Abstract
A study was conducted in irrigated ecosystem in Kanhor village of Trishal upazila of Mymensingh District under the Old Brahmmaputra Floodplain soil in the command area of three deep tube wells with the objectives of identifying and characterizing cropping patterns, analyzing the dynamics of the major rice cropping patterns, determining the agronomic performance of the patterns and assessing soil quality and pattern efficiency. Seventy farmers were involved in the command areas, which were considered as the participating farmers of the study. The study site was once the Research Site of Cropping Systems Research and Development of the Bangladesh Agricultural University, which was one of the major sources of secondary data collection. Primary data were collected through interview schedule from the participating farmers, monitoring, field visit, crop cut, laboratory analysis, personal communication and literature search. The findings of the study indicate that the total number patterns were 22, in 1980-85, which increased to 185 during 2001-02 to 2007.due to increased number of rice varieties in the cropping patterns. Study of dynamism revealed that the number of appeared, disappeared and reappeared patterns were different in different years. In 2007, 39 patterns appeared, 48 disappeared and 44 patterns were reappeared. With the changing of cropping patterns farmers also started changing technology like variety, seed, fertilizer, pesticides, and agricultural implements to reach a goal of maximum productivity. Along with other reasons the most common reasons of changing cropping patterns were 'for high yield, Considering compatibility of the crop to the other crop in the pattern'. Fifteen stable cropping patterns were identified of which 12 patterns were three rice crop patterns and three were two rice crop patterns with seasonal fallow as recorded from 2001-07. From the analysis of 12 three crop patterns of rice it indicates that agronomic productivity did not exhibit any significant variation among them, Agronomic productivity of these 12 cropping patterns varied from 11.42 to 14.06 t ha1.The T. Aus rice (Hizac) -T. Aman (Balam)- Boro rice (BRRI dhan28) produced the numerically the highest grain productivity (14.06t ha1). Whereas T. Aus rice (Hizac) T. Aman (Pajam)- Boro rice (Pajam) gave the lowest grain productivity (11042 t ha1). The economic return in terms of gross margin was the highest in T. Aus rice (Hizac) T. Aman (Kalijira)- Boro rice (Hizac) pattern. Having Tk.146064 ha 1. Varietal diversity was characterized by quite a large number of modern rice varieties including the popular varieties like BRRI dhan 28, BRRI dhan29. The largest number of varieties were practiced in 2006-07(30 existing, 5 nearly appeared, 5 disappeared and 3 reappeared). In 1980s and in 1990s, modern varieties had the dominated trend over local ones. In early to mid 2000s (2006-07) BRRI dhan 28, BRRI dhan29, Balam. Bairaaifsa, Kiron, BR3, Kalijira and Chinisagar were the most popular and sustainable varieties to fit into the cropping patterns. Hizac seemed to be the best variety with wide adaptability for growing in all the three seasons like Aus. Aman and Boro. In the Research Site the soil was slightly clay and organic matter content was 1.30% in 1980. Though the farmers have been using chemical fertilizer below recommendation, they have been using sufficient organic fertilizer like cowdung compost, ashes and homestead wastes including recycling of crop residues in the crop field for production of rice from Rice - Rice- Rice cropping patterns without / minimum deteriorating of soil quality. Long term study indicated that the organic matter of the soil has been maintaining more or less at constant level from 1980-2007 (1.30%), slightly increased in 2007 (1.43%) indicating a sign of good organic matter management under the cropping pattern as mentioned. It may be mentioned here that 11.76 t ha1 of biomass was (4.48 t ha-1 cowdung, 0.73 t ha' homestead wastes and 7.55 t ha' crop residues) applied by the farmers of the research site. Except sulphur N, P and K. of the soil with fertilizer application was above the critical level. Pattern efficiency indicates that it varied from 2.96 to 6.81 t ha in the pattern T, Aus rice (BRRI dhan 28) T. Aman (Pajam)- Boro rice (Pajam )and T. Aus rice (Hizac) -T. Aman (Pajam)- Boro rice (ACI 1), respectively. From the finding of the study it indicates that farmer's planning and management of cropping patterns were based on scientific knowledge and skill and economic principles as tried in the study. From productivity point of view the yield of rice in all seasons showed increasing trends in spite of small scale disturbance like natural hazard exhibiting Rice- Rice- Rice /Rice- Rice system is a sustainable one.