Technology-oriented approaches to reduce chemical fertilization in agroecosystems without influencing the vegetable yield is a proficient method for sustainable agriculture and environmental safety. However, short-term studies are not capable to indicate the effects of various inputs in a long run; therefore, a six-year experiment was conducted in Ningxia, China. The experimental units were: no fertilizer control (CK: 0 kg N ha⁻¹), chicken manure (M: organic N 362 kg ha⁻¹), reduced chemical fertilizer (RCF: chemical N 992 kg ha⁻¹ + organic N 362 kg ha⁻¹), and conventional fertilizer (CF: chemical N 1515 kg ha⁻¹ + organic N 362 kg ha⁻¹). The study aimed to assess the effects of reduced fertilization on yield, nitrogen (N) use efficiency (NUE), N leaching, and the economic benefits. The results achieved herein indicate that RCF has significantly improved the NUE, reduced N leaching (23.7%), and improved the N economic benefit (NEB, 41.8%) as compared to the CF. Based on yield, net benefit, and NUE conditions, the optimum N application range was 634–821 kg N ha⁻¹ for tomato and 556–778 kg N ha⁻¹ for cucumber. The study concluded that reduced chemical application of N is an important factor to control environmental pollution and improve fertilizer use efficiency. Further experiments are suggested to examine the optimum N rate provision from chemical fertilizer and its ratio with organic fertilization.