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Cover crop can reduce the intensity of land use, and improve soil fertility and productivity in multiple-cropping systems. However, only a few studies have comprehensively evaluated soil health after cover crops in terms of management goal and soil multi-functionality. In this study, different minimum data set (MDS) methods were used to establish a soil health index (SQI) model to evaluate soil health of the winter smooth vetch-summer maize cropping system in southwest China. We analyzed thirty-five soil parameters (representing soil physical, chemical and biological properties) connected with the soil functions as potential soil health indicators in the phase of smooth vetch and maize under six management treatments (CK (control), N (N fertilizer), P (P fertilizer), NP (N and P fertilizer), NPW (N and P fertilizer + irrigation), CF (fallow)). Those managements were set in the smooth vetch phase (as a cover crop). The MDS using correlation analysis (cMDS), principal component analysis (pMDS) and random forest analysis (rMDS) from the total data set (TDS) were selected and then used for SQIs calculation, respectively. Cover crop by different management of irrigation and fertilization affected each soil property in different ways. All three SQIs were significantly correlated with SQI-TDS, validating the SQI models developed by three MDS methods (P < 0.05). Further, the SQI based on rMDS was the most accurate and sensitive, suggesting the RFA-based SQI reflects soil functions more adequately than the CA and PCA-based SQI. Cover crop by the management of fertilization or/and irrigation will not only improve soil health, but also enhance maize yield compared with fallow treatment, especially for NPW treatment. Fertilization treatments (N, P, NP and NPW) had higher soil health index, which was related to the better performance of soil in sustaining biological activity, physical stability and supporting function. In summary, the SQI model developed by the RFA method can provide a practical and robust tool for assessing soil health based on the management goal. • Cover crops can improve soil health index and maize yield. • Cover crops with balanced irrigation and fertilizer have better soil health. • Increasing soil health index significantly enhances maize yield. • Soil health index developed by random forest analysis had the most accurate ability. [ABSTRACT FROM AUTHOR]

Sustainable agriculture aims to manage soil and plant health while relying less on chemical inputs. The individual effect of organic amendments or resistant crop cultivars on the suppression of root pests through modulating soil and plant performance is being well documented. However, the interactions between organic amendments and crop cultivars are less well studied. A pot experiment was conducted across two tomato cultivars of distinct resistance to root-knot nematodes (RKNs, Meloidogyne incognita ) with three amendments including inorganic fertilizer (IF), conventional compost (CC) and vermicompost (VC). All treatments were inoculated with second-stage juveniles of M. incognita to simulate the root-knot nematode disease in field condition and to focus on the comparison among different soil amendment effects. Plant growth (shoot height, shoot biomass, root biomass and root C:N ratio), root defense metabolites (phenolics) and their related genes expression, and soil properties including pH, electrical conductivity, available nutrients, 3-indoleacetic acid (IAA), microbial biomass and activity were analyzed at 14 and 30 days post inoculation (dpi). Compared with inorganic fertilizer, vermicompost significantly decreased the numbers of nematode-induced galls on susceptible (Sus) and resistant (Res) cultivar roots by 77% and 42% respectively at 14 dpi, and by 59% and 46% respectively at 30 dpi. Vermicompost also significantly increased root defense metabolite concentrations, defense related gene expression, and improved soil properties ( p < 0.05) except for mineral nitrogen. Multivariate analyses further indicated that soil properties particularly pH, root primary and secondary defense metabolites were negatively associated with root gall. Moreover, soil microbial activity, pH and IAA concentration were the main soil properties positively associated with plant defense metabolites production and biomass for both susceptible and resistant cultivars. Overall, vermicompost could significantly suppress root pests via modulating soil properties as well as plant defenses, particularly for the susceptible plant. [ABSTRACT FROM AUTHOR]

