G. Kathiresan
In India more than 50 per cent of the total geographical area (328.7 million ha) is degraded, either due to natural causes or mismanagement or both. According to FAO estimates, 175 million hectares of the area is degraded and unfit for cultivation, of which, 7 million hectares is affected by salt. To meet the ever increasing food needs of humanity, these soils are to be reclaimed and made suitable to cultivate an economic crop. Soils with constraints like slow or excessive permeability, sub-soil hardpan, surface crusting, shallow depth and non-availability of nutrients, aeration, toxicity etc., affect normal crop growth. Suitable soil amelioration and crop management techniques may be adopted to overcome some of these constraints.
Manikandam Block of Trichirappalli district of Tamil Nadu, has 21,404 ha of total geographical area. Out of this, about 3,667 ha is declared as salt affected based on the soil pH value. About 1167 ha is strongly affected by salts with a pH of 9.2 to 10.3, whereas the remaining is moderately affected with a pH of 8.5 to 9.1 (Mohamed Haroon et al.2001).
Farmers in this region grow paddy in rainy season and keep the land fallow during remaining months of the year. Rarely, they raise daincha crop during South West monsoon. To address the issue of sodic soils, an experiment was conducted in the farm of Anbil Dhamalingam Agricultural College and Research Institute, Tiruchi.
The soil was with pH range of 8.7 to 8.9, EC of 1.24 to 1.26 dSm-1 and ESP of 15 to 17 was selected for experimentation. The cropping system of Daincha – Paddy – Vegetable and Vegetable – Paddy – Daincha were raised during the months of June to September, September to January and January to April in the years of 1999-2000, 2000-01 and 2001-02. The tested vegetables viz., Brinjal (Co2), Bhendi (Parbhani kranti), Cluster bean (Local), Cucumber (Co1), Water melon (Local), Sword bean (Local) and Mesta (Local) were raised. The trials were replicated thrice.
Cucumber has the habit of spreading on the surface soil up to 2.5m radius. It prevents the solar radiation to contact the surface soil directly. Thereby it reduces the soil temperature (up to 15cm depth) from 5 to 7oC. It prevents accumulation of salt on the surface soil from sub-soil layer through capillary movement. Soil surface-covering crop should be selected for salt affected soil to reduce the ill effects of the salt. The pH of the soil under Cucumber plant’s cover was reduced by 0.5 to 0.7 compared to the soil under direct sunlight. Moreover, among the vegetables, Cucumber (Co1) produced the highest yield as tender fruits of 9.7 tonne per ha under Daincha – Paddy – Vegetable system. The benefit-cost ratio of 7.01 was significantly superior to other vegetable crops.
Inclusion of Cucumber, variety Co1 in the cropping system of sodic soil during summer season has increased the income, cropping intensity and per day production of the farm besides reducing the salt accumulation on the surface soil.
G.Kathiresan, Professor (Agronomy), Sugarcane Research Station, Sirugamani-639 115.
