Biochar amendment and substituting chemical fertilizers with organic manure (organic substitution) have been widely reported to improve intensive vegetable production. However, considering its high potential for reducing carbon and reactive nitrogen (Nr) footprints, very few comprehensive evaluations have been performed on the environmental and economic aspects of biochar amendment or organic substitution. In this study, the comprehensive environmental damage costs from carbon and Nr footprints, measured using the life cycle assessment (LCA) methodology, followed a cradle-to-gate approach, and the carbon storage benefits were incorporated into the newly constructed net ecosystem economic benefit (NEEB) assessment frame in addition to the conventional product income-input cost-benefit methods. One kilogram of harvested vegetables for carbon/Nr footprints and one hectare of cultivated land per crop for cost and benefit were adopted as functional units considering the multi-cropping characteristics for intensive vegetable production. Five fertilization treatments were included: no fertilizer (CK); synthetic fertilizer application (SN); biochar amendment (NB); organic substitution (NM); and a combination of biochar and organic substitution (NMB). These were investigated for five consecutive years of vegetable crop rotations in a typically intensified vegetable production region in China. Adopting the revised NEEB methodology, NB significantly reduced carbon footprint by 73.0% compared to no biochar addition treatment. Meanwhile, NB significantly increased the total benefits by 9.7% and reduced the environmental damages by 52.7% compared to NM, generating the highest NEEB, making it the most effective fertilization strategy among all treatments. It was 4.3% higher compared to NM, which was not significant, but significantly higher than SN and NMB, by 23.0% and 13.6%, respectively. This finding highlights the importance of considering carbon storage benefit for properly assessing NEEB, which is important for developing effective agricultural management strategies and promoting intensive vegetable production with a more sustainable approach.
Biochar application, as a kind of soil amendment, significantly influences soil physical and mechanical properties. This study revealed the effects of biochar application on the physical and mechanical properties of a clay-type soil at different irrigation levels. Soil was treated with three levels of biochar application: B0 (0 t ha(-1)), B1 (25 t ha-(1)) and B2 (50 t ha b(-1)), and three levels of irrigation: T0 (1.2 pan evaporation Ep), T1 (1.0 Ep) and T2 (0.8 Ep). The results indicated that other treatments reduced the soil bulk density compared with the control treatment (CK) (B0T1). Compared to CK, the highest reduction in soil bulk density was 18%. Irrigation did not improve the soil bulk density and porosity at the same biochar application in the short term. Biochar enhanced the stability of the soil aggregates. Compared to CK, the largest MWD (mean weight diameter) was enhanced by 9%. The addition of biochar and decreasing irrigation could decrease soil cohesion. The addition of biochar and increasing irrigation could increase the soil internal friction angle. The soil cohesion first increased and then decreased as the soil water content increased. According to the fitting formula, the soil cohesion was found to be minimum at B2T2, which was a decrease of 39% compared to B0T1. At the same irrigation level, the soil internal friction angle decreased with increasing soil water content. Soil penetration resistance showed a decreasing trend with the application of biochar. The more irrigation there is, the larger the soil penetration resistance.
The accumulation of microplastics in agricultural soil brings unexpected adverse effects on crop growth and soil quality, which is threatening the sustainability of agriculture. Biochar is an emerging soil amendment material of interest as it can remediate soil pollutants. However, the mechanisms underlying biochar alleviated the toxic effects of microplastics in crops and soil were largely unknown. Using a common economic crop, peanut as targeted species, the present study evaluated the plant physiologica and molecular response and rhizosphere microbiome when facing microplastic contamination and biochar amendment. Transcriptome and microbiome analyses were conducted on peanut root and rhizosphere soil treated with CK (no microplastic and no biochar addition), MP (1.5% polystyrene microplastic addition) and MB (1.5% polystyrene microplastic+2% peanut shell biochar addition). The results indicated that microplastics had inhibitory effects on plant root development and rhizosphere bacterial diversity and function. However, biochar application could significantly promote the expressions of key genes associated with antioxidant activities, lignin synthesis, nitrogen transport and energy metabolism to alleviate the reactive oxygen species stress, root structure damage, nutrient transport limitation, and energy metabolism inhibition induced by microplastic contamination on the root. In addition, the peanut rhizosphere microbiome results showed that biochar application could restore the diversity and richness of microbial communities inhibited by microplastic contamination and promote nutrient availability of rhizosphere soil by regulating the abundance of nitrogen cycling-related and organic matter decomposition-related microbial communities. Consequently, the application of biochar could enhance root development by promoting oxidative stress resistance, nitrogen transport and energy metabolism and benefit the rhizosphere microecological environment for root development, thereby improved the plant-soil system health of microplastic-contaminated agroecosystem.