Impact of Nitrogen Reduction on Growth, Biochemical Compounds, and Metabolites in Two Rice Varieties

Many farmers continue using nitrogen fertilizers excessively and they must adhere to the appropriate dose recommended by the relevant agencies. The use of inorganic nitrogen fertilizers also continues to increase. The problem is that fertilizers are quite expensive, and the excessive use of these fertilizers can harm both the environment and human health. This study aimed to examine the effect of nitrogen dose reduction on the growth, yield, seed quality, physiochemical content, and secondary metabolites of the rice varieties 'Way Apo Buru' and 'Inpari 33'. The results analysis showed that differences in rice varieties had a significant effect on plant height. Treatment with nitrogen fertilizer had a significant effect on the total of panicle length and number of filled grains. Weight of 1000-grains was not affected by rice varieties and nitrogen application. The application of a dose of 40% 250 kg N on the 'Inpari 33' variety resulted in the highest content of flavonoids (28.49 mg g^-1), antioxidant activity (45.25%), and secondary metabolites content (3.70 mg g^-1). The 'Inpari 33' variety can be used as a food source with high antioxidant content, as it is not affected by free radicals and is tolerant to nitrogen deficiency. Gas chromatography mass spectrometry metabolomic analysis identified four characteristic compounds from the six samples, namely, 2-monoolein; hexadecanoic acid, methyl acid; 9, 12 octadecadienoic acid; and 11-octadecenoic acid, methyl ester. The reduction in nitrogen doses results in slower growth of crop yields and increased stress-related chemicals. The content of secondary metabolites varies, but secondary metabolite compounds are consistently produced at all nitrogen dose levels. The results imply that reducing the nitrogen dose is not advised, even though the excessive use of nitrogen fertilizers might produce residual content from the previous planting season.