ralph lauren outlet 2.2 Analysis of test results

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Milly (1984) pointed out that in most cases, soil moisture, soil heat flow of liquid is not important [13], so (4) can be simplified to:
C (T) / (t) =  · (λT)-L · (Dθvθ), (1) (θ) / (t) = · (Kh) - (K) / (Z), (2)

3 numerical model 3.1 equations and numerical scheme Early summer corn crop root water uptake can be ignored, so the system under study only considers the soil, cover and atmospheric factors, the field is parallel to the straw cover band equidistant in space and,[link widoczny dla zalogowanych], based on symmetry, only half the area of flow can be [21]. Philip and de Vries (1957) proposed a non-stable coupled soil heat flow equation as follows [21 ]:
Figure 2, cover edge of the temperature measured in the soil profile (1993.7.3-7.4)
Cover the soil under the strip of thermal dynamics and modeling of field trials

Abstract: This paper describes the growth of maize straw bands covering the period (between the lines, covered) under the conditions of soil thermal dynamics of the field trials. On this basis, the use of finite alternating direction difference method to simulate seedling establishment of soil cover band two-dimensional numerical model of moisture and heat transfer. which covers part of the soil surface boundary conditions determined by the energy balance equation. model input only conventional meteorological data, soil water and heat transfer parameters and cover parameters. Numerical results show that the model has some practical value.
Keywords: band cover the dynamic model to simulate water and heat
F (h) / (t) = · (Kh) - (K) / (Z). (5)
Surface evaporation of soil water movement by control of temperature and water potential gradient, but the traditional description of water transport in the unsaturated soil were assumed soil model law for the isothermal system, such as: Gardner (1959) [1], Hanks, etc. (1969) [2], Staple (1971) [3], Ren Li (1991) [4]. Philip (1957) derived from the theory, except at very low moisture conditions, or caused by the temperature The water flow is relatively unimportant [5,6]. However, Jackson et al (1974) calculations show that under field conditions, water vapor flow caused by the temperature of the soil water content in the medium can be significantly demonstrated [ ],[layer of water vapor flow (Papendick, 1973) [8], therefore,[link widoczny dla zalogowanych], simulate and analyze the evaporation of soil water dynamics should be considered in the transport of water and heat. Philip and de Vries (1957,1958) proposed describing the migration of soil water heat coupling theory [9,10], the past two decades, scholars at home and abroad under the conditions of soil water evaporation heat transfer coupling calculation carried out extensive studies [11,12,13,14,15, 16,17,18]. In the two-dimensional problem of soil water and heat transfer research, Jury and Bellantuoni (1976) developed a reflection of the uniformity of the surface covered and rectangular blocks of field soil temperature gradient in the movement of heat and moisture dimensional mathematical model and found that only consider including the relationship between temperature and heat conduction, the calculated and measured values was in good agreement [19,[link widoczny dla zalogowanych],20]. Chung and Horton (1987) on the ground covered by part of the heat flow in soil under the numerical test, but did not field test the measured data [21]. TRANSACTIONS (1989) on soil uneven, flat or undulating surface is not the usual two-dimensional numerical model of soil evaporation process was studied [22]. Sui Hongjian and Zeng Dechao et al (1992), cover with a numerical model under different soil temperature and moisture were simulated [23]. strip between the lines to investigate the coverage of the summer maize growth under the conditions of soil thermal dynamics , of the Beijing Experimental Station of Datong County yongledian conducted field trials, and in a simple and practical principles, according to Philip and de Vries (1957,1958) proposed soil heat flow theory and existing research results, to maize growth stage of wheat straw under cover bands for the background field trials to establish the soil moisture and heat transfer in two-dimensional numerical model. 2 field trials 2.1 Test Layout field corn rows of straw mulch between the bare width of about 30cm (corn row spacing of 60cm). cover the same amount of 400kg / mu. in the test area, the center line along the cover , edge and no cover bare soil temperature profile set 3, the level of these 3 sections were 15cm apart and 10cm. profile depth is measured points 5cm, 10cm, 20cm, 30cm, 50cm. in the cross-cover and soil PIPE interface with the ground temperature measured at the interface surface temperature measured in the control of surface and cover surface with straight thermometer temperature. used to measure soil temperature platinum resistance were carried out before installation, calibration. observed the use of multimeter Determination of platinum thermal resistance,[link widoczny dla zalogowanych], and then based indexing table and field correction standard curve fitting the corresponding soil temperature conversion. neutron tube buried in the middle layer of straw mulch, water dynamics by a calibrated neutron probe measurements. 2.2 Analysis of test results Figure 1 reflects the middle layer of straw covering soil temperature under the process of change over time. Figure 2, Figure 1, middle cover temperature measured in the soil profile (1993.7.3-7.4)
