As a major carbon pool on earth, soil organic carbon may act either as a sink or a source of atmospheric CO₂, a greenhouse gas. Soil organic carbon is also impacting fertility, and, in turn, crop yields. However, knowledge of the impact of cropping techniques on the long-term behavior of soil carbon is scarce. Several studies have shown that continuous cropping decreases soil organic carbon stocks, rapidly in the initial years then at a slower rate, approaching a new equilibrium after 30 to 50 years. For instance, a study of intensive corn cropping for 35 years on temperate soils showed a 50% decrease in soil organic carbon. Our study is located in the North Indian state of Punjab. It is the most intensively cultivated region in the country with a cropping intensity of 190%, predominantly of a rice-wheat system. Due to high nutrient demand and its continuous cultivation, the cropping system is presumed to adversely affect soil organic carbon and other soil properties. However, this has been postulated without any real-time data analysis on a regional scale. Therefore, we evaluated soil data for 25 years from 1981/82 to 2005/06 to investigate the impact of intensive agriculture on C sequestration and soil properties on a regional scale. The results showed that, unexpectedly, intensive agriculture has resulted in improved soil organic carbon (SOC) status. As a weighted average for the whole state, SOC increased from 2.9 g kg⁻¹ in 1981/82 to 4.0 g kg⁻¹ in 2005/06, an increase of 38%. Increased productivity of rice and wheat resulted in enhanced C sequestration in the plough layer by 0.8 tC ha⁻¹ per ton of increased grain production. Soil pH declined by 0.8 pH units from 8.5 in 1981/82 to 7.7 in 2005/06. This pH decline has positive implications for availability of phosphorus and micronutrients such as Zn, Fe and Mn. Changes in plant-available P in soil were related to the amount of fertilizer P applied. The status of available P in soils increased from 19.9 kg ha⁻¹ in 1981/82 to 29.2 kg P ha⁻¹ during 2005/06. The status of plant-available K in soil remained almost unaltered and averaged 106 and 123 mg kg⁻¹ soil in 1981/82 and 2005/06, respectively. The analysis showed that intensive cultivation of a rice-wheat system unexpectedly resulted in improved C sequestration, a favorable pH environment and amelioration of the soil salinity.

中文翻译：

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集约化农业中碳固存和土壤特性的25年记录

作为地球上的主要碳库，土壤有机碳可以充当大气CO ₂的汇或来源。，一种温室气体。土壤有机碳还影响肥力，进而影响农作物产量。但是，缺乏关于种植技术对土壤碳长期行为影响的知识。多项研究表明，连续种植会在最初几年迅速降低土壤有机碳储量，然后降低速度，在30至50年后达到新的平衡。例如，在温带土壤上进行35年密集玉米种植的研究表明，土壤有机碳减少了50％。我们的研究位于印度北部的旁遮普邦。它是该国耕种最密集的地区，种植密度为190％，主要是稻麦系统。由于对养分的需求很高，并且需要持续种植，据推测该种植系统会对土壤有机碳和其他土壤特性产生不利影响。但是，假定没有区域范围内的任何实时数据分析。因此，我们评估了1981/82年至2005/06年的25年的土壤数据，以研究集约化农业对区域范围内固碳和土壤特性的影响。结果表明，集约农业出乎意料地改善了土壤有机碳（SOC）的状况。作为整个州的加权平均值，SOC从2.9克/千克增加到 结果表明，集约农业出乎意料地改善了土壤有机碳（SOC）的状况。作为整个州的加权平均值，SOC从2.9克/千克增加到 结果表明，集约农业出乎意料地改善了土壤有机碳（SOC）的状况。作为整个州的加权平均值，SOC从2.9克/千克增加到^-1在1981年至1982年至4.0g千克^-1 2005/06，增加了38％。稻米和小麦的生产力提高导致每吨谷物产量增加，耕层中的碳固存增加0.8 tC ha ^-1。土壤pH从1981/82的8.5下降了0.8个pH单位，到2005/06的7.7。pH值的下降对磷和微量营养元素（如Zn，Fe和Mn）的有效性具有积极影响。土壤中植物有效磷的变化与施磷量有关。土壤中有效磷的状况从1981/82年的19.9 kg ha ^-1增加到2005/06年的29.2 kg P ha ^-1。土壤中植物有效钾的含量几乎保持不变，平均为106和123 mg kg ^-1土壤分别在1981/82年和2005/06年。分析表明，水稻-小麦系统的集约耕作出乎意料地导致了改善的碳固存，良好的pH环境和土壤盐分的改善。