Seasonal fallows – periods with no living plant cover – are frequently implemented in dryland cropping systems to allow recharge of soil moisture for the subsequent cash crop. Over time, repeated fallow periods deplete soil organic matter, a foundation of soil health that affects the long-term functional capacity of soils. Reducing fallow periods by growing cover crops (non-harvested crops terminated prior to reproductive development), double cropping (increasing the frequency of harvested crops), or rotating to ley pasture for several years, were investigated for their potential to improve or maintain soil functional attributes. These ‘reduced fallow’ systems were compared against a conventional cereal-based production system with seasonal fallows as well as against a permanent fallow. Soil in the reduced fallow systems had higher concentrations of total nitrogen and mineral-associated nitrogen compared with the conventional system and permanent fallow. Reduced fallow systems also had higher concentrations of total organic carbon and mineral-associated carbon than the permanent fallow, but not the conventional system. These changes were associated with greater soil microbial respiration and improved surface soil moisture storage at cash crop planting. The conventional, cover crop and ley pasture systems had similar soil structure with greater abundance of mega-aggregates. In contrast, the double crop system had greater abundance of micro- and macro-aggregates as did the ley pasture systems that were subject to tillage after three years in preparation for a return to cropping. The ley pasture also had substantially greater numbers of root-lesion nematodes (Pratylenchus thornei), surpassing the 2000 nematodes kg^-1 threshold for economic damage. The results demonstrate that different methods for reducing fallow periods can generate a range of outcomes that are not uniformly desirable in terms of soil functional attributes. Across the indicators assessed, the cover crop system generated the widest range of improvements in soil fertility and function compared with the conventional system. This suggests cover cropping may be a valuable tool for promoting soil health in subtropical dryland farming systems.

季节性休耕期——没有活植物覆盖的时期——经常在旱地种植系统中实施，以便为随后的经济作物补充土壤水分。随着时间的推移，反复的休耕期会消耗土壤有机质，这是影响土壤长期功能能力的土壤健康的基础。通过种植覆盖作物（在生殖发育之前终止的非收获作物）、双熟（增加收获作物的频率）或轮作麦草来减少休耕期数年，研究了它们改善或保持土壤功能的潜力属性。将这些“减少休耕”系统与具有季节性休耕的传统谷物生产系统以及永久休耕进行了比较。与传统系统和永久休耕系统相比，减少休耕系统中的土壤具有更高浓度的总氮和矿物伴生氮。减少休耕系统的总有机碳和矿物伴生碳浓度也高于永久休耕系统，但不是传统系统。这些变化与更大的土壤微生物呼吸和改善经济作物种植时的表层土壤水分储存有关。传统的覆盖作物和麦草系统具有相似的土壤结构，具有更丰富的巨型骨料。相比之下，双熟系统具有更丰富的微观和宏观聚集体，就像麦草系统一样，在三年后进行耕作以准备恢复种植。Pratylenchus thornei )，超过了 2000 线虫 kg ^-1的经济损失阈值。结果表明，减少休耕期的不同方法可能会产生一系列结果，这些结果在土壤功能属性方面并不统一。在评估的指标中，与传统系统相比，覆盖作物系统在土壤肥力和功能方面产生了最广泛的改善。这表明覆盖作物可能是促进亚热带旱地农业系统土壤健康的宝贵工具。