The optimal N:P:K ratio varies across soil types but is generally around 4:2:1
Manure and compost contain humus and living organisms that slowly release minerals as they decompose. Chemical fertilizers provide minerals (usually nitrogen, phosphorus and potassium) which dissolve in water and are immediately available to plants, but may not be retained in the soil for long. They may be leachedfrom the soil and pollute groundwater, rivers, and lakes. Chemical fertilizers (as well as pesticides) can also kill bacteria and other organisms in soil. This means that some time after their use, the soil will be less fertile than ever before.
Without micro-organisms, the soil will be will dependent on frequent addition of more and more chemical fertilizers. The variety of nutrients, which are normally produced by micro-organisms, may also be reduced. Thus, in many areas, the Green Revolution has actually resulted in a loss of soil fertility and ever- increasing costs to farmers.
Environmental resources like soil fertility and groundwater are built up over many-many years. Once destroyed it is very difficult to restore them. Similar environmental imbalances are being faced by other regions with large-scale use of HYVs.