoming more expensive and scarce while potato has higher food nutrients (no fat, higher vitamin C and quality protein compared to rice). Therefore potato can play an important role to ensure food security with enhancing nutrition value through more potato consumption. The average yield of potato is 13.32 t/ha which is very low compared to other potato producing countries like 43.2 t/ha in France, 44.7 t/ha in Netherlands and 44.6 t/ha in the USA in 2007. The production of potato was 2.93 million metric tons from 0.243 million hectares of land in Bangladesh during 1999-2000(BBS, 2000. In 2007-2008, the production of potato was nearly 8 million metric tons from 0.5 million hectares (Bangladesh Potato Campaign, 2008) while in 2015-2016, it was 9.47 million metric tons from 0.475 million hectares (BBS, 2016).
To increase production of food crops in Bangladesh, both vertical and horizontal expansions are needed. The possibilities of horizontal expansion for major food crops are very limited due to the scarcity of land. Vertical expansion by introducing new and appropriate production technologies e.g. suitable/alternate cropping pattern which helps increase cropping intensity is feasible and economical to enhance the yield and income ARTICLE INFO reducing per unit production cost. The major constraints for potato production in Bangladesh are (i) lack of quality seeds (ii) farmers have less scope to maintain the appropriate planting time due to long duration aman rice cultivation and (iii) incidence of diseases and pests due to late planting (Haque, 2010;Islam et al. 2014;and Siddique et al. 2015).
The amount of tuber infection which goes to stores through seed tubers ranges 0.01-3%, is more than enough to initiate late blight epidemic in the next crop season (Rahman et al. 2007). To secure good yields, the potato crop should be planted in such a time that all the three growth and developmental phases pass through favorable environmental conditions. The optimum planting time depends on (i) the most favorable temperatures extending over the longest period of the crop season, associated with less than maximum and above the minimum temperatures necessary for emergence after planting, (ii) the duration of cultivars, its reaction to high or low temperature, and susceptibility to late blight, (iii) soil moisture status under rainfed conditions and (iv) effective growing season depending on whether the crop is allowed to grow to maturity or lifted prior to maturity.
The optimum growth and development of potato require a temperature range of 15 O C-21 O C (Siddique et al. 2015). It is very important to know the growth and development of potato tubers in relation to time of planting under the short day and short growing season of the tropical areas like Bangladesh. Islam et al. (2014) observed that November was the best for potato planting which could avert the disease by maturing crop before the severe infestation period. They also found that due to use of long duration T. aman rice variety BR11 causing delay in potato planting in December, which ultimately reduced yield and favored crop failure due to late blight diseases. Scientists found that the planting between 10 to 20 th November was the best for the production of seed potatoes in Bangladesh whereas for ware potatoes planting could be delayed up to 1 st December. They found that seed quality deteriorated when planting was done after 20 th November, but the total yields were affected when planted after 1 st December.
Haque, 2010 pointed that most of the farmers of northern region of Bangladesh used to cultivate potato in the month of December, after harvest of their transplanted aman rice (November to mid-December) and received low yield compared to November planting. As recently developed short duration rice variety is the possible way to harvest rice in the month of October, of which farmers are now able to cultivate potato in right time (in November) to ensure good yield and income. Side by side, day laborers will get job not only from harvest of short duration rice in the lean period, but also to access job in the early November (Kartik month) by cultivating potato, especially from land preparation, seed sowing, then application of basal fertilizer as well as earthing-up after seed sowing. So the potato cultivation in early November is not only increases the production but a wider opportunity for day laborers to access job in the month of Kartik (lean period), when the food stocks of the poor people have been heavily depleted. Islam et al. (2014) observed that short duration rice created job opportunity for the poor in monga period (September-October) for harvesting rice. Keeping the views in mind, the experiment was undertaken to accommodate potato in short duration rice-based cropping pattern to increase yield and economic return and also to generate work in agricultural field in the off period during September-October.
Cognizant of the above facts, a research program has been designed on planting of potato in different dates with two most popular potato varieties in northern region of Bangladesh. The major objectives of this study are: 1. To identify the most appropriate time of potato production in northern region of Bangladesh under short duration ricepotatomungbean cropping pattern. 2. To assess the economic viability of potato cultivation in early November under short duration ricepotato mungbean cropping pattern to mitigate seasonal crisis.

Materials and Methods
The experiment was conducted at the RDRS Farm, Rangpur Sadar upazilla. The two most popular potato varieties (Cardinal and Diamont) with four different planting dates (7 th November, 22 nd November, 7 th December and 22 nd December) were tested through onstation research to identify suitable time of planting in support of short duration rice -potato -mungbean cropping pattern. Farmer traditionally followed the planting times in December, after harvesting T. Aman rice of long duration varieties. November planting dates were chosen to ensure timely planting, immediately after harvest of early aman rice (using short duration rice varieties), so that the cropping pattern help farmers and day laborers to get production and employment during lean period due to harvest of rice and planting of potato.
The experiment was laid out in a Randomized Complete Black Design (RCBD) with four replications. The unit plot size was 4m x 4m and the treatment combinations were as follows: The P H value of the soil was within the range of 5 to 5.5. The experimental plot was well ploughed.

