The high cost of imported soluble chemical fertilizers and the concern for environmental quality stimulated greater interest on the use of organic fertilizers and microbial inoculants as sources of nutrients for crop production. Numerous studies have shown that combined use of organic and inorganic fertilizers, usually at 50:50 ratio is best.  Long-term application of compost to soils helps maintain good physical properties, sustains healthy biological activities, and enhances proper soil chemical reactions. Green manure can replace 50-100 kg N from inorganic fertilizer.  Green manures also increase effectivity of N fertilizer.  

The indigenous fertilizers or nutrients found effective for different cereals, legumes, root crops, vegetables, sugarcane and medicinal crops include the following:  

• Manure of:  chicken, pig, carabao, goat 
• Green manure:  indigo, ipil-ipil, crotolaria, azolla, sesbania 
• Composted Agricultural Ecosystems straw, other crop residues, and market wastes 
• Industrial wastes: lumbang meal, coal ash, mudpress, biosludge 
• Ground rock phosphate 
• Peat 

The rhizobial inoculants are important in enhancing biological N fixation as source of NH₄-N.  The fungal inoculants that form mycorrhizal association enhance P uptake.  The following inoculants were developed:  

• Rhizobial inoculants for peanut, soybean, cowpea, mungbean, tapilan, winged bean. 
• Azospirillum
• Mycorrhiza - for pine, eucalyptus, and agoho