Agro-ecological Zones

Agriculture is highly dependent on soils and climate. The ever-increasing need for food to support the growing population in the country demands a systematic appraisal of its soil and climate resources in order to prepare effective land-use plans. India has a variety of landscapes and climate conditions and this is reflected in the development of different soils and types of vegetation. Based on climate data and an up-to-date soil database, the country has been divided into 20 agroecological zones. Each agro-ecological zone is uniform in terms of physiography, climate, and length of growing period and soil type for macro level land-use planning. Out of twenty Agro-ecological zones, the Ganga basin comprises of 12 agro-ecological zones as depicted here. The main contributing agro-ecological zones of the basin are describes below:

• Hot semi-arid ecoregion with alluvium-derived soils zone: The maximum part (30% of total basin area) of the Ganga basin is covered by this zone. It constitutes the parts of Uttar Pradesh, Rajasthan, New Delhi, Haryana and Madhya Pradesh. The climate of the region is characterized by hot and dry summer and cool winter. The annual precipitation ranges from 500 to 1000 mm with an increasing trend from west to east and the mean annual Potential Evapotranspiration (PET) ranges from 1400-1900 mm. The length of growing period ranges between 90 and 150 days. The soil moisture regime is typic-ustic and the soil temperature regime is hyperthermic.
  
  The natural vegetation comprises tropical dry deciduous and thorn forests. The region is under irrigated agriculture as well as traditional rainfed agriculture. The area is intensively cultivated for both kharif and rabi crops, such as rice, millets, maize, pulses, berseem, wheat, mustard and sugarcane.

• Hot subhumid ecoregion with red and black soils zone: The 14% of total basin area of the Ganga basin is covered by this zone. It constitutes the parts of Madhya Pradesh and Chhattisgarh. The climate of the region is characterized by hot summer and mild winter. The precipitation shows an increasing trend towards east. The mean annual rainfall ranges between 1000 and 1500 mm covering about 80 per cent of the mean annual PET (1300-1600 mm). The region remains fairly dry during the post-rainy period. The soil moisture regime is typic-ustic and the soil temperature regime is hyperthermic. The length of growing period ranges from 150-180 days. Rainfed agriculture is the common practice. Rice, sorghum, pigeon pea and soybean are common grown kharif crops. Gram, wheat and vegetables are common rabi season crops. The natural vegetation comprises tropical moist deciduous forest.  

• Hot subhumid (dry) ecoregion with alluvium-derived soils zone: The zone covers about 12% of total basin area of the Ganga basin. It constitutes the parts of Uttar Pradesh and Bihar. The agro-climate of the region is characterized by hot summer and cool winter. It receives an annual rainfall of 1000 to 1200 mm; 70 per cent of which is received during July to September and the annual PET of 1400 to 1800 mm. The region has length of growing period of 150 to 180 days. The soil moisture regime is ustic and the soil temperature regime is hyperthermic. Traditionally the rainfed and irrigated agriculture is common. The crops grown are rice, maize, barley, pigeon pea and jute in kharif season and wheat, mustard and lentil in rabi season. Sugarcane and cotton are grown at places under irrigated conditions. The natural vegetation comprises tropical dry deciduous forests.

• Hot subhumid (moist) ecoregion with alluvium-derived soils zone: The agro-ecoregion covers 12% of total basin area of the Ganga basin, comprising eastern plains covers north-eastern Uttar Pradesh and Northern Bihar including foothills of Central Himalayas. The climate of the region is characterized by hot, wet summer and cool, and dry winter. The area receives an annual rainfall of 1400-1800 mm which exceeds the mean annual PET demand (1300 and 1500 mm). The length of growing period ranges from 180 to 210 days in a year. The soil moisture regime is ustic and the soil temperature regime is udic. Rainfed agriculture with cultivation of rice, maize, pigeon pea, moong are common in kharif season and in post-rainy (Rabi) season, wheat, lentil, pea, sesamum, and at places, groundnut is grown on residual soil moisture with one or two protective irrigations at critical stages. The important cash crops such as sugarcane, tobacco, chilies, turmeric, coriander and potato are usually grown with supplemental irrigation. The natural vegetation comprises tropical moist deciduous and dry deciduous forests.

• Hot semi-arid ecoregion with medium and deep black soils zone: The ecoregion covers about 7% of the basin area and comprises of the western parts of Madhya Pradesh and south-eastern parts of Rajasthan. The climate of the region is characterized by hot and wet summer and dry winter. The annual precipitation in the region ranges from 500 to 1000 mm and the annual PET is (1600 to 2000 mm. The length of growing period ranges from 90 to 150 days in a year. The dominant soil moisture regime in the area is typic-ustic. The soil temperature regime is hyperthermic. Dry land farming is the common practice in the region. The Kharif crops usually      cultivated in the area are sorghum, pearl millet, pigeon pea, groundnut, soybean, maize and pulses and the common Rabi crops are sorghum, safflower, sunflower and gram. Wheat is grown under irrigated conditions. The natural vegetation comprises dry deciduous forest.

• Hot subhumid (moist) to humid (inclusion of perhumid) eco-regions with alluvial-derived soils: The agro-ecoregion forms 6% total basin area, comprising the plains of the Ganga river, covers parts of the West Bengal. The climate of the area is characterized by hot summer and       mild to moderately cool winter. The rainfall in Ganga Plain ranges between 1400 and 1600 mm. The length of growing period, in general, is more than 210 days in a year. The soil moisture and temperature regimes are udic-ustic and Hyperthermic, respectively. In view of the high rainfall, the rice based cropping system is common in Ganga Plains. The rice and jute are main crops grown in rainy season under rainfed condition and rice, wheat, and sugarcane during the rabi season under irrigation. The natural vegetation comprises tropical moist and dry deciduous forests.

• Warm subhumid to humid with inclusion of perhumid ecoregion with brown forest and podzolic soils: The agro-ecoregion forms 6% of the total basin area and comprising of the hilly areas of Uttarakhand. The region is characterized by mild summer and cold winter with annual rainfall in general varies from 1000-2000 mm. Rainfed farming is the traditional practice in the valleys and on terraces. The common crops grown are wheat, millet, maize and rice. The terraced uplands are cultivated for paddy and/or horticultural plantation crops, like apples. The natural vegetation comprises Himalayan moist temperature, subtropical pine and sub-alpine forests.

The other zone are Hot subhumid ecoregion with red and yellow soils, Hot subhumid ecoregion with red and lateritic soils, Hot subhumid to semi-arid ecoregion with coastal alluvium-derived soils, Hot arid ecoregion with desert and saline Soil and Warm perhumid ecoregion with brown and red hill soils have little contribution in the agro ecological region of Ganga basin. (Source: www.fao.org)