Nutrient Mining in Assam
 In Assam, plant nutrient mining is stripping the soil of its inherent productivity potential. Crop yields in Assam are much lower than all India averages. Rice, the single most important food crop, has average yield of about 1,372 kg/ha compared to the Indian average of 1,990 kg/ha. Similarly, yields of pulses and oilseeds are about 500 kg/ha (India averages 630 kg/ha for pulses and 856 kg/ha for oilseeds). The nutrient status of soils in different agro-climatic zones of Assam shows P is low to medium in all zones except the Barak Valley. K status is low to medium for all zones. Poor soil fertility coupled with low and unbalanced fertilizer use are constraining crop yields and stripping the soil of its inherent fertility. The plant nutrient balance scenario is highly negative:
Nutrient balance in agro-climatic zones of Assam ('000 tonnes).
Zones | N | P2O5 | K2O |
Upper Brahmaputra Valley Zone | (-) 37.9 | (-) 9.9 | (-) 47.0 |
North Bank Plain Zone | (-) 44.7 | (-) 12.4 | (-) 53.3 |
Lower Brahmaputra Valley Zone | (-) 78.3 | (-) 20.6 | (-) 94.5 |
Central Brahmaputra Valley Zone | (-) 24.2 | (-) 5.9 | (-) 42.0 |
Hills Zone | (-) 15.0 | (-) 4.1 | (-) 17.1 |
Barak Valley Zone | (-) 8.7 | (-) 5.8 | (-) 22.6 |
Total | (-) 218.7 | (-) 58.7 | (-) 276.5 |
Source: Borkakati et al. (2001), Fertiliser News, 46(5), pp. 61-63.
Plant nutrients removed by rice alone equaled the total NPK consumption of the state. Soil nutrient mining will have serious consequences of deterioration of soil health and further decline of crop productivity. Urgent steps are therefore needed to sustain agricultural production at a high level. Potassium mining is highest among the three major plant nutrients due to very low use of potash by farmers in Assam. Programs to convey to farmers the importance of balanced fertilization to improve farm profit could help change the situation. PPIC has initiated research and education programs in Assam in collaboration with the State Agricultural University to improve crop yield and farmer profit through balanced fertilizer use. The program plans to extend this to different crops to show the potential of increasing productivity and farm profit. Promotional literature covering the importance of P and K for sustained crop production, in the regional language, was developed for distribution among farmers to make them aware of the benefits of balanced and efficient plant nutrient use.
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