Rice

Crop Rotation - Crop Development

Why rice is important?

• Rice is one of the world’s most important cereal crops, and is farmed in many regions of the world in some of the most diverse climatic and agronomic conditions. Rice and wheat are two of the most important cereal crops and together make up the majority of the world’s source of calories. They feed the world.
• Being a flood crop, field forming and maintenance of rice fields can be expensive. Though possible, it is very complicated to crop rice without flooding.
• If properly cropped, rice can give yields from 5 to 7 tons/hectare. It is the most important cereal for human nourishment in Asia.
• Rice is grown under flooded conditions; therefore, it is best produced on land that is nearly level. Level tracts of land minimize the number of waterretaining barriers or levees required per unit of area. The practice of growing rice on “zero grade” or level fields has greatly gained in popularity and is highly recommended.

Tillage

Ploughing is still broadly used in rice cropping. In North Hemisphere the best choice is ploughing in fall, particularly when soil are clayish and heavy. The goal is oxygenation of fields and thus a better management of organic matter, which can transform in humus relatively more quickly. Manure and residue can be easily incorporated into soil. Working depth of 20-25 centimetres is sufficient, anyway we do not have to remove hard pans when present: hard pans are useful for maintaining water in the fields. A disk ripper applied in autumn is considered an alternative to plough, but working depth should be not deeper more than 20 centimetres. Disk harrows, tine harrows and rototiller are used for secondary tillage.

Seeding

• Dry seeding is an easier way to plant rice and normally performs well in fields where the seedbed has been well-prepared and/or red rice is not a severe problem.
• Rice can be dry seeded using a grain drill. When the rice is drill-seeded, a well-prepared, leveled and weed free seedbed is advantageous. A well-prepared seedbed will facilitate uniform seeding depth, which is important in establishing a uniform stand.
• Seeding depth is important with all varieties. It is especially critical with semi-dwarf varieties because these varieties have inherently slower development during the seedling stage, and the mesocotyl length is shorter than conventional-height varieties. Therefore, semi-dwarf varieties should be seeded no deeper than 2 centimeters (¾ inch) to maximize uniform stand establishment.
• Conventional-height varieties may be planted somewhat deeper, but seeding depths greater than 3.8 centimeters (1.5 inches) should be avoided with any variety, in order to avoid lack of oxygen to seed when germinating.
• Where soil moisture is adequate, a flush, or surface irrigation, following seeding may not be necessary. When soil moisture is insufficient and rainfall is not imminent, the field should be flushed within 4 days of seeding to ensure uniform seedling emergence.
• This pattern simplifies tillage operations and completely avoid damages due to waves during germination. When rice is dry-drilled, tillering is normally inferior if compared with water-planted crop, thus seed rate should be increased of 10%. Dry drilled rice is less subject to lodging.

Crop Protection - Spraying

• Weeds are some of the most troublesome pests in rice production in the world. Weeds compete with rice for nutrients, space, and light. Direct losses from weed competition are measurable and can be great. Indirect losses such as increased costs of harvesting and drying, reduced quality, and reduced harvest efficiency are not readily measured but also reduce profits.
• Five basic herbicide application timings should be considered when choosing a herbicide:
1. Burndown prior to planting
2. Pre-plant incorporated
3. Pre-emergence prior to planting or preemergence after planting
4. Delayed pre-emergence
5. Post emergence

Harvesting

• Optimum grain moisture content for harvesting is 20-22%; for varieties with larger kernels best content is 23-24%. Moisture content should be tested during the warmest hours of the day in last phase of maturation.
• Late harvesting means too dry kernels and worst quality of product (sun cracking); an early harvest means higher costs for drying at the farm.
• Combines are equipped with wheels or tracks, depending on nature of soils. Rotary combines are broadly used on rice, because of gentler threshing (grain on grain), complete thrashing of the panicle and higher productivity. Grain losses at 1% are acceptable.
• Harvesting is better carried out when moisture content in grains is 20% or less, 18% is ideal.
• Normal timeframe of Harvest is end of August through October, depending on varieties, locations, and sowing timing.
• Harvesting, if started at the incorrect time or performed on a poorly maintained combine, can be responsible of important field losses of up to the 25% and can result in damage to the combine.
• In order to get a good quality product when harvesting, it is important to register the rotation speed of the drums at a lower level than for wheat or other cereals. This avoids getting cracked grains or half cracked grains.