Laboratory Research on Polarized Optical Properties of Saline-Alkaline Soil Based on Semi-Empirical Models and Machine Learning Methods

Currently, soil salinization is a serious problem affecting agricultural production and human settlements. Remote sensing techniques have the advantages of a large monitoring range, rapid acquisition of information, implementation of dynamic monitoring, and low impact on the ground surface. Over the past two decades, many semi-empirical bidirectional polarized distribution function (BPDF) models have been proposed to accurately calculate the polarized reflectance (Rp) on the soil surface. Although there have been some studies on the BPDF model based on traditional machine learning methods, there is a lack of research on the BPDF model based on deep learning, especially using laboratory measurement spectrum data as the processing object, with limited research results. In this paper, we collected saline-alkaline soil in the field as the observation object and measured the Rp at multiple angles in the laboratory environment. We used semi-empirical models (the Nadal–Bréon model, Litvinov model, and Xie–Cheng model) and machine learning methods (support vector regression, random forest, and deep neural networks regression) to simulate and predict the surface Rp of saline-alkaline soils and compare them with experimental results. The measured values of the laboratory are compared and fitted, and the root mean squared error, R-squared, and correlation coefficient are calculated to express the prediction effect. The results show that the predictions of the BPDF model based on machine learning methods are generally better than those of the semi-empirical BPDF model, which is improved by 3.06% at 670 nm and 19.75% at 865 nm. The results of this study also provide new ideas and methods based on deep learning for the prediction of Rp on the surface of saline-alkaline soils.

Evolution of Salt Tolerance in Arabidopsis Thaliana on Siliceous Soils Does Not Convey Tolerance to Saline Calcareous Soils

Purpose Alkaline salinity constrains crop yield. Previously, we found local adaptation of Arabidopsis thaliana demes to saline-siliceous soils (pH≤7) and to non-saline carbonate soils. However, any natural population of A. thaliana was localized on saline-alkaline soils. This suggests that salinity tolerance evolved on saline-siliceous soils may not confer tolerance to alkaline salinity. This hypothesis was explored by addressing physiological and molecular responses to saline-alkaline conditions of A. thaliana demes differing in salinity and carbonate tolerance.Methods A. thaliana native to saline-siliceous soils (G3), to non-saline carbonate soils (G1), or to soils with intermediate levels of these factors (G2) were cultivated in common gardens on saline-siliceous or saline-calcareous substrate. Hydroponics and irrigation experiments confirmed the phenotypes. Growth, mineral concentrations, genome differences, and expression of candidate genes were assessed in the different groups.Results G3 performed best on saline-siliceous soil and in hydroponics with salinity (pH 5.9). However, G3 was more sensitive to saline-alkaline conditions than G1 and G2. Fitness under saline-alkaline conditions was G2 > G1>G3 and G2 best maintained ion homeostasis under alkaline salinity. Whole genome scan did not differentiate among the groups, while distinctive patterns for FRO2, NINJA, and CCB4 were found and confirmed by qPCR.Conclusion In A. thaliana, salinity tolerance evolved on saline-siliceous soils does not provide tolerance to alkaline salinity. Plants from soils with intermediate conditions (G2) have more plasticity to adapt to alkaline salinity than those locally adapted to these individual stress factors. Higher expression of NINJA and CCB4 may contribute to this better adaptation.

Organic Amendments and Elemental Sulfur Stimulate Microbial Biomass and Sulfur Oxidation in Alkaline Subtropical Soils

Sulfur deficiency arising due to intensive cultivation, use of sulfur free fertilizers and reduction in atmospheric sulfur depositions has become a major issue limiting crop production in many parts of the world. Elemental sulfur could be a good source of available S, but its slow oxidation is a problem for its efficient use as a sulfur fertilizer. Main objective of the study was to assess the effect of organic amendments (OA) and elemental sulfur (ES) on microbial activities, sulfur oxidation and availability in soil. A laboratory incubation experiment was carried out for a 56 days period using two sulfur deficient alkaline soils. Organic amendments (OA), i.e., farmyard manure (FYM), poultry litter (PL) and sugarcane filter cake (SF), were applied (1% w/w) with or without elemental sulfur (ES) at 50 mg kg−1. Application of ES alone or in combination with OA significantly increasedCO2-C evolution, microbial biomass, and enzyme activities in the soils, except dehydrogenase activity (DHA) which was not affected by ES application. Combined application of OA and ES had a more pronounced effect on microbial parameters compared to ES or OA applied alone. Ratios of dehydrogenase activity-to-microbial biomass C and arylsulfatase activity-to-microbial biomass C were high in ES+FYM and ES+SF treatments, respectively. Elemental sulfur got sufficiently oxidized resulting in significant improvement in plant available S. Relatively more ES was distributed into C-bonded-S than ester bonded-S. Increase in sulfur availability in ES+OA amended soils was the combined function of sulfur oxidation and mineralization processes through improved microbial activity.

