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Five Square Model – An innovative practice to reduce soil salinity

Sutapa De, Saikat Pal and Purnaba Dasgupta

Severe water logging resulting in soil salinity has made crop cultivation difficult for farmers in Sunderbans region. Five Square model emerged as an innovative solution which farmers adopted and reaped good benefits.

The government scaled up the water harvesting structures through MGNREGA programme

The Sundarbans is the largest single block of tidal halophytic mangrove forest in the world. The area receives good annual rainfall which is much higher than the annual average rainfall of India. Sundarbans receive rainfall, to the tune of 1800 mm to 2000 mm in a year. Almost 70% of the rainfall takes place in the month of July, August and September of the year. This high rainfall in three months results in huge water logging, as the terrain is flat.

Agriculture is the major source of livelihoods. Paddy is grown during the monsoon season. The agriculture land suffers from severe water logging in rainy season and soil salinity in the winter and summer. There is also very minimum rainfall in the winter and summer months (November to April) of the year. The salinity in the soil and the shallow ground water increases in these dry months which again does not allow the second crop to grow. Salts become active in the winter and salinity reaches maximum values in the summer. In the summer, no crop can be grown as there are no sources of sweet water supply for irrigation.

The Initiative

In 2009, the entire Gosaba block of South 24 Parganas district was destroyed by Aila cyclone. Entire land got converted from sweet to saline soil owing to excessive water logging. It was impossible to grow crops.  With sea water inundation, growing a single rice crop was also at stake. However, the heavy rainfall during 2010-12 helped in reducing salinity to a certain extent. At this point of time, PRASARI, an NGO working in the area tried to find out ways to address the problem of soil salinity and help farmers build their livelihoods.


With sea water inundation, growing a single rice crop was also at stake in the saline agriculture area.


In order to reduce salinity and improve incomes, PRASARI organised a sharing workshop with Gram Panchayat and the community. Problems were identified which highlighted issues like salinity, stagnant water and low incomes. Solutions were also identified through community participation.

Land shaping was found to be an ideal solution to begin with.  Following discussions, a technological model was designed. It included creating rain water harvesting structures, shaping/raising the land bed and strengthening field bunds with the excavated soil thus ensuring easy drainage to counter waterlogged situation. It also included ways of optimising utilization of land-water-human resource to  ensure a quantum jump in the family’s annual income to prevent distressed migration. For example, integration of kharif rice (through SRI-system of rice Intensification) and residual mainland moisture use through mustard as second crop (using SRI principles);  growing two vegetables in a year on the strengthened field bunds; improved carp and prawn culture in the water harvesting tank, ensured additional incomes. This is a bottom up trend for area or patch treatment, which helps in making that particular area free from water stagnation and salinity.


Box 1: What does the land treatment do?

  • It provides a gentle slope to facilitate runoff: avoiding water logging.
  • Raised land bed facilitates leaching and surface wash of salinity-thus reducing it to a great extent.
  • High field bunds protect the plots from flooding.
  • Harvested rain water ensure staple and cash crops from beds and bunds.
  • Fish is an assured source of income from Water harvesting structure.
  • Almost a bigha of land has the potential to generate annual income of Rs. 50000, sufficient to prevent migration.

“Five-Square” Model

Such water harvesting structure (WHS) is named as “five-square” model, designed for a bigha (1/3 rd of an acre of land) and would provide good water supply for the treated plots, based on the water availability and crop water requirements. The dimension of the structure (55 ftX55ft; five square depicts 55 ft.) for one third of an acre of the land may vary with the plot dimension. If calculated, the structure requires 20% of the plot size (i.e. one fifth of the plot). For any plot with length-L and width-B, the structure’s length-L1=L/2.5 and width B1=B/2. So the WHS area will be L1XB1=(L/2.5) X(B/2) =(LXB)/(2.5X2) =Plot area/5. The size of the structure has been decided based on the discussion and preferences of the farmers. There are three different layers each of 3 ft. depth.

Community level workshops were organised inviting Geotechnical engineers, Agricultural scientists and soil scientists, where in “Five Square Model” was discussed and advantages recognised. 

