| With intending to explore tillage practices that increase soil structure property, reduce its losses and maintain sustainable productivity, effects of different tillage practices on soil structure property and fertility in soil plough layer were investigated. The experiment was conducted at a located experimental station for six years in Loess Plateau of central Gansu province where the area represents semiarid.The experiment contain four treatments, namely conventional tillage (T), no-tillage no straw cover (NT), conventional tillage with straw incorporated (TS) and no-tillage with straw cover (NTS). The main results obtained were listed as follows:1 NS,NT and TS had positive effects on soil aggregate; NTS, NT and TS were all good for the forming of water-stable aggregate which was >0.25mm, with NTS increased most. In Pea-wheat-peat (P-W-P) and spring wheat-pea-spring wheat (W-P-W) rotation fields, higher contents of water-stable aggregate which was >0.25mm were observed in NTS, NT and TS than T, and the highest in NTS. Among four treatments, the contents of water-stable aggregate which was >0.25mm in the depth of 0 to 5 cm were significantly higher than those in 5 to 10 and 10 to 30 com depth.After seven years of NT, TS and NTS, the soil bulk density decreased to a different extent compared with T. In P-W-P and W-P-W rotation fields, soil bulk density followed the order: T>NT>TS>NTS in the depth of 0 to 5 cm and T>TS>NT>NTS in the depth of 5 to 10 cm. however, the contrary tendency was found for soil porosity; it was NTS>TS>NT>T in the depth of 0 to 5 cm and NTS>NT>TS>T in the depth of 5 to 10 cm. Thus, NT reduced soil bulk density and porosity, with NTS changed most.2 NT, TS and NTS increased soil organic carbon with NTS increased most. In the depth of 0 to 30 cm, compared with T, soils with P-W-P rotated, NTS, TS and NT increased organic carbon content by 16.92%, 7.80% and 6.81%, respectively, while soils with W-P-W rotated, TS, TS and NT increased organic carbon content by 11.98%, 6.93% and 7.25%, respectively. Hence, NTS was more favorable to the accumulation of soil organic carbon.The similar effects were found to the soil nitrogen as well as soil organic carbon. Total phosphorus content ranged from 0.78 to 1.09 g·kg-1 in soil depth of 0 to 30 com under different tillage practices. With P-W-P and W-P-W rotated soils, total phosphorus content changed in the order of NTS>TS>NT>T in depth of 0 to 10 cm. In soil with NT treated, total phosphorus varied from 0.82 to 1.09 g·kg-1, whereas in soils with T treated, it varied from 0.80 to 0.90 g·kg-1. Therefore, NT increased soil total phosphorus content to some extent, among which NTS improved most significantly.As for potassium, its total content in P-W-P rotated plough soil varied from 20.26 to 24.52 g·kg-1 under NT treatment, compared with T treatment that its total potassium content ranged from 20.97 to 22.58g·kg-1. Comparatively, in W-P-W rotated plough layer its total content ranged from 20.12 to 24.34 g·kg-1, compared with T treatment that its total potassium content ranged from 21.08 to 21.88g·kg-1.it suggested that soil potassium changed differently as compared to nitrogen and phosphorus.3 Tillage practices had different effects on crop yield. Pea and spring yielded in the order of NTS>TS>NT>T. |
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