Agriculture Reference
In-Depth Information
must pay a yearly tax on this land. Donio is constrained by the fact that his rent is rice
and so he must grow rice. In many African countries where the chief assigns land to
farmers, they are constrained by the necessity of always planting the land to a crop
or lose the land. While this may not seem like an imposition, it does mean that the
farmer is not free to experiment with crops that are very different from the main
crop grown. For instance, if the normal crop is millet, growing faba beans may be
seen as not growing a crop! A´da and Octavio own their land, and this gives them
the freedom to grow a wide variety of crops and animals, thus producing a balanced
diet for the family as well as a continuing income.
11.5.5 Weather
Climate is not controllable—rainfall and temperature are variable from year to year,
however, they fall within some common ranges, and these can be exploited by
farmers in two ways. It is easy to find, from local research done by local governmental
or educational organizations, the average dates for the start and end of climatic
conditions, rainfall, and temperature that mark the growing season. Optimum dates
or conditions for crop planting and harvesting can then be used to plan farming
operations. Planting at the optimum time is one of the most important farming
operations in terms of obtaining the best yields.
In areas with excessive rainfall farmers can either use drainage to remove excess
water or plant crops, such as rice and taro, that can grow in flooded conditions. There is
even a rice variety that grows taller as water becomes deeper such that it can produce
grain even under flooding conditions.
In areas of insufficient rainfall two things can be done: conserve rainwater or carry
out irrigation. A number of different approaches can be used to conserve water. One is
to prevent water leaving the field and thus infiltrating into the soil. In this way the soil
holds the most water for crop production. To go along with this approach, maintaining
or increasing soil organic matter will maintain or increase the soil's ability to take water
in and hold it.
Another aspect of this is that conservation of water is accomplished using the same
methods used to conserve soil. It is not possible to separate soil and water conservation.
Soil erosion occurs in two steps: destruction of soil structure by raindrops hitting bare
soil structures, also called splash erosion. This is the initial step in soil erosion. The
second step is movement of soil particles off or out of the field by water flowing
over the soil surface. Note that preventing water from moving over the soil surface
prevents erosion, but if water cannot move out of the field by moving across the
surface, it must either infiltrate into the soil, thus conserving it, or evaporate.
The second way is to prevent water escaping from soil either from the surface or
down into the lower portions of the soil where roots cannot penetrate. Mulch can be
used to limit evaporation from soil surface, thus conserving soil water. Any type of
material may be used as mulch such as straw, leaves, paper, or plastic. Mulch will
also affect soil temperature, so this effect must also be kept in mind.
A layer of water-impermeable material, such as plastic, can be placed in the soil at
some depth, such as 30 cm deep. The depth used must be determined by the expected
