Soil Alkali-hydrolyzed Nitrogen Research Articles

Community structure and species composition of typical Quercus variabilis natural secondary forest at the northern foothills of the Qinling Mountains, China

We investigated species composition and community structure of a typical Quercus variabilis natural secondary forest in the northern foothills of the Qinling Mountains, within the dynamic monitoring plot of deciduous broad-leaved forest at the Louguantai experimental forest farm in Zhouzhi County, Shaanxi Province. The results showed that there were 3162 individual woody plants with diameter at breast height ≥1 cm in the plot, which were belonged to 42 species, 36 genera, and 25 families. The community genus's areal type was dominated by the temperate component, which accounted for 44.4%, and followed by the tropical component. The community was dominated by several tree species. The top three species with respect to importance value were Q. variabilis, Pinus tabuliformis, and Quercus aliena, with the sum of their importance value being 64.7%. The average DBH of all woody plants was 7.58 cm. The distribution of all individuals and dominant species in the tree layer was approximately normal, with more medium-size individuals. The community structure was stable. The community was poorly renewed, with a trend of population decline. Biodiversity indices varied considerably among different plots, being lower than those of subtropical broad-leaved evergreen forests. There was a significant correlation between community species distribution and environmental factors. Soil and topography explained 42.4% of the variation in community distribution. Altitude and soil alkali hydrolysable nitrogen had a significant effect on community distribution. Altitude, soil total phosphorus, and organic matter content significantly affected the species diversity of Q. variabilis communities. The stronger adaptability of Q. variabilis populations allowed them to become dominant in low-nutrient environments, which limited species diversity in the community.

Effects of Climate on Variation of Soil Organic Carbon and Alkali-Hydrolyzed Nitrogen in Subtropical Forests: A Case Study of Zhejiang Province, China

Subtropical forests play an important role in the global carbon cycle and climate change mitigation. In order to understand the effects of climate factors on soil carbon in subtropical forest ecosystems, it is necessary to make full use of carbon sequestration potential. Soil organic carbon (SOC) and soil alkali-hydrolyzed nitrogen (SAN) were tested in 255 plots of subtropical forests in Zhejiang Province, and their forest reserves from 2020 in Zhejiang Province were compared with those from 2010. The results showed that SOC content significantly increased, but SAN content decreased over those ten years. Combined with random forest (RF) and correlation analysis, the contribution of different climate factors (temperature, precipitation, etc.) to soil carbon storage was analyzed, and the main driving factors were evaluated. The RF model explained that winter (December to February) and spring (March to May) were the most dominant drivers to the 0–10 cm and 10–30 cm increases in SOC. There was a significant positive correlation between precipitation and SOC accumulation (0–30 cm) during winter and spring. The minimum temperatures in summer (June to August) and autumn (September to November) were negatively correlated with SOC accumulation (0–30 cm). Increasing the precipitation or irrigation (cloud seeding) in winter could improve the carbon sequestration capacity of subtropical forest soils. This study provides a new perspective on the sensitivity and potential response of the carbon cycle to climate change in subtropical forest ecosystems.

Effects of compound water retention agent on soil nutrients and soil microbial diversity of winter wheat in saline-alkali land

Water retention agents have been applied to agricultural fields to improve the growing conditions of crops, but the potential of these agents in saline soils is poorly understood. The effects of compound water retention agents on nutrient content and soil microbial diversity of saline winter wheat soils were investigated in a field experiment with no water retention agent (CK) and 30 kg hm2 of commercial attapulgite water retention agent (T4) as control and different amounts of compound water retention agents as treatments (15 kg hm2-T1, 30 kg hm2-T2, 45 kg hm2-T3). The study showed that the application of water retention agents increased the soil water content. From anthesis to harvest stage, the decreases in soil alkali-hydrolyzed nitrogen, available phosphorus, available potassium and organic matter content were greater in T2 and T3 than in the other treatments. At harvest stage, the alkali-hydrolyzed nitrogen content of T2 was significantly lower than that of CK and T4 6.19–8.83% and 4.62–5.39%, respectively. The soil available phosphorus content of T2 was significantly lower than that of CK 8.14–8.83%. The relative abundance of Actinobacteria, Proteobacteria and Acidobacteria as well as the Shannon and Simpson indices of T2 reached their maximum at harvest stage. T2 showed the best performance in terms of overall number of OTUs. The compound water retention agent may regulate soil nutrient content and accelerate plant nutrient accumulation by regulating soil water content and soil microbial abundance composition.Graphical abstract

