Coir pith and elephant dung: sowing substrates alternative to river sand for rubber (Hevea brasiliensis) nurseries

The sowing medium plays an important role in the production of good quality budded plants of rubber. Nowadays, the search for alternative high-quality and low-cost materials as sowing media in rubber nurseries is a necessity due to the increasing demand, environmental constraints and rising costs for river sand, the most widely used sowing medium during the last decades. To study the effects of different media on seed germination and seedling growth of rubber, experiments were conducted using river sand as the control and several other media viz., leached coir pith, dried elephant dung, reclaimed sea sand, fine quarry dust, course quarry dust, rubber wood saw dust and rubber wood chips. Germination attributes were significantly affected by the sowing medium. In the first experiment, seeds sown in coir pith recorded significantly higher values for germination percentage, germination value, germination index, rate of germination (lowest E50), as compared to those in river sand (control) and other media. In the second and third experiment, seeds sown in coir pith and elephant dung recorded significantly higher values for germination as compared to those in other media and the values were on par with those in river sand. Seedlings raised from seeds sown in all media in the first experiment achieved buddable size (>6mm stem diameter) after three months. Considering the cost, availability and germination attributes, leached coir pith and dried elephant dung are identified as ideal sowing substrates alternative to river sand for rubber nurseries.