Improving the physical properties and water retention of sandy soils is of critical importance in arid and water-scarce regions such as Saudi Arabia. The impacts of organic amendments of different particle sizes coupled with natural clay deposits on improving the soil physio-chemical characteristics, nutrient availability, and growth of Sudan grass were investigated in this study. A loamy sand soil was amended with natural clay deposits at 2.5%, 5.0%, and 10% (w/w) application rates, and in combination with 1.0% (w/w) wheat straw of different particle sizes. The water infiltration, evaporation, and retention characteristics of the amended soil were studied for 9 weeks, and then Sudan grass was grown for 7 weeks. The impacts of the particle size of wheat straw on soil properties and nutrient availability were significant (p < 0.05) when combined with clay deposits. The highest application rate of clay (10%) demonstrated the highest water content (20.63–21.73%), and increased P and K availability to 35.54 and 6980 mg kg⁻¹, respectively, in soil, which were 33% and 88% higher, respectively, compared to the control. Plant N, P, and K concentrations were increased to 0.95%, 0.26%, and 4.33%, respectively, which were 2–3.5-fold higher than the control. Therefore, the integrated application of natural clay deposits and wheat straw of fine particle size could be an effective strategy in improving plant production in water-scarce regions.

Biochar (BC) applications have multiple impacts on crops’ nutrient availability, growth and yield depending on the feedstock type and pyrolysis conditions. Pot and field experiments were conducted to examine the effects of biochars (BCs) prepared from three different feedstocks, Acacia modesta wood biochar (AWB), Dalbergia sissoo wood biochar (DWB) and poultry litter biochar (PLB), on soil’s nutrient availability, uptake by wheat (Triticum aestivum) and sunflower (Helianthus annuus) crops and their yield attributes. All BCs were applied at the rate of 10t ha⁻¹ in each treatment in both experiments, and pot and field trials were designed according to a two-factor factorial completely randomized design (CRD) and two-factor factorial randomized complete block design (RCBD), respectively. The concentration of soil NO₃-N, NH₄-N, Olsen P and extractable K increased by 98.5, 296, 228 and 47%, respectively, in the pot experiment with the application of PLB+polyhalite (PH) treatments. Similarly, in field experiments, NO₃-N, NH₄-N and Olsen P contents increased by 91, 268 and 156% under the PLB+PH treatment, respectively. However, in both experiments, soil’s microbial biomass phosphorus (MBP) was significantly higher after AWB+PH treatment, and the increments were 127 and 109% while microbial biomass nitrogen (MBN) contents were 16 and 14% higher than the control under DWB+PH and AWB+PH treatments, respectively, in the field experiment. Similarly, combined PLB+PH increased the total organic carbon (TOC) of soil by 193%. Moreover, PLB+PH co-applications with PH significantly increased sunflower grain yields by up to 58% and the harvest index by 45%. Overall, no negative impact with respect to BCs was observed on the soil’s nutrient content and plant growth. Hence, for immediate crop benefits and soil health, using nutrient biochar (PLB) alone or in combination with chemical fertilizers is recommended.

Vast areas of natural rangelands in the Kingdom of Saudi Arabia (KSA) suffer from deterioration due to the scarcity of vegetation cover and poor soil quality. Assessing soil quality in rangelands is crucial to identifying degraded lands and to implementing proper sustainable management practices. In this study, a total data set (TDS) containing 27 physical and chemical soil indicators was generated for three rangelands (Al-Fahyhyl, Al-Sahwa, and Al-Tamryate) in KSA. Principal component analysis (PCA) and analytic hierarchy process (AHP) analysis were employed to establish a minimum data set (MDS) and to evaluate key physical and chemical properties affecting soil quality, along with the associated weight factor for each indicator. Results indicated that the MDS represented ≥70% of the total variability of the TDS and accurately estimated the soil quality index (SQI) based on determined physical and chemical soil properties in the study regions. Linear regression indicated high correlation between SQI-TDS and SQI-MDS, with the R² ranging between 0.51–0.87. On the surface layer (0–30 cm), the MDS contained seven soil indicators (sand, dispersion ratio (DR), mean weight diameter (MWD), bulk density (BD), total organic carbon (TOC), available phosphorus (Pa), and available potassium (Ka)), whereas in the sub-surface layer it contained six indicators (sand, DR, MWD, BD, TOC, Pa, and Ka). In all regions, sand had the largest weight factor (0.4514–0.4835), followed by TOC (0.2441–0.2512). Under the arid climate present in all the study sites, sand and TOC levels are crucial for nutrient retention, soil structure, and water retention. Most of the study areas had very low and low SQI (Al-Fahyhyl, 74.4%; Al-Sahwa, 61.8%; and Al-Tamryate, 81.7%), indicating an immediate need for suitable agricultural practices such as reduced tillage, increased organic amendments, and proper water management. The outcomes of this study offer valuable insights for land managers, legislators, and agricultural stakeholders to pinpoint regions in need of development, conduct comprehensive and continuous monitoring of SQI in rangeland areas, and implement land management plans for rangeland rehabilitation and environmental sustainability.

Compost application to soil is an effective strategy to enhance soil fertility, promote plant growth, and support sustainable agriculture. Nevertheless, the variability in the responses of plants to compost amendments across different compost types, concentrations, exposure durations, application media, and across different physiological traits of plants is not well understood. In this study, we performed a meta-analysis using data from 92 peer-reviewed scientific articles to better understand the effect of compost amendments on plant physiological, biochemical, and yield traits. The results of this study showed that compost amendment significantly improved plant growth parameters, and the increase in shoot biomass and plant height was the highest (~19.4–42.7%), followed by root length (20.4%) and root biomass (19.7%), indicating the important role of compost in promoting root development. In addition, photosynthetic efficiency was significantly enhanced, and total chlorophyll and carotenoid content increased by 13.5–49.1%. The yield-related traits, total yield, and 100-grain weight responded positively and significantly increased by ~18%. There were variations among different plant species and different exposure conditions. The mechanistic interaction between compost components, soil agrochemical properties, and plant physiological and yield responses should be further explored to maximize the benefits of compost application in sustainable agriculture.