紫色土施用PAM后的土壤微结构变化和减缓季节性干旱功能的研究

The nutrients and fertilizer of purple soil are enrichment in the Three Gorges region. However, the effects of seasonal drought severely handicap the regional agricultural production. the soil structure directly influence soil infiltration, evaporation and ability of water stock, further influence the storage capacity and the ability of sustained anti-drought of soil reservoir storage. Based on the characters of self-structure and drought of the purple soil, using the organic macromolecular (PAM) to improve the structure of purple soil in order to enhance the ability of water stocks and anti-drought. And use the high techniques of microscopy and CT scanning and imaging to analyze the effects of soil micro structure of the purple soil. While research on the characters of water holding capacity of purple soil with different PAM concentration by measuring the the curves of soil water retention and the evaporation experiment of temperature and humidity control to research the water holding characters of purple soil with different PAM concentration. And by the Artificial Simulation of Rainfall to analyze the soil infiltration and the redistribution of soil moisture in the soil profile. While passing through the cultivation experiment and the drought simulation to research the quantity relationship between the PAM concentration and the ability of anti-drought of purple soil. The objects of this research was from the scope of soil micro-structure to clarify the mechanism of soil water stocks and anti-drought ability of purple soil under the condition of PAM. Meanwhile point out the appropriate concentration of PAM with different frequency of drought stress. Aimed to offer the theories and data supporting to mitigate the seasonal drought and enhance the production and yields of agriculture by using the organic macromolecular (PAM) in the Three Gorges region.

紫色土矿质养分储量丰富，在三峡库区分布广泛，但季节性干旱严重阻碍库区农业生产?土壤结构直接影响土壤入渗?蒸发和储水性能,从而影响"土壤水库"的"库容"及其" 持续供水抗旱能力"?针对紫色土自身结构和易旱特征,拟采用有机高分子PAM对紫色土进行结构改良,增强其蓄水抗旱能力?本研究拟通过显微手段和CT扫描成像等测试,分析PAM对紫色土尤其是碎屑土微结构的影响；通过土壤水分特征曲线、控温控湿的蒸发试验，研究不同浓度PAM的紫色土持水特征；利用人工模拟降雨试验,分析PAM对土壤入渗及水分在土壤剖面的再分布影响;开展小区栽培试验,人工模拟持续干旱条件下,研究PAM用量与紫色土抗旱性能之间的量化关系?本研究旨在从微结构角度阐明PAM对紫色土蓄水抗旱性能的作用机理，指出应对不同程度干旱的PAM最佳施用量，为该区应用PAM缓解季节性干旱，提高农业生产能力提供理论依据和数据支持

西南地区油菜种植以冬油菜为主，其种植面积约占全国油菜总播种面积的90%。西南地区以紫色土分布广泛，其透水性能力强，储水能力弱，易受干旱。紫色土地区冬油菜生育期长达200天以上，水分在其生长过程中十分重要。季节性与工程性缺水严重制约了西南地区油菜的生产。 .聚丙烯酰胺（PAM）是利用强吸水性树脂或淀粉等制成的高分子聚合物，能迅速吸收和保持比自身质量高几十倍、几百倍的水分,在干旱状态缓慢释放水分供作物吸收利用。其能够通过改变土壤结构提高降雨入渗率、减少蒸发及提高土壤持水能力，影响土壤蓄水抗旱性能，从而显著提高降水利用率及作物水分利用效率（WUE）。但是西南紫色土地区使用PAM进行抗旱研究较少，用量和效果不明，需要相关数据参考和技术支持。.针对上述难题，本项目开展PAM对紫色土微结构作用机理及应对季节性干旱量化研究。.研究发现聚丙烯酰胺（PAM）能够显著提高紫色土中>0.5mm水稳性团聚体含量，且随着PAM用量越大效果越显著。对0.25～0.50mm团粒来说，紫色土中施入量低于0.15%时，可以有效促进团粒结构的形成，超过临界值0.15%时，团聚体含量反而会降低，进而抑制紫色土的通气透水性。.PAM的施入影响土壤水分的入渗、蒸发及持水特性。 PAM的施入能够降低水分向土壤深层运移的速度，减少土壤深层渗漏。PAM能够抑制土壤蒸发，浓度越大，抑制蒸发的能力越强。施加PAM能够显著增加紫色土的最大持水量，在土壤低吸力段(0～100kpa)表现尤为显著。.PAM对干旱胁迫具有一定的缓解作用，可促进油菜生长及产量形成。PAM在油菜苗期和薹花期施用效果较其它时期的增产效应更为显著。苗期施用时，在不旱、小旱、中旱、重旱和特旱，推荐处理AH1P5、AH2P4、AH3P3、AH4P4和AH5P4较对照分别增产5.98%、8.33%、5.67%、9.30%和3.23%。薹花期处理时，推荐处理BH1P2、BH2P1、BH3P4、BH4P3和BH5P3较对照分别增产1.78%、0.00%、7.39%、13.64%和16.55%。.项目通过大田、盆栽试验，研究施用聚丙烯酰胺PAM抗旱、增产效应及施用量，通过室内模拟试验、大田及盆栽取土相结合的方式分析PAM改土效应，并从紫色土的入渗、蒸发、蓄水、持水性能以及土壤水稳性团聚体变化等角度阐明聚丙烯酰胺（PAM）对土壤水分及土壤结构的作用机制。