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C d), T s -base temperature at which f Nmin (t) equals 1 ( o C), T soil -daily mean soil temperature (ºC), U N -potential N uptake (kg ha -1 ), U Nr -potential N demand by fibrous roots (kg ha -1 ), W -dry weight of the entire plant excluding fibrous roots (t ha -1 ), W r -dry weight of fibrous roots (t ha -1 ), Z osmo -soil depth used in the calculation of mean osmotic pressure (cm), Z smin -depth of soil below which no N mineralization is assumed to take place (cm), ΔW r -root dry weight increment (t ha -1 ).

Soil nitrogen is a key indicator of soil quality and plays a significant role for plant growth. Therefore, it is very important to study soil nitrogen distribution, especially in semi-arid area of western China. Fewer scholars paid attention to the effect on soil nitrogen due to coal mining in semi-arid mining areas of western China. In this paper, soil samples of different locations were tested in both the loess region and the aeolian sand region in the Daliuta mining area in Shaanxi Province. The impacts of mining subsidence on soil nitrogen were investigated. The soil nitrogen distributions between the loess region and the aeolian sand region were compared, and used the principal component analysis method to evaluate soil quality in semi-arid mining area. The results showed that the comprehensive score of soil quality in the loess region was as follows: the internal pulling stress zone (NLS) > the external pulling stress zone (WLS) > the compressive stress zone (YS) > the neutral zone (ZX). The content of soil total nitrogen in YS-zone was the lowest in the loess region. The loss of nitrogen increased with time in the mining area, in which the total nitrogen loss at the depth of 0−15 cm was 0.27 g/kg, and the alkaline nitrogen loss at the depth of 0−15 cm was 1.08 mg/kg. In the aeolian sand region, the comprehensive score of soil quality was as follows: WLS > FC (the non-mining zone) > ZX > NLS > YS. The amount of soil nitrogen content in the loess region was larger than that in the aeolian sand region. It was found that for the loess region, the relationship between total nitrogen and nitrate nitrogen showed a significant positive correlation. It was also a significant positive correlation between ammonium nitrogen and alkaline nitrogen. In the aeolian sand region, there was a significant positive correlation between total nitrogen and alkaline nitrogen. There was no significant correlation among other nitrogen forms.

Quantitative assessment of soil physical quality is of great importance for eco-environmental pollution and soil quality studies. in this paper, based on the S-theory, data from 16 collection sites in the haihe river Basin in northern China were used, and the effects of soil particle size distribution and bulk density on three important indices of the S-theory were investigated on a regional scale. the relationships between unsaturated hydraulic conductivity K i at the inflection point and S values (S/h i ) were also studied using two different types of fitting equations. The results showed that the polynomial equation was better than the linear equation for describing the relationships between -log K i and -log S, and -log K i and -log (S/h i ) 2 ; and clay content was the most important factor affecting the soil physical quality index (S). the variation in the S index according to soil clay content was able to be fitted using a double-linear-line approach, with decrease in the S index being much faster for clay content less than 20 %. in contrast, the bulk density index was found to be less important than clay content. the average S index was 0.077, indicating that soil physical quality in the haihe river Basin was good.Keywords: friability, hard-setting, S index, soil water retention curve.

Article Title: An explicit hydrological algorithm for basic flow and transport equations and its application in agro-hydrological models for water and nitrogen dynamics Year of publication: 2010 Link to published article: http://dx.doi.org/10.1016/j.agwat.2010.08.004Publisher statement: Zhang, K. et al. (2010). An explicit hydrological algorithm for basic flow and transport equations and its application in agro-hydrological models for water and nitrogen dynamics. Agricultural Water Management, Vol. 98(1), pp. so that the calculations can be made on a layer basis. This drastically simplifies the 9 procedure of modeling water and solute transport in soil using the basic equations. 10The proposed algorithm was tested against the complex finite element (FE) numerical 11 scheme in simulating soil water and solute transport in different soils via numerical 12 experiments. The results showed that the proposed algorithm with a uniform soil layer 13 thickness of 5 cm and a small time step of 0.001d was able to achieve the identical 14 accuracy as the FE method. Tests of the proposed algorithm in simulating water and 15 nitrogen dynamics against data from a field experiment on wheat revealed that the 16 predicted results with the simple algorithm were in good agreement with the time-17 course measurements of soil water and mineral N concentration at the various depths 18 in the profile, suggesting that the proposed algorithm performed well and can be 19 reliably applied in agro-hydrological models. The simplicity and accuracy of the 20 algorithm will encourage scientists to use basic equations for soil water and solute 21 transport more in the future for improving performance of agro-hydrological models. 22 23

How to cite: Yang D, Bian Z, Zhang K, Xiong J, Lei S. Modeling root growth, crop growth and n uptake of winter wheat based on SWMS_2D: model and validation. Rev Bras Cienc Solo. 2017;41:e0150064. ABSTRACT: Simulations for root growth, crop growth, and N uptake in agro-hydrological models are of significant concern to researchers. SWMS_2D is one of the most widely used physical hydrologically related models. This model solves equations that govern soil-water movement by the finite element method, and has a public access source code. Incorporating key agricultural components into the SWMS_2D model is of practical importance, especially for modeling some critical cereal crops such as winter wheat. We added root growth, crop growth, and N uptake modules into SWMS_2D. The root growth model had two sub-models, one for root penetration and the other for root length distribution. The crop growth model used was adapted from EU-ROTATE_N, linked to the N uptake model. Soil-water limitation, nitrogen limitation, and temperature effects were all considered in dry-weight modeling. Field experiments for winter wheat in Bouwing, the Netherlands, in 1983-1984 were selected for validation. Good agreements were achieved between simulations and measurements, including soil water content at different depths, normalized root length distribution, dry weight and nitrogen uptake. This indicated that the proposed new modules used in the SWMS_2D model are robust and reliable. In the future, more rigorous validation should be carried out, ideally under 2D situations, and attention should be paid to improve some modules, including the module simulating soil N mineralization.

Based on soil sampling, lab experiment and support resistance monitoring, the disturbance of soil physical quality indices between different underground mining stages of No 52303 working face was studied in semi-arid region of western China. Soil sampling was conducted in same locations before and after mining in 2014. This study proved that soil water content, soil cohesion and soil porosity were greatly decreased, while bulk density and dry density were increased by coal mining. In comparison, coal mining had slight effect on organic matter, internal fraction angle, and D1 and D2 percent. Underground pressure monitoring showed that P1 during stage 2 was significantly greater than that during stage 1, indicating the large difference of pressure characteristics in tail areas of working face between two stages. Both soil water content and soil cohesion were decreased during two stages in two sites. Soil cohesion was strongly correlated to soil water content, and D1 and D2 percent in 2013 and 2014. Coal mining subsidence increased the cumulative probability to reach the same value of soil water content and soil cohesion. The cover depth produced different elastic and plastic zone widths between sites by theoretical model calculation, consistent with the support resistances in tail areas of working face. Higher pressure might cause a more serious destructive rock-soil body and a larger groundwater level decrease. The dryer and more serious erosive soil column induced by coal mining is a non negligible matter for the semi-arid region.