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Making Fortified Compost

How can compost be made from low quality organic resources such as maize stover, wheat straw or wood chips?  This is can accomplished using a procedure developed at Moi University by J. Robert Okalebo, Mary Kifuko and Keziah Ndungu. The technique can also be applied in processing of a wide range of other “low quality” organic resources.

Fortifying compost is a recent development that processes organic resources containing few plant nutrients into organic fertilizer.  The procedure follows:

1. Chop crop residues to 30-45 cm in length to increase the surface area of microbial activities.

2. Spread the chopped material in five successive layers of 30 cm high by 2.0 m wide into windrows 25 m long (» 500 kg in each layer).

3. At every 30 cm layer, evenly broadcast 3.75 kg DAP (or any other nitrogen-bearing fertilizer) for fortification lowering the C:N ratio from 80 to about 12.

4. Apply 1.0 kg of organic soil uniformly as a “starter inoculant”. Farmyard manure, sugarcane mill filter mud or pond sediments are suitable materials for this purpose.

5. Apply 20 litres of water at the same height to enhance dissolution of fertilizers and to moisten the stover for microbial activity.

6. Repeat steps 1 to 5 until the 25 m windrows are 1.5 m in height

7. Allow the heap to react for one month and then invert (turn) it using a pitchfork. Apply 100 liters of water to the windrow after turning,  particularly when conditions are dry.

8. Biological activity is monitored by pushing a stick into the middle and sides of the stack. The stick is pulled periodically and felt by hand for any temperature changes.

9. Composting continues until the pile cools and the finished material appears dark brown or grey.

Composting requires four to six months and at maturity, about 1900 kg of fortified compost is produced. Mature compost is odourless and has a fine texture.  Fortified compost made from wheat straw and manure contained 2.2% nitrogen, 0.4% phosphorus, 1.4% potassium and 52% organic matter. This process speeds the rate of decomposition and greatly improves the value of lower

 quality organic resources. In addition, fortification with chemical fertilizers compensates for losses in nutrients during the composting process.  Due to the potential impact expected from wider promotion and application of this technology, FORMAT intends to organize fortified composting activities in several areas in Kenya during 2004 and 2005.   Further details on fortified composting are available from the book “Organic Resource Management in Kenya.