Effects of agricultural management on chemical and biochemical properties of a semiarid soil from central Spain

摘要

Long-term agricultural management may change soil C sequestration and alter soil C and N dynamics. The objective of this study was to investigate the impact of several tillage regimes with different intensity on C and N stocks in a Calcic Haploxeralf with a leguminous/cereal rotation under semiarid conditions after 15,18 and 21 years of management. Seven chemical and biochemical properties (total C, total N, delta C-13, delta N-15, FDA hydrolysis, beta-glucosidase and urease activities) were measured in a soil (0-5 cm, 5-10 cm, 10-20 cm, 20-30 cm) under the following agricultural management: fallow (F), notillage (NT), zone-tillage subsoiling with a paraplow (ZT), conventional tillage with mouldboard plow (CT), minimum tillage with chisel plow after NT (MTN) or CT (MTC). The results showed that soil reached a steady state of organic matter sequestration 15 years after starting the experiment and that C and N stocks varied greatly with agricultural management, particularly in the top 0-10 cm, and followed the order: F approximate to NT approximate to ZT > MTN approximate to MTC > CT. Fallow and less intensively cultivated soils (NT, if) exhibited strong vertical gradients of most properties analyzed (total C, total N, FDA hydrolysis, urease and beta-glucosidase activities) with values decreasing with depth, followed by minimum tillage treatments (MTN, MTC) whereas similar values along soil profile were observed in CT treatment. No significant differences in soil delta C-13 values were detected among plots with different land use or tillage systems; however, the delta N-15 values suggested that, although tillage system did not affect significantly N-cycling processes, a change from "open" to "closed" N cycling occurred when cultivated soils were set aside