摘要:针对华北平原缺水地区农田生产效益偏低和地下水严重超采导致的生态环境问题，以建立节水、高产、固碳的华北平原缺水区保护性耕作集成技术为目标，在国家科技支撑计划长期支持下，建立了华北平原历时最长的保护性耕作长期定位试验平台（2001年-），开展了小麦/玉米两熟制保护性耕作理论和关键技术研究，集成了农机农艺结合的高产节水型保护性耕作技术体系，并在河北省进行广泛示范推广。主要结果：1）华北平原冬小麦/夏玉米一年两熟区保护性耕作具有固碳、减排、节水、提高土壤质量等生态效应。长期保护性耕作具有土壤养分分层表聚现象：0~5 cm土层的土壤C、N、P、K、有机质含量高于5~10 cm土层，旋耕（RT）和免耕（NT1：秸秆直立免耕；NT2：秸秆粉碎免耕；NT3：整秸秆覆盖免耕）处理土壤有机碳（SOC）的层化比率为1.74~2.04，显著高于翻耕处理（CK和CT）的1.37~1.45。保护性耕作的固碳效应与机制：保护性耕作实施9年后不同耕作方式年固碳量（0~30 cm）NT2处理为840 kg·hm-2·a-1、RT处理为780 kg·hm-2·a-1、CT处理为600 kg·hm-2·a-1，14年后土壤有机碳（0~30 cm）发生了变化，NT2处理为540 kg·hm-2·a-1、RT处理为720 kg·hm-2·a-1、CT处理为710 kg·hm-2·a-1；长期免耕减少了土壤的扰动而降低了土壤碳的矿化率，土壤碳的累积主要固定在土壤大团聚体的颗粒有机碳中，固定态碳首先进入活性易分解有机碳库，然后缓慢转入稳定碳库。保护性耕作的减排效应：不同耕作系统全球增温潜力的计算结果表明，免耕是大气增温的碳汇，而其他耕作系统为碳源。NT处理每年农田生态系统净截留碳947~1 070 kg（C）·hm-2；CK、CT和RT每年向大气分别排放等当量碳3 364 kg（C）·hm-2、989 kg（C）·hm-2和343 kg（C）·hm-2。保护性耕作的土壤微生物多样性机制：保护性耕作显著提高了土壤中真菌、细菌、氨氧化古菌和亚硝酸还原酶（nirK）基因的反硝化微生物的多样性，但对氨氧化细菌与含nirS基因的反硝化微生物的多样性影响不大。保护性耕作节水保墒的土壤结构与水力学机制：常规耕作对土壤有压实的作用，而保护性耕作改善了土壤结构，有效提高了储水孔隙、导水率、田间持水量和有效水含量，秸秆覆盖又能有效减少土壤蒸发，具有开源与节流双重节水机制。2）建立了趋零蒸发的麦田玉米整秸覆盖全免耕种植模式。在小麦/玉米一年两熟种植区，首次提出了玉米整秸秆覆盖小麦全免耕播种的种植模式，实现了小麦玉米全程全量秸秆机械化覆盖，形成土壤无效蒸发趋于零的保护性耕作体系与方法；研制了实现趋零蒸发的4JS-2型梳压机和2BMF-6型小麦全免耕播种机组，比目前推广的2BMFS-6/12小麦免耕播种机减少作业动力45.2%，降低作业费用33.3%。3）建立了3年一深松（翻）的少免耕-深松轮耕模式，集成了节水高产保护性耕作技术体系。制定了华北平原冬小麦/夏玉米一年两熟区保护性耕作技术体系等河北省地方标准，与农业、农机部门联合示范，推动了河北省保护性耕作技术的推广和应用。成果在河北平原冬小麦/夏玉米一年两熟区进行了示范推广，社会效益和生态效益显著，2013年获河北省科技进步一等奖。
关键词:华北平原/
水资源短缺/
冬小麦/夏玉米一年两作/
保护性耕作/
秸秆覆盖/
免耕
Abstract:The intensive exploitation of groundwater for farmland irrigation has led to the decline of groundwater level and the development of eco-environmental problems in the North China Plain (NCP). In order to establish water saving, high yield, carbon sequestration and conservation tillage integration technology system in NCP, a long-term conservation tillage experimental platform was established from Oct. 2001 in the Luancheng Agro-Ecosystem Experiment Station, Chinese Academy of Sciences, which included six treatments, CK (deep plowing and wheat row seeding without maize straw return), CT (deep plowing and wheat row seeding with smashed maize straw incorporation), TR (rotary tillage and wheat row seeding with smashed maize straw incorporation), NT1 (non-tillage and wheat furrow seeding with maize straw incorporation), NT2 (non-tillage and wheat furrow seeding with smashed maize straw incorporation) and NT3 (non-tillage and wheat row seeding with maize straw mulching). Studies on conservation tillage theory and key technologies of winter wheat-summer maize double cropping system integrated with agricultural machinery were conducted at the platform. The agronomic water-saving conservation tillage techniques of high yield systems were widely demonstrated in NCP. The results showed that 1) conservation tillage had obvious effects on carbon sequestration, emission reduction, water saving and soil quality improvement. Long-term conservation tillage induced soil nutrient accumulation at the soil surface. Also C, N, P, K and organic matter contents were higher in the 0-5 cm soil layer than in the 5-10 cm soil layer. Soil organic carbon (SOC) stratification ratio under RT and NT1, NT2 and NT3 treatments was in the range