Application of chemical fertilizers can definitely increase tapioca yield.  It is convenient to use, but costly.  Generally, the recommended compound fertilizer grades are 15-15-15 and 13-13-21, because they are largely available.  The optimal rate of application is 300-600 kgs per hectare, all at one time.  For tapioca planted early in the rainy season, the fertilizers can be  applied right after the first weeding at about 1-2 months of planting. For tapioca planted toward the end of the rainy season, fertilizer application can take place about 2-3 months after planting.  Further delay may result in slower growth.  The suitable time of application is a few days after the rain.  In order to avoid fertilizer loss, the farmers should dig a hole about 20-30 cms from the plant, then put in the fertilizers and cover it with the backfill .  Some farmers use a hand tractor with plough on the field along the tapioca rows for first weeding, and then spread the fertilizers.  This saves labour cost. The chemical fertilizer can be more effective, if farmers use it together with organic fertilizers such as compost and cattle manure in proper proportion.