基于15N同位素示踪盐渍化农田向日葵氮素利用规律

Nitrogen Utilization Pattern of Sunflower in Saline Farmland Based on 15N Isotope Tracer

为探明盐渍化农田不同施氮水平下向日葵氮素吸收利用规律,采用N同位素示踪技术进行田间微区试验,以不施氮处理(N0)为对照,设计3种施氮水平(N1=150 kg/hm^(2)、N2=225 kg/hm^(2)、N3=300 kg/hm^(2)),于向日葵成熟期测定植株和0—100 cm土层土壤N同位素丰度及总氮含量,研究各处理肥料氮素的去向及其利用机制。结果表明:向日葵氮素吸收量随施氮量的增加而增加,成熟期作物氮素吸收量在N2水平较不施氮显著增加38.7%;土壤氮和肥料氮对作物当季氮素吸收的贡献比例为84.9%和15.1%。N2水平下,肥料氮的贡献比例较N1增加35.7%,土壤氮的贡献比例较N1降低4.3%。肥料氮残留量随土层深度增加而减少,土壤中47.4%的残留肥料氮主要集中在0—20 cm土层。不同施氮水平下肥料氮去向均表现为氮肥损失率>氮肥残留率>氮肥利用率,N2施氮水平下氮肥利用率较N1、N3显著提高22.7%和14.6%,土壤残留率较N1、N3减少8.5%和8.6%。综合考虑向日葵氮素吸收利用及土壤中氮素残留情况,225 kg/hm^(2)施氮量下氮肥利用率为27.4%,氮肥残留率为32.3%,氮肥损失率为40.3%,是中度盐渍化农田较适宜的施氮量。

To investigate the nitrogen absorption and utilization patterns of sunflower under different levels of nitrogen application in saline farmland,a field micro-area experiment was conducted using ^(15)N isotope tracing technique,and three levels of nitrogen application(N1=150 kg/hm^(2),N2=225 kg/hm^(2),N3=300 kg/hm^(2))were designed with no nitrogen application treatment(N0)as the control.The ^(15)N isotope abundance and total nitrogen(TN)content of sunflower and 0-100 cm soil layer were measured at maturity of sunflower to study the fate and utilization mechanism of fertilizer nitrogen in each treatment.The results showed that the nitrogen absorption of sunflower increased with the increasing of nitrogen application,and the nitrogen uptake of the sunflower at maturity increased significantly by 38.7%at the N2 level compared with no nitrogen application.The contribution of soil N and fertilizer N to the nitrogen uptake of the sunflower in the current season was 84.9%and 15.1%,respectively.At the N2 level,the contribution ratio of fertilizer N increased by 35.7%compared with N1,and the contribution ratio of soil N decreased by 4.3%compared with N1.The residual fertilizer N decreased with the increasing of soil depth,and 47.4%of residual fertilizer N in the soil mainly concentrated in the 0-20 cm soil layer.At different N application levels,the fate of fertilizer N showed loss rate>residual rate>utilization rate,and under the nitrogen application level of N2,N utilization rate significantly increased by 22.7%and 14.6%compared with N1 and N3,respectively,and the soil residual rate reduced by 8.5%and 8.6%compared with N1 and N3,respectively.Considering the nitrogen uptake and utilization of sunflower and the nitrogen residue in soil,under 225 kg/hm^(2) of nitrogen application,the nitrogen utilization rate was 27.4%,the nitrogen residue rate was 32.3%and the nitrogen loss rate was 40.3%,which was a more suitable nitrogen application rate for moderately salinized farmland.