According to the FAO, 828 million people were facing acute food insecurity in 2021. Fertilization is a critical input factor in crop production and food security achievement. Therefore, fertilization is a critical input factor in crop production and food security achievement. However, there is room for improvement in the application of fertilizers in certain regions. Thus, new fertilizers with a relatively low cost could enhance farmers’ access to these essential inputs. Phosphogypsum (PG) is used as fertilizer because it contains many nutrients essential for plant growth, including calcium, sulfur, and phosphorus. A two-year field experiment was conducted using two Moroccan PG products (PG1 and PG2, obtained from two different industrial sites), applied at four rates (0, 1.5, 3, and 4.5 t/ha). The aim was to assess the impact of PG source and rate on barley crops, including yield component, nutrients uptake, and heavy metals content. The study’s findings revealed that as the rate of PG application increased, there were significant enhancements in the number of spikes, tillers, grains, total biomass, grain yield, and thousand-grain weight. In fact, when compared to the control, the application of 1.5, 3, and 4.5 t/ha of PG led to a remarkable increase in grain yield by 21%, 34%, and 39%, respectively. Furthermore, the uptake of nutrients (N, P, K, Ca, Mg, and S) by the shoots and grains was significantly influenced by the PG application rates, with higher rates resulting in greater nutrient uptake. Notably, the application of PG had no discernible impact on the heavy metal content in shoots, grains, or soil.

Fertilization is a critical input factor in crop production and food security achievement. However, there is room for improvement in the application of fertilizers in certain regions. Thus, using low-cost fertilizers, such as phosphogypsum (PG), could enhance farmers' access to these essential inputs. A two-years field experiment was conducted using two Moroccan PG products applied at four rates (0, 1.5, 3, and 4.5 t/ha). The aim was to assess the impact of PG source and rate on barley crop, including yield component, nutrients uptake, and heavy metals content. The study's findings revealed that as the rate of PG application increased, there were significant enhancements in the number of spikes, tillers, grains, total biomass, grain yield, and thousand grains weight. In fact, when compared to the control, the application of 1.5, 3, and 4.5 t/ha of PG led to a remarkable increase in grain yield by 21%, 34%, and 39%, respectively. Furthermore, the uptake of nutrients by the shoots and grains was significantly influenced by the PG application rates, with higher rates resulting in greater nutrient uptake. Notably, the application of PG had no impact on the heavy metal content in shoots, grains, or soil.

Phosphorus (P) deficiency is one of the major constraints for sustainable crop production in calcareous soils. This study aimed to elucidate the key soil characteristics modulating the variability of soil Olsen P in these typical soils. A comprehensive soil sampling initiative (1.5 samples per hectare) was conducted on a 100-ha farm, considering 31 attributes that included soil physical and chemical properties, and geographic attributes. Three machine learning algorithms-partial least squares regression (PLSR), random forest (RF), and cubist regression (CR)-were employed to understand key variables controlling soil Olsen P. Furthermore, the same data set was used to spatially map the variations in Olsen P levels using ordinary kriging. The results revealed that soil chemical factors, specifically exchangeable manganese and zinc, cation exchange capacity, and carbonate, played a crucial role in controlling P levels. Among the machine learning models, the best performing model was RF (R2 = 0.95, RMSE = 1.30 mg kg-1) followed by CR (R2 = 0.92 and RMSE = 1.43 mg kg-1). Additionally, the analysis using a Gaussian semi-variogram model showed a good performance (R2 = 0.78, RMSE = 2.05 m) in visualizing the spatial distribution of Olsen P, revealing its heterogeneity. The resulting pattern of Olsen P distribution may be attributed not only to soil properties but also to external factors, such as sediment transport through watercourses across the study area and atmospheric deposition from a nearby P mining site. Overall, the combination of geostatistical methods and machine learning approach demonstrates a significant potential in understanding the complexity of soil available P (Olsen-P) that could help to develop sustainable and precise P management.

