Grain growth of lowland rice under nitrogen application rates and planting methods
1997
Rangsan Apakupakul (Prince of Songkla Univ., Songkhla (Thailand). Faculty of Natural Resources. Dept. of Plant Science)
Two experiments were conducted from September 1995 to February 1996 during the wet season. An outdoor pot experiment with six levels of N application rates: 0(NO), 75(N1), 125(N2), 187.5(N3), 250(N4) and 312.5(N5) kg N/ha were used. An on-farm experiment with two planting methods; wet sown rice and transplanted rice, which received 75 kg N/ha were carried out in six farmers'fields. The experimental design was randomized complete block by using each farmer's field as a block. The results indicated that the logistic function is the best model for fitting the data of grain growth from anthesis until physiological maturity at 95 percent of the maximum grain weight. Changes in the rate of grain moisture content were divided into three different phases which coincided with the ripening stages. Fertilizer N and planting methods had no effect on grain filling parameters of this rice cultivar. Variations of final grain weight (95 percent of maximum weight), maximum rate and duration of grain filling ranked from 20.18 to 21.32 mg, 0.0892 to 0.1051 mg/deg Cd and 265.9 to 306.1 /deg cd, respectively. A very highly significant negative relation (P0.001) was observed between the maximum rate and duration of grain filling. The differences in the number of panicles per unit area and the number of spikelets per panicle amongst treatments due to compensation effect should be taken into consideration in grain growth and development of the tillering crops.
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