Rice [discusses topics of rice crop physiology as they relate to productivity]
1983
Yoshida, S.
Rice has a high relatively high leaf photosynthetic rate, ranging from 40 to 50 mg CO2/dm2 per hour. Leaf orientation is closely correlated with culm length; more erect leaves are associated with shorter culm length. Rice crop can attain maximum leaf area index (LAI) values of 10 or higher when planted at close spacing and with high nitrogen levels. Crop growth rate (CGR) reaches maximum at LAI of about 6 for IR8, an improved variety, and about 4 for Peta, a tall traditional variety. No optimum LAI exists. The maximum CGR is usually around 30-36 g/m2 per day. Harvest indices of improved semidwarf indica varieties are around 0.45-0.55. Using data of on harvest index and maximum recorded grain yield, total dry matter production per crop is estimated at 22.7 t/ha and 30.6 t/ha. Efficiency of absorbed nitrogen to produce rice grain is estimated at 50 kg rough rice/kg N absorbed regardless of yield level and planting time. Nitrogen recovery percentages usually ranges from 30% to 50% in the tropics. Growth and yield of rice are climatically controlled. Temperature effects rate and duration of growth and development, solar radiation largely determines productivity, and rainfall determines the rainfed rice crop period and stability. Potential rice yield can be estimated by a formula based on effective grain-filling period, photosynthetic efficiency and incident solar radiation
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