Phosphorus is an essential macro-nutrient that often limits plant productivity in agricultural soils, particularly in alkaline-calcareous soils. In these soils, phosphorus availability is primarily controlled by sorption and precipitation reactions. This paper critically reviews and synthesizes the principal strategies through which rhizosphere processes modulate phosphorus bioavailability in such typical soils, providing a valuable resource for researchers and practitioners on the current state of knowledge. The review also emphasizes the importance of rhizosphere processes and their applications in developing sustainable farming practices. It focuses on recent advancements in root exudation, anatomical and molecular mechanisms, and their interactions with key agricultural practices. Furthermore, it synthesizes and discusses cutting-edge rhizosphere research, pinpointing opportunities for future explorations. Several knowledge gaps were identified. For instance, there is a paucity of information regarding the trade-offs between root morphological and physiological traits (e.g., root exudates) in response to phosphorus deficiency. Additionally, metabolomics needs to be integrated to unravel the molecular mechanisms involved in rhizosphere interactions. Further research is also required to identify specific plant and microbial traits that contribute to rhizosphere acidification in calcareous soils.

The direct application of phosphate rock (PR) has been found suitable for acidic soils. Still, efforts are needed to improve its reactivity to match grassland P demand. This research aimed to investigate changes in the dissolution of two Moroccan sedimentary PRs (Ben Guerir and Khouribga) in response to four rates of phosphogypsum (PG)—a by-product of the phosphate fertilizer industry. We conducted a 60-day incubation study using two acid soils from New Zealand. The soils were treated with PRs at 100 mgP kg −1 of soil either alone or combined with PG, which was applied at 0, 1, 3 and 9 t ha −1 (approximately the equivalent of 0, 0.9, 2.7, and 8.1 g of PG kg −1 of soil, respectively). The dissolution rates were determined from the differences in residual calcium (Ca) extracted with 1 M HCl. Soil pH, Olsen P, exchangeable aluminium (Al) and Ca and Ca saturation were analyzed at the end of the experiment. Phosphate rocks and PG’s physicochemical properties were characterized. Phosphogypsum addition increased Olsen P by 34% and 59% at 9 t ha −1 compared to 0 t ha −1 in Molesworth and Lindis Peaks soils, respectively. However, PG did not affect the dissolution of P Rs in the different of soil types. Khouribga PR was more reactive than Ben Guerir PR, especially in the Molesworth soil where soil pH and base saturation were lower and P retention was higher compared to Lindis Peaks soil. Particle size distribution was the key factor that contributed to the observed greater reactivity of the Khouribga PR. Both P Rs showed dissolution rates >50%, suggesting their suitability for direct application on acid soils. Being an important source of sulphur and some P, PG if combined with PR, can promote and complement PR’s direct use as fertilizer on acid soils. Moreover, the development of new fertilizer products by combining these two materials should be encouraged.

Nitrogen (N) and phosphorus (P) are critical to pasture productivity; however, limited information is available on how the single and combined additions of N and P affect soil P fractions and seasonal changes in microbial and biochemical processes linked to P cycling under pasture systems. A two-year field trial was conducted where N (0 or 250 kg ha−1 yr−1) and P (0 or 50 kg ha−1 yr−1) were applied in a full factorial design to an intensively managed grass-pasture system. Changes in plant growth and nutrient uptake, soil microbial biomass P, soil phosphatase activities, and soil inorganic and organic P fractions were assessed by regular sampling. Phosphorus addition increased Olsen P and shoot P uptake but not shoot biomass compared to the control. In contrast, N addition decreased Olsen P by 23

