Urea addition promotes metabolism and utilization of nitrogen in cucumber

Nitrogen (N) forms include ammonium [NH4+-N], nitrate [NO3-N], and urea [CO(NH2)2]. Urea is the most common nitrogen fertilizer in agriculture due to its inexpensive price and high N content. Although the reciprocal influence between NO3-N and NH4+-N is well known, CO(NH2)2 interactions with these inorganic N forms have been poorly studied.

Researchers studied the effects of different nitrogen forms with equal nitrogen on dry matter, yield, enzyme activity, and gene expression levels in cucumber. NO3-N treatment with equal CO(NH2)2 promoted nitrate reduction, urea utilization, and the GS/GOGAT cycle but reduced the nitrate content. UR-2, NR-2, NR-3, NiR, GOGAT-1-1, and GS-4 were upregulated in response to these changes.

NH4+-N treatment with equal CO(NH2)2 promoted nitrogen metabolism and relieved the ammonia toxicity of pure NH4+-N treatment. UR-2, GOGAT-2-2, and GS-4 were upregulated, and GDH-3 was downregulated in response to these changes. Treatment with both NO3-N with added equal CO(NH2)2 and NH4+-N with added equal CO(NH2)2 enhanced the activities of GOGAT, GS, and UR and the amino acid pathway of urea metabolism; manifested higher glutamate, protein, chlorophyll, and nitrogen contents; and improved dry matter weight.

A greater proportion of dry matter was distributed to the fruit, generating significantly higher yields. Therefore, the addition of urea to ammonium or nitrate promoted N metabolism and N utilization in cucumber plants, especially treatments with 50% NO3-N + 50% CO(NH2)2, as the recommended nitrogen form in this study.

Access the full study at Agronomy

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