Biosphere

Analysis of historical and future land use/land cover (LULC) dynamics using spatiotemporal data is crucial for better management of natural resources and environmental monitoring. This study investigated LULC transformations over a span of 60 years (1984–2044) for the Giba basin in northern Ethiopia. ArcGIS and the Cellular Automata and Artificial Neural Network (CA-ANN) model were used to develop the historical (1984, 2004, 2014, and 2024) and projected future (2034 and 2044) LULC maps of the basin, respectively. The results show that LULC categories experienced shifts from one class to another by 35%, 33%, and 40% in 2004–2014, 2014–2024, and 2004–2024, respectively. During 1984–2024, the largest and smallest percentage of positive changes were observed in settlement (7700%) and shrubs and bushes (25%), which increased from negligible to 78 km² and from 1668 km² to 2082 km², respectively. Furthermore, barren land and forestland showed the largest (−80%) and smallest (−37%) declines, which decreased from 956 km² to 187 km² and from 164 km² to 103 km² during the same period, respectively. Overall, the last 40 years witnessed considerable changes to LULC dynamics in the Giba basin. Cropland, water bodies, and settlements showed a continuously increasing trend throughout the historical study period, while grassland exhibited a continuous decreasing trend. Results of the CA-ANN model showed that the majority of the LULC categories (including water body, forest, bushes and shrubs, grassland, and barren land) will decrease, except for a slight increase of cropland (+6%) and settlements (+16%), which is projected to increase from 2570 km² to 2733 km² and from 78 km² to 91 km², respectively, in the next two decades, from 2024 to 2044. In general, high population increase, changes in government policies, and armed conflicts were found to be the most influential driving factors of LULC changes in the basin.

Potassium (K) is present in soils mainly in minerals, including feldspar. However, most of it is unavailable to plants. In the in-dyked alluvial soils of the Mekong Delta, available K is typically low despite the abundance of K-bearing feldspar, leading to nutrient imbalances and yield constraints. This study aimed to (i) select potential feldspar-potassium-solubilizing purple nonsulfur bacteria (K-PNSB), (ii) determine their ability to enhance hybrid maize seed vigor (Zea mays L.), and (iii) evaluate their effects on the growth of maize seedlings. Fifty-eight K-PNSB strains were isolated from maize-cultivated in-dyked alluvial soils, with soluble K concentrations ranging from 0.108 to 15.0 mg L⁻¹. Among these, strain M-Sl-03 released the highest K concentration under microaerobic light conditions, whereas strains M-Sl-01 and M-Sl-06 produced best under aerobic dark conditions. In addition, two more strains, M-Sl-02 and M-Wa-06, were also selected for their K solubilization ability. The selected strains were identified as Cereibacter sphaeroides strains M-Sl-01 and M-Sl-02, Rhodopseudomonas palustris strain M-Sl-03, and Rhodoplanes pokkaliisoli strains M-Sl-03 and M-Wa-06, according to their 16S rDNA region. None of them exhibited toxicity to germinating maize seeds. Both individual strains and the five-strain mixture significantly improved seed vigor. At a 1:1000 dilution, individual and mixed inoculants increased the vigor index of maize seeds by 47.5–68.8%. In addition, the selected PNSB strains contributed to improving the growth of maize seedlings, particularly plant height and root dry biomass. These promising strains have potential for application as biofertilizers to support hybrid maize cultivation.

Organo-mineral fertilizers can slow N release to plants, reducing N losses to the environment and enhancing N use efficiency (NUE). Yet, this greater NUE is not always coupled to greater crop yields, which warrants further investigation. Here, we assessed the relationship between N-NH₃ losses from volatilization and wheat (Triticum aestivum L.) biomass and N status. The following treatments were tested: conventional urea (U, 45% N), urea treated with NBPT (N-(n-butyl) thiophosphoric triamide) (U + NBPT, 45.6% N), S-coated urea (U + S; 37% N), Se-coated urea (U + Se; 45% N), organo-mineral fertilizer Azoslow 29 (OMF, 29% N + 50% Azogel^®). The above treatments and non-fertilized control were tested in two soils (LVd and LVAd, 71 and 25% clay, respectively). Semi-open static collectors were used to determine N-NH₃ volatilization 1, 2, 4, 8, 11, 15, 18, 23, 29, and 36 days after application of treatments. Wheat was cultivated for 35 days, and shoot dry mass and total leaf N were determined after harvest. Cumulative N-NH₃ losses from OMF (27 and 32% of N applied in the LVd and LVAd soils, respectively) did not differ from U and (26–32%) and U + Se (24–31%), likely due to organic matter inputs enhancing urease activity in soils. Nevertheless, OMF resulted in 2–4 times greater wheat dry matter than U, U + Se, and U + S, with similar dry mass of U + NBPT for LVAd soils. OMF application enhanced total N removal in wheat leaves relative to the unfertilized control and most N sources. N-NH₃ losses did not reduce biomass yield, but were negatively linked to N accumulation in wheat. The OMF enhanced wheat biomass and nutrition while sustaining environmental quality and promoting circularity in agroecosystems.