Population growth and an increasing demand for food cause the intensification of agriculture leading to soil degradation and a decrease in the soil organic carbon (SOC) stock. Agroforestry systems such as alley cropping are gaining more and more attention as a practice to maintain and/or increase SOC in agroecosystems. The aim of this study was to add to the knowledge on SOC in alley cropping systems and to evaluate the contribution of introducing trees into agricultural landscapes by conducting a meta-analysis of the available data. The soil carbon (C) input will increase with time. Our findings suggest that a beneficial effect on SOC occurs after approximately a decade of alley cropping practice adoption. Furthermore, the effect of alley cropping is more beneficial in regions with lower initial SOC concentration compared to that in regions rich in SOC. Higher relative SOC is observed in the tropical region compared to that in the temperate climate zone. The establishment of alley cropping systems on agricultural land needs to consider several parameters such as alley width and tree species when designing such systems to achieve the highest possible tree and crop productivity while increasing SOC.

The grain yield and concentrations of Fe, Zn, Se, Cd, and P in two winter wheat genotypes and in vitro bioaccessibility of Fe and Zn under the effect of different nitrogen fertilization and Zn-Se foliar application were evaluated. The total grain Fe, Zn, and Se concentrations, as well as Fe and Zn concentrations, after in vitro digestion were under the strongest effect of foliar Zn-Se application. On the other hand, Fe and Zn bioaccessibility (%) were under the most substantial effect of genotype. Regarding the need to increase concentrations of essential micronutrients in wheat grain, foliar Zn-Se application is a reliable and accepted agricultural practice, but to improve mineral bioaccessibility in human nutrition, foliar Zn-Se application should be combined with the most responsive genotypes. For this reason, further research on the genotype specificity of wheat regarding micronutrient bioaccessibility should be carried out.

Selenium (Se) is a nonmetal that is essential for humans and other animals, and is considered beneficial for plants. The bioavailability of Se strongly influences its content in the food chain. Soils are the main source of Se, and their Se content primarily influences its availability, along with other soil properties. A field survey was conducted on soils of Southeast Europe, specifically in Croatia (Osijek), Bosnia and Herzegovina (Sarajevo, Banja Luka, Mostar, and Prud), and Serbia (Novi Sad). Soil samples were taken from the arable soil layer (0–30 cm depth), and two types of Se availability were measured: Se extracted using pure HNO₃ (Se_Tot) and Se readily extracted in water (SeH₂O). Only soils from the Mostar area had Se concentrations above deficit levels (0.5 mg kg⁻¹), with the highest values of cation exchange capacity (CEC), soil organic matter (SOM) measured as loss of ignition (LOI), total C, total N, Zn_Tot and Cd_Tot. The connections between the chemical characteristics of the soil and SeH₂O were investigated. Principal component analysis (PCA) explained 73.7% of the variance in the data set in the first three principal components (PCs). Using the provided data, we developed a partial least squares (PLS) regression model that predicted the amount of SeH₂O in the soil, with an accuracy ranging from 77% to 90%, depending on the input data. The highest loadings in the model were observed for LOI, CEC, total C, total N, and Se_Tot. Our results indicate the need for biofortification in these key agricultural areas to supplement the essential dietary requirements of humans and livestock. To efficiently and economically implement biofortification measures, we recommend utilizing regression models to accurately predict the availability of Se.

Intercropping arable crops in orchards is a sustainable land use for intensifying agricultural production, under the condition of plants’ complementarity in sharing resources. This study investigated the aspects of water use and yields in intercropped systems of walnut and crops. To assess possible temporal complementarity between crops and trees, a summer crop—buckwheat—and a winter crop—barley—were intercropped in walnut orchards. The land and water productivity were studied under two designs: in an older, denser orchard and a younger one, with wider tree spacing. The results showed a reduction in yields and water productivity (WP) of intercrops due to the competition with walnut trees, with the exception of buckwheat in the younger orchard, where this summer crop surprisingly achieved the highest yield and WP. Nevertheless, in the system with mature fruiting trees, intercropping with winter barley was 53% more productive per unit of land and 83% more water-productive than growing walnut and barley separately but also 48% more land-productive and 70% more water-productive than the walnut–buckwheat system. Our results indicate positive effects of trees on microclimates but also emphasize the importance of species selection and systems design on the overall productivity of intercropped systems.

The incorporation of trees on traditional agricultural land has the potential for providing beneficial conditions for understory crops by altering the microclimate. Under these assumptions, we conducted a study on maize productivity intercropped in a 14-year-old walnut orchard by measuring growth and yield parameters, and water and nutrient uptake. Overall, we found that walnut trees decreased maximum air temperature and increased air humidity, especially during hot summer months characterized by precipitation deficit. A 30% reduction in maize yield per total area was a result of significantly reduced plant density, which could be a walnut-specific effect due to juglone excretion. Productivity per plant increased as shown by a significantly higher harvest index and 1000 kernel weight. No meaningful differences were found in terms of maize grain nutrient productivity, nutrient recovery, or nutrient use efficiency. On the systems level, we observed an advantage of the walnut-maize system compared to its respective monoculture systems—land and water equivalent ratios showed that for gaining the same yields as in intercropped system, walnut and maize grown separately would need 32% more land and 31% more water. Our study implies there are some beneficial outcomes to growing maize with trees, although further research should focus on investigating walnut as an option, due to its possible allelopathic effects.

Acid soils with pH values below 5.5 have a negative effect on agricultural production. For this reason, liming is applied as a measure to raise the soil pH to the optimum (pH = 6–7). The aim of our research was to evaluate and compare the effectiveness of four liming materials (wood ash from biomass powerplant, filter dust from cement factory, blast furnace slag from iron factory, and carbocalk (limestone, a by-product from a sugar factory)) in combination with and without solid digestate (a by-product from biogas plant) as organic fertilizer. Two field trials were set up to determine the effect of the studied materials to neutralize the acidity, and the impact on soil fertility and nutrient status in the soil. The results showed that all four liming materials raised the pH of the soil. Out of these four, wood ash showed to be the best while blast furnace slag was the worst. The yield of alfalfa increased with the application of all four lime materials. Application of liming materials with solid digestate increased soil organic matter and had slightly higher yields compared to liming materials without solid digestate. The highest yields were achieved with the application of wood ash, probably due to somewhat higher concentrations of potassium and phosphorus in wood ash. Further research on the financial aspects of investigated by-products application is necessary to exploit their potential as a liming material.