Maclean et al. - 2002 - Rice almanac source book for the most important e

Large-scale mechanized rice farmers in the United States use equipment such as this minimum till air drill
that plants 65 rows at a time with a holding capacity of 10,000 pounds of seed. Source: Jay Cockrell, Texas
Rice Newsletter.
with less than 50 mm of rainfall during the
growing season, to the humid subtropical Gulf
Coast of Louisiana, Texas, and Florida, where
rainfall may total 700–1,000 mm. In all these
environments, rice is grown as a single crop per
year, but can be ratooned in the warmest,
southernmost regions of the Gulf Coast states.
Approximately 40% of Texas and
southwestern Louisiana rice area is ratooned
annually. All rice in the U.S. is irrigated and
direct-seeded. In California, pregerminated seed
is seeded into standing water by aircraft.
Southwestern Louisiana is also wet-seeded. Dry
seeding with a mechanized grain drill is the most
common method of planting in the southern U.S.
Rice is grown on natural flatlands. Nearly
100% of these flatlands in California and
approximately 40% in the southern U.S. have
been further leveled by laser-directed machinery.
In rice monocrop systems, the land may be
leveled to a slope of 0.02 to 0.05 m/100 m. In
rice–row crop systems, grades of 0.1 to 0.2 m/100
m are required for drainage or irrigation of the
rotation crop. Precision leveling has greatly
facilitated water management and is considered
second only to the introduction of semidwarf
varieties as contributing to increased rice yields.
In California, where the rain-free
environment and high latitude provide maximum
solar radiation and low disease pressure, farm
yields average 8–9 t/ha. In the humid southern
rice environments, disease (primarily blast and
sheath blight), warm nights, cloudy days, and
frequent thunderstorms at heading limit average
yields to about 6.5 t/ha.
74 Rice almanac