Research on the Application of Coal Gasification Slag in Soil Improvement

SEM, particle size analysis, and contaminant content of coarse coal gasification slag (CCGS) produced by Shenhua Xinjiang Chemical Co., Ltd. were measured, respectively, and the physicochemical properties of the soil after improvement using gasification slag were investigated in this paper. The results showed that the slag was porous, the particle size was small and the pollutant content was extremely low. Its pollutants were closely related to the pollutants in the raw coal. The coarse slag had a limited effect on soil particle size and texture improvement; the soil water retention performance increased with the increase of proportion of the slag, while pH and conductivity decreased; the improvement effect on soil SOM and available potassium was remarkable; the larger the proportion of the slag, the stronger the effect on maintaining soil alkali-hydrolyzed nitrogen, ammonium nitrogen, and available phosphorus. However, the effect was small, and increased the ion content, especially the cation in soil, and the sum of the eight soil ions before and after evaporation decreased. The results demonstrated that the CCGS generated by the corporation is feasible for soil improvement, and the study has important reference value for the comprehensive utilization of coal gasification slag.

Remediation and Micro-Ecological Regulation of Cadmium and Arsenic Co-Contaminated Soils by Rotation of High-Biomass Crops and Sedum alfredii Hance: A Field Study

Rotation of high-biomass crops and hyperaccumulators is considered to be an effective, safe and economical method for the remediation of medium-mild heavy metal contaminated soil, but the present studies pay more attention to the removal efficiency rather than changes in soil micro-ecology. In order to explore the remediation effect of hyperaccumulators rotated with high-biomass crops on Cd and As co-contaminated soil, Cd hyperaccumulator ecotype (HE) Sedum alfredii Hance and crops were selected to construct a field experiment, five rotation modes including Sedum alfredii Hance-Oryza sativa L. (SP), Sedum alfredii Hance-Sorghum bicolor (L.) Moench (SS), Sedum alfredii Hance-Zea mays L. (SM), Sedum alfredii Hance-Hibiscus cannabinus L. (SK), Sedum alfredii Hance-Trichosanthes kirilowii Maxim. (ST), and investigated the effects of these modes on the removal efficiency, soil physiochemical properties and micro-ecological effects (soil nutrients, enzyme activities and microbial diversity) through a field experiment. The results showed that total soil Cd from the five rotation modes (SP, SS, SM, SK and ST) decreased by 25.1%, 20.3%, 34.5%, 6.3% and 74.3%, respectively, and total soil As decreased by 42.9%, 19.8%, 39.7%, 39.7% and 45.7%, respectively. The rotation significantly increased soil organic matter by 47.39–82.28%, effectively regulated soil pH value and cation exchange capacity. The rotation modes also significantly increased soil alkali-hydrolysable nitrogen by 9.09–50.91%, but decreased soil available phosphorus and rapidly available potassium. Except for urease, the soil enzyme activities increased overall. The Alpha diversity increased, and soil microbial structure optimized after rotation. ST mode was the most effective remediation mode, which not only reduces the content of Cd and As in the soil, but also effectively regulates the soil micro-ecology. The results from this study have shown that it is feasible to apply Sedum alfredii Hance and the high-biomass rotation method for the remediation of Cd and As co-contaminated soil.

Effects of exogenous microorganisms on seedling growth and soil microbial community of Casuarina equisetifolia