, The plant part of the solar radiation can be fully accepted. In the late summer corn, due to overburden compaction on soil aeration and thermal conditions have adverse effects, and band coverage but may be waived, and perhaps this is the band cover the reasons for higher yield. So, for the drilling of crops, this cover is clearly worthy of recommendation form.
Figure 5 The yield of different coverage
C (T) / (t) = · (λT), (3)
(8)
The alternating direction implicit (ADI) finite difference method to discrete equation (3) and (5), then the two-dimensional problem to only one-dimensional problems to deal with, ADI equation is as follows: X direction implicit type, Z directions explicitly:
Figure 3 were under cover and away from the edge of the edge of 10cm, cover bare soil temperature dynamics. At this point of summer corn seedlings, the shading effect is very weak, so that only cover on the solar radiation has a shielding drying, the surface temperature can reach above 42 ℃, and in the cover layer of the soil surface, about the maximum temperature is about 32 ℃. can be seen from Figure 2, cover the soil surface under the edge of the temperature change is much smaller than bare ground (Figure 3 ) rather than the center line under cover of temperature amplitude (Figure 1). In addition, the observation of ground temperature dynamics that increase with depth, soil temperature amplitude decreases, an increase of phase lag, which is a cycle of soil temperature wave typical propagation. Figure 4 band coverage, full coverage and no coverage of the process of soil surface temperature map, icon shows that the conditions bands covering the whole range of soil under the surface temperature between coverage and no coverage It compared with no coverage, can play a role in reducing surface water evaporation, but at the same coverage over the whole surface under high temperature is conducive to corn emergence and growth. Figure 5 band coverage , full coverage and no coverage of the final yield of maize under comparison chart, icons visible, bands covering the highest yield of corn, indicating that although the amount of coverage and full coverage (400kg / mu) the same band coverage on water, soil moisture to promote agricultural production more effective. Wheat straw mulch on water conservation section <LABEL class=lb onclick=Corn is detrimental to early growth. Cover only the laying of the strip between the crop rows, on the one hand can reduce the inter-row soil surface evaporation invalid; another Figure 4 soil surface temperature
Equation (2) can be written as:
. Equation (10) to (13) are tridiagonal equations, boundary conditions, with the chase method. Internal node of the coefficient of the arithmetic mean of the adjacent nodes to determine . 3.2 on the boundary conditions in the finite difference method to deal effectively with flux boundary condition is the most difficult part of the [21]. In this paper, heat top and bottom of the problem for the Dirichlet boundary conditions. heat and water left and the right to use Neumann boundary conditions, that there is no flow boundary conditions. For the flow problem, the top non-zero flux Neumann boundary conditions, bottom Dirichlet conditions. not covered by bare soil in the surface and cover with soil layer interface, the flow Q
[1] [2] [3] Next [/b]
(9)
Figure 3 10cm from the edge of cover bare soil measured at the temperature (1993.7.3-7.4)

where:
Represents time where superscript, subscript on behalf of space, i is the line marked, j is the column labeled, F for the water retention capacity (m-1). Because equation (6) to (9 ) in the coefficient depends on the variable itself, so the equation is nonlinear. In this paper, explicit linear, that is, the value of previous time step to approximate equation (6) to (9) of the coefficient. After finishing, the equation (6) to (9) can be written as:
Where C is the soil volumetric heat capacity (J / m · ℃), T is soil temperature (℃), t is time (s), λ is the thermal conductivity (W / m · ℃), L is the vaporization of the volume of latent heat (J / m), θ is the volumetric water content (m / m), D  θv is isothermal vapor diffusivity (m 2 / s), K is hydraulic conductivity (m / s) , h is negative (m), Z is the vertical distance, down is positive (m),  for the gradient operator. consider this only in soil surface moisture on the impact of heat and moisture transfer, not Groundwater vapor flow [21], so that equation (1) can be written as:
(6) (7)
(4)
Z direction implicit, X direction explicitly: More articles related to topics：

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