Soil Phosphorus Distribution as Affected by Irrigation Methods in Plastic Film House

Water-saving irrigation methods have been increasingly used for vegetable cultivation in greenhouse or plastic film house. However, there is limited information concerning the effect of water-saving irrigation methods on soil phosphorus （P） behavior. In this experiment, drip and subsurface irrigation methods were applied, with furrow irrigation method as control, in Mollic Gleysols. Soil P distribution throughout the depth was significantly affected by irrigation methods. Total, Olsen, organic and inorganic P contents were greater in the topsoil （0-10 and 10-20 cm） than in the subsoil （20-30, 30-40, 40-50 and 50-60 cm）. The Olsen P content throughout 0-60 cm layer under drip and subsurface irrigation treatments was lower than that under the furrow irrigation treatment. However, the total, organic and inorganic P contents from 20 to 60 cm under drip irrigation treatment were higher than or close to those under furrow irrigation treatment, but were lower under subsurface irrigation treatment than under furrow irrigation treatment. Under subsurface irrigation treatment, the contents of total, organic and inorganic P at the 0-10 cm layer were 78.0%, 1.3% and 3.7% greater than those at the 10-20 cm layer, respectively. But Olsen P content at the 10-20 cm layer was 5.7% larger than that at the 0-10 cm layer. These suggested that soil P behavior could be manipulated by soil water management to some extent. 在

Non-smooth finite-time stabilization for a class of nonlinear systems

In this paper, global finite-time stabilization problem for a large class of nonlinear control systems is considered. An iterative design approach is given based on Lyapunov function. The finite time stabilizing control laws are constructed in the form of continuous but non-smooth time-invariant feedback.