Abstract:

Partial substitution of organic fertilizer nitrogen for chemical fertilizer nitrogen is one of the ways to achieve sustainable crop development.This study explored the appropriate ratio of wheat organic nitrogen partial substitution for chemical nitrogen,as well as the characteristics of nitrogen accumulation,transportation,and utilization after substitution,in order to provide a basis for nitrogen fertilizer reduction and efficiency enhancement technology for winter wheat in Hebei Region.Field experiments of the following nine treatments were conducted in Ningjin,Hebei from 2021 to 2023:T1,non-nitrogen,and application of chemical P and K fertilizer alone;T2,high efficiency fertilization treatment,and application of chemical N,P and K fertilizer alone;T3—T7,substitution of 20%,40%,60%,80% and 100% the chemical N rate of T2 with organic fertilizer,respectively;T8,traditional fertilization,and application of chemical N,P and K fertilizer alone;T9,substitution of 100% chemical N rate of T2 with organic fertilizer,and spraying liquid nitrogen fertilizer at the erecting stage.The results of two years of experiments showed that the 100% substitution rate+liquid nitrogen treatment could achieve the highest wheat yield.Secondly,the yield of the 40% substitution rate treatment was equivalent to that of the high efficiency fertilization treatment,and it was much higher than that of the traditional fertilization treatment in the second year of the experiment.The 100% substitution rate+liquid nitrogen treatment increased the nitrogen content in stems and leaves by spraying available nitrogen during the erecting period,and the nitrogen accumulation in plants was equivalent to that of high efficiency fertilization and traditional fertilization treatments.Treatment with 40% and 80% substitution rates also achieved nitrogen accumulation equivalent to the highly efficient fertilization treatment.The 20%—100% substitution rate treatment (including liquid nitrogen treatment) could achieve a higher nitrogen transfer rate in stems and leaves,as well as the contribution rate of nitrogen transfer to grain.Among them,the 100% substitution rate+liquid nitrogen treatment had good fertilizer nitrogen absorption and utilization effect,achieving higher fertilizer nitrogen accumulation,nitrogen utilization rate,and nitrogen harvest index.Nitrogen fertilizer effect of the 100% substitution rate+liquid nitrogen treatment was equivalent to or slightly higher than that of highly efficient fertilization treatment.Secondly,the treatment with the 40% substitution rate had a similar or slightly lower nitrogen fertilizer effect than the highly efficient fertilization treatment.In summary,the 100% substitution rate+liquid nitrogen treatment showed better wheat yield,plant nitrogen accumulation,nitrogen transport rate,grain nitrogen accumulation,and nitrogen efficiency,followed by the 40% substitution rate treatment.

Key words: Wheat, Organic fertilizer, Nitrogen accumulation, Nitrogen transport