亚热带红壤—作物系统对季节性干旱的响应与调控

发布时间：2018-04-25 06:12

本文选题：干旱程度 + 根系分布　；参考：《华中农业大学》2017年博士论文

【摘要】：干旱是造成农业损失最严重的自然灾害之一,即使在湿润多雨的亚热带红壤区也频发季节性干旱。人们对季节性干旱的发生机制及其调控进行了深入研究和实践,然而,多是单一研究土壤或作物对季节性干旱响应,缺乏对土壤-作物系统对季节性干旱响应及缓解季节性干旱对策的系统探讨。本研究在充分认识亚热带红壤区季节性干旱时空特征的基础上,通过设置不同的作物种植时期、耕作措施,探索从时间和空间上减缓季节性干旱的途径。通过设置不同的施肥措施和秸秆覆盖等水保措施,分析土壤水分、作物生长及根系分布、土壤结构变化与季节性干旱的关系;从土壤、作物、施肥、田间管理多方面探讨对土壤-作物系统对季节性干旱的响应及季节性干旱的发生机制,得到如下主要结论:1.亚热带红壤区季节性干旱具有鲜明的时空特征。该区每年7~10月蒸发量大于降雨量,7~8月份蒸发量是降雨量的2.1倍,两者相差达265.8 mm,此时段最易发生干旱。林地、草地、裸地和农田四种土地利用方式中,农田7~8月份处于作物需水旺盛期,且根系多分布在0-30 cm土层。因此,每年7~8月农田0-30 cm土层易发生季节性干旱,且连续干旱超过12天不利于玉米生长,玉米生长前期遇旱减产风险大于后期遇旱。调整播期或促进根系下扎可能会减少季节性干旱危害。2.错开作物需水旺盛期或关键期与季节性干旱易发时段将有利于避旱。连续两年从5月中旬开始每15天播种一期玉米,每年播种五期。以正常播期6月中旬为参照,播期前移,玉米产量无显著变化;播期后移,玉米籽粒产量显著下降,减产达23.3%-52.6%;不同播期间茎叶干重差异不显著。不同播期玉米成熟期的根系90%以上均分布在0-30 cm土层,且无明显分层,根质量密度也无显著差异。播期前移可能会避开作物后期遇旱,但是改变播期并没有改善根系分布,也没有明显的避旱效果,播期后移作物反而减产。通过调整播期来减缓季节性干旱的效果不佳。3.相对于常规耕作,短期的深耕、免耕和压实均改善0-40 cm土层水分状况,提高田间持水量3%-5%和有效水含量22%-50%,且主要影响0-20 cm土层。与常规耕作相比,短期的深耕提高玉米籽粒产量25.8%,15 cm×40 cm土体玉米总根质量密度21%;短期的免耕和压实则分别减产16.7%和21.6%,分别降低玉米总根质量密度21%和50.5%;短期的深耕降低了0-10 cm表层玉米根系比例约10%,提高30-40 cm深度根系比例43%;短期的免耕和压实分别提高10.5%和6.2%,降低30-40 cm深度根系比例10.5%和54.5%。该区季节性干旱多发于0-30 cm土层,下层土壤含水量充足,仅提高表层土壤有效水对缓解季节性干旱作用有限;而短期的深耕促进根系下扎,吸收深层水分。针对时空特征鲜明的亚热带红壤季节性干旱,短期深耕缓解红壤干旱效果优于其它耕作措施。4.与长期免耕不施肥相比(CK),长期免耕施用化肥(NPK)、有机肥(鸡粪,OM)和化肥配合秸秆覆盖还田(NPK+S)显著提高土壤有机质含量和土壤氮磷钾含量;轻微提高(小于7%)0-40 cm土层田间持水量、有效含水量和吸水速率,且主要影响0-20 cm土层;NPK和OM分别降低地表非饱和导水率50.7%和67.7%,NPK+S则提高128.0%;NPK、OM和NPK+S分别降低表层土壤第一阶段蒸发失水速率23.7%、36.8%和50.0%,分别提高夏玉米叶面积37.6%、45.1%和46.9%和根质量密度47.7%、133.0%和103.4%。玉米各生育期根干重、根深度、深层根系分布比例从高到低依次是NPK+SOMNPKCK,且根系90%均分布在20 cm以上土层。与CK相比,三种施肥均提高玉米产量和水分利用率3-4倍,但是在发生持续干旱时,均增大玉米CWSI1.1-5.2倍。长期免耕施肥虽然促进了根系生长,但是大量根系分布在20 cm表层土壤,加之施肥显著增大叶面积,导致在发生持续干旱时,表层土壤失水快,作物CWSI高,加剧表层土壤干旱和作物水分胁迫。5.亚热带红壤区前期水蚀后期干旱。本研究通过在作物间设置无水保措施的作物对照(CK)和百喜草带(B)、秸秆覆盖(SM)、聚丙烯酰胺表施(PAM)、稻草覆盖+PAM(SPAM)、百喜草带+PAM(BPAM)5种水保措施,研究雨蚀地表结构变化对旱季性干旱的响应,结果表明,夏玉米生育期0-30 cm土壤储水量CK与B、PAM和BPAM措施差异在5%以内,与SM和SPAM措施差异为7.4%和8.2%。与5种水保措施不同,降雨后作物对照(CK)显著(p0.05)降低0-20 cm土壤的WSA0.25和0-30 mm土层孔隙率及平均孔径,显著(p0.01)增加结皮覆盖率。CK措施下土壤的WSA0.25是5种水保措施土壤WSA0.25含量的63%-88%,土壤孔隙率是5种水保措施的79%-97%。我们用干旱强度I和干旱程度D量化土壤失水速率和土壤干旱状况。相关分析表明,干旱强度I与结皮大小、结皮覆盖率显著正相关,与WSA0.25显著负相关。干旱程度D与结皮覆盖率显著正相关,与WSA0.25和0-15 mm孔隙率显著负相关,且土壤0-15 mm孔隙率对I和D的影响最大。CK措施连续干旱20天的平均I值和最后D值分别是5种水保措施1.2-2.5倍和1.1-1.4倍。水蚀改变地表结构,虽然对土壤储水量影响很小,但是显著提高了表层土壤失水速率和干旱程度。雨蚀改变地表结构提高地表失水速率是季节性干旱形成的原因之一。6.秸秆覆盖作为一种水保措施被广泛运用。本试验通过设置三个秸秆覆盖和施氮水平研究土壤-作物系统对土壤水热状况的响应,结果表明,秸秆覆盖轻微提高0-30 cm土壤含水量(小于5%),对土壤0-5 cm土层最大降温3.3℃-6℃,最大增温0.7℃-2.5℃,其降温效果大于增温效果。