Biochar, a carbon-rich by-product of organic matter pyrolysis, has a variety of physiochemical properties beside a variety of applications. This review highlights some physical and chemical characteristics of herbaceous, woody, and sewage waste biochar under different pyrolysis conditions, as well as soil and foliar applications of biochar. The controlling role of pyrolysis temperature was the reason for selecting the discussed biochar types in the study. This review concludes that increasing pyrolysis temperature mainly raised the values of some chemical properties of the biochar, such as pH, electrical conductivity (EC), ash content, total phosphorus (TP), and a few values of physical properties like porosity and specific surface area (SSA). On the other hand, yield and total nitrogen (TN) decreased with rising pyrolysis temperature. Among biochar application methods to soil, mixing biochar with soil before planting is one of the best methods of application, and in most cases, biochar reapplication improved soil properties, while foliar application of biochar has positive effects on plant growth and yield parameters, ranging from low rates to the highest ones.

The influence of three levels of water supply (unlimited (WW); water stress during flowering (RO); rainfed (P)) on radiation properties and yield of two soybean varieties (Sinara, Sin; Sigalia, Sig) were evaluated. Sin is considered to be tolerant to water stress. The effect of leaf area index, year, variety, and meteorological variables on evapotranspiration (ET) was analysed by hierarchical regression. This study attempted to identify how water supply affects the crop–light relationship between photosynthetically active radiation (PAR) transmission and radiation use efficiency (RUE), which were involved in qualitative and quantitative traits related to soybean production (biomass and yield attributes: seed yield, 1000-grain weight, oil and protein content). Unstandardized coefficients of air temperature (T_a) showed that a 1 °C increase in daily mean T_a induced a higher ET, on average 0.16 mm day⁻¹. Soil moisture strongly affected sowing time. When averaged across three seasons at flowering, 97.7, 95.1 and 97.3% of incoming PAR were intercepted by the canopies of plants in WW, RO and P, respectively. The average extinction coefficient (k) and RUE pooled across both varieties were 0.42 and 1.32 g MJ PAR⁻¹ for WW, and 0.46 and 0.98 g MJ PAR⁻¹ for RO, respectively, compared with 0.44 and 1.15 g MJ PAR⁻¹ for P. As expected, water treatment significantly affected all yield traits: RO decreased yield whereas WW increased yield compared to P. Practically, both varieties are suitable for cultivation under water stress during flowering but Sin showed greater yield under unlimited watering and rainfed conditions.

Field crop production must adapt to the challenges generated by the negative consequences of climate change. Yield loss caused by abiotic stresses could be counterbalanced by increasing atmospheric CO₂ concentration, but C₃ plant species and varieties have significantly different reactions to CO₂. To examine the responses of wheat, barley and oat varieties to CO₂ enrichment in combination with simulated drought, a model experiment was conducted under controlled environmental conditions. The plants were grown in climate-controlled greenhouse chambers under ambient and enriched (700 ppm and 1000 ppm) CO₂ concentrations. Water shortage was induced by discontinuing the irrigation at BBCH stages 21 and 55. Positive CO₂ responses were determined in barley, but the CO₂-sink ability was low in oats. Reactions of winter wheat to enriched CO₂ concentration varied greatly in terms of the yield parameters (spike number and grain yield). The water uptake of all wheat cultivars decreased significantly; however at the same time, water-use efficiency improved under 1000 ppm CO₂. Mv Ikva was not susceptible to CO₂ fertilization, while no consequent CO₂ reactions were observed for Mv Nádor and Mv Nemere. Positive CO₂ responses were determined in Mv Kolompos.