Trying on the ground

In the year 2012-13, PRASARI shared the idea of “five square” model with local Gram Panchayat (GP) at Kochukhali,Gosaba Block. Panchayat agreed to invest through MGNREGA on a single structure to examine the efficacy of the ‘solution’. ‘Phanida’ a marginal farmer from Kochukhali agreed to take the ‘risk’. In the month of May-2012, the Panchayat Engineer agreed to provide the ‘field lay out’ after a lot of technical debate,s especially on the ‘soil stability’.

The five square model on the ground

Workshop with the GP representatives was organised with a special focus on beneficiary selection and technical monitoring. Beneficiary selection through community meeting was done through water flow mapping, patch marking of revenue villages and fixing minimum criteria for beneficiary selection.

Technical training was provided to the labour for developing structure which included, cutting process and design, bund design, process of land shaping along the slopes, channels and outlets.

Once the excavation and land shaping were over, the challenge was to grow crops on the shaped land and bunds. The soils were expected to have huge salinity as the soil from deeper layers was excavated and uniformly deposited on beds and bunds. The field was separated from the adjacent plots and ponding of water allowed for a while. Draining out water later carried away maximum possible salts from the field.

Thereafter, three types of production systems were initiated – SRI on main land, egg-plant, cucurbits and peas on the field bund and a few carp fingerlings (just to test whether they can survive in the very first year) in the tank. Sowing of SRI paddy was taken up a little late to allow the rain water to drain. SRI which takes 10-15 days less for crop maturity, had compensated for the cropping time loss. In the very first year, the bund has been tried with cucurbits, solanaceae species and peas to track the response of different species. Also, we agreed not to go for prawn culture in the very first year as prawn seeds are little expensive.

Apart from crop coverage, special focus was given to track the changes in the very first year.  Data on water logging, soil and pond water qualities and salinity levels were tracked. pH paper strips and Portable Diffractometer were used to determine the salinity percentage.

Five Square Model Data (2018-19)
Name of the farmer: PhanindranathMondal, Kachukhali, Gosaba
Soil parameters
  Bund Field Outside
Date Salinity PH Level Salinity PH Level Salinity PH Level
(%) (%) (%)
July 3 5 5.5 4.9 7.5 6.3
August 2.5 5.1 5 5.2 7 6.2
September 2 5.2 4.5 5.4 6.5 5.5
October 1.5 5.4 3 4.8 4.5 5.8
 November 0 5.4 1.5 5 4 5.8

 

Five Square Model Data (2018-19)
Name of the farmer: PhanindranathMondal, Kachukhali, Gosaba
Tank Water Quality
Date Salinity PH Level
(%)
July 5 3
August 6 3.5
September 6 4
October 3.5 4
November 2 4.3

Impact and spread 

Pisciculture and agriculture were the two main activities taken up at these five square models, which improved incomes. Presently, a variety of vegetables are grown on these models such as creepers and Solanaceae species (bitter gourd, tomato, spinach, brinjal, green chillies, beans etc). Among the beneficiaries, Biswajit Mahato of Pathankhjali GP, Gosaba Block deserves special mention, He has earned a considerable amount of income from his five square model. Biswajit has invested Rs 21,790 in the last financial year for vegetable cultivation (ladies’ finger, bitter gourd and brinjal), from which he has earned Rs 59,720. He has also succeeded in fish farming which he has mostly used for home consumption.

Inspired by the results of five-square model, the Panchayat and Block took initiative to construct such models in their locality. A number of such models have been constructed.

Panchayat and Rural Development Department has also taken up this technology to build water harvesting in all the 19 Blocks in Coastal Sundarbans. The programme is being implemented through MGNREGA programme.

Creation of water harvesting structures and its replication has been taken up by Block Agriculture Department, especially in Sandeshkhali II Block, North 24 Parganas district. This has been implemented through PMKSY project at block level, wherein 41 such water harvesting structures (five square models) have been created, under the supervision of PRASARI.

Land shaping technology if adopted on a larger scale, would result in an entire delta region free from salinity and water stagnation. Better income generation would further result in poverty reduction and reduced migration.

 

Sutapa De, Saikat Pal and Purnabha Dasgupta

PRASARI

17b-Bapujinagar,

Jadavpur, Kokata-700 092

www.prasari.org

Email: sutapaprasari@gmail.com