Back ground

Ramanathapuram is one of the coastal districts of Tamil Nadu having a seacoast extending to nearly 260 kms.  The entire coastal belt gets abundant sunshine in the summer and moderate to heavy precipitation in winter. The district has a hot tropical climate with temperature ranging from 22.30 C (minimum) to 37.80 C (maximum). The relative humidity is high at 79% on an average and it ranges from 80% to 90% in the coastal areas. The mean annual rainfall is 850 mm with summer, south west monsoon, north east monsoon and winter contributing 14, 17, 60 and 9 per cent of the total rainfall respectively.

The soil type of this district is widely varying with soils containing more of clay to sandy soils with a top sandy layer of 30 to 50 cm over a hard clay pan.  the depth of sandy layer recedes from sea coast to inland.  Sub soil clay layer is lateritic in nature. The pH of soil ranges from 8.1 to 8.6 and the EC is more than 3.0 dSmm -1 in most of the area. Sandy soils occur in the coastal stretch of Kadaladi, R.S.Mangalam, Mandapam, Ramanathapuram, Thiruppullani and Thiruvadanai blocks of the district and vast stretches of saline and alkaline soils are also found in the coastal blocks. The permeability rate of the sandy soil is upto 5 cm/hour and therefore, water availability to the crop cultivation in the coastal areas is very less.

The fertility status of the soil showed that nitrogen status is low in all blocks and phosphorus status is also low in all blocks except Thiruppullani, Kamudhi and Kadaladi where it is medium. Nutritional disorder is a common phenomenon observed in all the crops cultivated in this district and zinc deficiency is very common. Nitrogen deficiency is due to higher leaching of “N” fertilizer resulted from the sandy nature of the soil and high intensity of rainfall and phosphorus deficiency resulted due to fixation. Micronutrient deficiency owing to its lower organic matter content and low cation exchange capacity is also very common. Micro organism load in these soils seems to be low and the decomposition of organic matter takes significantly longer period than normal soils.

Agriculture in the coastal belt of the district is entirely influenced by soil fertility status and precipitation. The poor fertility status of soil combined with uneven and erratic distribution of the rainfall has resulted in poor crop success rate in the coastal belt of the district. Hence to make agriculture viable in this area and to sustain the farming families with good and assured returns, new and innovative technologies have to be introduced for sustainable agriculture.

Project Rationale

Paddy, chilli, groundnut, blackgram and gingelly are the major crops cultivated in the Ramanathapuram district. The area, production and productivity of the major crops are as detailed below

The productivity of the crops cultivated in the district is low owing to poor fertility status of the soil. The yield gap for all the crops cultivated in the district is high and it can be reduced only by enriching the fertility status of the soil viz., improving the physical, chemical and biological properties of the soil. In addition coastal sandy plains are underlain by heavy clayey soils at a depth of 2 to 3m. Rain water percolating in these land forms can be potentially harvested and used for irrigation. Due to excessive percolation in these soils and due to the presence of top sandy layer to a depth of 30 to 50 cm, it is not possible to irrigate the crops with conventional methods like furrow/flat bed systems. Also when pumps with high HP motors are employed, it results in excessive withdrawal of water resulting in ground water salinization. Hence farmers at present collect water from the ring wells manually and irrigate, by which they are able to maintain only 25 cents of the farm. Non availability of electricity for the pumpsets also aggravates the problem. Hence more scientific way of utilization of the available fresh water from the shallow aquifers will help the farmers in efficient crop cultivation in the coastal areas.

