In agroecosystems, temporal diversification creates a sequence of short-lived habitats through time. Crop species as well as the diversity of crops grown in sequence might affect soil biodiversity and nutrient cycling processes. In the present study, we focused on a long-term crop rotation established in 2006 in Lower Saxony, Germany on a Luvisol. Winter wheat (WW) and silage maize (SM) were grown in continuous cultivation as well as in rotations. WW rotations span up to six years (including silage maize, sugar beet, winter rape and/or grain pea). Over two years, microbial biomass carbon (MBC) as well as kinetics (Michaelis-Menten V_max and K_m) of extracellular hydrolytic enzymes (β-glucosidase (BG), N-acetyl-β-glucosaminidase (NAG) and acid phosphomonoesterase (AP)) were measured in topsoil (0–10 cm depth) three times during the growing season. Continuous wheat increased soil microbial parameters compared to continuous maize as indicated by the higher microbial biomass to soil organic carbon ratio and higher potential enzymes activities involved in the C- and N-cycles (V_max of BG and NAG). The efficiency of these enzymes was lowest in continuous maize (highest K_m of BG and NAG). Maize and sugar beet as preceding crop of WW significantly decreased MBC in the 1^st year but not in the 2^nd year WW. Sugar beet decreased BG activity as well as its substrate affinity (increased K_m). The effect of sugar beet on MBC and enzyme kinetics depended on the preceding crop and lessened with grain pea as the preceding crop. Soil microorganisms in the wheat phase benefited from winter rape as the preceding crop, shown by an increased biomass and efficiency to turn over chitin and peptidoglycan (decreased K_m of NAG). Differences between cultivated crops, cropping history and fluctuations within the year in soil microbial biomass and enzyme kinetics are shown.

在农业生态系统中，时间上的多样化会随着时间的流逝形成一系列短暂的栖息地。作物种类以及依次生长的作物的多样性可能会影响土壤生物多样性和养分循环过程。在本研究中，我们集中于2006年在德国下萨克森州使用Luvisol建立的长期作物轮作。冬小麦（WW）和青贮玉米（SM）可以连续种植以及轮作。WW轮换周期长达6年（包括青贮玉米，甜菜，冬季油菜和/或豌豆）。在过去两年中，微生物生物量碳（MBC）以及动力学（Michaelis-Menten V _max和K _m在生长季节中，在表土（0-10厘米深）中测量了三倍的细胞外水解酶（β-葡萄糖苷酶（BG），N-乙酰基-β-葡萄糖苷酶（NAG）和酸性磷酸单酯酶（AP））。与连续玉米相比，连续小麦增加了土壤微生物参数，这表现为较高的微生物生物量与土壤有机碳比，以及参与C和N循环的较高潜在酶活性（BG和NAG的V _max）。这些酶的效率在连续玉米中最低（BG和NAG的最高K _m）。玉米和糖用甜菜如前述WW的作物在1显著下降MBC^第一年，但不是在2^次WW年。甜菜降低了BG活性及其底物​​亲和力（增加了K _m）。甜菜对MBC和酶动力学的影响取决于前茬，而豌豆作前茬则减弱。小麦期的土壤微生物受益于冬季油菜作为前茬作物，表现为提高生物质和周转几丁质和肽聚糖的效率（NAG的K _m降低）。显示了耕作作物之间的差异，耕作历史以及一年中土壤微生物生物量和酶动力学的波动。