The aim of the investigation was to determine if the CWSI could be used to determine when the irrigation water should be applied to maize under Hungarian changeable weather. Three water treatments were applied: “Ad libitum” watering in lysimeter’s growing chambers, irrigated treatment (use of CWSI), and rainfed control. The theoretical approximation of crop water stress index was applied in our long-term investigation. Among the 17 consecutive seasons between 1989 and 2005 included in the study there were seven arid and four humid seasons. The remaining summers had semi-humid character. To represent the influence of drought on water stress index of maize we chose the year of 2000, the driest and warmest season from the beginning of weather observations of Keszthely. As a counterpoint stress index results of 1997 served as an example of humid seasons. The degree of the deviation in CWSI as a result of different weather may vary, but the tendency in arid or humid seasons remained the same. The basic parameter of CWSI, the canopy temperatures were measured using a hand-held infrared thermometer. Relevant meteorological and plant data were collected locally. Our final conclusion was that there is no problem in use of CWSI during arid summers, where radiation is undisturbed and the cloudiness does not disturb the canopy temperature sampling. In arid seasons increases in assimilatory surface size and yield of maize in irrigated treatments were between 20–35% and 10–30%, respectively. The extra production seems to be enough to cover the irrigation costs. There is also no problem in humid seasons, where the sky is often covered by clouds, but there is no need to irrigate maize in Hungary. In semi-humid weather not only the environmental circumstances may disturb the plant temperature measurements and calculation of CWSI (doubtful results caused by changeable radiation and wind), but the probable yield surplus — below 5% — is also negligible. The irrigation costs are higher than the production gain during semi-humid seasons. In Hungary about one third of the seasons have characteristics of an arid weather where sampling of canopy temperatures provides reliable basis to calculate CWSI and plan irrigation timing

A field experiment was conducted with soybean to observe evapotranspiration (ET) and crop water stress index (CWSI) with three watering levels at Keszthely, Hungary, during the growing seasons 2017–2020. The three different watering levels were rainfed, unlimited, and water stress in flowering. Traditional and converted evapotranspirometers documented water stress levels in two soybean varieties (Sinara, Sigalia), with differing water demands. ET totals with no significant differences between varieties varied from 291.9 to 694.9 mm in dry, and from 205.5 to 615.6 mm in wet seasons. Theoretical CWSI, CWSI_t was computed using the method of Jackson. One of the seasons, the wet 2020 had to be excluded from the CWSI_t analysis because of uncertain canopy temperature, T_c data. Seasonal mean CWSI_t and T_c were inversely related to water use efficiency. An unsupervised Kohonen self-organizing map (K-SOM) was developed to predict the CWSI, CWSI_p based on easily accessible meteorological variables and T_c. In the prediction, the CWSI_p of three watering levels and two varieties covered a wide range of index values. The results suggest that CWSI_p modelling with the minimum amount of input data provided opportunity for reliable CWSI_p predictions in every water treatment (R² = 0.935–0.953; RMSE = 0.033–0.068 mm, MAE = 0.026–0.158, NSE = 0.336–0.901, SI = 0.095–0.182) that could be useful in water stress management of soybean. However, highly variable weather conditions in the mild continental climate of Hungary might limit the potential of CWSI application. The results in the study suggest that a less than 450 mm seasonal precipitation caused yield reduction. Therefore, a 100–160 mm additional water use could be recommended during the dry growing seasons of the country. The 150 year-long local meteorological data indicated that 6 growing seasons out of 10 are short of precipitation in rainfed soybean.

The goal of the present paper is to investigate whether any objectively defined and statistically significant changes can be discovered in one of the longest homogenized instrumental temperature records in East-Central Europe. Thus, it is hoped that the present analysis will add to earlier attempts and elucidate the persistence of the warming period observed in the early 20th century. Similar to the global tendency, the Early Twentieth Century Warming (hereinafter, ETCW) period can be identified between 1931 and 1951 in the annual mean temperature time series of Keszthely, a small town in Hungary. The Mann-Kendall trend test was used to determine whether a monotonic trend was present, as it is not possible to regard the residuals of the linear trend as normally distributed. A significant rising trend can be observed in the warming period in spring of the years between 1925 and 1951. In case of summer and autumn, this period cannot be characterized as having any significant identifiable trend. A rise in the mean can, however, be recognized. Overall, the specific regional manifestation of the global ETCW may clearly be illustrated in this study via detailed statistical analysis of the temperature records for Keszthely, a location with one of the longest temperature records in Hungary. However, other regions surrounding Hungary show similar climatic trends, emphasizing the fact that the behaviour presented here is not unique to Central and Eastern Europe.