To assess the impacts of the technologically advanced RPG farming system on water productivity for MV paddy production, two contrasting villages- RPG farming system for Bilpabla in Khulna and YRMV paddy farming for Chanchra village in Jessore district were selected. The Bilpabla village was selected purposely because the people have vast experience of RPG farming system like other parts of Khulna district and they directly or indirectly depend on their daily livelihood on various gher-farming activities. On the hand, Chanchra village located in Jessore district was also purposely selected because the farmers cultivate MV paddy throughout the year. Moreover, the Jessore is neighboring of Khulna district. Ninety (90) RPG farmers and 100 YRMV paddy farmers were randomly selected. The farm survey was carried out during November 2006 based on the agricultural cropping year 2005.
Moreover, two case studies (two gher farming–named RPG-1 and RPG-2 in discussion section) were also considered for the study to measure the water level of gher plot during one year rice and prawn production cycle. Water level in canal (from bottom of canal to ridge of paddy field) and mid paddy field of gher plots (from bottom of paddy field to dike of gher plot) was measured in every week (after every 7 days) from 1 May 2006 to 30 April, 2007 and registered in a record book. In addition, the quantity of water (m3) used as irrigation was also measured during MV boro paddy production in RPG farming system.
4. Rice-prawn gher farming system
The term rice-prawn gher refers to a modification of paddy field that has been used for prawn and paddy cultivation. The mid field (locally known as Chatal) of gher is surrounded by high wide dikes and canals that lies the periphery of the dikes. The whole land of gher is filled up with rain-water from June to December and resemble to a pond. During this time, farmers cultivate prawn (Macrobrachium rosenbergii) and fish (Catla catla; Labeo rohita; Cirrhina mrigala; Cyprinus carpio; Puntius sarana; Pungasias pangasias, etc). The entire land becomes dry naturally from January to April except canals. The canals retain sufficient water for MV boro paddy during this time. As a result, farmers can grow MV boro paddy on chatal.
It is observed from field survey that on an average about 60% area is used for MV boro paddy under RPG farming system. The mid field of RPG farming system widely varies from 45% to 75% in the study area. Two case studies were used to make sure the general information of physical construction of RPG farming in the study Bilpabla village in 2006-07. The two RPG farming are indicated as RPG-1 and RPG-2.
It is observed from two case studies that about 3,449 m2 (RPG-1) and 3,412 m2 (RPG-2) area were used for MV boro paddy production out of total RPG farming area 5,990 m2 and 6,252 m2, respectively. In other words, only 58% and 55% area is used for MV paddy cultivation, respectively, in RPG-1 and RPG-2 farming. A small portion of RPG farm is used for seedbed as seeding of MV paddy cultivation. This small seedbed is used for MV paddy cultivation after seedling. Canals are the attractive parts of the RPG farming system, which belongs to the areas of about 1,979 m2 and 2,070 m2, respectively, in RPG-1 and RPG-2. A significant area is also used for high dikes and small ridges. The high dikes are used to protect RPG from floods during rain season and separate from the other gher plots. The height of the dikes is usually 1.0-2.0 meter, which mainly depends on the location of gher plots. Farmers make high dikes to protect gher as well as prawn from the unexpected floods due to heavy rain. Sometimes heavy monsoon rain overflows the gher plot during prawn production even though high dikes. If the gher overflows, the prawn and other fish easily move to another gher plots. Farmers temporarily put long nets on the dikes to protect prawn movement during flooding times.
5. Cropping pattern of the study villages
Currently three types of paddy are producing in Bangladesh in three distinct seasons: aus (April to August), transplanting aman (T. aman) (August to December), and boro (January to April). Among them, aus and T. aman paddy are produced in rainfed water and MV boro paddy is produced in irrigated water (ground water or rivers and canals). Modern varieties paddy were introduced in Bangladesh for the boro and aus season in 1967 and aman season in 1970. In 2002, only 32% area was irrigated under MV paddy production in Bangladesh, (BBS, 2002). Irrigation and chemical fertilizers are not used local aus and T. aman paddy production because the paddy fields go under water. Farmers transplant MV boro paddy from mid-January to mid-February, and harvest from mid-April to mid-May. Farmers usually use chemical fertilizers, pesticides, and irrigation for boro paddy production. Along with paddy crops, farmers also cultivate oil seeds, potato, and vegetables in the comparatively high land during the winter season.