Biochar and biogas slurry have been proved to improve the quality of some soil types, but the long-term effects on fluvo-aquic soil are not fully understood. This study aimed to compare the continuity effects of peanut-shell biochar and biogas slurry on the physicochemical properties, microbial population size, and enzyme activities of fluvo-aquic soil. We conducted a four-year field experiment of winter wheat-summer maize rotation in the North China Plain. Along with equal nitrogen inputs, three treatments were applied—conventional fertilizers, peanut-shell biochar, and hoggery biogas slurry—after which various soil quality indicators were compared. Compared with those of control, both biochar and biogas slurry increased the soil total nitrogen and organic matter content, and improved soil aggregation, microbial biomass, and actinomycetes. Biogas slurry decreased soil pH and improved urease and protease activities. With biochar and biogas slurry treatments, wheat yield increased by 8.46% and 23.47%, and maize yield by 18% and 15.46%, respectively. Biogas slurry increased the content of crude protein and starch in the grains. Both biogas slurry and peanut-shell biochar improved fluvo-aquic soil nutrient content, water-stable macroaggregates, and microbial population, which might be related to their high nutrient content, large specific surface area, adsorption capacity, and functional groups. Biogas slurry generally exhibited stronger effects than biochar probably because of its richness in nutrients and bioactive substances.

Anthropogenic activities such as mining, manufacturing, and application of fertilizers release substantial quantities of cadmium (Cd) into the environment. In the natural environment, varying pH may play an important role in the absorption and accumulation of Cd in plants, which can cause toxicity and increase the risk to humans. We conducted a hydroponic experiment to examine the impact of pH on cadmium (Cd) solubility and bioavailability in winter wheat (Triticum aestivum L.) under controlled environmental conditions. The results showed that Cd concentration was significantly reduced in wheat with an increase in pH from 5 to 7, while it was dramatically increased at pH ranging from 7 to 9. However, in both cases, a significant reduction in physiological traits was observed. The addition of Cd (20, 50, and 200 μmol L^-1) at all pH levels caused a substantial decline in wheat growth, chlorophyll and carotenoids contents, nutrient availability, while elevated cell membrane damage was observed in terms of electrolytic leakage (EL), osmoprotectants, and antioxidants activity. In our findings, the negative effects of acidic pH (5) on wheat growth and development were more pronounced in the presence of Cd toxicities. For instance, Cd concentration with 20, 50, and 200 μmol L^-1 at acidic pH (5) reduced shoot dry biomass by 45%, 53%, and 79%, total chlorophyll contents by 26%, 41%, 56% while increased CAT activity in shoot by 109%, 175%, and 221%, SOD activity in shoot by 122%, 135%, and 167%, POD activity in shoot by 137%, 250%, and 265%, MDA contents in shoot by 51%, 83%, and 150%, H₂O₂ contents in shoot by 175%, 219%, and 292%, EL in shoot by 108%, 165%, and 230%, proline contents in shoot by 235%, 280%, and 393%, respectively as compared to neutral pH without Cd toxicities. On the other hand, neutral pH with Cd toxicities alleviated the negative effects of Cd toxicity on wheat plants by limiting Cd uptake, reduced reactive oxygen species (ROS) formation, and increased nutrient availability. In conclusion, neutral pH minimized the adverse effects of Cd stress by minimizing its uptake and accumulation in wheat plants.

The interest in reusing wastewater for irrigation is being popularized in most countries. The objective of this study was to evaluate the effects of different wastewater and nitrogen fertilizer on soil fertility and plant quality, as well as to identify the optimal irrigation mode in the North China Plain. A total of nine treatments, including control (groundwater, no fertilizer), piggery wastewater, reclaimed water, and saline water, combined with nitrogen fertilizer (300 kg/ha and 200 kg/ha), were conducted in a greenhouse in 2019 (Xinxiang, Henan Province). Soil pH, electrical conductivity, organic matter, heavy metals contents, and cucumber yield and quality were analyzed. The results showed that: (1) compared with the underground water (control), soil pH value with a decrement of 0.21 units in piggery wastewater (PW), and 0.24 units in saline water treatments (SW). Soil electrical conductivity (EC) value significantly increased by 5.8~20.9% in PW and SW treatments, while there was no significant difference in EC in reclaimed water. The highest EC (770 µS/cm) was recorded in SW treatment. (2) No dramatic difference on the concentrations of soil lead (Pb) and cadmium (Cd) in the PW, RW, and SW treatments, compared with the control, but soil organic matter, copper (Cu), and zinc (Zn) concentrations in wastewater treatments were increased by 2.1~43.4%, 24.4~27.0%, and 14.9~21.9%, respectively. (3) There were no significant differences in cucumber yield and quality in RW treatment, while there was a slight decrease by 1.4% in yield in the SW treatment. The highest cucumber yield was observed in PWH treatment, with an increment of 17.5%. In addition, the contents of Vitamin C, soluble sugar, and protein were also improved by PW treatment. In this study, PW treatment showed the strongest ability to promote cucumber yield and quality, thus indicating that piggery wastewater irrigation with 300 kg/ha nitrogen would be the optimal practice in this region. Long-term study is necessary to monitor potential risk of heavy metals on the quality of soil and plant.

