The development of critical levels for sap nitrate and chlorophyll meter reading (SPAD test) in the case of various crops is of great importance for growers in characterizing a plant’s N status. A field experiment with spring oat (Avena sativa L.) was carried out on loamy soil in Debrecen, Hungary, using a small-plot design. Ammonium nitrate was broadcast at rates of 0, 30, 60, and 90 kg N/ha in three replicates. The total N content of the plant, sap nitrate content, and SPAD values were measured at jointing when the first node appeared above the soil surface (Feekes 6) and at boot stage (Feekes 10). Regression analysis between total N content and sap nitrate showed cubic and linear relationships with r² = 0.7982 (Feekes 6, whole plant) and 0.9625 (Feekes 10, upper developed leaves), respectively. Optimal grain yield was obtained when sap nitrate exceeded 650 mg/L and 540 mg/L at Feekes 6 and Feekes 10, respectively. There were linear and logarithmic relationships between total N content and SPAD values with r² = 0.8058 and 0.6258 at Feekes 6 and 10. Optimal grain yield occurred over SPAD values of 43 and 48 at Feekes 6 and 10, respectively. Optimal N rate was 60 kg N/ha on the experimental site.

Previous pepper studies indicated that biomass production and the amounts of bioactive compounds were dependent on light sources, maturity processes and pepper genotypes. However, the above topic has received little attention in supplemental light versus cultivar combinations under a hydroponic growing system. Therefore, the aim of this study was to evaluate the biomass production (fruit, root, stem and leaf) and fruit bioactive compounds (vitamin C, total flavonoid content and antioxidant capacity-AC-FRAP, total polyphenol-TPC) of two pepper cultivars (‘Fehérözön’-Fö and ‘Szegedi 80’-S80) in three fruit maturity stages (green, beaker and red) under two LED light treatments (full-F and blue-white-BW spectrums) in a deep water culture hydroponic system. The stem biomass and water use for total and fruit biomass were significantly different for cultivars and light treatments. Light treatments, maturity stages and cultivars had significant effects on fruit biomass production and on all bioactive compounds. However, the results on the bioactive compounds varied according to the green, beaker and red maturity stages of the two pepper cultivars. In correlation analyses, 30 pair-variables correlated significantly and nine showed values r > 0.9 for fruit weight versus (vs.) vitamin C, fruit weight vs. AC-FRAP, fruit weight vs. TPC, vitamin C vs. AC-FRAP, vitamin C vs. TPC, AC-FRAP vs. TPC, and flavonoid vs. TPC. This study suggested that additional lights and maturity features of cultivar genotype strongly determined the biomass and bioactive compounds of pepper under a deep water culture hydroponic system.

The effects of intensive and reduced tillage, fertilization, and irrigation on soil chemical and microbiological parameters were studied in a long-term field experiment in Hungary. The treatments were plowing tillage, ripper tillage, strip tillage; control (without fertilization), NPK fertilization (N: 160 kg/ha; P: 26 kg/ha; K: 74 kg/ha); and non-irrigation and irrigation. Soil samples were collected through maize monoculture in the fall of 2021 in the 30th year of the experiment. The soil organic carbon, total nitrogen, soil microbial biomass (based on PLFA analysis), and soil enzyme activity were observed to be significantly high in the strip tillage plots, but were lower in the ripper tillage plots, and even lower in the plowing tillage plots. The fungal, arbuscular mycorrhiza fungal, and bacterial biomasses were significantly higher in the strip tillage and ripper tillage plots compared to the plowing tillage plots. The strip tillage treatment was found to be the most favorable cultivation method for improving the microbial biomass and activity of Chernozem soil, followed by the ripper tillage and plowing tillage treatments. The long-term use of chemical fertilizers greatly reduced the soil microbial biomass and negatively impacted the soil microbial community, leading to a decrease in fungi and Gram-negative bacteria. The ratio of cyclopropyl PLFA precursors to cyclopropyl PLFAs, as a “stress factor”, indicated the most stressful bacterial environment was that found in the fertilized, non-irrigated plowed soil.

Soil microbial communities are crucial for ecosystem services, soil fertility, and the resilience of agroecosystems. This study investigated how long-term (31 years) agronomic practices—tillage, NPK fertilization, and cropping system—along with measured environmental variables influence the microbial biomass and its community composition in Chernozem soil under corn cultivation. The polyfactorial field experiment included three tillage treatments ((moldboard (MT), ripped (RT), strip (ST)), two fertilization regimes (NPK (N: 160; P: 26; K: 74 kg/ha), and unfertilized control) and two cropping systems (corn monoculture and corn–wheat biculture). The soil samples (0–30 cm) were collected in June and September 2023. Microbial biomass and community structure were quantified using phospholipid fatty acid (PLFA) analysis, which allowed the estimation of total microbial biomass and community composition (arbuscular mycorrhizal (AM) fungi, fungi, Gram-negative (GN) and Gram-positive (GP) bacteria, actinomycetes). Our results showed that microbial biomass increased from June to September, rising by 270% in unfertilized plots and by 135% in NPK-fertilized plots, due to higher soil moisture. Reduced tillage, especially ST, promoted significantly higher microbial biomass, with biomass reaching 290% and 182% of that in MT plots in June and September, respectively. MT had a higher ratio of bacteria-to-fungi compared to RT and ST, indicating a greater sensitivity of fungi to disturbance. NPK fertilization lowered soil pH by about one unit (to 4.1–4.8) and reduced microbial biomass—by 2% in June and 48% in September—compared to the control, with the particular suppression of AM fungi. The cropping system had a smaller overall effect on microbial biomass.

Nitrogen (N) is a crop macronutrient of major importance, which affects both plant growth and yield. In this paper we discuss the humus content (%) and various soluble N forms (NO3 -, total N, nitrate-N, ammonium-N, and organic nitrogen) available in humus sand soil samples originating from the Pallag Experimental Station of Horticulture at the University of Debrecen, Hungary. We found 45.4% nitrate-N and 13.8% nitrite-N of total N content present in the soil. Considering the percentage distribution of soluble N forms present at the Pallag Experimental Station, we recommend using this soil in further pot experiments, given that this has optimal nutrient supply capacity. In addition, we examined possible statistical correlations between humus% and N forms.

Protecting humankind’s natural resources and soils, including forestry, represents a top priority in agriculture. Addressing climate change should prioritize preserving and enhancing organic carbon, specifically humus, in soils. In this paper, we examine the impact of soil preparation on soil humus and microbial life during the reforestation of Southern Nyírség, Hungary. We determined soil plasticity, pH in distilled water solution, the quantity and quality of humus content, the total number of bacteria and microbial fungi, as well as CO₂ production. In addition to stump removal and plowing, the wealthiest layer of organic matter was detached from the surface. A significant decrease in humus content (HU%) was observed at the five experimental sites (loss of 19.20–40.14 HU% at 0–30 cm depth). Soil organic matter is concentrated in the stump depositions. According to the results, the quantity of humus content is strongly correlated with the measured parameters of soil life, specifically with the number of microbial fungi (r = 0.806 **) and the total number of bacteria (r = 0.648 **). Another correlation (r = 0.607 **) was assessed between the humus content and CO₂ production. This study helps to understand the importance of the no-tillage methods used in reforestation.