• Adding organic materials to chemical fertilizer enhances crop yield and soil quality. • Organic materials with part chemical fertilizer (ORC) is the best regimes. • Crop yield-soil quality balance respond variously to climate and soil conditions. • Biochar, organic fertilizer or ORC can promote sustainable agricultural development. The contradiction between rapid soil degradation and increased food demand is becoming increasingly prominent. Reasonable recycling of agricultural waste can affect soil productivity and environmental health, thus playing a crucial role in the sustainability of agricultural production. Through a meta-analysis of 160 studies in the region of upland double cropping in China, we evaluate crop yield and soil quality responses to organic amendments. Results indicated that soil quality index (17.6%–26.3%) and crop yield (6.0%–9.0%) were significantly increased by adding organic amendments to chemical fertilizer. Combination of organic materials with total chemical fertilizer (OTC) and with part chemical fertilizer (ORC) significantly increased the yield by 8.3% and 8.7% and soil quality by19.5% and 18.4%, respectively. However, application of organic materials alone (O) decreased yields (by −0.6%), but significantly increased soil quality (by 49.1%). On average, organic amendments resulted in higher crop yield and soil quality index, despite variability introduced by tillage regimes and conditions of soil and climate. Relatively larger positive effect in crop yield and soil quality occurred with mean annual precipitation >1000 and <600 mm, respectively. Additional analyses found that biochar, organic fertilizer or ORC can promote sustainable agricultural development via improving crop yields, soil quality, and reducing nitrogen losses. Our results provide the first systematic review of effect of the organic amendments on the balance between soil quality and crop yield. The findings suggest that impacts of adding organic amendments to chemical fertilizer may be used as the foundation for policies. However, the combined use of organic amendments and other farmland management practices still present an area that needs further research in order to promote sustainable development of agriculture. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the effects of alternative farming on soil quality parameters, such as microbial communities, size, activity and soil nutrient content, is of central importance to concepts of sustainability. Combining organic amendments with chemical fertilizer is a promising approach to develop more sustainable fertilization strategies. We investigated the impacts of quantity, type and application time of organic amendments on temporal dynamics of paddy soil microbial biomass, activity, carbon fractions and nutrient status under a long-term field experiment in a rice–rice cropping system. We established treatments with seven fertilization practices characterized by different quantities and application times of green manure (GM), farmyard manure (FYM) and rice straw (RS) in combination with low amount of chemical fertilizers. We further established one treatment with only recommended amount of chemical fertilizer and an unfertilized control. At all sampling times, organic amendments with low amount of chemical fertilizer enhanced microbial biomass, activity and nutrient availability more than recommended amount of chemical fertilization only and an unfertilized control, with higher quantities of FYM resulting in stronger effects than all other organic amendments. The strongest increase of microbial biomass, activity, carbon and nutrient availability was generally found in the treatment with the most diverse resources and highest amount of organic amendments. Principle component analysis indicated that most soil variables measured were correlated to total soil organic C. Regression analysis indicated that the integrated paddy soil properties were closely related to yearly C input and rice yield. Strong temporal dynamics were demonstrated for all soil variables, indicating that we need multiple time sampling strategies to explore the overall influences of fertilization practices on paddy soil. Our results indicate that the development of effective fertilization practices, especially by manipulating the quantity and type of organic amendments, may improve long-term sustainability of paddy soil ecosystems. [Copyright &y& Elsevier]

The “energetic equivalence rule” predicts that abundance should always scale as the −3/4 power of body size within a trophic group, but if the body size–abundance allometry (BSA) of soil fauna in fact is labile then the relationship could potentially be used as a standard descriptor for shifts in community functional structure in response to environmental change. To assess the possibility that the BSA could serve as an index of community functional structure, we measured the effect of fertilization on the slope and intercept of the BSA in nematode communities in a rice–wheat crop rotation over three years. Fertilization increased the BSA intercept but did not affect the slope in either rice or wheat phases, which highlights the stable scaling of BSA. [ABSTRACT FROM AUTHOR]

The application of organic fertilizers affects soil aggregates, nutrient situations and bacterial communities. However, the direct and indirect effect of different resource-derived organic fertilizers on soil bacterial communities and their links to soil aggregate is poorly understood. Here, we carried out a field experiment for three years to investigate the linkages between soil aggregates and bacterial diversity in a dryland red soil. Six treatments were compared: (no fertilizer (CK), chemical fertilizer (CF), 60% chemical fertilizer + straw at 4500 kg ha−1 (RFS), 60% CF + biochar at 1500 kg ha−1 (RFB), 60% CF + pig manure at 15000 kg ha−1 (RFP), and 60% CF + vermicompost at 15000 kg ha−1 (RFV)). The application of pig manure or vermicompost (animal-derived organic fertilizer) enhanced the soil pH, the content of large macroaggregate (>2 mm), organic matter, available phosphorous and available nitrogen, while decreased the content of small macroaggregate (0.25–2 mm) and microaggregate (<0.25 mm) compared with other treatment. Relative abundances of the dominant bacterial phyla varied across chemical and organic fertilizer treatments, primarily by increasing Bacteroidetes, Gemmatimonadetes, and decreasing Chloroflexi, Acidobacteria and Planctomycetes. Organic fertilizers particularly animal-derived organic fertilizer enhanced the Richness, Shannon and Pielou indices of soil bacteria compared with chemical fertilizer treatment. The regulation of animal-derived organic fertilizers on bacterial community structure (accounting for 53.04% of the variance) was greater than that of plant-derived organic fertilizers (straw and biochar, accounting for 7.69% of the variance). The bacterial alpha diversity showed positive correlation with large macroaggregate, but a negative correlation with small macroaggregate. Further, structural equation models indicated that animal-derived organic fertilizers impacted bacterial diversity positively by regulating resource availability through soil aggregates. However, for the plant-derived organic fertilizers, bacterial diversity was negatively affected by soil aggregates alone, but this was not regulated by fertilization. In addition, animal-derived organic fertilizer also positively affected soil bacteria diversity indirectly via changing soil pH and resource availability. Overall, the different impacts of animal- and plant-derived organic fertilizers on soil bacterial community highlighting the pivotal role of soil habitat architecture and resource chemistry changed by organic fertilizers in the regulation of soil bacteria, which may influence soil quality and agricultural sustainable development. • Animal-derived organic fertilizer (AOF) decreased 0.25–2 and <0.25 mm soil aggregates. • AOF increased >2 mm soil aggregates, pH, organic matter, available P and N. • AOF affect soil bacterial community structure than plant-derived (POF). • AOF affect bacterial community mainly via changing aggregates, pH and resource availability. • Aggregates affect bacterial diversity alone under POF, but not regulated by fertilization. [ABSTRACT FROM AUTHOR]

