硒、锌元素配施对紫花苜蓿产量、植株体内硒锌积累和氨基酸含量的影响

Effect of combined applications of selenium and zinc on herbage yield, Zn, Se accumulation and amino acid content of alfalfa

在严重缺硒缺锌的石灰性土壤中,采用锌、硒两因素三水平(纯锌施用量分别0、0.10、0.40 g·kg^(-1),纯硒施用量0、0.30、1.80 mg·kg^(-1))完全设计盆栽基施的方法,以紫花苜蓿为对象,研究了硒、锌元素配施对紫花苜蓿产量、硒锌积累量和氨基酸含量与组成的影响,并采用氨基酸评分(AAS)、化学评分(CS)和必需氨基酸指数(EAAI)对紫花苜蓿氨基酸组成特点进行综合评价,从而探讨硒、锌复合微肥对紫花苜蓿营养价值的影响。结果表明,除单施低锌处理(0.10 g·kg^(-1))外,其他处理均显著提高苜蓿干草产量,硒是提高产量的主要因素,锌对提高苜蓿干草产量有促进作用,两者配合效果最好;单施硒或硒锌配施均极显著提高了苜蓿硒含量,硒锌间表现为协同作用;单施锌极显著提高了苜蓿锌含量,配施适量硒促进了紫花苜蓿对锌的吸收,但过量施硒不利于苜蓿对锌的吸收。各处理紫花苜蓿总氨基酸含量(T)在15.88～18.89 g·100 g^(-1)(以干重计),以低硒低锌处理(Se_1Zn_1)含量最高,高硒高锌处理(Se_2Zn_2)含量最低。各处理紫花苜蓿必需氨基酸含量(E)在5.11～6.45 g·100 g^(-1),以低硒高锌处理(Se_1Zn_2)含量最高,Se_2Zn_2处理含量最低;低硒(Se_1Zn_0)、高硒低锌(Se_2Zn_1)、高锌(Se_0Zn_2)与低硒高锌(Se_1Zn_2)等处理紫花苜蓿氨基酸E/T值接近40%。所有处理紫花苜蓿蛋白质的第一限制氨基酸均为含硫氨基酸(蛋氨酸+胱氨酸)。可见,在严重缺硒和锌的石灰性土壤中,施锌量0.1～0.4 g·kg^(-1),施硒量0.3 mg·kg^(-1)不仅能提高紫花苜蓿产量,而且能改善其氨基酸组成和品质。

This experiment investigated the effect of added zinc(Zn) and selenium(Se) in calcareous soils with severe Zn and Se deficiencies, on alfalfa yield and herbage Zn, Se, and amino acid content in a pot experiment. The design was a 3×3 complete factorial with three levels of Zn(0, 0.10, 0.40 g·kg-1), and three levels of Se, also(0, 0.30, 1.80 mg·kg-1). A comprehensive evaluation of alfalfa herbage amino acid composition as indicated by the amino acid score(AAS), chemical score(CS) and essential amino acid index(EAAI), was also undertaken. It was found that all treatments expect for Zn alone at 0.10 g·kg-1 significantly increased alfalfa herbage yield. Se alone provided a greater increase in alfalfa herbage yield than Zn alone, and combined Se-Zn applications had the best effect. Similarly, alfalfa Se content was significantly increased by Se application, with combined application of Se and Zn showing a synergistic effect. Application of Zn significantly increased alfalfa Zn content, and combined application of Zn and Se at the lower rate promoted Zn absorption, whereas Se application at the higher rate was not conducive to Zn absorption. The total amino acid content of alfalfa herbage ranged from 15.88-18.89 g·100 g-1, with the Se1Zn1 treatment having the highest value, and the Se2Zn2 treatment having the lowest. Meanwhile essential amino acid content of alfalfa herbage ranged from 5.11-6.45 g·100 g-1, with the Se1Zn2 treatment having the highest values, and the Se2Zn2 treatment having the lowest value. The treatments Se1Zn0, Se2Zn1, Se0Zn2 and Se1Zn2 all had an essential∶total herbage amino acid value close to 40%. The first limiting amino acids in all treatments were the sulfur-containing amino acids(methionine+cystine). The results obtained in this study suggest that in the severely Se and Zn deficient calcareous soil tested, the optimal Zn application rate was 0.1-0.4 g·kg-1 soil, and the optimal Se application rate was 0.3 mg·kg-1 soil. These rates not only improved alfalfa herbage yield, but also improved amino acid composition and quality.