ABSTRACT
Rice is the most important food crop in the world. Rice is produced under a wide variety of climatic conditions throughout the world, ranging from the wettest areas to deserts. Irrigated rice is grown in bunded, puddle fields. Upland rice is grown under diverse landforms varying from low-lying valley floors to undulating and steep slopes with high runoff and lateral water movement. The flood-prone ecosystem is quite diverse, and rice types must be able to tolerate conditions ranging from temporary submergence to long periods of stagnant water, or daily tidal fluctuations. Weeds are the most important biological constraint to rice production. Cases of multiple herbicide resistance in rice weeds are beginning to emerge but thus far do not pose the management challenges of Lolium rigidum in Australia. Puddling and transplanting are ancient practices associated with the domestication of rice.