Legume establishment and persistence in New Zealand hill and high-country soils are largely limited by high soil acidity and associated aluminum (Al) toxicity. The present study aimed to evaluate the effect of four rates of phosphogypsum (0, 1, 3, and 9 t ha−1) on Al speciation in the soil solution and to examine which species are mostly impacting total dry matter (TDM) yield of lucerne. Glasshouse and incubation experiments were conducted using three acid soils with different exchangeable Al concentrations: Molesworth, Glenmore, and Lindis Peaks. The distribution of Al species was modeled using visual Minteq. Partial least square (PLS) regression was used to evaluate the relationships between Al3+ and other variables in the soil-soil solution system. In the planted and incubated Molesworth soils, Al3+ and hydroxylated Al (Al–OH) fractions decreased significantly at 1 and 3 t of phosphogypsum ha−1 compared to 0 t ha−1. However, in the planted Glenmore and incubated Lindis Peaks soils, these two fractions remained unchanged. The contribution of variables in Al3+ concentration depended on the soil type. However, the loading plot of the whole soil data set (n = 62) showed that Al–OH, base saturation, soil/soil solution pHw, and exchangeable Al were the main explanatory variables for the variation in Al3+ concentration. The TDM yield of lucerne was better explained by Al3+, Al-F, and Al-DOM than exchangeable Al. Reasonable amounts of phosphogypsum (1 to 3 t ha−1) can help to alleviate Al toxicity in acid soils (pH ≤ 5.3), but higher application rates should be avoided.

Liming effects on soil phosphorus (P) availability via biological P cycling are not clear. We conducted an 18-month field experiment on a long-term (60 years +) permanent fertilized grassland in a relatively dry environment. The aim was to examine the impact of liming on P biochemical processes and dynamics. Lime was applied at the beginning of the experiment to produce a soil pH range of 5.4–7.0, with no fertilizer P treatments. Soil sampling was conducted throughout the experimentation period at 0–75 mm. All soils were analysed for moisture content, pH, Olsen P, resin P, exchangeable aluminium (Al), microbial biomass P (MBP) and enzyme activities. At the final sampling, the soil samples were analysed for total C, total N and anaerobic mineralizable N (AMN). A sequential P fractionation was conducted for 0–30 mm depth samples. Liming effects on soil pH and P processes were limited to the surface 30 mm only, where labile inorganic P (Pi) fraction increased by 42

Legumes play critical dual roles in grazed grassland ecosystems; providing nitrogen inputs and high-quality feed for grazing livestock. However, many species fail to persist in acidic, low fertility soils. A glasshouse study was conducted to investigate the response of lucerne (Medicago sativa) to phosphogypsum (PG), lime and soluble P + S fertilizer (PS) application to two soils. Phosphorus and sulphur were applied through either PG (0, 1, 3 and 9 t ha−1) or P + S fertilizer at equivalent rates to PG. Both PG and PS were applied with or without lime, which was applied at 2 t ha−1. Yield and nutrient uptake of the lucerne was measured, while the soil was analyzed for pH, Olsen P and exchangeable aluminum. Yield responses were significantly different between the two soils. Maximum yields and P and S uptakes were obtained under PG 9 t ha−1 combined with lime. Exchangeable Al decreased in both soils under 1 ha−1 of PG compared with the control. At the highest rate, Olsen P increased by 8 and 6 mg kg−1 for PG and by 6 and 11 mg kg−1 for PS compared with the control for Glenmore and Molesworth soils respectively. Phosphogypsum showed positive effects on P and S bioavailability.

In this work, we modelled the response of soil water repellency (SWR) persistence to the decrease in moisture in drying soils, and we explored the implication of soil particle size distribution and specific surface area on the SWR severity and persistence. A new equation for the relationship between SWR persistence and soil moisture (θ) is described in this paper. The persistence of SWR was measured on ten different hydrophobic soils using water drop penetration time (WDPT) at decreasing levels of gravimetric water content. The actual repellency persistence showed a sigmoidal response to soil moisture decrease, where Ra(θ)=Rp/1+eδ(θ−θc). The suggested equation enables one to model the actual SWR persistence (Ra) using θ, the potential repellency (Rp) and two characteristic parameters related to the shape of the response curve. The two parameters are the critical soil moisture θc, where the Ra increase rate reaches its maximum, and the parameter δ affecting the steepness of the curve at the inflexion point of the sigmoidal curve. Data shows that both soil carbon and texture are controlling the potential SWR in New Zealand pastures.