Abstract:

Planting pattern is the key factor affecting the carbon sink and economic benefits of farmland ecosystem. To optimize reginal cropping systems, develop low-carbon green agriculture, and ensure sustainable agriculture development, it is of great importance to clarify the carbon sink characteristics and economic benefits under different planting patterns. In this study, a field experiment was conducted from 2020 to 2021 in southern Anhui, China, including four planting patterns: single-cropping rice, tobacco-rice rotation, rice-wheat rotation, and ratoon rice. Life cycle assessment was used to evaluate the net carbon sink and economic benefits. In addition, the carbon footprint compositions and influencing factors of different cropping patterns and crops were investigated. The results showed that, (1) the economic net income followed the order of tobacco-rice rotation>ratoon rice>rice-wheat rotation> single-cropping rice. The high output value of tobacco contributed to the high income of tobacco-rice rotation. The highest rice yield was found in the ratoon rice cultivation, in which the total grain yield of the first and regeneration seasons was 12921.5 kg∙hm^-2. (2) The net carbon sink followed the order of rice-wheat rotation>ratoon rice>single-cropping rice>tobacco-rice rotation. Compared with the rice-wheat rotation, N₂O emission and total carbon emission were significantly decreased by 37.2% and 9.2%, respectively, in ratoon rice. The CH₄ and N₂O emission accounted for 54.5% and 18.0% of carbon footprint in ratoon rice. (3) CH₄ emission was reduced through controlling farmland water, increasing fertilizer use efficiency, and leaving piles appropriately for ratoon rice, which is vital to control carbon emissions. The carbon footprint of flue-cured tobacco (Nicotiana tabacum L.) was mainly consisted of N₂O, chemical fertilizer, and agricultural film, and each of them accounted for more than 20% of the total emissions. In addition, the proportion of labor force (accounted for 11.7%) and fuel oil (accounted for 12.7%) in flue-cured tobacco planting were much higher than those in rice and wheat. (4) The tobacco-rice rotation obtained higher economic benefits and the high harvest of both tobacco leaves and grain yield. However, the carbon sink was negative in tobacco-rice rotation. It is necessary to study how to mechanization production and energy saving and consumption reduction of tobacco leaf baking. The ratoon rice obtained high grain yield in rice, and was low in input cost and carbon emissions, consistent with the national carbon peak and neutrality goals. In conclusion, this study quantitatively evaluated the carbon sink and economic benefits of different planting patterns, and provided a technical model and theoretical basis for energy saving, emission reduction and low-carbon green agriculture.

Key words: carbon sink, carbon footprint, economic benefit, rotation, ratoon rice, fertilizer use efficiency

摘要：

种植模式是影响农田生态系统碳汇效应和经济效益的关键因素。探明不同种植模式碳汇特征及经济效益,对于优化当地种植模式、发展低碳绿色农业和保障农业可持续发展具有重要意义。该研究在安徽皖南地区2020—2021年设置单季稻、烟稻轮作、稻麦轮作、再生稻种植等4种种植模式,采用生命周期评价法评价了各种植模式的净碳汇效应和经济效益,系统地分析了各模式及作物的碳足迹构成、大小及其影响因素。结果表明,（1）各处理经济净收益的大小表现为烟稻>再生稻>稻麦>单季稻。烟叶高产值保障烟稻轮作的高经济效益;再生稻种植的水稻（Oryza sativa L.）产量为各种植模式中最高,其头季和再生季产量合计为12921.5 kg∙hm^-2。（2）各处理净碳汇大小表现为稻麦>再生稻>单季稻>烟稻。再生稻N₂O排放量和碳排放总量比稻麦轮作分别显著降低37.2%和9.2%,再生稻生态系统的CH₄和N₂O分别占碳足迹构成的54.5%和18.0%。（3）通过控制农田水分、提高肥料利用率以及对再生稻适当高留桩等方式降低CH₄排放是再生稻种植模式减少碳排放的关键。烤烟（Nicotiana tabacum L.）生态系统碳足迹构成中N₂O、肥料和农膜所占总排放的比例均超过了20%,并且其劳动力（11.7%）和燃油（12.7%）所占比例远大于水稻和小麦（Triticum aestivum L.）。（4）各种植模式中,烟稻轮作具有较高的经济效益,是保障烟粮双丰收的高效种植模式,但是呈现负碳汇效应,因此,应重点加强该模式机械化生产和烟叶烘烤节能减耗方面的研究。而再生稻水稻产量高,且成本投入和碳排放较低,符合中国倡导的“双碳”理念,应在该区和类似区域大力推广。综上,该研究定量评价了皖南地区4种种植模式的经济效益和碳汇效应,为该区和类似区域农业节能减排和绿色高效生产提供了技术模式及理论依据。

关键词: 碳汇, 碳足迹, 经济效益, 轮作, 再生稻, 肥料利用率