Rice (Oryza sativa L.)-based cropping systems are different from other row crops due to the flood-irrigation scheme used from about one month after planting to a few weeks prior to harvest. The frequent cycling between anaerobic (i.e., flooding during the growing season) and aerobic (i.e., generally, the remainder of the year) conditions can influence the rate of soil organic matter (SOM) decomposition, which can greatly influence carbon (C) and nitrogen (N) storage and sequestration in the soil over time. Therefore, a study was conducted on a silt-loam soil (fine, smectitic, thermic, Typic Albaqualf) at the Rice Research and Extension Center near Stuttgart, which is in the Mississippi River Delta region of eastern Arkansas, to evaluate the long-term effects of rice-based crop rotations [with corn (Zea mays L.), soybean (Glycine max L.), and winter wheat (Triticum aestivum L.)], tillage [conventional-tillage and no-tillage (NT)], soil fertility (optimal and sub-optimal), and soil depth (0- to 10- and 10- to 20-cm) after 12 years (1999-2011) of consistent management on SOM, total and water-stable aggregate (WSA) C, total and WSA N, soil physical properties (WSA structure, bulk density, penetration resistance), soil chemical properties (Mehlich-3 extractable nutrients, pH, and electrical conductivity), and soil surface carbon dioxide (CO2) respiration. Results showed that SOM, total C, and total N concentrations increased over time under the NT treatment and in all rotations that did not include corn in the top 10 cm, but were not affected by the fertility treatment applied. The NT/0- to 5-cm treatment combination had 3 to 6 times greater WSA C and N content than all other tillage-depth combinations in the top 10 cm, which did not differ among one another. Despite rotation trends in total C and N, rotations with increased frequencies of corn generally had greater WSA C and N contents compared to rotations with wheat. However, there were no consistently significant differences in soil surface CO2 flux between tillage treatments and/or among crop rotations after 10- and 11-years of imposed treatment combinations. Results from this long-term experiment suggest that rice rotated with a higher-residue-producing crop, such as corn, may lead to greater C and N sequestration for longer periods of time due to the aggregated form that is predominantly present in the soil. It appears that the management practices of NT and high-residue-producing crop rotations establish a new, greater soil C content equilibrium over time. This long-term research study is important because the results enable a greater understanding of the decadal effects that rice-based crop rotations and conservation management practices have on the physical, chemical, and biological properties of the soil, which in turn, provides insight to the longer-term sustainability of these systems so that they can remain highly productive without detrimental effects to the environment and the soil resource.
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机译：基于水稻（Oryza sativa L.）的种植系统与其他大田作物不同，这是因为从种植后约一个月到收获前几周使用了洪水灌溉方案。厌氧（即生长期的洪灾）和有氧（即一年中的剩余时间）之间频繁的循环会影响土壤有机质（SOM）的分解速率，从而极大地影响碳（C）和氮（N）的存储和固存随着时间的推移。因此，在阿肯色州东部密西西比河三角洲地区斯图加特附近的水稻研究与推广中心，对粉壤土（精细，近晶，热，典型的阿尔巴夸尔夫）进行了研究，以评估长期稻米轮作的影响[玉米（Zea mays L.），大豆（Glycine max L.）和冬小麦（Triticum aestivum L.）]，耕作[常规耕种和免耕（NT）]，在对SOM，总水稳性骨料（WSA）进行一致管理的12年（1999-2011）之后，土壤肥力（最佳和次佳）以及土壤深度（0至10厘米和10至20厘米） C，总和WSA N，土壤物理性质（WSA结构，堆积密度，抗穿透性），土壤化学性质（Mehlich-3可提取的养分，pH和电导率）和土壤表面二氧化碳（CO2）呼吸作用。结果表明，在NT处理下以及在所有轮作中，顶部和下部10 cm的SOM，总C和总N浓度均随时间增加，但不包括玉米，但不受施肥处理的影响。 NT / 0至5厘米处理组合的WSA C和N含量是前10厘米中所有其他耕种深度组合的3至6倍，彼此之间没有差异。尽管总C和N呈旋转趋势，但与小麦相比，玉米频率升高的旋转通常具有更高的WSA C和N含量。但是，在耕作处理之间和/或施行处理组合10年和11年后，轮作之间的土壤表面CO2通量没有一致的显着差异。这项长期实验的结果表明，由于水稻等高残留作物轮作使用的水稻，由于长时间存在于土壤中的聚集形式，可能导致更高的固碳和固氮能力。长期以来，NT和高残留作物轮作的管理实践似乎建立了新的更大的土壤碳含量平衡。这项长期研究很重要，因为其结果可以使人们更好地了解基于水稻的作物轮作和保护管理做法对土壤的物理，化学和生物学特性的年代际影响，从而反过来为这些系统具有更长期的可持续性，因此它们可以保持高产，而不会对环境和土壤资源造成不利影响。
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