Regulation of Phosphorus and Zinc Uptake in Relation to Arbuscular Mycorrhizal Fungi for Better Maize Growth

Zinc (Zn) is an important micronutrient for plants, whose deficiency in alkaline soils creates hurdles in the achievement of optimum crop growth. Moreover, overuse of phosphorus (P) fertilizers often causes Zn immobilization in the soil. The employment of arbuscular mycorrhizal fungi (AMF) could be potentially environmentally friendly technology in this regard. Therefore, a pot experiment was conducted to assess the beneficial role of AMF (Glomus species) on maize under low and high P and Zn levels. Seven levels of Zn (0, 20, 40, 60, 80, 100 and 120 mg Zn kg−1 soil ZnSO4·7H2O) and three levels of P (0, 14.5, 29 and 58 kg ac−1 as single superphosphate) were applied with (M+) and without AMF (M−). The results showed that a high application rate of Zn (100 and 120 mg Zn kg−1 soil) restricted P translocation in plants and vice versa. Moreover, the nutritional status of mycorrhizal plants (AM) was better than non-mycorrhizal (NM) plants. AM plants showed a maximum positive response at 20 mg Zn kg−1 soil, or 29 kg P ac−1. In response to 20 mg Zn kg−1 soil, root colonization was maximum, which enhanced the maize nutrient concentration in shoots. In conclusion, AMF inoculation (M+) with P (29 kg ac−1) and Zn (20 mg kg−1) is efficacious for improving maize’s growth and nutrition. More investigations are suggested at the field level under different agroclimatic zones to ascertain whether P (29 kg ac−1) or Zn (20 mg kg−1) with AMF is the best treatment for maize growth optimization.

Application of GIS Technologies in Land Improvement in the Shabran-Sumgait Region

The article presents the results of a soil cover study carried out in Azerbaijan. It was found that the soils of the study area are slightly saline, which is more common on irrigated lands. Solonetzic soils are widespread in the Shabran-Sumgait region. The negative impact of alkaline soils on the development and crop yield of cultivated plants is due to the presence of soda and absorbing sodium and magnesium cations in the soil solution. It was revealed that 36.3% of soils with. Gyulamli, Shabran region, was heavily salinized. It is necessary to control the flows of the collector and drainage network in agricultural areas.

Reactions of two xeric-congeneric species of Centaurea (Asteraceae) to soils with different pH values and iron availability

Centaurea scabiosa L. and C. stoebe Tausch are known to co-exist naturally in two extremely different types of open dry habitats in the temperate zone, alkaline xerothermic grasslands and acidic dry grasslands. However, knowledge about their preferences to edaphic conditions, including soil acidity (pH), and iron (Fe) availability is scarce. Therefore, experimental comparison of soil requirements (acidic Podzol vs alkaline Rendzina) of these species was carried out. The study was designed as a pot experiment and conducted under field conditions. Fe availability was increased by application of Fe-HBED. Reactions of plants to edaphic conditions were determined using growth measurements, leaf morphometric measurements, chlorosis scoring, chlorophyll content and chlorophyll a fluorescence (OJIP) quantification as well as determination of element content (Ca, Mg, Fe, Mn, Zn and Cu). Growth and leaf morphometrical traits of the studied congeneric species were affected similarly by the soil type and differently by the chelate treatment. Increased availability of Fe in Rendzina contrasted the species, as treatment with 25 µmol Fe-HBED kg−1 soil promoted growth only in C. stoebe. Both species turned out to be resistant to Fe-dependent chlorosis which was also reflected in only minor changes in chlorophyll a fluorescence parameters. Both species showed relatively low nutritional demands. Surprisingly, Fe-HBED did not stimulate Fe acquisition in the studied species, nor its translocation along the root:shoot axis. Furthermore, contrary to expectations, C. scabiosa took up less Fe from the acidic than alkaline soil. C. scabiosa not only absorbed more Ca and Zn but also translocated greater amounts of these elements to shoots than C. stoebe. Both species acquired more Mg on Podzol than on Rendzina which suggests adaptation allowing avoidance of aluminum (Al) toxicity on acidic soils. Overall, it seems that C. scabiosa prefers alkaline soils, whilst C. stoebe prefers acidic ones.

Seasonal changes of macronutrients concentration in olive trees grown in acid and in alkaline soils

Leaf samples from mature olive (Olea europaea L. cv. ‘Kalamon’) trees were collected monthly from April 2018 to March 2019 from two olive orchards, cultivated one in acid and one in alkaline soil, located in Western Greece. Nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations in the leaves were determined and seasonal variation curves were calculated for each nutrient and orchard. The seasonal concentration patterns of N, P, K, Ca, and Mg nutrients were almost similar in both soils. Seasonal variation nutrient curves independently of soil acidity varied according to vegetation stages and no significant differences in nutrient concentrations were observed at different development stages between olives grown in the acid or the alkaline soils, with only one exception the leaf K concentration. The nutrient concentration measured in wintertime was at a sufficient level for optimum olive growth in both orchards. These concentrations could be used as reference values for leaf analysis interpretation and for developing an optimum fertilization program under Mediterranean climatic conditions.