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Growth, nitrogen uptake, and yield of upland rice (Oryza sativa L.) varieties as affected by biochar and nitrogen application in Ratanakiri, Cambodia
Thesis Abstract:
Two experiments were conducted in Ban Pong Village, Ban Pong Commune, Veunsai District, Ratanakiri Province in the northeast Cambodia from August to November 2014. Upland rice varieties—Lavak, Dinok, Romdoul, and Kjey—were used to determine the effects of biochar incorporation in combination with varying N fertilizer levels on the growth, yield and yield components, and nutrient use efficiency of selected upland rice varieties; evaluate the response of upland rice varieties to biochar application under field condition in Cambodia based on growth, dry matter, and yield parameters; and determine the effect of field application of biochar on soil properties and growth with Cambodian upland rice varieties.
In the first experiment, 60 kg N ha-1 and 12 t biochar ha-1 application improved grain yield by 14.89 g and 12.93 g, respectively. The interaction between 60 kg N ha-1 and 12 t biochar ha-1 application consistently increased grain yield (16.34 g) of upland rice variety. Therefore, the best combination of biochar and N levels was 12 t and 60 kg, respectively. Growth, efficiency, and yield parameters were consistently the highest, with the application of each combinations and levels.
In the second experiment, relatively higher grain yields were obtained with biochar and nitrogen on Romdoul (2.51 Mg ha-1) and Lavak (2.45 Mg ha-1), followed by Dinok (1.98 Mg ha-1) and Kjey (1.42 Mg ha-1). However, Romdoul produced yield that was relatively higher than that of Lavak. This suggests that relatively high but decreasing shoot weight of Romdoul during reproductive stage contributed to the production of reproductive components. Therefore, all the Cambodian upland rice varieties evaluated performed best with the application of combined at the rate of 60 kg N ha-1 and 12 t biochar ha-1. With the same level of fertilizer application, Romdoul responded very well among the four test varieties.