| 其他摘要 | 农业用水短缺、利用效率不高是我国农业生产和发展所面临的重要问题之一。水资源缺乏不仅直接影响作物产量，还会引起土壤盐碱化、石漠化加剧等环境问题，进而破坏农业生态，降低土地生产力。因此，寻求一种有效的科技手段来改善土壤保水能力、增强土壤水分利用率、提高农业生产力成为了解决这一问题的关键所在。生物炭技术是将作物秸秆、林业废弃物、动物粪便等生物质材料或其衍生物进行高温炭化，然后以适当的方式和标准将其施用于土壤以获得相应经济、生态和环境收益的科学技术和理念。生物炭因具有稳定的化学性质，较高的比表面积和丰富的孔隙结构，使其具备改善土壤性质、增强土壤保水能力、提高土地生产力的较大潜力，故被广泛的关注和研究。但也有研究表明，由于可能存在的疏水特性，生物炭未必会提高土壤的持水能力。为认识生物炭对干旱地区土壤持水能力和土地生产力的影响，本文选择了新疆喀什和贵州开阳两处不同成因的干旱地区作为研究区域，测量了不同生物炭处理土壤的水分特征曲线和饱和导水率等水力参数的变化，并结合生物炭的大田试验，系统的研究了生物炭的施用对两地土壤持水能力和土地生产力的影响，为生物炭在不同地区土壤改良的应用提供了理论支持和方法参考。同时，为了实现生物炭农业产能最大化，本研究还在大田试验的基础上，引用ANSWER模型模拟预测了该条件下两地的作物产量，拟通过模拟结果与实测数据的对比分析，探索出一种经济高效的方法来评价生物炭技术提高农业产能的潜力，推动生物炭技术的应用与发展。研究的主要结论如下：（1）生物炭对新疆灌淤土和贵州黄壤的水分特征曲线有相似的影响规律：在土壤低吸力段（<100kPa），土壤的含水量与生物炭添加量呈正相关；在高吸力段（>100kPa），土壤含水量与生物炭添加量呈负相关。土壤田间持水量随生物炭施用量增加而提高，凋萎含水量随生物炭施用量增加而降低。van Genuchten模型拟合两种土壤的水分特征曲线得到的土壤水力参数符合实际规律，模拟结果与实测值误差小，为模拟生物炭处理土壤的水分特征曲线提供了科学的参考。此外，灌淤土的饱和导水率高于黄壤，增加生物炭施用量均能提高两种土壤的饱和导水率。但在相同生物炭配比下，生物炭对黄壤的饱和导水率影响更大。总体来讲，对于灌淤土和黄壤，生物炭均能起到提高土壤持水能力的作用，同时增强了土壤水分的有效性，使得土壤中的水分更容易被植物利用。（2）生物炭能降低土壤容重，提高土壤田间持水量。添加5%和10%的生物炭，分别使灌淤土的容重降低了14%和32%，田间持水量提高了36%和45%；使黄壤的容重降低了15%和30%，田间持水量提高了9.4%和13.8%。生物炭还能降低土壤电导率，相同配比下，生物炭对新疆灌淤土的电导率影响较大，对贵州黄壤的电导率影响不显著。生物炭有效提高了黄壤中的养分含量。施入5%和10%的生物炭较对照组的NO3--N含量分别提高了73%和154%，NH4+-N含量提高了17%和42%，有效磷含量分别提高了159%和263%。生物炭还提高了黄壤中有机质含量，施入5%和10%的生物炭较对照分别提高了156%和334%。生物炭能提高新疆棉花、贵州玉米和油菜的产量。施入5%的生物炭，棉花产量较对照提高了26%；施入5%和10%的生物炭，玉米产量较对照提高了7.5%和31.7%，油菜产量较对照提高了12.6%和46.1%。生物炭作为土壤改良剂施用于农田，能提高干旱区土壤的生产力。该研究结果不仅可以直接指导新疆棉花、贵州玉米和油菜的生产，还可以为我国其他干旱地区的农业生产和农田管理提供借鉴。（3）ANSWER模型模拟结果显示，棉花、玉米和油菜的产量均与生物炭的施入量呈正相关。并且生物炭对作物产量的影响，会受到灌溉量及土壤电导率的制约：①相同灌溉量下，土壤的电导率越高，生物炭的增产效果越明显；②随着灌溉量增加，生物炭的增产效益逐渐增大，当灌溉量增加到某一值时，增产曲线出现“拐点”，继续增长灌溉量，生物炭增产量减小；③生物炭的增产效应因作物种类不同而存在差异。ANSWER模型模拟结果反映了生物炭能通过影响土壤水分和含盐量从而提高作物产量。但对比模拟结果与田间实测值发现，模型中，添加5%生物炭对新疆喀什棉花的最大增产量为15%，添加5%和10%的生物炭对贵州玉米的最大增产量分别为6.0%和7.2%，对油菜的最大增产量分别为3.3%和4.0%，这一结果远小于田间试验的统计值。原因可能是因为ANSWER模型设计时仅涉及了土壤水分和含盐量对作物产量的影响，而未将土壤的其他化学性质、微生物等影响因素考虑在内，所以未能完全反映出生物炭对农作的增产效应。使用ANSWER模型模拟生物炭对作物产量的影响，还需对模型进行进一步的改善，这也为开发适用于生物炭技术的农田生态模型提供了一定的理论指导。; The shortage and inefficiency of agricultural water has always been a key issue to agricultural production and development. The lack of water resources not only directly affects the crop yield, but also causes the secondary environmental problems such as soil salinization and rocky desertification, and thus undermines the agricultural ecology and reduces the land productivity. Therefore, to find an effective and green technology to improve soil water holding capacity, enhance soil water use efficiency and improve agricultural productivity has become the key to solve the above-mentioned problems.Simply put, biochar is the carbon-rich product obtained when biomass, such as wood, manure or leaves is heated in a closed container with little or no available air, and then it is applied to farmland to obtain corresponding economic, ecological and environmental benefits. Because of its stable chemical properties, high specific surface area and abundant pore structure, biochar has the function of improving the soil properties, enhancing the soil water retention capacity and increasing the land productivity, which makes biochar a widely concerned and studied subject. However, some studies have shown that biochar may not improve soil water holding capacity due to its possibly hydrophobic properties. In order to determine the effect of biochar on soil water holding capacity and land productivity in arid area, this study selected Kashi, Xinjiang and Kaiyang, Guizhou as research area. By measuring the soil hydraulic parameters, such as the soil water retention curve and the saturated hydraulic conductivity, and the crop yield with different biochar addition in tested plots, we systematically studied the effect of biochar application on the water holding capacity and productivity of the two soils, and provided theoretical support and reference for the application of biochar on soil improvement in different areas. Meanwhile, this study also used the ANSWER model to simulate the crop yield in the biochar-amended soil and compared it with the existing field observation data, in order to explore a cost-effective method to evaluate the potential of biochar technology on improving agricultural productivity. The main conclusions are listed as follows:(1) The biochar has a similar effect on the water retention curve of Xinjiang anthropogenic-alluvial