Biodegradable microplastics (MPs) may enter soils either as pristine materials during agricultural plastic use or through organic fertilizers after partial degradation during composting. Their impacts on soil properties may be influenced by climatic conditions. The aim of this study was to investigate how (i) MP degradation state (pristine or composted) and (ii) physical stress cycles (alternating freeze–thaw, drying–rewetting) influence soil properties. To this end, one Cambisol was exposed in controlled conditions to three types of MPs at a concentration of 1% (w/w), with four soil incubation replicates: a conventional polyethylene (PE) film, and two biodegradable films, a poly(butylene adipate terephthalate) and starch (PBAT/starch) film, and an ethylcellulose-based (EC-based) film. MPs were introduced either as pristine or after composting, then visible fragments were removed after a 59-day incubation period, to evaluate the effects of incubation on soil physical properties after removal of visible plastic fragments, rather than their physical presence. However, some leachates or small plastic fragments may still be present. Incubation was conducted either under constant conditions or under alternating physical stress cycles. Soil physicochemical and aggregation properties were measured and SOC composition analyzed using Rock-Eval® pyrolysis. Soil responses varied primarily according to plastic type and degradation state. No significant effects on the measured properties were observed during the 59-day incubation with PE MPs, whether pristine or composted, whereas state-dependent responses were observed for biodegradable MPs. Pristine PBAT/starch and EC-based MPs changed soil pH and electrical conductivity, and increased mean weight diameter (MWD). Composting attenuated several of these effects, particularly for PBAT/starch. For EC-based MPs, composting attenuated responses for mean weight diameter and SOC content, whereas pH and electrical conductivity showed opposite trends between pristine and composted MP treatments. Alternating physical stress cycles selectively modulated specific soil properties in a treatment- and plastic composition-dependent manner, with effects mainly observed for MWD, soil pH, and electrical conductivity.
IntroductionAgrivoltaic (APV) systems can modify soil microclimate, but their short-term Q9 effects on soil organic matter (SOM) and microbial functioning remain incompletely understood.MethodsWe assessed SOM fractions and microbial activity in permanent grassland and raspberry shrubland under and outside APV over two years (2024–2025), sampling two soil depths. Three replicate plots represented each vegetation × APV combination. Thermogravimetric SOM fractions and oxidizable carbon were evaluated alongside dehydrogenase activity, basal respiration, substrate-induced respiration (SIR), and microbial functional diversity (MFD).ResultsResponses varied among vegetation types, APV conditions, depths, years, and measured variables. SIR responses showed significant interactions among all four factors, indicating context-dependent patterns rather than a uniform APV effect. Changes in oxidizable carbon and thermogravimetric SOM fractions were selective, while MFD showed lower-order effects but no four-way interaction. Exploratory PCA showed that associations among microbial indicators and SOM fractions varied across vegetation–APV combinations and soil depths.DiscussionThe results reveal treatment- and year-dependent differences already within this short observation period. They support the hypothesis that microbial indicators and SOM fractions may respond differently to APV conditions, a possibility that requires testing through longer-term monitoring.
Reducing synthetic-fertilizer use without sacrificing rice yield or grain quality remains difficult because quality traits may respond differently. We conducted a systematic review and multilevel meta-analysis of field experiments in China. Eligible studies compared organic fertilizer alone or combined with reduced synthetic fertilizer against a synthetic-fertilizer-only control. After excluding 13 effects with ineligible comparators, the dataset contained 420 treatment-control effects from 40 studies. Outcomes comprised yield and 10 grain-quality traits. We analyzed original-direction log response ratios (lnRR) with trait-specific multilevel random-effects models. We used experiment-clustered CR2 variance estimates and Satterthwaite inference. Prespecified moderators were soil organic matter, total nitrogen, available phosphorus, and nitrogen substitution rate. We controlled the within-trait false discovery rate. The pooled yield association was -0.52% with a 95% confidence interval from -6.25% to 5.57%. This interval did not establish equivalence or assured yield maintenance. Head rice rate increased by 2.05% with a 95% confidence interval from 0.28% to 3.86% and a nominal P value of 0.025. Rapid Visco Analyzer (RVA) breakdown increased by 6.70% with a 95% confidence interval from 0.79% to 12.96% and a nominal P value of 0.030. Prediction intervals for both outcomes crossed zero. Confidence intervals for the other eight quality traits also included zero. No moderator association remained significant after false-discovery-rate control. However, the yield association with substitution rate had an adjusted P value of 0.071 and remained exploratory. Removing ineligible comparators did not reverse any pooled direction, but it changed the magnitude or heterogeneity of setback, chalkiness, and breakdown. Organic-fertilizer substitution showed trait-specific associations rather than uniform benefits. The evidence applies to the included Chinese field studies. It does not establish causal mechanisms, overall quality improvement, or assured yield maintenance.
In semi-arid regions, low organic carbon and coarse-textured agricultural soil limit nutrient retention and promote excessive application of chemical fertilizers, which in long run increases the risk of the heavy metal accumulation in agricultural soils and subsequent transfer into food crops. This study evaluated low-cost amendments such as rice husk biochar (BC), coal fly ash (FA) and their Fe-modified forms, with and without fertilizer, for improving soil quality, spinach (Spinacia oleracea L.) productivity, and Pb-Cd immobilization in artificially contaminated sandy soils from Bathinda, Punjab, India. A pot experiment (with 5% w/w amendment) was conducted during winter season 2025–2026 in the field conditions, and the amendments were characterized using XRD, SEM, EDX, and FTIR. The results demonstrated that biochar combined with fertilizer (BCF) produced the greatest improvement in soil physical and chemical quality, by increasing total organic carbon by 738%, available N, P, K up to 165%, while reducing soil bulk density (up to -22.6%) compared to control. These improvements translated into substantial yield enhancements relative to control by significantly increasing plant length, root length, and fresh weight. FA-based treatments with fertilizer (FAF) produced comparatively smaller improvements in nutrient availability and crop yield because of their limited effect on soil physical properties. Compared to raw BC or FA, Fe-modified BC/FA effectively reduced DTPA-extractable fraction of Cd and Pb (Pb up to 69% and Cd up to 80%, respectively compared to CK), with greatest reduction was observed in Fe-modified FA (FeFA), followed by FeFAF and FeBCFAF treatments. This decline in phytoavailable metal fractions was associated with significant reduction of Pb and Cd concentrations in spinach roots and leaves by 57-73% and 59-87%, respectively. Overall, the combined application of Fe-modified BC or Fe-modified FA with fertilizer in pot experiments demonstrated simultaneous improvement of soil fertility, crop productivity and minimized metal transfer to crop. However, this study should be conducted in field scale and optimize the amendments dose and fertilizer application rates to validate this finding before its wider application in the semi-arid regions of Punjab.
