In India, 49 million hectares area is affected by soil acidity, of which 25 million hectares have pH below 5.5. Such soils in India are mainly found in North-Eastern Region and Western Ghats with sporadic distribution in Jharkhand, Himachal Pradesh, Orissa, West Bengal, and Chattisgarh.
In these states, soil acidity in general and subsoil acidity in particular are the major factors for low productivity potential of these soils. The productivity potential in these soils is far less than normal soils In acidic soil, aluminum (Al) is one of the most abundant metals in the earth’s crust and is considered as the main abiotic stress that causes 25–80% yield losses in crop plants grown on soils containing excessive aluminium.
Al affects 40-70% of the world arable lands. In soils, it is found in the form of insoluble aluminosilicates or oxides. When pH of the soil drops below 5.0, Al is soulbilized in the form of phytotoxic Al3+ ions which becomes toxic for many crops.
Among various aluminum toxicity symptoms, the first visible symptom is rapid inhibition of root growth which can occur within hours or even minutes of exposure to Al 3+.
There are two common ways to mitigate Al toxicity: one by liming and another by using tolerant cultivars. Al toxicity can be reduced through application of lime for raising the soil pH.However, this amendment does not bring permanent remedy to sub-soil acidity and liming may not always be practical or a cost effective way.
The most appropriate strategy to overcome Al toxicity is to use tolerant genotypes. Keeping in view, a study was undertaken to evaluate pea germplasm under acidic conditions.
An aluminium tolerant line (PC-55-11-1-2) was also found to be tolerant to soil acidity. A pea strain tolerant to low pH was tested with and without lime amendments to establish the role of biological amendments for sustaining productivity in acidic soils under low input conditions.
The pea line ‘PC-55-11-1-2’ has performed better without liming application. Liming alone increased the pod yield by 16 % at pH 4.8 in the acidity sensitive (PC-493-5) genotype. However, the Al tolerant line gave 20% higher yield without application (Fig 1).
Fig1. Response of Al tolerant and Al sensitive genotype in pea under low pH condition (pH 4.8)
Thus, response of the benefits particularly the resource-poor backward class farmers of Arunachal Pradesh aluminium tolerant line was more than application of lime. Developed technology (biological amendments) ensures an additional net return of Rs. 16,000/- per hectare and thus greatly benefits particularly the resource-poor backward class farmers of Arunachal Pradesh.
Dharmendra Singh1* and Rajendra Singh2
1. College of Horticulture and Forestry, Central Agricultural University, Pasighat,791102, Arunachal Pradesh
2. Division of Soil Science, Indian Agricultural Research Institute, New Delhi-12
* Present Address: Division of Genetics, Indian Agricultural Research Institute, New Delhi-12