Successive application of controlled-loss urea improves grain yield and economic benefit in maize-wheat cropping systems

Controlled loss urea (CLU) as a new type of nitrogen fertilizer has attracted much attention due to its significant advantages in saving labor costs, increasing crop yield, improving nitrogen use efficiency (NUE), and protecting ecological environment of farmland. However, there have still been few reports on mechanism of successive controlled loss urea application affecting crop yield, NUE and economic benefits. A six-year field located experiment at the same nitrogen (N) level with 240 kg ha−1 per season from 2015 to 2021 was conducted to systematically study the effect of CLU application on grain yield, soil nutrients, accumulation of soil NO3- and economic benefits in wheat and maize rotation farmland in Northern China. The six N treatments have been carried out in the trial including controlled loss urea as once-time basal fertilizer during cultivation, common urea (U) as once-time basal fertilizer during cultivation, 60 % controlled loss urea as basal fertilizer plus 40 % common urea as topdressing fertilizer at jointing stage (CLTU), 60 % common urea as basal fertilizer plus 40 % controlled loss urea as topdressing fertilizer at jointing stage (UTCL), 60 % common urea as basal fertilizer plus 40 % common urea as topdressing fertilizer at jointing stage (i.e. traditional fertilization, UTU), and no N applied as a control (CK). The results showed that, compared with CK, N application across 6 consecutive years markedly increased grain yield of wheat, maize and annual; compared with UTU, the CLU treatment increased grain yield of wheat, maize and annual by 4.7 %-13.7 %, 4.7 %-13.7 % and 2.3 %-11.4 %, respectively. Furthermore, compared with CK, during 8 consecutive years of fertilizer positioning test, each N application treatment increased the content of total N (TN), soil organic matter (SOM) and inorganic nitrogen in 0–20 cm topsoil by 2.44 %-48.14 %, 0.43 %-42.27 % and 0.82 %-79.80 %, respectively, especially in the CLU, UTU and CLTU treatment, UTU treatment performs better than other treatment in 2021–2021 and 2022–2023. In addition, the study also found that soil NO3- was mainly accumulated in the 0–120 cm soil layer, and peak value appeared at the 80–100 cm, and the CLU treatment was significantly lower than other treatment. Meanwhile, after 6 years of wheat and maize rotation planting, N agronomic efficiency, N partial factor productivity and economic benefit in the CLU treatment were significantly higher than those of the other N treatment, and the ratio of benefit and cost (B/C) reached 2.50. Therefore, in the current context of traditional N application level and labor shortages in the research area, the CLU application as once-time basal fertilization can not only increase grain yield of wheat and maize, economic benefit and NUE that reduces the carbon footprint in agricultural production, but also improve the soil environment, reduce NO3- accumulation in deep soil layer and prevent NO3- pollution in groundwater.