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Bringing back the soil

Rainfed lands are less productive and are also subjected to soil erosion. Replenishing such lands with the lost soil by applying tanksilt will not only help farmers improve their soil fertility, but also enhance the water storage capacity of the tanks. Vayalagams, the people institutions in South India have shown that this is possible.

Tanksilt collected from the tanks. Photo: N Venkatesan

Tanksilt collected from the tanks. Photo: N Venkatesan

Tamil Nadu is endowed with more than 40,000 irrigation tanks, about 80% of which are small tanks commanding less than 40 hectares each. These tanks were formed many centuries ago as water harvesting structures to offset the vagaries of monsoons. Despite that, more than 60% of the net area sown in Tamil Nadu is cultivated only under rainfed condition due to poor water resources available in the State.

These rainfed agricultural lands form a major part of the catchment area which contribute to the tank’s storage. High intensity rainfall leads to heavy surface run off resulting in the erosion of valuable nutrient rich top soil from the rainfed agricultural lands. They are further carried along with the running water and deposited as silt in the tanks adversely affects its storage capacity.

Traditionally, the application of tank silt to rain-fed agricultural lands was a common practice among South Indian farmers, which not only replenished the soil with nutrients, but also improved the moisture retention capacity of the soil. But this practice of applying tank silt to the agricultural lands has slowly vanished during the past decades, owing to several reasons like farm mechanization, excessive use of chemical fertilizers, high costs, and restrictions imposed by the revenue staff at the village level.

Studies conducted by the Central Research Institute of Dryland Agriculture (CRIDA, Hyderabad) in Nallabelli and Regonda mandals of Telangana reveal that, with tank silt application, soil moisture retention has gone up by 4 -7 days; higher plant population and higher plant height, increased yields (maize by 700 kg/ha and cotton by 1000 kg/ha), savings on chemical fertilizers ranging from Rs.2500/- to Rs.3750/- per ha. were observed.

Studies on several irrigation tanks in Karnataka by the University of Agriculture Sciences, Bangalore, show that the tank silt have plant-nutrients which can enrich the land and increase land productivity.

Vayalagams- A people’s own initiative

DHAN Foundation has been facilitating the rehabilitation of tank systems through Vayalagams. “Vayalagams”, are nested people institutions, promoted and maintained by local communities. Vayalagams have their own systems and procedures and implement programmes for the development of the area.

The local community staff at each block promotes and maintains 15 to 20 Vayalagams at one cascade of water bodies within the vicinity of 3 to 5 panchayats. This cascade would have 350 to 500 farmers. One Vayalagam community staff can manage these members organized as 25 to 30 microfinance groups. They regularly meet to carry on savings and credit activities. After 3 to 4 years, the surplus generated would be enough to meet the cost of the staff.

The thrust for the first three years is on social mobilization, then another three years of financial mobilization through their savings and credits, the subsequent three years for their linkages mostly for livelihoods interventions and fourth set of three years for civic inter-mediation as four generation concept. Accordingly, DHAN links them with mainstream or other authorities to mobilize resources.

Tank silt application – demonstrating value

Tanksilt applied to farm land. Photo: N Venkatesan
Tanksilt applied to farm land. Photo: N Venkatesan

During 2008-2009 and 2009-2010, Dhan Foundation conducted demonstrations on the technology of tank silt application along with the soil moisture retainers (farm yard manure/coir waste). These demonstrations conducted in two seasons was supported by the Ministry of Water Resources, Government of India under Farmers Participatory Action Research Program (FPARP).

The demonstrations were conducted on the fields of 30 farmers covering an area of 30 hectares located in Madurai district in Tami Nadu and Chittoor and Nalgonda districts of Andhra Pradesh. While 20 were demonstrated in drylands, 10 were conducted in lands having supplementary irrigation facility. Around 50% of the unit cost of Rs.14000 was shared by the farmers.

The FPARP demonstrations resulted in an additional yield of about 15% in dry lands and about 25% in irrigated lands. Encouraged by the results, farmers from Madurai, Sivagangai, Ramnad, Theni, Tiruvallur, Kanchipuram, Chittoor and Nalgonda availed loan for the application of tank silt in their fields. Around 275 farmers were sanctioned an amount of forty lakh rupees by NABARD under the Umbrella Programme on Natural Resources Management (UPNRM), for applying tank silt on an area covering 228 acres.

Facilitating use of tank silt in farmers fields

It was largely observed that whenever the desilting of tank bed was taken up and farmers were encouraged to use the fertile tank silt in their fields, their response was poor. Farmers had financial and other constraints in using the tank silt effectively on their fields. Realizing the importance of recycling the tank silt and the nature of constraints, a rehabilitation programme was taken up with the support of Sir Dorabjee Tata Trust (SDTT) in Karnataka in 2009-11. Under this programme farmers were helped to use the entire quantity of silt removed from the tank beds (leaving the gritty soil material for bund strengthening work) on their agriculture lands. More than 900 farmers benefitted by applying tank silt on an area of 1963 hectares. (See Table 1)

Table 1: Application of tank silt by Karnataka farmers
Block No of Tanks Volume of silt
used in fields
Area applied
with tank silt
No of
farmers benefited
Yadgir 7 19388 1081 587
Gurmitkal 4 13324 882 342
Total 11 32712 1963 929

Overcoming challenges

Farmers in Tamil Nadu faced problems in transporting silt from the nearby tanks as objections were raised by the local Revenue staff. Even after discussing with the higher authorities, the problem did not resolve. At last, one association with the support of Dhan Foundation used the Right to Information Act and found that there were no government orders preventing the transportation of tank silt. Through these efforts farmers were able to desilt tanks and use the tanksilt for field application.

N Venkatesan
Programme leader, DHAN Vayalagam (Tank) Foundation,
1A, Vaidyanathapuram East Cross Kenneth Road, Near 7th Day Adventists school, Madurai-625016, Tamil Nadu
E-mail: n.venkatesan@dhan.org