Variability and Modelling of Soil Moisture, Salt and Organic Matter Content in a Gravel-Sand Mulched Jujube Orchard

Characterization of the variability of soil moisture, salt content and organic matter content (SOM) is of great significance in agricultural production management and sustainable soil utilization. We present a case study of the variability and modelling with the depth of soil moisture, salt and SOM in a gravelsand mulched jujube orchard, using Geostatistics and Kriging interpolation. Soil moisture, salt and SOM were measured in 256 samples collected from a gravel-sand mulched jujube orchard in the 0-10, 10-20, 20-30 and 30-50 cm. Soil moisture, salt and SOM were more variable in the surface soil, due to several environmental factors, the coefficients of variation (CV) of soil were lower than 23%, indicating weak to moderate variation. The coefficient of variation of moisture and organic matter decreased with the depth and the salinity increased with the depth. There is a significant correlation between each soil layer, which decreases with the increase of the soil layer. The accuracy of the function model with depth as an independent variable and soil properties as a dependent variable is higher than 0.88. To master the relationship among soil depth, salinity, soil moisture and organic matter content can provide theoretical value for agricultural comprehensive management. INTRODUCTION Soil moisture, salt and organic matter content (SOM) are important components of soil. Soil moisture, salinity and SOM can provide a theoretical basis for soil dynamic change, ecological environment management and soil salinization. Under the background of global change, the problem of soil desertification, salinization and productivity decline caused by scarce precipitation and intense evaporation is increasingly serious. Characterizing soil moistures variability in space and time is critical to managing water resources, and optimize agricultural practices (Mascaro et al. 2019). The spatial distribution of soil salt can reflect the status and degree of soil salinization (Chervan et al. 2019). SOM is an important factor to characterize soil fertility and soil quality (Wright et al. 2005). Therefore, mastering the spatial pattern of soil moisture, salt and SOM is beneficial to the rational utilization of soil resources and the sustainable production of dryland crops (Liu et al. 2006, Ahmed et al. 2010). Many scholars have studied soil moisture, salt and organic matter (referred to as SOM). Researches on soil moisture and salt mainly focus on the analysis of the spatial distribution (Hao et al. 2015, Yang et al. 2017). The relationship between different vegetation, soil quality or utilization type and soil moisture and salt (Selim et al. 2013, Zhang et al. 2018), and the coupling relationship between moisture and salt (Ding et al. 2015). Some studies on the spatial variation of moisture, salt and nutrients in surface soil have a certain rule, among which the spatial variation of soil salt is affected by structural factors (Gaston et al. 2001, Shen et al. 2015). Wang et al. (2012) collected soil samples to analyse the variation of soil moisture content and salinity with depth. Liu et al. (2011) found that SOM had a significant effect on soil moisture content under natural and air-dried conditions, which was beneficial to soil moisture retention. Moreover, Zhang et al. (2012) found that the spatial distribution of SOM was mainly affected by terrain indices, soil texture and soil genetic types. The spatial variation of soil properties mainly includes the variation of the horizontal direction and vertical direction, the spatial variability of soil properties in different soils in the vertical direction and its main influencing factors are not the same. The effect and interaction of various processes in the soil profile can produce variable soils (Liu et al. 2014, Harguindeguy et al. 2018). Gravel and sand are commonly used as mulch in the semi-arid loessal regions of northwestern China to conserve the sporadic and limited rainfall for reliable crop production (Feng et al. 2018, Lü et al. 2013). Gravel-sand mulches on soil surfaces can improve soil conditions, conserve moisture, reduce the accumulation of 2020 pp.1557-1565 Vol. 19 p-ISSN: 0972-6268 (Print copies up to 2016) No. 4 Nature Environment and Pollution Technology An International Quarterly Scientific Journal Original Research Paper e-ISSN: 2395-3454 Open Access Journal Nat. Env. & Poll. Tech. Website: www.neptjournal. com Received: 19-12-2019 Revised: 23-01-2020 Accepted: 28-03-2020