不同有机培肥模式下双季稻田碳汇效应与收益评估

本研究基于1981年开展的有机肥长期定位试验,研究了不同有机肥种类、用量和施用方式对稻田生态系统碳排放、系统碳固定与净碳汇的影响,并对各处理经济效益进行了比较,为实现农业低碳、高值、高效生产提供理论参考。本研究所选取的有机肥处理包括:不施肥对照(CK);早稻施用绿肥紫云英15 t·hm-2,晚稻不施有机肥(M1);早稻施用两倍绿肥紫云英30 t·hm-2,晚稻不施有机肥(M2);早稻施用绿肥紫云英15 t·hm-2和猪粪15 t·hm-2,晚稻不施有机肥(M3);早稻施用绿肥紫云英15 t·hm-2+晚稻施用猪粪15 t·hm-2和冬季稻草覆盖4 500 kg·hm-2(M4);长期施用化肥(NPK)等5个处理。每5年于晚稻收获后采集土样测定土壤有机碳含量,并测定每年的早晚季水稻产量与生物量,用于估算系统收益与碳收支(5年平均)。结果表明:与不施肥对照相比,各施肥处理水稻产量均显著提高(P0.05),增幅为30.88%~96.52%,且随着施肥年限的增加,M4处理增产作用最大。长期施用有机肥显著提高红壤稻田土壤固碳能力,且有机肥用量增加系统土壤固碳能力增强,M2、M3、M4处理土壤固碳量显著高于M1、NPK和CK处理;稻田植株固碳量也显著提高(P0.05),M4和M3最高,双季稻植株固碳量为6.76~8.83 t(C)·hm~(-2)·a~(-1)。长期施用有机肥下稻田系统净碳汇显著增加,与对照相比施肥处理(M1、M2、M3、M4、NPK)系统净碳汇增加1.43~3.93 t(C)·hm~(-2)·a~(-1),系统碳汇效应显著(P0.05)。同一处理不同施肥年限由生产活动所引起的碳排放量保持不变,系统净碳汇量差异主要表现在系统固碳量上,其变化趋势与水稻产量变化趋势基本一致。长期施用有机肥显著降低了化肥投入,稻田生态系统经济效益显著增加(P0.05),并以M4处理最高,达25 683.7$·hm~(-2)·a~(-1)。综上结果表明:长期施用有机肥显著提高双季稻田碳汇效应与经济效益(P0.05),绿肥紫云英与猪粪和秸秆配施稻田生态系统碳汇效益与经济效益较单施绿肥紫云英优势明显。

Evaluation of net carbon sink effects and costs/benefits of double-cropped rice fields under different organic fertilizer applications

For theoretical reference on low carbon,high profit and efficient agriculture,a long-term organic fertilizer experiment was conducted since 1981 to study the effects and economic benefits of different organic fertilizers,fertilizer doses and application methods on carbon emission and carbon sink in paddy field ecosystems.Treatments of non-fertilizer (control),Astragalus sinicus application in early rice (15 t·hm-2) (M1),double amount of A.sinicus application in early rice (30 t·hm-2) (M2),A.sinicus application (15 t·hm-2) plus pig manure application (15 t·hm-2) in early rice (M3),A.sinicus application in early rice (15 t·hm-2) plus pig manure application in late rice (15 t·hm-2) with straw mulching (4 500 kg·hm-2) in winter (M4),and NPK-chemical fertilizer in both early and late rice (NPK) were set up in the experiment.The soil samples were collected once every five years to measure organic carbon content after late rice harvest.Then rice biomass and yield were measured once every five years to evaluate the economic and carbon costs/benefits (5-year average) of the ecosystem after early rice and late rice harvest.Results showed that compared with the control,M1,M2,M3,M4 and NPK treatments significantly increased rice yield (P ＜ 0.05) in a range of 30.88％-96.52％.Increase in the years promoted rice yield most under M4 treatment.Long-term organic fertilizer application significantly increased SOC (soil organic carbon) content and soil carbon sink ability.Soil carbon sink of M2,M3 and M4 treatments were significantly higher than that of M1,NPK and CK treatments.Crop carbon sink under long-term organic fertilization treatments,which was 6.76-8.83 t(C)·hm-2·a-1 for double-cropped rice,was improved greatly.Compared with the control,net carbon sink under M1,M2,M3,M4 and NPK treatments increased significantly (P ＜ 0.05) with increment of 1.43-3.93 t(C)·hm-2·a-1.Carbon emission caused by production activity of each treatment remained unchanged for different years of fertilizer application.The differences in net carbon sink among treatments were mainly caused by variation in carbon sink of ecosystem,whose changing trend was similar to that of rice yield.Long-term organic fertilizer application significantly reduced chemical fertilizer input,but also significantly increased the economic benefits of double-cropped rice (P ＜ 0.05) to a maximum of 25 683.7 ￥·hm-2·a-1 (under M4 treatment).In conclusion,long-term organic fertilizer application significantly increased soil carbon sink and economic benefits.Besides,an integrated application of A.sinicus,pig manure and crop straw was obviously advantageous over sole application of A.sinicus in terms of increasing net carbon sink effects and economic benefits of paddy field ecosystem.