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.TOEFL Listening Comprehension TranscriptNarrator
Listen to part of a university lecture on agriculture.
Good afternoon, class. We''ve been looking at various of the world''s population problems and their possible solutions over our last few classes, and today I''d like us to take a quick look at one of the solutions to the growing problem of supplying enough food for us all. It''s called "dry land farming".
Dry land farming is a, a set of agricultural practices, agricultural techniques, that should be, or need to be, used to produce profitable crops in areas where the rainfall- or the snowfall- is slight, is erratic, or is very seasonal, and is generally less than about fifty centimeters a year. All over the world, there are countries that must use these less-than-optimal lands to grow their food- the North American prairies, the South American pampas, the Russian steppes, the Middle East- all these areas have marginal rainfall, precipitation. Almost half of India''s arable- cultivatable- land, 47 out of a total of 108 million hectares, is dry land, as opposed to land fed by adequate rainfall. Originally, these lands were covered with well-adapted grasses, but today much of the natural cover is gone, and these vast plains are seen as, potentially at least, our global breadbasket.
Now, dry land farming is something that must be practiced in places where the land is inherently only barely suited for food production in the first place, and you can''t make a silk purse out of a sow''s ear, but there''re a number of things you can do that can improve the situation, the conditions, for successful farming.
Water is of course a key, or the key, requirement, and the little precipitation that does fall must be captured and conserved and used sparingly. Providing windbreaks, and providing some slight shade, and leaving residues from previous crops can often save water, keep it from evaporating so quickly. And weeding can save the water that the weeds would otherwise drink up. If the countryside is hilly, terracing can be used, and this goes along with contour plowing to prevent run-off. In some areas, it may even be feasible to build cisterns so that rainwater can be collected and stored. Also, planting the seeds carefully, with consideration- choosing precisely the right time to plant them, choosing the optimum seed depth, and so forth, can help use the available moisture most efficiently.
Mentioning seeds brings me to the next point: crop choice. Drought-resistant varieties, heat-tolerant varieties, of wheat or corn, for instance, must be chosen or developed. Varieties that can stand hot, dry conditions, whose seeds will germinate in such adverse conditions, and which have growth cycles, life cycles, that are fitted to the conditions they must face. With careful attention to these choices and to these practices we are talking about here, even crops like watermelons have been grown successfully in dry lands!
So, conserving and carefully distributing what rainfall is available and choosing crops that can best tolerate dry conditions are key factors for success. And the soil itself is also a key factor.
Dry land soils are, as you might expect, relatively poor in nutrients, because dry conditions allow a lot of topsoil to be blown away. So the quality of the thin topsoils must be preserved and maintained as carefully as possible. The most obvious help here is fertilizers, but other techniques like mulching- putting a protective cover over the field, like old vegetable matter, plant stalks and leaves, for instance, or plastic sheeting- and minimal tillage, minimal plowing, help solve this problem of soil deterioration, as well as the other main soil problem, erosion. Erosion can also be fought with windbreaks and strip-farming, which is the planting of alternate strips of land each growing season.
As I said before, dry lands by their nature are not very good, relatively speaking, for growing our food, and part of that is that they are more susceptible to low crop yields or complete crop failures. This is something that dry land farmers must always keep in mind and must always plan for, be ready to deal with.
If the year turns ugly, if it is even dryer and colder or hotter than usual, the farmer must be ready and willing to abandon his effort for that year, and in that way to save his fertilizers and his seeds and his energies. On the other hand, in promising years, where the weather is boding fair, the farmer should be quick to take advantage of it- by boosting yields with extra or broader plantings, by extending his growing cycle, and so on- and of course by working longer and harder at it.
With such approaches as these- and others we develop- the productivity of such marginal dry lands may be able to help us keep up with our irresistibly growing populations. We can at least take hope in the thought that the natives of the arid American southwest- the Hopi, the Zuni, the Navajo- survived for hundreds of years on dryland farming, in an area with a rainfall of less than twenty-five centimeters a year!
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