Biochar combined with organic and inorganic fertilizers promoted the rapeseed nutrient uptake and improved the purple soil quality

Partial substitution of chemical fertilizer by organic fertilizer increases yield, quality and nitrogen utilization of Dioscorea polystachya

This field experiment aimed to investigate the effects of different ratios of organic and inorganic fertilizers with maintaining equal nitrogen application rates on the yield, quality, and nitrogen uptake efficiency of Dioscorea polystachya (yam). Six treatments were set, including a control without fertilizer (CK), sole application of chemical fertilizer (CF), sole application of organic fertilizer (OM), 25% organic fertilizer + 75% chemical fertilizer (25%OM + 75%CF), 50% organic fertilizer + 50% chemical fertilizer (50%OM + 50%CF), and 75% organic fertilizer + 25% chemical fertilizer (75%OM + 25%CF). The experiment followed a randomized complete block design with three replications. Various yield parameters, morphology, quality indicators, and nitrogen utilization were analyzed to assess the differences among treatments. The results indicated that all fertilizer treatments significantly increased the yield, morphology, quality indicators, and nitrogen utilization efficiency compared to the control. Specifically, 25%OM + 75%CF achieved the highest yield of 31.96 t hm-2, which was not significantly different from CF (30.18 t hm-2). 25%OM + 75%CF exhibited the highest values at 69.23 cm in tuber length and 75.86% in commodity rate, 3.14% and 1.57% higher than CF respectively. Tuber thickness and fresh weight of 25%OM + 75%CF showed no significant differences from CF, while OM and 50%OM+50%CF exhibited varying degrees of reduction compared to CF. Applying fertilizer significantly enhanced total sugar, starch, crude protein, total amino acid, and ash contents of D. polystachya (except ash content between CK and OM). Applying organic fertilizer increased the total sugar, starch, crude protein, total amino acid, and ash contents in varying degrees when compared with CF. The treatment with 25%OM+75%CF exhibited the highest increases of 6.31%, 3.78%, 18.40%, 29.70%, and 10%, respectively. Nitrogen content in different plant parts followed the sequence of tuber > leaves > stems > aerial stem, with the highest nitrogen accumulation observed in 25%OM + 75%CF treatment. Nitrogen harvest index did not show significant differences among treatments, fluctuating between 0.69 and 0.74. The nitrogen apparent utilization efficiency was highest in 25%OM + 75%CF (9.89%), followed by CF (9.09%), both significantly higher than OM (5.32%) and 50%OM + 50%CF (6.69%). The nitrogen agronomic efficiency varied significantly among treatments, with 25%OM + 75%CF (33.93 kg kg-1) being the highest, followed by CF (29.68 kg kg-1), 50%OM + 50%CF (21.82 kg kg-1), and OM (11.85 kg kg-1). Nitrogen partial factor productivity was highest in 25%OM + 75%CF treatment (76.37 kg kg-1), followed by CF (72.11 kg kg-1), both significantly higher than 50%OM + 50%CF (64.25 kg kg-1) and OM (54.29 kg kg-1), with OM exhibiting significantly lower values compared to other treatments. In conclusion, the combined application of organic and inorganic fertilizers can effectively enhance the yield, quality, and nitrogen utilization efficiency of D. polystachya. Particularly, the treatment with 25% organic fertilizer and 75% chemical fertilizer showed the most promising results.

The impact of different preceding crops on soil nitrogen structure and nitrogen cycling in tobacco-planting soil