• Organic input can improve soil quality by the interaction of soil properties. • Use animal-derived organic fertilizer had better soil quality than plant-derived. • AP, AN, GP and AK were selected as a minimum data set for evaluating soil quality. • Information from soil indicators is integrated into a standardization framework. • Appropriate methods of scoring and weighting are determined in the framework. Organic fertilizer applications can increase soil fertility and productivity and reduce chemical fertilizer use. However, few experimental studies have focused on effects of organic fertilizers on soil quality in a field ecosystem. The overarching goal of this study was to develop a soil quality index (SQI) for fertilization management in red soil farmland in China. The specific objectives were to determine 1) appropriate soil quality indicators, 2) a suitable weight assignment method (PCA, principal component analysis or MRA, multiple regression analysis) and 3) the optimal scoring function (standard or linear or non-linear). We analyzed 40 soil physical, chemical, biochemical and biological properties under nine fertilization treatments (CK (no fertilizer), CF (chemical fertilizer), RF (60% chemical fertilizer), CFS (chemical fertilizer + straw), RFS (60% chemical fertilizer + straw), CFB (chemical fertilizer + biochar), RFB (60% chemical fertilizer + biochar), RFP (60% chemical fertilizer + pig manure), RFV (60% chemical fertilizer + vermicompost)) as potential soil quality indicators. Principal component analysis and correlation analysis were applied to determine the indicators responsive to management and for the confirmation of the six SQIs. Available phosphorous, nitrogen, potassium and gram-positive bacteria were chosen as the minimum data set from the total of 40 soil indictors. Management of organic and inorganic fertilizers affected each soil property in different ways, and the index based on the minimum data set, calculated using standard scoring function and weight assignment method of multiple regression analysis, was most accurate and sensitive. Application of a pig manure or vermicompost significantly increased SQI values relative to other treatments, followed by straw or biochar treatments which were higher than a single application of chemical fertilizer. These results indicate that the addition of organic fertilizers will not only improve soil quality, but also enhance rapeseed and sweet potato yield compared to chemical fertilizers. Additionally, the SQI method can provide a practical and quantitative tool for the evaluation of soil quality. [ABSTRACT FROM AUTHOR]

• We describe microbial biomass role in C sequestration in fertilized paddy soil. • Organic inputs increase microbial growth and necromass accumulation. • Organic inputs do not alter microbial CUE in bulk soil, but reduce CUE in rhizosphere soil. • Microbial CUE is lower in rhizosphere soil than in bulk soil. Microbial anabolism relative to catabolism, reflected by the C use efficiency (CUE), determines the fate of C transformation in soil. Understanding how the microbial CUE and microbial necromass respond to fertilization is crucial for the evaluation of the C sequestration potential in intensively managed paddy soils. We examined the microbial CUE, microbial biomass turnover, and necromass accumulation in rice rhizosphere and bulk soils subjected to long-term (31 years) fertilizations: no fertilizers (control), mineral fertilizers alone (NPK), mineral fertilizers plus rice straw incorporation (NPK-Straw), and mineral fertilizers combined with a low or a high amount of organic manure (NPK-lowM or NPK-highM). The microbial CUE was determined by 18O incorporation into DNA. Microbial necromass accumulation was quantified by the biomarker analysis of amino sugars. Rice straw and manure incorporation reduced the microbial CUE in the rhizosphere soil, whereas the CUE remained constant in the bulk soil. CUE was lower in the rhizosphere soil than in the bulk soil due to nutrients uptake and root exudate release by rice plants, leading to a higher C/nutrient ratio in the rhizosphere. Organic inputs strengthened these rhizosphere processes and could thus weaken the relative potential of C sequestration. The microbial CUE decreased with the increase of the available C/N ratio in the rhizosphere but not in the bulk soil. The microbial CUE mainly depended on the respiration in the bulk soil and on the microbial growth in the rhizosphere soil, indicating the divergent microbial utilization of organic substrates between rhizosphere and bulk soils. In both rhizosphere and bulk soils, organic inputs promoted the microbial biomass growth rate and further increased the amount of microbial necromass by 27–52 % compared with NPK alone, which was highly correlated with the soil organic C pools. Despite enhancing rhizosphere respiration, our findings highlight that rice straw and manure applications increase C sequestration in paddy soils by enhancing the net flux of microbial biomass formation, and consequently promoting necromass accumulation. [ABSTRACT FROM AUTHOR]