soil and Guizhou yellow soil. In the soil low suction section (<100kPa), the soil water content is positively correlated with the addition of biochar while in the high suction section (> 100kPa), soil water content and biochar addition are negatively correlated. The soil water holding capacity increases while the wilting water content drops with the increase of biochar application rate. The soil hydraulic properties obtained by the van Genuchten model are in good agreement with the actual law, which provides a scientific reference for simulating the soil water retention curve of biochar treatment. In addition, the anthropogenic-alluvial soil has higher saturated hydraulic conductivity than yellow soil. Biochar addition can improve the saturated hydraulic conductivity for both soil and greater effect could be seen on yellow soil. In general, biochar could improve the water holding capacity while enhancing the water availability for both anthropogenic-alluvial soil and yellow soil, which facilitate the utilization of soil water by plants.(2) Biochar could reduce the soil bulk density and increase the soil field capacity. 5% and 10% biochar addition could reduce bulk density of anthropogenic-alluvial soil by 14% and 32%, and increase water holding capacity by 36% and 45%, respectively. The same amount of biochar could reduce bulk density of yellow soil by 15% and 30%, and increase water holding capacity by 9.4% and 13.8%, respectively. Biochar could also reduce the electronic conductivity for both soil and has greater impact on anthropogenic-alluvial soil in Xinjiang.Biochar effectively improves the nutrient content in yellow soil. With 5% and 10% addition of biochar, the content of NO3--N increases by 73% and 154%, the content of NH4+-N increases by 17% and 42%, and the available phosphorus content increases by 159% and 263%, respectively. Biochar also increases the content of organic matter in yellow soil. 5% and 10% biochar addition results in 156% and 334% increase in organic matter content, respectively.Biochar also contributes to the improvement of crop yield in Xinjiang and Guizhou. 5% biochar addition could increase cotton yield by 26%. 5% and 10% biochar could increase maize yield by 7.5% and 31.7%, and rapeseed yield by 12.6% and 46.1% respectively. The study reveals that biochar is a kind of soil conditioner with great potential to keep water and nutrients, and improve land productivity in arid area.(3) The simulation results of ANSWER model show that increasing the application of biochar can raise the yield of cotton, maize and rapeseed. Besides, biochar could couple with the irrigation quantity and the electronic conductivity of irrigation water to influence the crops growth:①With the same amount of irrigation, the higher the electronic conductivity of soil is, the higher yield boosting effect of biochar is. ②With the increase in the amount of irrigation, the yield boosting effect of biochar gradually increases. When the amount of irrigation is increased to a certain value, an "inflection point" in the yield curve appears. After that, more irrigation will lead to a decrease with the yield increase of biochar. ③The yield boosting effect of biochar differs due to different crop species.The simulation results of ANSWER model reflect the law that biochar can improve crop yield. However, compared with the results of field experiment, it can be seen that 5% biochar addition could improve 15% of cotton yield in Kashi while 5% and 10% biochar addition could increase 6.0% and 7.2% of maize yield, and 3.3% and 4.0% of rapeseed yield in Kaiyang, respectively. This result is much smaller than the field experiment results. A possible reason for this discrepancy is that ANSWER model only takes the effects of soil water and salt content on crop yields into account, but neglect the other chemical and microbial factors which may affects the crop yields as well. Therefore, the potential of biochar on improving agricultural productivity could not be fully predicted. In general, to use the ANSWER model to predict the effect of biochar on crop yield, some improvement is needed. It also provides some theoretical guidance for the development of farmland ecological model which is applicable for biochar technology. |
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