Root and tuber crops play an important role in food security and nutrition for the global population especially the small and marginal farmers and the tribal community. They have the capacity to produce maximum edible energy per hectare per day than any other crop. It contributes to the income of the small and marginal farmers through fresh sale and value addition. Root and tuber crops act as insurance crops and safety shields against natural disaster. These groups of crops provide greater potential to combat long-term poverty, food, and nutrition security. Its commercial value and its role in the household food security and poverty alleviation were long back recognized in many parts of our country. Tribal population in India depends mainly on the tuber crops for their livelihood.
Tuber crops are mostly used as a commercial crop and it forms an important source of starch for the starch industry. In India, the cassava area and production in 2016-17 was 2.06 lakh ha and 4.34 million tonnes respectively (Source: India Agristat, net source) and in Tamil Nadu, it was 0.91 lakh ha and 2.81 million tonnes. The ICAR-CTCRI had developed 16 varieties of cassava which gives increased production and productivity. Many of these varieties are rich in starch. In many parts of Tamil Nadu, mostly in the tribal belts, the farmers are cultivating local varieties which result in lesser yields when compared with new improved varieties.
Cassava grows well even in the hilly regions and the Institute has taken efforts to introduce the improved varieties in the hill ecosystem of Tamil Nadu. The Pachamalai hills (78o29’34” to 78o39’29” East longitude and 11o8’52” to 11o28’39” North latitude with an altitude ranging from 500 to 1070 meters above mean sea level) are the hypsographic type of hills situated in Eastern Ghats of Tamil Nadu. It has a total geographical area of 507.52 sq. km. It is represented in the Survey of India (SoI) toposheets at 1:50,000 scale in the sheets of 58I/11, 12 and 15. The hill consists of over 80 villages spread in three panchayats over two districts viz. Salem and Tiruchirappalli whereas the Perambalur district forms the northern boundary.
A tropical climate prevails in the hill with a maximum temperature ranging from 23 to 310C and the minimum temperature of 14 to 160C in the past 10 years. The total annual rainfall in this region ranges from 257.7 mm (2016) to 891.2 mm (2017) with a 10-year average of 771.71 mm.
Out of this, 132.49 mm was recorded as summer rainfall (January to May), 269.01 mm during southwest monsoon period (June to September) and 370.21 mm during North East monsoon period (October to December). The soils are red and belong to the order, Alfisols. The texture of the soil varies from sandy loam to sandy clay loam with loamy soils in few areas.
Surface gravelliness with coarse soil texture is also a common feature especially in northern parts of the hill. The Pachamalai hill is a green hill range inhabited by the Malaiyalee (hillmen) tribes who depends mainly on agriculture for their livelihood. The socio-economic conditions of the tribes are generally poor and their exposure to diverse income generating activities is very limited. They have unique culture and social norms. Even though they encounter social and environmental problems, they still depend on agriculture for their livelihood as they are unaware about crop diversification. Soil acidity, erosion, surface and sub surface hardening are considered to be the major constraints for successful cultivation of crops including tuber crops like cassava. All these limitations together with the declining soil carbon content considerably reduced the soil water and nutrient use efficiency, yield potential and starch quality of cassava which affected the farmers’ livelihood considerably in recent years.
The total cultivable area in the hill is 6764 ha. The major crops grown are cassava, paddy, mango, castor, grapes, jack fruit, tamarind, lemon, coconut, turmeric, banana, silver oak with few areas under minor millets. The cultivation of field crops including cassava is featured with denuding of the forest cover. As a result, the soil quality in general and carbon stocks in particular is considerably reduced. Analysis of soil carbon stocks of Tiruchirappalli district, portions of the hill was found to have low average carbon stocks (1.78±0.87 kg m-2; n=10) as compared to Salem district (2.31 ±1.09 kg m-2; n=34), both in Tamil Nadu.
Among the crops, cassava is the major crop and occupies an area of 5185 ha. It is grown for industrial (starch) purpose and sustains the livelihoods of scheduled tribal farmers. The common cassava variety usually seen in the hills is predominantly H-165 which was introduced 15 years back. It is grown as a continuous monocrop under rainfed conditions for more than a decade by clearing the forestlands. Amount of rainfall (water) and fertilizer (major nutrients) are considered by the farmers as the major factors which influences the cassava yield. The hill climate is conducive to obtain increased starch content and quality, as compared to plains. This is an added advantage for cassava cultivation in the hilly regions.
The tillage and planting operations are usually carried out during July- August and harvest will be in the month of June-July depending on the onset of rainfall and prevailing market price of starch. Farmers adopt primary tillage to surface depth (15-18 cm), low or no addition of farm yard manure (FYM) and additions of either complex (17-17-17) or physical mixtures (8-8-16) fertilizers @ 175-175-215 NPK, kg per hectare. Applications of biofertilizers and soil test-based additions of fertilizer nutrients especially micronutrients are not practiced in by the farmers.
In order to sustain the soil health of the fragile ecosystem and to realize higher tuber/starch yield and enhanced income of farmers, a study was conducted during 2015-16 and 2016-17 at two villages viz. Vengamudi (110 19’17.4” N; 780 34’31.1” E; 806 m above msl) and Neivasal (110 22’20.8” N; 780 20’48.4” E; 945 m above msl) with a recently introduced cassava variety of ICAR-CTCRI, Sree Athulya (4-2) along with two soil management practices (SMP) viz. deep tillage (25-30 cm) and soil test based application of major nutrients @ 105-105-125 NPK, kg per hectare.
During the years 2016 and 2017, the above said soil interventions resulted in remarkable impact in Sree Athulya tuber yield (in actual, 21.75 t ha-1) and starch price ( Rs.8,666 per ton) as compared to H-165 (20.26 t ha-1 and Rs. 5,066/- respectively). Survey conducted in December, 2017 revealed that the variety, Sree Athulya has spread to 25 acres (2017) as against 35-40 setts with which this variety was introduced during 2012 and in due course the area under cultivation will be around 100 acres. The net income of the farmers also increased considerably to Rs. 1,28,486/- per hectare (average of 2 years viz. 2015-16 and 2016-17) because of the adoption of introduced variety (Sree Athulya) as compared to H-165 (Rs.62,637/-). The income increase was due to the savings in fertilizer cost (in terms of complex (17-17-17, N-P-K) /physical mixtures (8-8-16, N-P-K) fertilizers) which is Rs.4473- 5140 per hectare.
Sustaining the cassava production in relation to soil carbon sequestration and soil health practices are considered as major challenges in any hill ecosystem. To achieve this, further research on simple and farmer friendly soil carbon sequestration and other soil health enhancing practices with emphasis on biofertilizers and micronutrients such as Zn, B etc. under diverse soil texture/soil quality conditions needs to be undertaken. This will help to adopt appropriate location specific soil water and crop nutrient management and conservation practices by the farming community. Such practices would help in further preventing soil erosion and degradation.
All these would improve their livelihood, under a safe and protected environment. New interventions to improve the socio-economic conditions of the tribals the improved sweet potato varieties enriched with beta carotene and anthocyanin developed by the Institute will be introduced into the cropping system of the farming community to improve productivity, sustainability and income of the resource poor farmers through tuber crops. Such initiative would also help them to achieve food and household nutrition security.
Article By
Ramesh (Principal Scientist, Division of Crop Production, CTCRI),
Archana Mukherjee (Director, CTCRI),
M.N. Sheela (Principal Scientist and Head, Division of Crop Improvement, CTCRI)
Sheela Immanuel (Principal Scientist and Head, Section of Extension and Social Sciences)
