不同种植年限苜蓿土壤熟化过程中腐殖质性质的研究

Characteristics of Humus in Soil Maturity Process at Different Planting Ages of Alfalfa

综合研究了陇东黄土高原黄绵土不同苜蓿种植年限土壤的有机质含量、腐殖质组成、形态及胡敏酸的光学特征等。结果表明,随苜蓿种植年限延长,黄绵土土壤有机质含量逐步提高且品质得到改善,开垦地和撂荒地则相反。10～20a苜蓿地土壤表层至下层松/紧比有升高的规律,说明种植苜蓿主要对20—40cm土层肥力影响较大。胡敏酸的色调系数(△logK)和相对色度(RF)分析结果进一步表明,苜蓿种植年限在5～15a间,土壤胡敏酸向着品质提高的方向演化,种植苜蓿时间过长则腐殖质品质下降,胡敏酸结构趋于老化,耕地撂荒胡敏酸品质降低。

This paper studies the optical characteristics of organic matter, humus composition and form, and humic acid at different planting ages of alfalfa in soils on the Longdong Loess Plateau. Results show that as the year of planting alfalfa goes by, soil organic matter content is gradually increased and its quality is im- proved. However, the situations of both reclaimed land and abandoned land are opposite to that of alfalfa field. From soil surface to underlying layers, ratio of looseness to tightness in alfalfa field planted for 10-20 years is increased, which means that planting alfalfa mainly affects soil fertility in the soil layer of 20--40 cm. The analyses of color tone coefficient （△logK） and relative chromaticity （RF） of humic acid indicate that when the time of continuous cropping is between 5 and 15 years, the quality of humic acid tends to be improved. If the time of planting alfalfa is too long, the quality of humus acid may be reduced, the structure of humic acid may become aging, and the quality of humic acid on abandoned land may be reduced as well.