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Figure15.1 shows the two crop fields [Plots A and B] have been treated by manures and chemical fertilizers respectively, keeping other environmental factors same. Observe the graph and answer the following questions.

(i) Why does plot B show sudden increase and then gradual decrease in yield?

(ii) Why is the highest peak in plot A graph slightly delayed?

(iii) What is the reason for the different pattern of the two graphs?

Answers (1)


1.Plot B shows a sudden increase in the yield percentage of crop because when chemical fertilizers are used on the crop, they boost the yield suddenly; however, this increase in yield is temporary as the chemical fertilizers reduces the organic matters present in the soil and it also ends up killing the required micro-organisms.

2. Plot A shows a delayed peak because when the plot is treated by manures, the small amount of nutrients is released into the soil at a very slow rate. The manure being rich source of organic matter leads to an increase the fertility of the soil.

3. The different pattern of the two graphs is observed because of the two separate methods used to increase the yield of crop in the plots. Manure being the organic way carried out the transfer of nutrients into the soil at a slow rate, enriching the soil. Whereas the chemical fertilizers enhanced the soil fertility for a temporary period of time. The continuous use of chemical fertilizers on Plot B led to killing of micro-organisms required for soil. This affected the soil fertility and reduced the yield percentage.

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