核桃大豆间作土壤微生物生物量碳氮、氮素营养与酶活性特征

Changes of Soil Mineral Nutrition, Microbial Biomass Carbon, Nitrogen and Enzyme Activity Under Walnut and Soybean Intercropping in Dry Farming Area

摘要:

为掌握旱作区核桃大豆间作下土壤质量变化，探明土壤矿质营养、微生物生物量碳氮和酶活性变化特征及其相关性，以元林核桃(Juglans regia cv. L.)为研究对象，测定分析了核桃硬核期、坚果成熟期和落叶期3个关键物候期核桃大豆间作、核桃单作两种栽培模式下土壤矿质营养、微生物生物量碳(MBC)、微生物生物量氮(MBN)以及酶活性特征。结果表明：①间作显著提高了核桃生育期土壤有机质(SOM)含量，降低了核桃生育前期(硬核期和坚果成熟期)0 ~ 60 cm土层土壤碱解氮(AN)、有效磷(AP)含量和表层(0 ~ 20 cm)土壤速效钾(AK)含量，降低了土壤AN和AP的深层积累，加速了作物对营养元素的吸收利用，提高了养分利用效率；②间作提高了核桃生育期深层(40 ~ 60 cm)土壤MBC含量和硬核期土壤MBN含量，增加了坚果成熟期和落叶期0 ~ 40 cm土层土壤MBN含量，维持了深层土壤MBC含量；③间作条件下，土壤β-葡糖苷酶(BG)、磷酸单酯酶(AKP)、α-纤维素酶(CBH)、N-乙酰葡糖胺糖苷酶(NAG)和亮氨酸氨基肽酶(LAP)活性均以坚果成熟期最高、硬核期最低，而硬核期5种酶活性均显著低于单作处理，坚果成熟期和落叶期均高于单作处理，表现出较大的波动性；④Pearson相关性分析表明，土壤MBC与全氮(TN)、AN和SOM极显著正相关(P<0.01)，间作下土壤MBC、MBN与AKP均显著相关(P<0.05)；土壤BG、AKP、CBH、NAG和LAP之间均极显著正相关(P<0.01)。综上可见，旱作区幼龄核桃园间作大豆，可以显著增加核桃生育期SOM、AN和AP含量，降低土壤AN和AP的深层积累，提高深层土壤MBC含量，增大坚果成熟期土壤酶活性，加速作物对营养元素的吸收利用。

Abstract:

In order to understand the changes of soil quality under walnut and soybean intercropping in dry farming area, explore the correlations among soil mineral nutrition, microbial carbon and nitrogen and enzyme activity, Yuanlin (Juglans regia cv. L.) was selected as the study material, two cultivation modes of walnut and soybean intercropping and walnut monoculture were set, soil mineral nutrition, microbial biomass carbon (MBC) and nitrogen (MBN) and enzyme activities were determined in the hardcore, maturity and deciduous stages of walnut. The results showed that intercropping significantly increased the content of soil organic matter (SOM). The contents of alkali-hydrolyzed nitrogen (AN), available phosphorus (AP) in 0–60 cm soil depth and available potassium (AK) in 0–20 cm soil in hardcore and nut maturity stages were significantly reduced. At the same time, the accumulation of AN and AP were reduced in deep soil, thus the absorption and utilization of nutrients by crops were accelerated. Compared with single cropping, intercropping increased soil MBC content in deep soil (40–60 cm) at the whole growth stage and soil MBN content at the hardcore stage. At maturity and deciduous stages, soil MBN content was increased in 0–40 cm, which maintained soil MBC content in deep soil. Under intercropping conditions, the activities of β-glucosidase (BG), phosphomonesterase (AKP), α-cellulase (CBH), N-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP) in soil were the highest at the maturity stage and the lowest at hardcore stage. The activities of the above enzymes in hardcore stage were significantly lower than those of single cropping, while were higher than those of single cropping in maturity and defoliation stages, which showed great fluctuation. 4) Pearson correlation analysis showed that soil MBC was positively correlated with total nitrogen (TN), AN and SOM (P<0.01). Both soil MBC and MBN were significantly correlated with AKP activity under intercropping (P<0.05). The activities of the five enzymes were positively correlated with each other (P<0.01). In conclusion, interplanting soybean in young walnut orchard in dry farming area can significantly increase the contents of SOM, AN and AP at walnut growth period, reduce the accumulation of AN and AP but increase the content of MBC in deep soil, promote soil enzyme activities at nut maturing stage, thus improve the absorption and utilization of nutrients by crops.