Sl. No. Treatments
Recommended doses of fertilizers and manure suggested by Tuber Crops Research Center (TCRC), BARI, Gazipur were used. Cow dung was incorporated in the soil during land preparation at the rate of 10 t/ha. Urea, Triple Super Phosphate (TSP), muriate of potash (MoP), gypsum, zinc sulphate and boric acid were used respectively at the rate of 325, 220, 250, 120, 14 and 6 kg per hectare. Urea, TSP, MoP, gypsum, zinc sulphate and boric acid were the sources of N, P, K, Ca, Zn and B, respectively. Seed tubers were collected from Breeders Seed Production Center, BARI, Debigonj, Panchagarh. Row to row spacing (within plot) and tuber to tuber (within row) was 60 cm and 25 cm respectively. Each plot had 7 rows and in each row 13 seed tubers were sown. Two times weeding was done at an interval of 30 days. Earthing-up was executed two times throughout the entire growing period, one at 30 days and another one at 60 days after planting. Irrigation was scheduled two times just after earthing-up. The whole crops were harvested after 90 days of planting while one row was harvested after 60 days of planting.

Statistical Analysis
The data obtained on the plant growth parameters and yield were processed by analysis of variance (ANOVA) using MSTAT-C program. The significance of the differences among the treatment means were evaluated by least significant difference (LSD) test (P=0.05).

Results and Discussion
Effect of variety on the yield and yield components The effect of two varieties (Diamont and Cardinal) on the yield, yield components and crop duration was varied significantly (Table 1). Diamont variety produced the higher yield (23.3 t/ha) compared to Cardinal variety after 90 days planting (22.5 t/ha) and higher number of potato per plant (10 and 10.7) at both 60 and 90 days of planting. Size of tubers (grade less than 25 mm. and 25-45 mm.) of Diamont variety after 60 days of planting was also higher (3.4 and 6.3 respectively). The Diamont variety also produced higher yield after 60 days of planting (16 t/ha). The probable reasons might be due to plantation of larger sized tubers per hill and higher plant heights of Diamont variety (Azad et al. 2017

Effect of planting time on the yield and yield components
The effect of planting time on the yield and yield components are presented in Table 2. There was no significant effect of planting time on percentage of emergence after 15 days of planting. Also no significant effect was found on number of plants per sub-plot after 45 days and 60 days of planting. The result revealed that plant height (69.4 cm) after 60 days of planting, potato yield per plant (380.5 gm) after 60 days of planting, and yield per hectare (29 t/ha) after harvesting of 90 days planting were significantly higher in 22 nd November planting as compared with 7 th November, 7 th December and 22 nd December planting time. The above research findings strongly support the other research results while the temperature had a great influence on the production, as temperature of 22 nd November is some favorable for potato production than 7 th November. Islam et al. 2014 pointed that November is the best for potato planting which can avert the disease by maturing crop before the severe infestation period. In case of potato yield per plant after 90 days of planting, potato grading of 25-45 mm size after 60 days of planting, tuber weight after 60 days and 90 days of planting and yield after 60 days of planting has no significant differences observed between 7 th November and 22 nd November planting. The highest yield was contributed by large number of leaves and stems which helped in deposition of greatest photosynthesis and ultimately maximized the yield (Alam et al., 2003).

Interaction effect between varieties and plating time on the yield and yield components
All the plants character varied significantly due to interaction effect between planting time and variety (  November was higher compared to other planting dates, mostly because of less production cost due to use of less pesticides because of favorable weather and higher market price of early potato harvests. Thus, from the economic point of view, 7 th November planting could be recommended.  Table 5) that the marginal rate of return (MRR) was the highest with 7 th November planting due to less production cost because of less pesticide uses in favorable weather and higher market price for early potato harvests. Thus from the economic point of view, 7 th November planting could be recommended.

Conclusion
The yield of Diamont and Cardinal potato variety was higher under 22 nd November planting, but the highest net profit was calculated in both varieties under 7 th November planting due to lowest production cost. The economic return of 7 th November planting was higher than other planting dates. The cost of production was gradually higher in case of late plantings due to use of higher amount of pesticides in the crop field. These pesticides were mainly used to protect late blight disease, which was caused due to late plantings like 22 nd November, 7 th December and 22 nd December. The crops planted late generally falls in the foggy, cloudy and comparatively warm weather in late February that favor late blight diseases, where early planting can escape this damage as crop may harvest before cloudy and comparatively warm weather in late February. It may be concluded that potato could be cultivated during 1 st half of November month, after harvesting of short duration rice in October that will bring harvesting of potato in 1 st half of February, which can ensure highest net income from potato cultivation, and enables farmers to cultivate next crop like mungbean as an additional income. Thus from the economic point of view, potato cultivation may be recommended on 1 st half of November which enables farmers to harvest potato within 1 st week of February which can ensure highest net income from potato cultivation. After potato harvests, farmers may go easily for additional crop cultivation like mungbean in the month of February which requires only 60-70 days for harvesting.