The objective of this study was to evaluate the individual and synergic effects of the application of Biochar (B), Humic Substances (HS), and Gypsum (G) on the soil properties of a saline–sodic soil, and plant growth and seed quality (polyphenols, protein and yield) of quinoa. Treatments included (B) 22 t ha−1, (HS) 5 kg ha−1, and (G) 47.7 t ha−1. Two quinoa genotypes from Arid Zones (AZ-51 and AZ-103) were selected and established in eight treatments. The B + HS + G combined treatment resulted in increases in root biomass of 206% and 176% in AZ-51 and AZ-103, respectively. Furthermore, electrical conductivity (ECe), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP) decreased significantly in all treated soils. When compared to the control, ESP decreased 11-fold in the G treatment, and 9–13-fold in the B + G; B + HS; and B + HS + G treatments. Similarly, soil microbial biomass increased 112% and 322% in the B + HS + G treatment in AZ-51 and AZ-103 genotypes, respectively. Therefore, it can be concluded that the application of combined amendments (B + HS + G) represents an alternative for reclaiming degraded soils, including saline–sodic soils.
Chilean dryland areas of the Mediterranean climate region are characterized by highly degraded and compacted soils, which require the use of conservation tillage systems to mitigate water erosion as well as to improve soil water storage. An oat (Avena sativa L. cv. Supernova-INIA) -wheat (Triticum aestivum L. cv. Pandora-INIA) crop rotation was established under the following conservation systems: no tillage (Nt), Nt + contour plowing (Nt+Cp), Nt + barrier hedge (Nt+Bh), and Nt + subsoiling (Nt+Sb), compared to conventional tillage (Ct) to evaluate their influence on soil water content (SWC) in the profile (10 to 110 cm depth), the soil compaction and their interaction with the crop yield. Experimental plots were established in 2007 and lasted 3 yr till 2009 in a compacted Alfisol. At the end of the growing seasons, SWC was reduced by 44 to 51% in conservation tillage systems and 60% in Ct. Soil water content had a significant (p < 0.05) interaction with tillage system and depth; Nt+Sb showed lower SWC between 10 to 30 cm, but higher and similar to the rest between 50 to 110 cm except for Ct. Although, SWC was higher in conservation tillage systems, the high values on soil compaction affected yield. No tillage + subsoiling reduced soil compaction and had a significant increment of grain yield (similar to Ct in seasons 2008 and 2009). These findings show us that the choice of conservation tillage in compacted soils of the Mediterranean region needs to improve soil structure to obtain higher yields and increment SWC.
A soil quality database (SQDB) is a collection of soil samples described by a given set of parameters, allowing farmers, scientists and other stakeholders to make informed decisions about practices, processes and policies for soil use and management. If each parameter is considered as a dimension of the space spanned by the SQDB, extracting information becomes a difficult task when the number of parameters is >3. A widely used approach to explore multidimensional data sets is the self‐organizing map (SOM) method, which is suitable for clustering, visualization and extraction of information from multidimensional data. We applied the SOM method as an exploratory technique to an unlabelled SQDB to extract knowledge – data patterns and data associations – from the data set (the time and location of each sample were unknown). The SQDB used in this study is a set of 1240 unlabelled samples within the Central Valley of Chile, covering ca 7500 km2. The predominant soils are Andisols with a large organic matter content (7–12%), small bulk densities (0.6–1.0 g/cm3) and large water‐holding capacity. We identified three patterns: (i) isolated region within the map with close neurons (smooth transitions), (ii) two or more regions with predominantly large or small values and (iii) homogeneous map with small values with an isolated region of large values. These patterns show that the data set represented more than two groups that were not necessarily related. For pH, no important associations with other investigated parameters were observed. Previous studies carried out by the local agricultural research station showed that pH values below 5.5 constrain nutrient uptake. Thus, locations presenting pH<5,5 should be subject to seasonal monitoring to assess management practices that mitigate soil acidity. The component plane for organic matter indicates that ca. 50% of the soil samples had contents <8% related to soil series characteristics and management practices. As the k‐means is initialized by random partitions, the two‐step approach (clustering the map representing the input data) is less sensitive to variations in the input data (subsamples) than is the direct application of k‐means to the input data, but it also reduces the computational cost. The ability of SOMs to visualize multidimensional data sets helps gain an understanding of the data in the exploratory phase, such as the association and integration of physical, chemical and biological parameters.
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