Effect of Fertilization on Soil Quality

Mild organic substitution is advantageous for sustainable agricultural development. In order to determine the proper fertilization strategy, it is essential to investigate the impact of substituting chemical fertilizers with varying levels of organic manure on soil nutrients, microbial communities, and crop productivity. Four treatments were implemented: no fertilizer, sole chemical fertilizer, 20% organic manure substitution, and 40% organic manure substitution. Bacterial and fungal communities were characterized through high-throughput sequencing of the 16S rRNA gene V3–V4 region and the V4 region, respectively. The 20% and 40% organic manure substitutions increased soil organic matter (SOM) content, total nitrogen (TN) content, and reduced soil pH compared to the control (CK). The 20% organic manure substitution showed the most significant improvements in soil alkaline phosphatase, urease, and invertase activities. Soil nutrient enhancement increased bacterial alpha diversity, with a milder impact on fungal alpha diversity compared to bacteria. Different fertilization treatments elevated the relative abundance of bacterial Bacteroidetes (8.11%, 21.25%, and 1.88%), Actinomycetes (12.65%, 26.36%, and 15.33%), and fungal Ascomycota (16.19%, 10.44%, and 12.69%), known for degrading recalcitrant organic matter. The sole chemical fertilizer treatment increased the pathogenic Cheatotryiales. Shared species, primarily from bacterial Actinomycetes, Firmicutes, Proteobacteria, and fungal Ascomycota phyla, were found at 20% and 40% organic manure substitution levels. Specifically, the 20% organic manure substitution level promoted the relative abundance of beneficial plant growth-promoting taxa, Oxalobacteraceae and Massilia, and suppressed pathogens, with an increase in the relative abundance of the Purpureocillium genus and Mortierellomycota. These findings suggest that a 20% OF substitution can maintain crop yield, enhance soil nutrients and enzyme activities by fostering beneficial soil bacteria, inhibiting soil-borne pathogens, and refining microbial community structure. Full article

Conventional fertilizer management can destroy the structure of soil. Replacing chemical fertilizers with organic fertilizers can improve soil quality and nitrogen use efficiency. We aimed to study the effects of organic fertilizer substitutions for chemical nitrogen fertilizer on soil fertility and nitrogen use efficiency in order to clarify the effectiveness of the available nutrient management measures in improving soil quality and increasing foxtail millet yield. A field experiment was carried out over two consecutive years, and a total of six treatments were set up: no fertilizer (CK), chemical nitrogen fertilizer alone (N), the substitution of 25% of chemical nitrogen fertilizer with bio-organic fertilizer (N25A1), the substitution of 25% of chemical nitrogen fertilizer with fermented mealworm manure (N25B1), the substitution of 50% of chemical nitrogen fertilizer with bio-organic fertilizer (N50A2), and the substitution of 50% of chemical nitrogen fertilizer with fermented mealworm manure (N50B2). The results of this study show the following: (1) Compared with chemical nitrogen fertilizer, the substitution of organic fertilizer for nitrogen fertilizer reduced the bulk density and solid phase of the soil, and it increased the total porosity, water content, liquid phase, and gas phase of the soil. (2) Compared with nitrogen fertilizer, the use of an organic fertilizer increased the contents of nitrate nitrogen, ammonium nitrogen, and total nitrogen in the soil by 13.59~52.56%, 4.47~18.27%, and 4.40~12.09%, respectively. The content of alkaline nitrogen increased by 1.70~32.37%, and the contents of soil available potassium, available phosphorus, and organic matter also increased. (3) The activities of sucrase, urease, glutaminase, and asparaginase were improved by replacing chemical nitrogen fertilizer with organic fertilizer. The N25 treatments performed better than the N50 treatments, and fermented mealworm manure performed better than biological organic fertilizer. (4) A moderate application of organic fertilizer (N25) can increase the grain yield, ear weight, grain weight, and 1000-grain weight of foxtail millet, whereas excessive application of organic fertilizer (N50) can reduce foxtail millet yield. (5) Replacing chemical nitrogen fertilizer with organic fertilizer can improve the agronomic use efficiency, physiological efficiency, biased productivity, harvest index, and apparent use efficiency of nitrogen fertilizer. In this study, the substitution of 25% of chemical nitrogen fertilizer with fermented mealworm manure was the best combination for restoring crop productivity and soil quality. Full article

In this study, we investigated the effect of partially substituting inorganic nitrogen with bio-organic fertiliser on the ‘Tianhong2’ Fuji apple planting in Xinjiang. Bio-organic fertiliser was applied, and nitrogen was reduced by 20% (T2), 40% (T3), and 60% (T4) during the blooming and fruit expansion periods with conventionally fertilised fields used as control (T1); soil nutrient, soil enzyme activity, leaf nutrients, fruit quality, and yield were measured. The total nitrogen (TN), total phosphorus (TP), total potassium (TK), total calcium (TCa), available phosphorus (AP), available potassium (AK), and soil organic matter (SOM) contents, as well as the soil catalase (S-CAT), soil uretrase (S-UE), soil saccharase (S-SC), and soil nitrate reductase (S-NR) activities, significantly increased in the experimental soils compared with those in T1. In addition, TP, TCa, and total magnesium (TMg) content in apples significantly increased. Compared to T1, the T2 and T3 treatments significantly improved the fruit yield and quality, increasing the sugar–acid ratio, soluble protein, soluble sugar, peel carotenoid, and anthocyanin content and reducing peel chlorophyll content. The brightness (L*), red–green axis (a*), yellow–blue axis (b*), colour intensity (C), and tone (h°) values changed. The yield per hectare and nitrogen fertiliser partial productivity values were significantly increased. Overall, the T2 treatment resulted in the best outcome for the Yili area. In conclusion, partially substituting inorganic nitrogen with bio-organic fertiliser can effectively increase soil and leaf nutrient content and improve fruit yield and quality. Full article

