6th Grade - Science

LESSON PROBLEM: Botany: Why does rice grow better in water?


STUDY GUIDE

Rice - Family: Gramineae; Genus: Oryza

Oryza includes two cultivated species, commonly known as African Rice and Asian Rice. African Rice is grown in West Africa, while the more common Asian rice is grown in most parts of Asia and all around the world, including the United States. Rice is considered a semiaquatic plant, though some varieties also thrive on dry land. Rice is one of the most water-efficient sources of nutrition available.

1 ServingGallons of Water Required
Beef1231
Cantaloupe40
Rice25


Most types of rice require moist growing conditions so they cannot grow in areas of low rainfall unless the rice field is artificially irrigated. While rice needs water to grow, it does not require standing water to grow. The idea that rice needs to be grown in water is a misconception. However, rice is almost always grown in water filled fields, called paddies. While not required, there are benefits to the rice plant when grown in such conditions. Rice fields flood more easily than other row crop fields, because rice is grown in clay soils. Water does not readily drain through clay soil. Most other crops will not grow in this type of soil.

An advantage of this growing condition is weed control. Major plant cell functions like elongation and multiplication require oxygen. Flooded fields have less available oxygen for plant roots. This prevents the germination and growth of weeds that would compete with the rice plant for nutrients and sunlight in the field.

Standing water is also a deterrent to insects that threaten rice such as the army worm and chinch bug. Standing water also offers a kind of temperature control for the crop. Anyone who lives near a body of water knows that water temperature changes more slowly than land temperature. So, on hot days the water filled fields keep the rice cool, and then warm it on cool nights. Standing water also helps in preventing excessive salt accumulation and the soil depletion.

The interesting thing about rice is not that it grows in flooded fields, but that it can tolerate flooded conditions. Rice plant leaves and the stems contain a series of internal air tunnels that funnel air down to the roots. In this way it is similar to aquatic plants. One third of the rice plant needs to be above water for this mechanism to work. Rice that is totally under water will die. That is why the water level is carefully monitored and controlled in rice fields.


ACTIVITIES

What are the advantages of growing rice in standing water? Are there any disadvantages? What are they?


EXTENDED LEARNING

Do some research and find out how to grow rice. Grow three different groups: one with less water than is recommended (no standing water), one with the amount of water recommended (some standing water) and one with more water than is recommended (excessive standing water). Display your results in a report.


VOCABULARY
  • germinate
  • aquatic
  • irrigate
  • weed
  • chinch bug


    Click here to play Rice Rampage!
  • Baldo is actually a type of specialty rice grown right here in the U.S. Other types include basmati, jasmine and arborio.
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