Soil extracellular polysaccharides (EPSac) can improve irrigation water productivity in agriculture by increasing soil aggregate stability and retaining water on and around plant roots. However, limited studies assay soil EPSac directly from field trials and to date no studies have examined the long-term confounding impacts of organic amendments and deficit irrigation on soil EPSac and the underlying microbial communities. We quantified soil aggregate stability, EPSac content, chemical properties, and microbial community compositions and abundances in separate field studies in turfgrass and tomato. Soil samples were collected 4–5 years after soil amendment with compost, biochar, their combination, or biosolids from plots that had received full and deficit irrigation regimens for 4 years. Amending the soil with compost, with or without biochar co-application, enhanced soil total carbon, aggregate stability, EPSac, and total soil microbial biomass and shifted microbial community structures, trends which were more pronounced under turfgrass than for tomato. In both sites deficit irrigation treatments had higher quantities of soil EPSac per unit of microbial biomass. Indicators of microbial physiological stress and ubiquitous classes of soil bacteria were associated with soil EPSac production. These results provide mechanistic understanding of organic amendment benefits in drought-impacted and deficit-irrigated agriculture.

土壤细胞外多糖 (EPSac) 可以通过增加土壤团聚体稳定性和在植物根部及其周围保持水分来提高农业灌溉水生产力。然而，有限的研究直接从田间试验中分析土壤 EPSac，迄今为止，还没有研究检查有机改良剂和亏缺灌溉对土壤 EPSac 和潜在微生物群落的长期混杂影响。我们在草坪和番茄的单独田间研究中量化了土壤团聚体稳定性、EPSac 含量、化学性质以及微生物群落组成和丰度。在用堆肥、生物炭、它们的组合或生物固体改良土壤后 4-5 年收集土壤样品，这些土壤样品来自已接受 4 年完全和亏缺灌溉方案的地块。用堆肥改良土壤，有或没有 biochar 共同应用，提高了土壤总碳、聚集体稳定性、EPSac 和总土壤微生物生物量，并改变了微生物群落结构，这些趋势在草坪草下比番茄更明显。在这两个地点，亏缺灌溉处理每单位微生物生物量具有更高数量的土壤 EPSac。微生物生理应激指标和普遍存在的土壤细菌类别与土壤 EPSac 的产生有关。这些结果提供了对受干旱影响和灌溉不足的农业中有机改良剂益处的机械理解。在这两个地点，亏缺灌溉处理每单位微生物生物量具有更高数量的土壤 EPSac。微生物生理应激指标和普遍存在的土壤细菌类别与土壤 EPSac 的产生有关。这些结果提供了对受干旱影响和灌溉不足的农业中有机改良剂益处的机械理解。在这两个地点，亏缺灌溉处理每单位微生物生物量具有更高数量的土壤 EPSac。微生物生理应激指标和普遍存在的土壤细菌类别与土壤 EPSac 的产生有关。这些结果提供了对受干旱影响和灌溉不足的农业中有机改良剂益处的机械理解。