The form and distribution of organic carbon in soil affect its stability and storage, and nitrogen (N) fertilization can affect the transformation and accumulation of soil organic carbon (SOC), whereas how the N fertilizer rate affects SOC storage by regulating its fractions in a potato continuous cropping system is unknown. A 6-year field experiment was conducted to study the effect of different N fertilizer rates (NE (Nutrient Expert) –N, NE–1/2N, NE, and NE+1/2N) on the changes in SOC and its fractions in a potato continuous cropping system in North China. Soil NO₃⁻-N gradually increased with increasing N fertilizer rates, whereas the N fertilizer rate had less effect on NH₄⁺-N. Compared with the NE−N treatment, the increasing N fertilization increased the SOC and its components, whereas these C fractions did not continue to increase or began to decrease after N fertilization exceeded the rate applied in the NE treatment. While the increase in mineral-associated organic C (MAOC; 16.1–17.2% and 26.1–52.7% in the 0–20 cm and 20–40 cm layers, respectively) was greater than that of particulate organic C (POC; 3.7–7.4% and 11.5–16.4% in the 0–20 cm and 20–40 cm layers, respectively), the increase in bacterial necromass C (BNC; 9.2–21.8% and 28.9–40.4% in the 0–20 cm and 20–40 cm layers, respectively) was greater than that of fungal necromass C (FNC; 6.2–10.1% and 7.1–24.9% in the 0–20 cm and 20–40 cm layers, respectively). Furthermore, the increase in FNC was greater than that of BNC in the 20–40 cm layer of the same treatment. SOC was significantly and positively correlated with MAOC and FNC, and the correlation between SOC and both MNC and FNC was more significant in the 20–40 cm layer than in the 0–20 cm layer. Overall, in the potato continuous cropping system in North China, N fertilization improved SOC storage by increasing MNC to form MAOC, and optimizing N fertilization based on the NE system could better balance the increase and mineralization loss of SOC to achieve high SOC sequestration. Full article

As the largest organic carbon input to agroecosystems, crop straw can solve the problem of soil quality degradation in greenhouse vegetable fields, harmonize the balance between soil nutrients and energy, and improve soil quality to maintain the sustainable production of greenhouse vegetables. However, the microbial mechanism of the straw decomposition process under different temperatures and fertilization treatments in greenhouse vegetable soils has not been clarified. Soil samples were used to investigate the biology of straw decomposition in the soil at three incubation temperatures (15, 25, and 35 °C) through a soil incubation experiment (60 d) under different fertilization treatments. Fertilization treatments for this long-term field experiment included chemical fertilizer (CF), substitution of half of the chemical N fertilizer with manure (CM), straw (CS), or combined manure and straw (CMS). The results showed that soil hydrolase activities tended to decrease with increasing temperature during straw decomposition. Compared with the CF, organic substitutions (CM, CMS, and CS) increased soil β-glucosidase, β-cellobiosidase, N-acetyl-glucosaminidase, and β-xylosidase activities during straw decomposition. Soil CO₂ emission rates were the highest at each incubation temperature on the first day, rapidly declining at 25 °C and 35 °C and slowly declining at 15 °C. The soil CO₂ cumulative emissions tended to increase with increasing temperature under different fertilization treatments. PCA showed that the responses of soil enzyme activities to temperature at 7, 15, and 30 d of straw decomposition were stronger than those of fertilization. In summary, both fertilization treatment and incubation temperature could influence soil CO₂ emissions by affecting soil physicochemical properties and enzyme activities during straw decomposition, whereas incubation temperature had a stronger effect on straw decomposition than fertilization, as indicated by PLS-PM and three-way ANOVA. Considering the influence for fertilization on the straw decomposition process at different incubation temperatures, the straw applications (CMS and CS) were more suitable to temperature changes. Full article

The soil microbial community is critically important in plant nutrition and health. However, this community is extremely sensitive to various environmental conditions. A pot experiment was conducted during the wheat seedling stage to better understand the influences of the coupled application of nitrogen (N) and microbial decomposing inoculants (MDI) on the soil bacteria community under different water regimes. There were two levels of water and six levels of fertilization. The results reveal that water stress increased the relative abundance of Acidobacteria and decreased that of Firmicutes and Proteobacteria. The application of 250 kg N ha⁻¹ altered the diversity of the bacterial community but increased the relative abundance of nitrifying bacteria. Nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions were negatively correlated with Myxococcota and Methylomirabilota while positively correlated with Patescibacteria. These two gases were also positively correlated with nitrifying bacteria, and the correlation was more significant under the full irrigation regime. These findings indicate that MDI does not substantially influence the soil bacterial community and its relationship with greenhouse gas emission at the wheat seedling stage and that the abundance of the soil bacterial community would mainly depend on the rational control of the amount of N and water applied. Full article