Biotic factors such as pests, insects and diseases reduce the crop production. These adverse effect on the plants and thus decrease the production. A pest causes damage to our crops by feeding. Weeds also reduce crop productivity by competing with the main crop for nutrients and light.
Similarly, abiotic factors such as temperature, wind, rain, drought, salinity etc. affect the net crop production. For example droughts and floods have a great impact on crops sometimes, destroying the entire crop. Salinity can lead to the death of crops if they are not resistant to it.