Question

Why should preventive measures and biological control methods be preferred for protecting crops?

Answer 1

Hint:
The preventive measures and biological pest control measures use nature’s prey-predator mechanism for controlling the parasitic pests negatively affecting the crops. These methods possess various advantages over traditional chemical pest control techniques.

Complete answer:
The traditional methods, which utilize chemical fertilizers have various harmful or deleterious effects on the environment. These compounds have the potential to cause soil pollution, makes the soil deprived of its natural nutrients, affects the ecosystem of various microbes present in the soil, and also pollutes the groundwater resources. Prolonged usage of these materials also causes toxicity in the crops, and also the animals consuming it. Due to these effects, various innovative techniques are used thereby decreasing the usage of these harmful chemicals.
The alternate methods thus implemented are preventive measures and biological control methods. The various preventive measures used are, sowing the seeds at the right time, which is at the correct season, where the yield is maximized and leaving it unsown for the soil to regenerate its nutritive content for the rest of the year. Another method is by intercropping techniques, whereby the crops are interchanged throughout the year. One type of seed is sown and after harvesting the seed the soil is cultivated with another type of crops, thereby interchanging the crops. The method of mixed cropping is also used by cultivating different crops in the same land at the same time. Usage of varieties of plants that are resistant to various pathogens also is an important technique in the preventive measures taken.
The biological pest control methods utilize biopesticides against the various pests infecting the crops. One of the major examples of a biofertilizer is a bacterium named as Bacillus thuringiensis, which protects the developing cotton balls from the larvae of the ball worms which feed on it. It is an eco-friendly pest control method.

Note:
The usage of manures does not pose much threat to the soil since it is produced from the plant debris and animal excreta after its decomposition. These materials make the soil rich in organic materials and improve the nutritive capacity of the soil.