With a pot experiment, the Biolog microplate and phospholipid fatty acid (PLFA) technology were used to explore whether the application of bacteria, Bacillus amyloliquefaciens (YB706) and Burkholderia (BK8), could improve the soil nutrient, microbial community and growth of Casuarina equisetifolia. The results showed that the concentrations of soil alkali-hydrolyzed nitrogen and available phosphorus of C. equisetifolia treated with YB706 and BK8 increased significantly compared with the control (CK), but the concentrations of total nitrogen, total phosphorus, total potassium and available potassium changed little, plant height increased by 59.1% and 63.9%, respectively, and the chlorophyll content of plant treated with BK8 increased by 81.9%. The average well color development values showed a pattern of YB706>CK>BK8. The utilization rate of different carbon sources showed the same trend except the amino acids. Both YB706 and BK8 treatments significantly increased the richness and quantity of soil microorganisms. The PLFA of all kinds of microorganisms was BK8>YB706>CK except actinomycetes. The ratio of soil fungi to bacteria was increased compared with CK. The Simpson, Shannon, Brillouin and McIntosh indices of rhizosphere soil microbial community in YB706 and BK8 treatments were significantly increased. Our results suggested that application of YB706 and BK8 could improve the growth rate of C. equisetifolia seedlings, effectively increase the contents of soil available nutrients, increase soil microbial diversity, and improve soil microbial environment.

Control of Southern Root-knot Nematodes on Tomato and Regulation of Soil Bacterial Community by Biofumigation with Zanthoxylum bungeanum Seed

Biofumigation is an environmentally friendly strategy used to control nematodes and plant diseases. The volatile oil of Zanthoxylum bungeanum has high insecticidal and antibacterial activity. However, it is not known if the seed of Z. bungeanum is a suitable material for biofumigation to control southern root-knot nematodes (SRKN) on tomato, and how it may regulate the soil bacterial community structure. We used pot experiments in the greenhouse to determine the effects of Z. bungeanum seeds on SRKN, plant growth parameters, soil physicochemical and microbial characteristics. A total of 26 volatile components, including nematicidally active substances, were identified from Z. bungeanum seeds. Z. bungeanum seed biofumigation significantly reduced the SRKN population by 88.89% and 81.55% on the 50th and 100th day after transplanting, respectively. Compared to the control, the total soluble sugar, soluble solids, soluble protein, titratable acid, root activity and the fruit yield per tomato plant increased significantly. The content of soil alkali-hydrolyzed nitrogen, available potassium and the soil enzyme activities were also significantly increased. The soil bacterial diversity and the co-occurrence network complexity were increased by Z. bungeanum seed biofumigation. Relatively more keystone OTUs in biofumigation soil had potential plant growth-promoting capabilities. The function of Z. bungeanum seed increasing tomato production in SRKN-infected soil depends on directly killing SRKN and improving soil properties. These results indicate that Z. bungeanum seed can be used as both a nematicide and a high quality organic fertilizer in tomato production.

Effects of Soft Rock and Biochar Applications on Millet (Setaria italica L.) Crop Performance in Sandy Soil

In arid and semi-arid regions, desertification threatens crop production because it reduces the soil’s capacity to retain water and soil nutrients. At two fertilizer levels (90 kg N hm−2 and 45 kg P hm−2 and 270 kg N hm−2 and 135 kg P hm−2), the effects of soft rock (sand: soft rocks = 3:1) and biochar (4500 kg hm−2) applications on soil moisture, soil nutrients, and millet (Setaria italica L.) photosynthesis, yield, and its agronomic traits (biomass, thousand kernel weight, harvest index) were investigated in a field experiment in the Mu Us Sandy Land of China in 2018–2019. The addition of biochar and soft rock singly increased soil water content, alkali-hydrolyzed nitrogen (AN), total nitrogen (TN) and phosphorus (TP), and organic matter content significantly, suggesting that their application may increase the nutrient and water holding capacity of soil. Application of biochar and soft rock singly increased the net photosynthesis rate of millet flag leaf, at the flowering stage, from 15.97% to 56.26%. Biochar and soft rock application increased the yield range (2109.0 kg hm−2 to 5024.7 kg hm−2) from 5.26% to 54.60% under the same fertilizer level. Correlation analyses showed grain yield was significantly correlated with photosynthesis rate at the flowering stage, which was significantly correlated with soil AN at flowering, soil TP at flowering and harvest, and soil TN at flowering. These results indicated that the application of biochar and soft rock singly could increase soil fertilizer holding capacity to improve the photosynthesis rate at flowering, and, therefore, lead to improvements in crop yield.

Effect of Pennisetum giganteum z.x.lin mixed nitrogen-fixing bacterial fertilizer on the growth, quality, soil fertility and bacterial community of pakchoi (Brassica chinensis L.).