Considering the above constraints, having viable strategies to tide over the above situation is highly warranted. Soil breeding with the suitable amendment available at cheap cost to enrich the fertility status, improve water holding capacity and to reduce permeability of the soil should be given the top most priority. Tank silt is one such amendment and it is the deposited suspended matter or eroded soil in tank, which comes along with surface runoff caused due to intensive rainfall. The application of tank silt with good physical and chemical properties helps in enhancing the water holding capacity of soil, reduces the runoff losses and there by improves moisture content of soil. Tank silt application not only enhances physical properties but also improves soil chemical and biological properties, which together increase the fertility of soil. Annadurai et al. (2005) noticed the increased productivity of sunflower, groundnut, cotton, sugarcane, soybean, gingely, tomato, onion, brinjal, turnip, cucumber and chilli crops in Tirunelveli and Kannyakumari districts of Tamil Nadu when light textured soils were amended with tank silt. The availability of tank silt is abundant due to the existence of 1841 tanks in the district. Since this amendment has ability to improve the fertility status and water holding capacity of soil, scope for field crop cultivation in the coastal areas of the Ramanathapuram district is very high. It would be further augmented by adoption of suitable irrigation methods like irrigation by mini portable sprinkler/ Microirrigation which has been successfully test verified and proven one in coastal area of Ramanathapuram district.

Project Strategy

• Soil breeding by application of tank silt.
• Supplemental irrigation with harvested rain water through mini portable sprinkler at critical stages of the crop.

Project Goals

• To improve physical and chemical properties of sandy soils with soil breeding in coastal area of Ramanathapuram district.
• To utilize the harvested rain water for crop cultivation in an efficient manner.
• To regulate harvested rain water supply to the crops by micro irrigation system.
• To ensure successful cropping in sandy soils of coastal area of Ramanathapuram district.
• To popularize soil breeding and water management strategies for better cropping in coastal saline soil areas.

Project components

(i). Target area

• This programme will be implemented in an area of 6 ha (3 ha in Thirupullani and Ramanathapuram each) along the coastal area based on soil fertility status and water suitability.
• Groundnut and chilli will be raised in the operational area.

(ii). Technical programme

• This project will be implemented in Thirupullani and Ramanathapuram blocks of Ramanathapuram district during the year 2011-2012.
• Tank silt, mini portable sprinkler, seeds and fertilizers for raising both crops (groundnut and chilli) will be supplied to the identified beneficiaries.

Preliminary study: Pot culture experiment (vegetative stage)

To fix the correct proportion of Tank silt
Source: Tank silt (saline and sodic free)

Treatments:

T1- Control (without application of Tank silt )
T2 - Application of 0.5% Tank silt (10 tonnes/ ha)
T3 – Application of 1.0% Tank silt (20 tonnes/ ha)
T4 – Application of 2.0 % Tank silt (40 tonnes/ ha)
T5 – Application of 2.5% Tank silt (50 tonnes/ ha)

Research subproject: Based on the result of pot culture experiment, the field experiment will be conducted. Agronomical performance of crops will be evaluated with improved method of nutrient management (DESSIFER based fertilizer application) after soil breeding. This will be implemented in an area of 1 ha (0.5 ha in Ramanathapuram and Thirupullani blocks).

(iii). Beneficiaries
The beneficiary group includes farmers/NGOs/SHGs. An area of 6 ha (farmer/NGO/SHG with minimum 1 ha) will be identified along the coastal area of the two blocks based on soil fertility status and irrigation water availability.

Deliverables

• The tank silt will be availed from the nearest system and non system tanks at cost involving transport, loading and unloading charges and it will be applied at 15 days interval and incorporated into the field by ploughing and irrigation before crop cultivation.
• The mini portable sprinkler will be supplied @ 1No. per farmer/NGO/SHG respectively.
• The inputs viz., seeds and fertilizers for raising the two crops (groundnut and chilli) will be supplied to the identified farmer/NGO/SHG.

• Measurable outcome
• Soil breeding with tank silt will enhance the soil fertility.
• Increase in yield of groundnut and chilli to the tune of 25% - 30% by soil breeding and water management strategies.
• Efficient utilization of rainwater (80%) in coastal areas, through micro irrigation systems.

Based on the outcome of the project, this technology can be extended to other coastal areas of the district to uplift the livelihood of the farming community.

 Contact:

Krishi Vigyan Kendra
Coastal Saline Research Centre
Tamil Nadu Agricultural University
Ramanathapuram – 623 503
Ph: 04567-230250
E- mail: arsramnad@tnau.ac.in