Soil organic carbon (SOC) and total nitrogen (TN) are key ecological indicators of soil quality in a given landscape. Their status, especially in drought-prone landscapes, is associated mainly with the land-use type and topographic position. This study aimed to clarify the effect of land use and topographic position on SOC and TN stocks to further clarify the ecological processes occurring in the landscape. To analyze the status of SOC and TN, we collected 352 composite soil samples from three depths in the uppermost soil (0–50 cm) in four major land-use types (bushland, cropland, grazing land, and plantation) and three topographic positions (upper, middle, and lower) at three sites: Dibatie (lowland), Aba Gerima (midland), and Guder (highland). Both SOC and TN stocks varied significantly across the land uses, topographic positions, and agro-ecosystems. SOC and TN stocks were significantly higher in bushland (166.22 Mg ha−1) and grazing lands (13.11 Mg ha−1) at Guder. The lowest SOC and TN stocks were observed in cropland (25.97 and 2.14 Mg ha−1) at Aba Gerima, which was mainly attributed to frequent and unmanaged plowing and extensive biomass removal. Compared to other land uses, plantations exhibited lower SOC and TN stocks due to poor undergrowth and overexploitation for charcoal and firewood production. Each of the three sites showed distinct characteristics in both stocks, as indicated by variations in the C/N ratios (11–13 at Guder, 10–21 at Aba Gerima, and 15–18 at Dibatie). Overall, land use was shown to be an important factor influencing the SOC and TN stocks, both within and across agro-ecosystems, whereas the effect of topographic position was more pronounced across agro-ecosystems than within them. Specifically, Aba Gerima had lower SOC and TN stocks due to prolonged cultivation and unsustainable human activities, thus revealing the need for immediate land management interventions, particularly targeting croplands. In a heterogeneous environment such as the Upper Blue Nile basin, proper understanding of the interactions between land use and topographic position and their effect on SOC and TN stock is needed to design proper soil management practices.

The use of anionic polyacrylamide (PAM) as a soil conditioner could help prevent soil loss by water. In this study, we determined the effective granular PAM rate that best reduces runoff and soil loss from Oxisols. Furthermore, the effectiveness of the selected PAM rate was tested by applying it in a mixture with gypsum (G) or lime (L). The study was conducted in two phases: (i) Dry PAM rates of 0 (C), 20 kg ha −1 (P20), 40 kg ha −1 (P40), and 60 kg ha −1 (P60) were applied onto soil surface and run for six consecutive rainfall storms of 70 mm h −1 intensity for 1 h duration, and the effective PAM rate was selected; and (ii) G (4 t ha −1 ) or L (2 t ha −1 ) were applied alone or mixed with the selected PAM rate. The P20 was found to be effective in reducing runoff in the beginning while P40 and P60 were more effective starting from the third storm through the end of the consecutive storms, but with no statistically significant difference between P40 and P60. Hence, P40 was selected as the most suitable rate for the given test soil and rainfall pattern. On the other hand, the mixed application of P40 with G or L increased infiltration rate (IR) in the first two storms through improving soil solution viscosity. However, effectiveness of the mixtures had diminished by various degrees as rain progressed, as compared to P40 alone, which could be attributed to the rate and properties of G and L. In conclusion, the variation in effectiveness of PAM rates in reducing runoff with storm duration could indicate that the effective rates shall be selected based on the climatic region in that lower rates for the short rains or higher rates for elongated rains. Moreover, combined application of PAM with L could offer a good option to both fairly reduce soil erosion and improve land productivity especially in acidic soils like Oxisols, which requires further field verification.

Soil structural stability is a vital aspect of soil quality and functions, and of maintaining sustainable land management. The objective of this study was to compare the contribution of four long-term land-use systems (crop, bush, grass, and forest) coupled with anionic polyacrylamide (PAM = 0, 25, and 200 mg L−1) application on the structural stability of soils in three watersheds of Ethiopia varying in elevation. Effect of treatments on soil structural stability indices were assessed using the high energy moisture characteristic (HEMC, 0–50 hPa) method, which provides (i) water retention model parameters α and n, and (ii) soil structure index (SI). Soil (watershed), land use and PAM treatments had significant effects on the shape of the water retention curves (α, n) and SI, with diverse changes in the macropore sizes (60–250; >250 μm). Soil organic carbon (SOC) content and SI were strongly related to soil pH, CaCO3 soil type-clay mineralogy, exchangeable Ca2+, and Na+ (negatively). The order of soil SI (0.013–0.064 hPa−1) and SOC (1.4–8.1%) by land use was similar (forest > grass > bush > cropland). PAM effect on increasing soil SI (1.2–2.0 times), was inversely related to SOC content, being also pronounced in soils from watersheds of low (Vertisol) and medium (Luvisol) elevation, and the cropland soil from high (Acrisol) elevation. Treating cropland soils with a high PAM rate yielded greater SI (0.028–0.042 hPa−1) than untreated bush- and grassland soils (0.021–0.033 hPa−1). For sustainable management and faster improvement in soil physical quality, soil properties, and land-use history should be considered together with PAM application.

Background: Mushrooms are a nutritious food source, being rich in protein, vitamins and minerals. They are also contains substances that enhance the immune system, fight infectious disease. Mushrooms can be cultivated on a variety of substrates, including agricultural and agro-industrial waste materials. The current study was amid to evaluate the phytochemical characteristics of Pleurotus species cultivated on different agricultural wastes.Methods: Mushrooms Pleurotus ostreatus and Pleurotus florida were cultivated on different agricultural wastes for the screening of phytochemical characteristics. Qualitative analyses of the phytochemicals were evaluated in methanolic, ethanolic and aqueous extracts of both Pleurotus spp. Total phenolic and total flavonoid contents of the extracts were determined by using Folin-Ciocalteu method and Spectrophotometric method with aluminum chloride.Result: Qualitative analyses revealed the phytochemicals alkaloids, saponins, flavonoids and tannins were present in methanolic, ethanolic and aqueous extracts of both Pleurotus spp. while anthraquinones and Phlobatannins were absent in aqueous extracts. The highest concentration of phenols and flavonoids were recorded in methanolic extracts of P. ostreatus and P. florida (48.17 mg GAE/g of extract and 56.57 mg of RUE/g of extract and 46.73 mg GAE/g of extract and 55.58 mg of RUE/g of extract respectively). The results supported the methanolic extracts of P. ostreatus and P. florida might indeed be potential sources of phytochemicals.