State one importance of photoperiod in agriculture.

Ravjot's mother always squeezes water from wet clothes in the spinner of a washing machine and then uses it to clean the floor:
$(a)$ Write the principle of the technique used in the above-mentioned process.
$(b)$ Write one more application of this technique.
$(c)$ What do you learn from Ravjot's mother?

Why should biological control methods be preferred for protecting crops?

Complete the crossword puzzle (Fig.).
Across
$1.$ Oil yielding plant $(9)$
$3.$ Crop grown in winter season $(4)$
$5.$ Fixed by Rhizobium $(8)$
$9.$ Common honey bee $(4)$
Downward
$2.$ Animal feed $(6)$
$4.$ $A$ micronutrient $(5)$
$6.$ Unwanted plant in crop fields $(4)$
$7.$ An exotic breed of chicken $(7)$
$8.$ Bottom feeders in fish pond $(7)$
$10.$ $A$ marine fish $(4)$

To get a better yield,Jaikishan increased the use of pesticides and fertilizers. Though in the initial years he got higher yield,after that,it declined. He was much worried. His friend Mahesh persuaded him to abandon this practice and start using organic manure.
$(i)$ Why are fertilizers used in a field?
$(ii)$ State the possible reason for the decline in yield.
$(iii)$ List two values shown by Mahesh.

Name the major nutrient which we get from fish.