Brewer’s spent grain represents approximately 85% of the by-products generated by the beer industry. It is acidic and rich in organic matter and nutrients. In Egypt, spent grain has no value and is available at no cost all year. Incubation and germination experiments were conducted to assess the potential of using spent grain and compost to increase soil fertility and squash (Cucurbita pepo L.) growth in a calcareous soil. Amendments were two rates of spent grain (13.5, 26.7gkg−1), two rates of compost (24.7, 49.4gkg−1), a blend of lowest rates of compost and spent grain and a control. Treatments were mixed with calcareous soil, placed in pots and incubated anaerobically under field conditions for one month. After incubation 15 squash seeds were planted in the soil pots. Highest rate of spent grain most effectively increased soil water holding capacity, organic matter, macronutrients, micronutrients, germination parameters, and reduced soil pH. Mixing compost with spent grain was more effective than high rate of compost in increasing water holding capacity, soil nutrients, and decreasing soil pH. While both treatments were equally effective in enhancing squash germination and increasing soil organic matter. Spent grain is more effective than compost in improving properties of calcareous soils, and is much less expensive

This review article discusses humic substances – specific organic compounds, which are the substantial part of the bioenergy matrix of the food chains of living creatures and the essence of the exchange interaction of those media. The dead organisms (mostly plants) are transformed into humic substances. A prerequisite for creating the monograph was a steady interest in humic substances from humus specialists (soil scientists, agricultural chemists, coal chemists, etc.) and biologists, physicians, and workers in agriculture, forestry, and communal services. At the same time, monographs are quite rare in the literature, where humic substances are described quite fully. Based on our experience in studying humic substances, we have attempted to characterize humic substances comprehensively. Collecting disparate information and analyzing it made it possible to obtain a more or less holistic view of such a unique natural object as humic substances. Much attention is paid to the colloidal properties of these specific compounds. We must not forget that humic substances are a necessary and mandatory component of all metabolic processes in the biosphere.

In Egypt, the total area of agricultural land is 3.36 million acres, which is 3.8% of the country entire territory. One of the main obstacles to agricultural production in Egypt is soil salinization and degradation. Therefore, saline-sodic soil reclamation in arid regions is highly relevant. This study aimed to use Azospirillum inoculation with eco-friendly organic wastes for free remediation of saline-sodic soils. In this work, nine treatments included two levels of spent grain (S1 and S2), two levels of compost (C1 and C2), a mix of both sources (C1S1), Azospirillum (A1), a mix of both sources with Azospirillum (A1S1 and A1C1) and untreated control. The treatments were previously incubated with soil at field capacity for five months under laboratory conditions at 28°C. The most relevant chemical and biological parameters were analyzed every month for five months. Results indicate that Azospirillum inoculation with spent grain increased soil organic carbon (TOC), dehydrogenase and urease enzymes, micro-nutrients iron (Fe²⁺), zinc (Zn²⁺), manganese (Mn²⁺), copper (Cu²⁺), and boron (B⁺), and macro-nutrients nitrogen (N), phosphorus (P) and potassium (K); while decreased exchangeable sodium percentage (ESP), pH and EC, by 75%, 12%, and 43% respectively, compared to initial conditions. A significant variation was observed in chemical and biological properties among all treatments in the order of S2 ≥ A1S1> A1 > C2 > C1S1 > A1C1 > C1 > control > initial. In conclusion, the addition of Azospirillum with the spent grain is highly recommended for the saline-sodic soil amelioration. It is more effective than compost to remediate and enhance saline-sodic soils fertility. Graphical abstract

An environmental friendly superabsorbent composite (SAC) based on rice, (Oriza sativa L.), husk was created by the scientific group at Faculty of Science, Tanta University, and City of Scientific Research and Technological Applications (SRTA-City), Egypt. SAC was tested for its ability to improve soil water retention, control the release of urea, and its biodegradability in soil. The effect of SAC on sweet pepper, Capsicum annuum, productivity under severe deficit irrigation conditions was studied. Doses of irrigation water representing percentage ∼16.7, 11.9, 7.1, and 2.4 of the actual crop water requirements (CWR) were tested in soil treated with 0.25, 0.50, 0.75, and 1.00 wt% SAC. The tested SAC lost ∼60% of its weight in 150 days. Soil water retention and urea release rates were improved plant growth in response to the addition of SAC. Application of ∼11.9% of CWR with 1.00 wt% SAC resulted in significantly better crop production than other treatments without SAC. This could annually save about 154.44 million cubic meters (MCM) to be directed for horizontal expansion and improve food security.

Calcareous soils are characterized by a high calcium carbonate content (calcite), which plays a crucial role in the soil structure, plant growth, and nutrient availability. The high content of CaCO₃ leads to the increment of the soil alkalinity, which results in a lowering of the nutrient availability causing a challenge for the agriculture in these soils. In this study, the calcite-solubilizing potential of the diazotrophic Azotobacter salinestris YRNF3 was investigated in vitro as a probable bio-agent for enhancing the calcareous soils properties such as soil pH and nutrient availability. Twelve diazotrophic bacterial strains were isolated from wheat rhizosphere collected from different wheat-cultivated fields in five Egyptian governorates. Using Nessler’s reagent, all isolated bacterial strains were found to have the ability to produce ammonia. By amplification of nifH gene, a PCR product of 450 bp was obtained for all isolated bacterial strains. For each isolate, three biological and three technical replicates were applied. All isolated diazotrophic bacteria were qualitatively screened for their calcite-solubilizing ability. To quantitatively investigate the calcite-solubilizing potential of A. salinestris YRNF3 in vitro, changes in the contents of soluble calcium (Ca²⁺), bicarbonate (HCO₃⁻), total nitrogen (TN), total protein (TP), and pH were daily measured in its culture filtrate along 10 days of incubation. The results showed that the pH values in the culture filtrate ranged from 5.73 to 7.32. Concentration of Ca²⁺ and HCO₃⁻ in the culture filtrate significantly decreased with the increment in the incubation time, while concentration of TN increased along the time. The highest TN concentration (0.0807 gL⁻¹) was observed on days 4 and 5, compared to that of the day 0 (0.0014 gL⁻¹). Content of TP in the culture filtrate also significantly increased along the incubation period. The highest TP content was recorded in day 4 (0.0505%), while no TP content was recorded on day 0. Furthermore, data obtained revealed that A. salinestris YRNF3 produced acid phosphatase at low activity (5.4 U mL⁻¹). HPLC analysis of the culture filtrate indicated production of different organic acids, namely lactic acid (82.57 mg mL⁻¹), formic acid (46.8 mg mL⁻¹), while acetic acid was detected in a low quantity (3.11 mg mL⁻¹). For each analysis, three replicates of each treatment were analyzed. Means of the tested treatments were compared using Tukey's HSD test at p ≤ 0.05. In conclusion, findings of this work suggested that A. salinestris YRNF3 has the potential to be a probable bioagent to be used for the reclamation of the calcareous soils by solubilizing CaCO₃, improving soil fertility, and promoting plant growth. However, further studies are needed to investigate its field application and their long-term effects on the soil properties and plant productivity. To the best of the author's knowledge, this is the first study reporting the calcite-solubilizing ability of a nitrogen-fixing bacteria. Having these two abilities by one microorganism is a unique feature, which qualifies it as a promising bioagent for reclamation of the calcareous soils.