| This thesis investigated responses of soil physical properties to short-term different soil management practices, long-term application of organic materials combined with chemical fertilizers or chemical fertilizers alone, and different land use patterns of Lou soil in Guanzhong Plain of Shaanxi, China. The short-term experiment included 7 treatments: 1, recommended NPK + high stubble; 2, recommended NPK; 3, farmers practice; 4, recommended NPK + chemical amendment; 5, recommended NPK + straw mulching; 6, recommended NPK + humic acid; 7, CK (control without N fertilizer). 18-year long-term experiment included 4 treatments: control without fertilization (CK), application of chemical fertilizer (NPK), application of organic manure + chemical fertilizer (MNPK) and application of organic straw + chemical fertilization (SNPK). 28-year long-term experiment included 4 treatments: control without fertilization (CK), single organic manure (M), a single application of chemical fertilizer (NP), and application of organic manure + chemical fertilizer (MNP). The land use patterns were cereal land, vegetable farm, natural vegetation and set-aside. The main results obtained are as follows:(1) The results of the 2-year different management experiments showed that the soil organic carbon content at 0-10cm layer was increased compared with the control treatment. Soil bulk density was reduced and total porosity was increased on treatments of high stubble, straw mulching, chemical amendment and humic acid relative to control. There were no significant differences observed between treatments on saturated hydraulic conductivity, soil aggregation stability. Furthermore, treatment effects on soil physical properties were minor in subsurface layer..(2) The results showed that compared with the control, the fertilization treatment improved field water holding capacity and total porosity by varying degrees, but decreased soil bulk density. Organic manure plus NPK fertilizers decreased soil bulk density by 8.9 %. Long-term fertilization could also increase water retention relative to CK. For the saturated hydraulic conductivity, no significant difference was found between fertilization treatments and the control. Long-term application of organic manure plus NPK and straw plus NPK can improve the soil aggregate stability. However, long-term application of NPK had negative effect on soil aggregate stability.(3) The results of 28-year long-term experiment showed that compared with the control, the fertilization treatment improved field water holding capacity and total porosity by varying degrees, but decreased soil bulk density. Organic manure plus NP fertilizers decreased soil bulk density by 10.9 %. Long-term application of organic manure or inorganic fertilizers plus organic manure could also increase soil water retention by 3.2-10.8 % relative to CK, while there was no significant difference of soil water retention observed between NP treatment and CK. For the saturated hydraulic conductivity and unsaturated hydraulic conductivity, no significant differences were found between fertilization treatments and the control.(4) The different land use patterns had significant effects on soil physical properties. Soil bulk density was the highest on cereal land, and the lowest on vegetable farm. In contrast, the result of soil porosity was the highest on vegetable farm, and the lowest on cereal land. Fallow after 3-5 years, pores,> 600μm and in sizes from 30μm to 90μm in equivalent diameter increased, <30μm in equivalent diameter decreased compared with the cereal land at 0-5cm soil depth. At 10-15 cm soil depth, only the equivalent diameter greater than 600μm was higher under fallow, and other pore sizes were similar to cereal land. The saturated hydraulic conductivity were not significantly different between land use, and in order as vegetable farm > fallow land> natural vegetation> cereal land. The stability of water stable aggregates was not significant between land use patterns. Over all, soil under vegetable farm had better soil physical environment than other land uses. However, cereal land remained good soil physical quality.In conclusions, long-term application of organic materials can increase soil organic carbon level which improve soil physical environment. Nevertheless, long-term application of chemical fertilizers did not significantly impact soil physical properties. It is clear that short-term soil management practices had minor effects on soil physical properties. In addition, cereal system under present management condition had no negative effects on any soil physical properties detected. |
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