Soil nitrogen content, structure, and nitrogen cycling play a crucial role in tobacco growth quality, with different preceding crops having varying impacts on tobacco cultivation soil. This study conducted using field experiments, employed three treatments with different preceding crops, namely tobacco, barley, and rapeseed, to investigate the effects of different preceding crops on soil nitrogen structure and the expression levels of soil nitrogen cycling-related functional genes in tobacco cultivation soil. The results indicated that different preceding crops had varying effects on the content of different nitrogen forms in tobacco cultivation soil. Ammonium nitrogen and nitrate nitrogen were the two nitrogen forms which were most influenced by preceding crops, with the ammonium nitrogen content in soils following barley and rapeseed preceding crops increasing by 82.88% and 63.56%, respectively, compared to sole tobacco cultivation. The nitrate nitrogen content in tobacco cultivation soil was 26.97% higher following barley preceding crops and 24.39% higher following rapeseed preceding crops compared to sole tobacco cultivation. Simultaneously, different preceding crops also affected the expression levels of nitrogen cycling-related genes in tobacco cultivation soil. In the nitrification process, amoA was significantly impacted, with its expression reduced by 64.39% and 72.24% following barley and rapeseed preceding crops, respectively, compared to sole tobacco cultivation. In the denitrification process, except for the narG gene, all other genes were subjected to varying degrees of inhibition when preceded by barley and rapeseed crops. Correlation analysis between soil nitrogen structure and the expression levels of nitrogen cycling-related genes revealed that increased nitrogen levels suppressed the expression of Arch-amoA. Additionally, ammonium nitrogen strongly influenced the expression levels of most soil nitrogen cycling functional genes. In conclusion, preceding crops alter soil nitrogen structure, possibly due to changes in soil microorganisms, and different preceding crops modified the expression levels of nitrogen cycling-related genes in tobacco cultivation soil, consequently affecting the proportions of various nitrogen forms in the soil.

Biochar and organic fertilizer drive the bacterial community to improve the productivity and quality of Sophora tonkinensis in cadmium-contaminated soil

Excessive Cd accumulation in soil reduces the production of numerous plants, such as Sophora tonkinensis Gagnep., which is an important and widely cultivated medicinal plant whose roots and rhizomes are used in traditional Chinese medicine. Applying a mixture of biochar and organic fertilizers improved the overall health of the Cd-contaminated soil and increased the yield and quality of Sophora. However, the underlying mechanism between this mixed fertilization and the improvement of the yield and quality of Sophora remains uncovered. This study investigated the effect of biochar and organic fertilizer application (BO, biochar to organic fertilizer ratio of 1:2) on the growth of Sophora cultivated in Cd-contaminated soil. BO significantly reduced the total Cd content (TCd) in the Sophora rhizosphere soil and increased the soil water content, overall soil nutrient levels, and enzyme activities in the soil. Additionally, the α diversity of the soil bacterial community had been significantly improved after BO treatment. Soil pH, total Cd content, total carbon content, and dissolved organic carbon were the main reasons for the fluctuation of the bacterial dominant species. Further investigation demonstrated that the abundance of variable microorganisms, including Acidobacteria, Proteobacteria, Bacteroidetes, Firmicutes, Chloroflexi, Gemmatimonadetes, Patescibacteria, Armatimonadetes, Subgroups_ 6, Bacillus and Bacillus_ Acidiceler, was also significantly changed in Cd-contaminated soil. All these alterations could contribute to the reduction of the Cd content and, thus, the increase of the biomass and the content of the main secondary metabolites (matrine and oxymatrine) in Sophora. Our research demonstrated that the co-application of biochar and organic fertilizer has the potential to enhance soil health and increase the productivity and quality of plants by regulating the microorganisms in Cd-contaminated soil.

Biochar-blended manure modified by polyacrylamide to reduce soil colloidal phosphorus leaching loss

Combined application of biochar and organic fertilizer improves soil structure and crop yield but may lead to increased loss of phosphorus (P). To reduce the P loss risk in this case, rice straw biochar (BC) and sheep manure (SM) were modified using polyacrylamide (PAM). The effects of using organic amendments (BC, SM, and PAM-modified organic mixtures) and no amendments (CK) on soil total and colloidal P leaching loss from paddy soils were evaluated through soil column leaching experiments. The soil leachate volume was increased by 8.91% with BC treatment and reduced by 15.3% with SM treatment. The total P leaching loss (973.9 μg kg^-1) from the BC-treated soil was higher than that from other treatments (541.4-963.5 μg kg^-1). However, there was much more colloidal P loss (480.0 μg kg^-1) from SM treatment. The optimal conditions for the preparation of BC and SM modified using polyacrylamide (PSB) for reducing P leaching loss were SM/BC = 4:1, 1% PAM, and 100 °C. Molybdate-unreactive P accounts for 58.61-86.89% of the colloidal P in the soil leachate with organic amendments. PSB reduced colloidal P loss (particularly in 10-220 nm range) by ~ 50% compared with BC and SM treatments. The colloidal P concentration in the leaching solutions was significantly correlated with TOC and susceptible to Fe and Al concentrations. Using PAM-modified mixture instead of manure and biochar as a soil amendment can effectively control P leaching from fields.