Question

why is grass grown on land after crop Production​

Answer 1

Explanation:

because there is some nutrition left after that

Answer 2

Answer:

Grazing by livestock is a means of deriving food and income from lands which are generally unsuitable for arable farming: for example in the United States, some 85% of grazing land is not suitable for crops.[3]

According to a report by the Food and Agriculture Organization, about 60% of the world's grassland (just less than half of the world's usable surface) is covered by grazing systems. It states that "Grazing systems supply about 9 percent of the world's production of beef and about 30 percent of the world's production of sheep and goat meat. For an estimated 100 million people in arid areas, and probably a similar number in other zones, grazing livestock is the only possible source of livelihood."[4]

Management

Grazing management has two overall goals, each of which is multifaceted:

   Protecting the quality of the pasturage against deterioration by overgrazing

       In other words, maintain the sustainability of the pasturage

   Protecting the health of the animals against acute threats, such as:

       Grass tetany and nitrate poisoning

       Trace element overdose, such as molybdenum and selenium poisoning

       Grass sickness and laminitis in horses

       Milk sickness in calves