(i) Following are the harmful effects of pesticides and fertilizers over a long period of time on soil: 

• The microorganisms present in the soil get harmed due to excessive use of fertilizers as chemicals in the fertilizers affect the life processes of microorganisms. Microorganisms being an integral part of the soil plays role in improving the fertility of soil and harm to them reduces the fertility of soil.
• Soil fertility is also reduced as there is no organic replenishment due to excessive use of fertilizers in soil. 
• When fertilizers are supplied in excess amounts and when are washed due to excessive irrigation, it causes water pollution as chemicals of fertilizers to affect the unique nature and properties of water.

(ii) Humus is the soil which is rich in decayed organic content i.e. in this degraded organic material is also present along with the soil. This kind of soil favours the growth of crops as they are rich in organic material and nutrients.