Book 4 Unit2 chemica or organic farming技术知识.ppt

conventional food organic food organic food What is the substance we put on the soil which makes crops grow?  fertilizers There are two kinds. They are chemical fertilizers and natural ones. How many kinds of fertilizers do farmers use? Which kind of fertilizers do farmers use when they are doing organic farming ? natural waste from animals Which kind of fertilizers do farmers use when they do chemical farming ? chemical fertilizers Chemical or organic farming? Reading Using chemical fertilizers for a long time can hurt the land and also people’s health. 1.Why are chemical fertilizers so popular in farming today? 2.Do you think it is really a great way? They are a great way to stop crop disease and increase production. No. Para1: A new discovery What problems can be caused by using chemical fertilizers? (disadvantage) Firstly, they damage the land by killing the helpful bacteria and pests. Chemicals also stay in the ground and underground water for a long time,which affects crops and, therefore, animals and humans. And many of the chemicals can lead to cancer or other illnesses. In addition, fruit, vegetables and other food grown with chemical fertilizers usually grow too fast to be full of much nutrition. Para2: several Problems caused by using chemical fertilizers What is the advantage of using natural fertilizer? Para3:The advantages of using organic farming. What is the advantage of using natural fertilizer? * Reduce diseases in crops and help them grow strong and healthy. * Make the soil richer in minerals and so more fertile. * Besides, keep the air, soil and water as well as the food supply free from chemical. Para4: Some methods to keep the soil fertile. How many methods are mentioned in this paragraph? And what are they? 2.What is the same goal of these different organic farming methods? The methods to keep the soil fertile 1 using natural waste from animals as