Biofertilizer plays a significant role in crop cultivation that had reduced its inorganic fertilizer use. The effects of inorganic fertilizer reduction combined with Pennisetum giganteum z.x.lin mixed nitrogen-fixing biofertilizer on the growth, quality, soil nutrients and diversity of the soil bacterial community in the rhizosphere soil of pakchoi were studied. The experiment composed of 6 treatments, including CK (no fertilization), DL (10% inorganic fertilizer reduction combined with Pennisetum giganteum z.x.lin mixed nitrogen-fixing biofertilizer), ZL (25% inorganic fertilizer reduction combined with Pennisetum giganteum z.x.lin mixed nitrogen-fixing biofertilizer), SL (50% inorganic fertilizer reduction combined with Pennisetum giganteum z.x.lin mixed nitrogen-fixing biofertilizer), FHF (100% inorganic fertilizer) and JZ (100% inorganic fertilizer combined with sterilized Pennisetum giganteum z.x.lin mixed nitrogen-fixing biofertilizer). Compared with conventional fertilization, the 25% reduction in chemical fertilizer applied with the Pennisetum giganteum mixed nitrogen-fixing biofertilizer resulted in higher plant height, plant weight, chlorophyll content, soluble protein content, soluble sugar content, vitamin C content, alkali hydrolyzed nitrogen content, available phosphorus content, available potassium content and organic matter content in pakchoi, and these variables increased by 11.81%, 8.54%, 7.37%, 16.88%, 17.05%, 23.70%, 24.24%, 36.56%, 21.09% and 19.72%, respectively. In addition, the 25% reduction in chemical fertilizer applied with the Pennisetum giganteum mixed nitrogen-fixing biofertilizer also had the lowest nitrate content, which was 53.86% lower than that with conventional fertilization. Different fertilizer treatments had a significant effect on the soil bacterial community structure. Compared with conventional fertilization, the coapplication of Pennisetum giganteum z.x.lin mixed nitrogen-fixing biofertilizer and inorganic fertilizer significantly increased the relative abundance of Proteobacteria and Actinobacteria in the soil. The results of the redundancy analysis (RDA) showed that soil organic matter, alkali-hydrolyzed nitrogen, available phosphorus, available potassium, pH and water content had a specific impact on the soil bacterial community. Among the factors, soil water content was the main factor affecting the soil bacterial community, followed by soil organic matter, soil pH, available potassium, soil available phosphorus and soil alkali-hydrolyzed nitrogen.

Primary Production of a Grassland in Nairobi National Park, Kenya

Taking the solar greenhouses with different cultivating years and vegetables in Ji'nan as test objects, this paper studied the amounts and frequency distribution of soil nutrients and the relationships between cultivating years and soil nutrients accumulation characteristics, and analyzed the factors causing soil salinization and acidification by fitting soil nutrients contents with cultivating years and vegetables. In the greenhouses, the contents of soil alkali-hydrolysable nitrogen, available phosphorus, available potassium, organic matter, and electrical conductivity were significantly higher than those in the open field, with an increment of 135.3%, 475.2%, 290.1%, 97.7%, and 188.7%, respectively, but the soil pH value was 0.31 lower than that of open field. The frequency distribution of soil nutrients presented a normal curve. Differences were observed in the soil nutrients contents in the greenhouses with different cultivating vegetables. The soil alkali-hydrolysable nitrogen content and electrical conductivity were in the order of tomato > cucumber > sweet pepper, soil organic matter content and pH value were cucumber > sweet pepper > tomato, soil available phosphorus content was cucumber > tomato > sweet pepper, and soil available potassium content was tomato > cucumber > sweet pepper. There was a mild tendency of soil acidification in soil alkali-hydrolysable nitrogen and available potassium. The decrease of soil pH was closely related to the accumulation of alkali-hydrolysable nitrogen. The soil nutrients accumulation in the greenhouses had the similar patterns, i. e. , rapid accumulation in the first two cultivating years, slowed down in the third and fourth year, and kept stable later, demonstrating a dynamic balance on the whole. All the nutrients contents were positively accumulated, while soil pH presented negatively. In the greenhouses with different cultivating vegetables, there was a significant correlation between soil nutrients and cultivating years, which could be fitted by conic curve or cubic curve.