Characterization of spatial variability of soil physicochemical properties and its impact on Rhodes grass productivity

Soil spatial variability characterization: Delineating index-based management zones in salt-affected agroecosystem of India

Farm level recommendation in salt-affected agricultural landscapes is practically difficult due to spatial variations in inherent soil salinity, diverse farming situations and associated land ownerships with small-scale production systems. This study presents spatial array analysis of 354 geo-referenced soil samples revealing widespread heterogeneity in soil sodicity and fertility status across salt-affected Ghaghar basin of Kaithal district in Haryana, India. Six principal components accounted for 73% of the total variability, and the most important contributors [electrical conductivity (EC_e), sodium adsorption ratio (SAR), DTPA extractable copper (Cu) and boron (B), soil organic carbon (OC) and available phosphorus (AP)] as minimum data set were used to develop the soil quality index (SQI). Geostatistical analysis revealed Circular (EC_e and AP), Exponential (SAR, OC and B) and Gaussian (Cu) as the best fit semivariogram ordinary kriging model with weak to moderate spatial dependence. Three soil management zones (SMZs) were delineated by grouping the entire area based on soil quality index (SQI). Fertilizer recommendations for rice-wheat cropping system in different SMZs were calculated using soil test crop response (STCR) equation to ensure balanced fertilization, resource saving and reducing environmental footprints. Gypsum requirement map was prepared for systematic allocation and distribution, and enabling farmers to precisely use the mineral gypsum in order to reclaim and reduce stresses led by sodic lands. The implications of this study showed zone-specific advocacy for gypsum application (as soil ameliorant) and balanced fertilization in sustainable restoration of sodic lands, improving nutrient use efficiency and stabilizing crop production in salt-affected regions of India and similar ecologies elsewhere.

Spatial variability of soil nutrients in seasonal rivers: A case study from the Guo River Basin, China

Agricultural non-point source pollution refers that substance such as nitrogen and phosphorus cause water environment pollution through surface runoff and underground leakage in agricultural production activities. Water environment pollution related to agricultural non-point source pollution in the Huaihe River Basin is becoming more and more prominent. Therefore, it is necessary to analyze the characteristic of soil nutrient in cultivated land and explore the spatial variation and influencing factors of soil nutrients at the watershed scale. A total of 239 topsoil samples were collected from the Guo river basin, and the related factors of soil organic matter (SOM), total carbon (TC), total nitrogen (TN), total phosphorous (TP), total potassium (TK) and potential of hydrogen (PH) were studied by using descriptive statistics and geostatistical methods. The results showed that TK and PH were weak variation, while SOM, TC, TN and TP were medium variation. Soil pH, TP, TK, TC and SOM had moderate spatial variability, which was caused by both random factors and structural factors such as soil texture, soil type, fertilization and local ecological restoration management. Soil TN showed a strong spatial correlation, mainly due to soil texture and soil type. If the recommended fertilization amount is still given based on the average value of soil nutrients ignoring the spatial heterogeneity, it will not only affect crop production efficiency and fertilizer utilization, but may also cause greater environmental pollution. This study can provide a theoretical basis for the management of agro-ecological environments throughout the basin area.