of 1.74-2.04, which was significantly higher than that of CK and CT (1.37-1.45). After 9 years of conservation tillage, soil carbon sequestrations (0-30 cm) were 840 kg·hm-2·a-1, 780 kg·hm-2·a-1 and 600 kg·hm-2·a-1 under NT2, RT and CT treatments, respectively. Then after 14 years of conservation tillage, soil carbon sequestrations were respectively 540 kg·hm-2·a-1, 720 kg·hm-2·a-1 and 710 kg·hm-2·a-1. Long-term non-tillage reduced soil disturbance and consequently decreased the mineralization rate of soil carbon. Soil carbon was mainly fixed in organic carbon particles of soil aggregates. The fixed carbon first changed into readily decomposable organic carbon and then slowly turned into stable carbon. Calculations of global warming potential under different tillage systems showed that farmland ecosystems under non-tillage with straw return served as carbon sink, with annual carbon retention of 947-1 070 kg(C)·hm-2 after subtracting directly or indirectly carbon emitted equivalent. Other treatments were carbon resource, with CK, CT and RT treatments annually discharging equivalent carbon of 3 364 kg(C)·hm-2, 989 kg(C)·hm-2 and 343 kg(C)·hm-2 respectively into the atmosphere. The mechanism of soil microbial diversity under conservation tillage was as follows:conservation tillage significantly improved the diversity indexes of soil fungi communities, bacteria communities, ammonia-oxidizing bacteria communities and denitrifying micro-organism communities with nirK gene. However, it had little effect on the diversity index of ammonia-oxidized bacteria communities and denitrifying micro-organisms communities with nirS gene. Conservation tillage showed significant water-saving effect, which resulted from improvements in soil structure, water-reservoir porosity and saturated hydraulic conductivity. Straw mulching also effectively reduced soil evaporation. 2) Non-tillage plus straw mulching with minimum soil evaporation model was established in winter-wheat/summer-maize double cropping system area. The unit of 4JS-2 straw combing press machine and 2BMF-6 non-tillage sowing machine with zero evaporation were developed, which reduced the operating rate by 45.2% and operation cost by 33.3%, compared with 2BMF-6/12 non-tillage sowing machine currently promoted. 3) A new soil rotation tillage model of deep plowing and deep sub-soiling every 3 years in non-tillage soil was established and integrated with water-saving, high-yielding and protective tillage technology system. A series of technical regulations of Hebei local standards in terms of conservation tillage of winter wheat/summer maize double cropping system were suggested. Cooperated with the Agricultural Bureau and Agricultural Machinery Bureau of Hebei Province, we demonstrated and promoted conservation tillage technologies in Hebei Province with remarkable social and ecological benefits. The main results won the first prize of Hebei Science and Technology Progress Award in 2013.
Key words:North China Plain/
Water resources shortage/
Winter wheat/summer maize double cropping/
Conservation tillage/
Straw mulching/
Non-tillage
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