关键词: 玉米, 秸秆还田后效, 氮肥利用率, 干物质积累, 氮素积累

Abstract:

【Objective】Maize straw return has been one of agronomic practices for improving soil fertility. The effect of straw return aftereffect on Nitrogen use efficiency (NUE) was considered, with the objective of suppling the theoretical guidance for proposing the straw return patterns being favorable to enhance the NUE.【Method】Based on the black soil with heavy clay content in the Hailun agro-ecosystem experimental station of Chinese Academy of Sciences, the micro-plot experiment was carried out using ¹⁵N isotope techniques in 2016 under the treatment of the straw return (10 000 kg·hm^-2) only once established in 2011. Seven treatments were set up, including control without maize straw return (CK), maize straw cover (D₀), maize straw incorporated within 0-20 cm soil depth (D_0-20), 0-35 cm soil depth (D_0-35), 20-35 cm soil depth (D_20-35), respectively, as well as maize straw placed on the 35 cm depth (D₃₅) and 50 cm depth (D₅₀).【Result】The aftereffect of maize straw return increased NUE by enhancing the cumulation of dry biomass and nitrogen in maize organs. The maize dry biomass shown in the decreasing trend of D_0-35>D_20-35>D_0-20>CK≥D₀>D₃₅>D₅₀, D_0-35 and D_20-35 treatments (Maize straw incorporated within deep soil) significantly increased by 7.1%-47.7% and 2.0%-39.1% (with exception of leaf), respectively (P<0.05), compared with other treatments. The different treatments didn’t impact the nitrogen (N) contents of maize organs, but D_0-35, D_20-35 and D_0-20 treatments significantly increased the N cumulation in maize organs (P<0.05) with the increase of 15.8%-20.2%, 8.5%-18.2% and 27.9%-39.5%, respectively (P<0.05), compared with CK, D₀, D₃₅, and D₅₀. The cumulation of ¹⁵N under D_0-35 and D_20-35 treatments significantly increased by 5.1%-38.4% and 9.3%-31.8%, respectively, compared with other treatments. ¹⁵N of more than 74.1% were accumulated in the grain, different treatments didn’t impact the ¹⁵N distribution in maize organs, indicating that NUE was increased by improving the N uptake of whole maize. The NUE and N retention rate reached the largest value under D_0-35 with the increase of 1.9-12.7 percentage and 6.9-21.2 percentage, respectively, However, the N loss under D_0-35 reached the lowest value with the decrease of 8.8-31.3 percentage. D₀, D₃₅ and D₅₀ treatments (straw return in some soil layer) didn’t significantly increased the NUE compared with CK treatment, meanwhile the N loss was higher 3.6 and 4.4 percentages than that in CK treatment. The result indicated that straw return in some soil layer had potential risk in the increase of N loss, constructing fertile cultivated soil layer by straw incorporation within deep soil depth was effective agronomic practice with high NUE. The correlation analysis demonstrated that root biomass, light fraction organic carbon and soil physical properties contributed the increase of NUE in study site. N contribution rate was significantly higher 3.74, 4.26, 3.79 and 4.51percentages in D_20-35, D₃₅ and D₅₀ treatments than that in CK treatment, no significantly difference was observed among treatments with straw return. 【Conclusion】NUE could be increased by enhancing soil fertility and improving soil structure under maize straw incorporated within deep soil, and constructing fertile soil layer in black soil with heavy clay content.

Key words: maize, maize straw return aftereffect, nitrogen use efficiency, dry biomass cumulation, maize straw incorporated within deep soil, nitrogen accumulation