In order to reveal the effects of microplastics (MPs) on the growth and rhizosphere soil environmental effects of wheat (Triticum aestivum L.), three microplastic types (polypropylene MPs (PP-MPs), high-density polyethylene MPs (HDPE-MPs), and polylactic acid MPs (PLA-MPs)), particle sizes (150, 1000, and 4000 μm), and concentrations (0.1, 0.5, and 1 g·kg⁻¹) were selected for a pot experiment under natural environment conditions. The differences in germination rate (GR), germination inhibition rate (GIR), growth characteristics, physicochemical properties, and enzymatic activities of wheat in rhizosphere soil were analyzed using statistical analysis and variance analysis. The results show that the germination rate of wheat seeds decreased under different MPs, and the HDPE-MPs, medium particle size (1000 μm), and medium concentration (0.5 g·kg⁻¹) had the greatest inhibitory effect on wheat seed germination. The effects of MPs on wheat seed growth characteristics were inconsistent; the germination potential (GP), germination index (GI), and vitality index (VI) showed a significant decreasing trend under the PLA-MPs and medium-concentration (0.5 g·kg⁻¹) treatment, while the mean germination time (MGT) showed a significant increasing trend; the GP and MGT showed a significant decreasing and increasing trend under the high-particle-size (4000 μm) treatment, respectively, while the GI and VI showed a significant decreasing trend under the medium-particle-size (1000 μm) treatment. The growth characteristics of wheat plants showed a significant decreasing trend under different MPs, with the SPAD, nitrogen concentration of the leaves, and plant height decreasing the most under PLA-MP treatment, the SPAD and nitrogen concentration of leaves decreasing the most under low-particle-size (150 μm) and low-concentration (0.1 g·kg⁻¹) treatments, and the decreases in plant height under the high-particle-size (4000 μm) and high-concentration (1 g·kg⁻¹) treatments being the largest. There were significant increasing trends for ammonium nitrogen (NH₄⁺), total phosphorus (TP), soil urease (S-UE), soil acid phosphatase (S-ACP), and soil sucrase (S-SC) under different microplastics, while the PLA-MPs had a significant increasing trend for nitrate nitrogen (NO₃⁻) and a significant decreasing trend for pH; there was a significant decreasing trend for total nitrogen (TN) under the HDPE-MPs and PLA-MPs, and for each particle size and concentration, the PLA-MPs and low-concentration (0.1 g·kg⁻¹) treatments showed a significant decreasing trend for soil catalase (S-CAT). The research results could provide certain data and theoretical bases for evaluating the effects of MPs on crop growth and soil ecological environments.

Adopting agroforestry practices in many developing countries is essential to combat climate change and diversify farm incomes. This study investigated the above and below-ground biomass and soil carbon of a citrus-based intercropping system in six sites (subdivisions: Bhalwal, Kot Momin, Sahiwal, Sargodha, Shahpur and Silanwali) of District Sargodha, Southeast Pakistan. Tree biomass production and carbon were assessed by allometric equations through a non-destructive approach whereas, soil carbon was estimated at 0–15 cm and 15–30 cm depths. Above and below-ground biomass differed significantly, and the maximum mean values (16.61 Mg ha⁻¹ & 4.82 Mg ha⁻¹) were computed in Shahpur due to greater tree basal diameter. Tree carbon stock fluctuated from 6.98 Mg C ha⁻¹ to 10.28 Mg C ha⁻¹ among selected study sites. The surface soil (0–15 cm) had greater bulk density, organic carbon, and soil carbon stock than the subsoil (15–30 cm) in the whole study area. The total carbon stock of the ecosystem ranged from 25.07 Mg C ha⁻¹ to 34.50 Mg C ha⁻¹ across all study sites, respectively. The above findings enable us to better understand and predict the carbon storage potential of fruit-based agroforestry systems like citrus. Moreover, measuring carbon with simple techniques can produce trustworthy outcomes that enhance the participation of underdeveloped nations in several payment initiatives such as REDD+.

The large amount of nitrogen application on the North China Plain has caused a serious negative impact on the sustainable development of regional agriculture and ecological environmental protection. Our aim was to explore the effects of nitrogen fertilization rate and groundwater depth on growth attributes, soil-water and soil-fertilizer contents, and the winter wheat yield. Experiments were carried out in micro-lysimeters at groundwater depths of 60, 90, 120, and 150 cm on the basis of 0, 150, 240, and 300 kg/ha nitrogen fertilization rates in the growth season for winter wheat. Results showed that plant height, leaf area index, soil plant analysis development, and yield without nitrogen application increased significantly with increases in groundwater depth. The optimal groundwater depths for growth attributes and yield were 60–120 cm and tended to be shallower with added nitrogen application. Soil moisture was lowered significantly with groundwater depth, adding a nitrogen application reduced soil moisture, and excessive nitrogen input intensified soil drought. Nitrate-N accumulation at the 120–150 cm depths was significantly higher than that at the 60–90 cm depths, and a 300 kg/ha (traditional nitrogen application rate) treatment was 6.7 times greater than that of 150 kg/ha treatment and increased by 74% more than that of the 240 kg/ha treatment at 60–150 cm depth. Compared with the yield of the 300 kg/ha rate, the yield of the 240 kg/ha rate had no significant difference, but the yield increased by 3.90% and 11.09% at the 120 cm and 150 cm depths. The growth attributes and yield of winter wheat were better, and the soil nitrate-N content was lower, when the nitrogen application rate was 240 kg/ha. Therefore, it can be concluded that nitrogen application can be reduced by 20% on the North China Plain.