盐渍化农田不同施氮水平对向日葵SPAD值的影响

Influence of different nitrogen application rates on SPAD values of sunflower in saline field

以内蒙古河套灌区主要经济作物向日葵为研究对象,对不同盐渍化程度（ S0：〈0．25%, S1：0．25%-0．5%, S2：〉0．5%）和施氮量（ N）水平（ N0：0 kg/hm2、 N1：90 kg/hm2、 N2：135 kg/hm2、 N3：180 kg/hm2）下向日葵相对叶绿素含量（ SPAD值）在不同生育期的变化特征进行分析。结果显示, SPAD值可以反映出向日葵的氮素供给状况,其在蕾期和花期与地上部分干物质量（蕾期R=0．576,花期R=0．655）和籽粒产量（蕾期R=0．774,花期R=0．758）均有显著的相关关系。向日葵SPAD值在不同生育期受到盐分和施氮量水平不同程度的影响。在轻度盐渍化程度（ S0）下, N1水平施氮量下的SPAD值在进入蕾期后均仅次于N3水平,该水平的施氮量可满足该环境中向日葵的生长；在中度盐渍化程度（ S1）下,当施氮量水平从N1增加到N2时, SPAD值有明显的增加。在重度盐渍化程度（ S2）下,各施氮肥处理的SPAD值相比于不施氮肥的N0水平,不仅没有显著上升,反而有部分出现明显下降。据此,提出了针对不同盐渍化程度农田的推荐向日葵氮肥施用量（ S0：90 kg/ hm2, S1：135 kg/hm2, S2：0 kg/hm2）,为经济合理地施用氮肥提供依据。

Taking sunflower （ Helianthus annuus L. ） , the main economic crop in Hetao irrigation district as the research ob-ject, to study the characteristics of SPAD values under different saline conditions （ S0： 〈0. 25%, S1： 0. 25% -0. 5%, S2：〉0. 5%） and nitrogen application rates （N0： N 0 kg/hm2, N1： N 90 kg/hm2, N2： N 135 kg/hm2, N3： N 180 kg/hm2） at different sunflower growth stages. The results indicated that SPAD values which had significantly linear relationships with the shoot dry matter （SDM） （bud stage： R=0. 576, flowering stage： R=0. 655） and seed yield （SY） （bud stage： R=0. 774, flowering stage： R=0. 758） in bud and flowering stages could reflect sunflower’s nitrogen nutritional status. Moreo-ver, different saline conditions and nitrogen application rates had different influence on sunflower SPAD values from seedling to maturity stage. The N1 treatment had the second highest SPAD values under S0 saline condition; the SPAD values under S1 sa-line condition went through an significant increase when the nitrogen application rates increasd from N1 to N2; compared with the N0 treatment, the N1 , N2 and N3 treatment showed no significant increase under S2 saline condition. Consequently, this experiment suggested reasonable nitrogen application rate for fields with different saline conditions （ S0： N 90 kg/hm2 , S1：N 135 kg/hm2 , S2： N 0 kg/hm2 ） , which could give advice on economical and rational application of nitrogen fertilizer.