论文内容
研究背景：
在全球范围内，在气候变化和作物生产集约化的影响下，具有低恢复力的农业土壤和脆弱土壤面临着退化和生态系统衰竭的风险。主要的土壤制约因素包括有机碳储量低、养分短缺和生态系统服务的变化，主要发生在非洲、中东、南美和亚洲国家。土壤养分耗竭和土壤有机碳减少在中国大陆、中欧和南欧、中东非洲、中南美洲以及美国中西部地区也很普遍。为了解决这个问题，生物炭通常是一种细颗粒有机碳混合物，正在作为土壤改良剂进行测试，以提高土壤肥力。研究人员已经证明，这些碳可以在土壤中储存数百年，有助于提高土壤肥力，并为作物生产提供许多其他好处。生物炭的支持者普遍认为，应该扩大生物炭的使用规模，以帮助减少或稳定大气中的二氧化碳浓度。
众所周知，稳定但多孔的生物炭是一种土壤调节剂，可以改善土壤的团聚性、孔隙度和缓冲能力，从而有助于提高土壤肥力和微生物活性。小池的水可提取碳可以增加微生物代谢利用的碳基质，从而潜在地增加微生物呼吸。此外，生物炭的可水提取池已被证明含有植物生长促进剂，因此可以用作液体肥料。然而，洗涤去除水溶性成分可能会改变生物炭的化学成分，从而潜在地影响作物的养分利用率。因此，了解可提取池是否会影响生物炭在改善土壤肥力和土壤气体排放以及植物性能方面的作用，可能是在农业增值生物炭产品商业化之前的优先研究需要。
研究内容：
水稻(Oryza sativa L.)是包括中国在内的大多数亚洲国家重要的主要粮食作物。使用农作物秸秆中的生物炭已被证明可以提高水稻产量和氮素利用效率，同时减少温室气体排放。然而，也有甲烷排放量在短期内增加的情况。生物炭对作物生长和产量、土壤性质、金属固定化和温室气体减排的影响在亚洲国家得到了广泛的研究。目前尚不清楚可提取池是否操纵生物炭在作物生长、土壤肥力和温室气体排放方面的功能，从而限制了生物炭在亚洲国家水稻农业中使用的扩大。
本文提出以下假设:首先，去除部分可提取OC组分和水溶性营养物质后，生物炭的提取会改变生物炭补充有机/无机营养物质的作用，从而促进作物生长;其次，提取会影响生物炭提高土壤有机碳储量、减少土壤呼吸和稻田甲烷等温室气体排放的作用;第三，由于水稻是在季节性洪水条件下栽培的，提取引起的上述效应的变化可能会持续很短时间，而且这种影响会因含有不同大小和水可提取部分组成的不同生物炭而有所不同。
在本研究中，我们通过对稻田在整个稻麦轮作周期中的比较研究，旨在探讨水可提取的生物炭池是否会影响土壤的物理化学性质、作物性状和产量、土壤呼吸和温室气体排放，以及这些变化是否因生物炭类型和稻麦轮作系统的时间跨度而不同。这一信息对于开发生物炭产品以提高作物生产力和稳定水稻农业气候具有重要价值。
Table 1. Basic properties and composition of the studied biochar with and without extraction. TOC, total organic carbon; DOC, dissolved organic carbon; TN, total nitrogen; MBB, bulk maize biochar; MBE, extracted maize biochar; WBB, bulk wheat biochar; WBE,extracted wheat biochar.
Table 2. Relative changes over control in soil physical and chemical properties under amendment of biochar with and without extraction. MBB, bulk maize biochar; MBE, extracted maize biochar; WBB, bulk wheat biochar; WBE, extracted wheat biochar. Lowcase letters indicate difference between bulk and extracted biochar from a single feedstock, and capital letters indicate difference between maize and wheat biochar for a single extraction treatment, respectively.
Table 3. Relative change over control in plant traits and grain yield under amendment of biochar with and without extraction. TGW , thousand grain weight; LAI, leaf area index; MBB, bulk maize biochar; MBE, extracted maize biochar; WBB, bulk wheat biochar; WBE, extracted wheat biochar. Lowcase letters indicate difference between bulk and extracted biochar from a single feedstock, and capital letters indicate difference between maize and wheat biochar for a single extraction treatment, respectively.
Table 4. Relative change over control in root morphology under amendment of biochar with and without extraction. MBB, bulk maize biochar; MBE, extracted maize biochar; WBB, bulk wheat biochar; WBE, extracted wheat biochar. Lowcase letters indicate difference between bulk and extracted biochar from a single feedstock, and capital letters indicate difference between maize and wheat biochar for a single extraction treatment, respectively.
Table 5. Tot a l C O2, CH4, and N2O emissions, and total global warming potential (non−CO2 GWP; kg·ha−1) and greenhouse gas intensity GHGI (kg·t−1 of rice wheat produced) from the rice-wheat growing season after under amendment of biochar with and without extraction. Non-CO2 GWP , global warming potential calculated of non-CO2 gas emissions; GHGI, greenhouse gas intensity, calculated with non-CO2 GWP on the basis of yield; MBB, bulk maize biochar; MBE, extracted maize biochar; WBB, bulk wheat biochar; WBE, extracted wheat biochar. Lowcase letters indicate difference between bulk and extracted biochar from a single feedstock, and capital letters indicate difference between maize and wheat biochar for a single extraction treatment, respectively.
Table 6. Annual global warming potential ((non-CO2 GWP; t C·ha−1·year−1), yield (t·ha−1) and greenhouse gas intensity (GHGI; t C·t−1 grain yield year−1) of the rice-winter wheat cropping rotation system under amendment of biochar with and without extraction. Non-CO2 GWP , Global warming potential, calculated of non-CO2 gas emissions; GHGI, greenhouse gas intensity, calculated with non-CO2 GWP on the basis of yield; MBB, bulk maize biochar; MBE, extracted maize biochar; WBB, bulk wheat biochar; WBE, extracted wheat biochar. Lowcase letters indicate difference between bulk and extracted biochar from a single feedstock, and capital letters indicate difference between maize and wheat biochar for a single extraction treatment, respectively.
Figure 1. Correlation of increase in soil available phosphorus to increase in leaf area index (LAI) (a) and to increase in thousand grains weight (TGW) (b) of rice (blue circle) and wheat (black circle) with biochar amendment.
研究结论：
在本研究中，研究了提取液对水稻和小麦种植体系中生物炭性能的影响。玉米和小麦分别在20 t·ha - 1和20 t·ha - 1条件下进行单次改良，土壤呼吸没有显著变化，但土壤质量和作物性能普遍提高。与提取的生物炭相比，未提取的生物炭改良剂提高了土壤肥力和作物生产力，同时没有温室气体排放。这一变化支持了未提取生物炭中可溶解的OC组分和丰富的有效磷的影响。因此，在解决生物炭在农业中的作用时，从作物残渣中热解的可提取生物炭池可以被认为是土壤肥力和作物生产力的关键参与者。未来的研究应重点关注生物炭改性土壤中微生物群落结构变化与碳循环之间的相互作用，以实现生物炭在农业中的有价值利用。
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