Subsurface Irrigation With Ceramic Emitters Improved the Water Productivity and Nitrogen Use Efficiency of Greenhouse Melons.

Increasing nitrogen use efficiency in agricultural fields is crucial for sustainable agricultural development. In a 2-year greenhouse study, we compared two methods, subsurface irrigation with ceramic emitters (SICE) and subsurface drip irrigation (SDI), to evaluate their effects on soil moisture and nitrogen distribution, photosynthetic efficiency and plant stoichiometry. The results showed that SICE can reduce the soil nitrate nitrogen content by approximately 20% while maintaining the soil moisture content at 70%–80%, improving the photosynthetic efficiency and melon yield. Under the optimal yield treatment (applying 60.67 kg of nitrogen fertilizer per hectare), compared with SDI, SICE increased yield by 8%, water productivity by 13%, nitrogen absorption efficiency by 4% and nitrogen use efficiency by 3%. In addition, by analysing the stoichiometric characteristics of melon at different nitrogen fertilizer application rates and growth stages under the two irrigation methods, we found that the main reason for the increase in SICE yield was the coupled effect of the increase in plant photosynthetic efficiency and the need for plants to maintain their internal stoichiometric balance.