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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]