施氮提高玉米产量,施氮加覆盖增产更多。不施氮时高覆盖量玉米籽粒产量显著降低,不施氮时覆盖10000 kg/hm2玉米籽粒减产达21%。覆盖总体降低土壤NO3--N含量,提高NH4+-N含量;施氮总体提高土壤NO3--N含量,降低NH4+-N含量。覆盖和施氮总体分别提高玉米吸氮量超过16.9%和23.6%。覆盖时增施氮肥,氮素生产率提高。低氮水平下覆盖降低氮素生产率,高氮水平下覆盖提高氮素生产率。秸秆覆盖的作用受氮水平限制,覆盖和施氮相互弥补,既有利于改善田间水热状况,又有利于提高作物产量和水分利用率。7.在阐明亚热带红壤区季节性干旱时空特征的基础上,通过不同播期、耕作、施肥和水保措施,对季节性干旱发生的原因及对策进行了探讨,结果表明:亚热带红壤农田根系分布和地表失水是该区季节性干旱发生的两个原因。为促进根系下扎和减少地表失水,我们建议每年夏季作物尽量深松耕、早播种、早施肥,耕作深度最好超过30 cm,避免6月中旬以后播种,同时有机肥配合化肥作为基肥深施土壤;尽量保持全年秸秆覆盖。
[Abstract]:Drought is one of the most serious natural disasters causing agricultural losses. Even in the wet and rainy subtropical red soil region, seasonal droughts are frequently occurring. The mechanism and regulation of seasonal drought are deeply studied and implemented. However, most of the study is on the response of soil or crops to seasonal drought, and the lack of soil crop system. On the basis of fully understanding the temporal and spatial characteristics of seasonal drought in the red soil region of the subtropical region, this study, on the basis of fully understanding the temporal and spatial characteristics of seasonal drought in the red soil region of the subtropical region, explored the ways to slow the seasonal drought from time and space by setting up different crop planting periods and cultivation measures. The soil moisture, crop growth and root distribution, the relationship between soil structure change and seasonal drought were analyzed, and the response of soil crop, fertilizer and field management to the response of soil crop system to seasonal drought and the occurrence mechanism of seasonal drought were discussed. The main conclusions were as follows: 1. subtropical red. Seasonal drought in the soil region has distinct temporal and spatial characteristics. The annual evaporation of 7~10 months in this area is greater than rainfall, and the evaporation amount in 7~8 month is 2.1 times of the rainfall, the difference between the two is 265.8 mm, the most prone to drought in this period. In the four land use ways of woodland, grassland, bare land and farmland, the month of farmland 7~8 is in the peak period of crop water demand, and the root system has many roots. It is distributed in the 0-30 cm soil layer. Therefore, seasonal drought is easy to occur in the 0-30 cm soil layer of farmland in 7~8 month, and the continuous drought for more than 12 days is not conducive to the growth of maize. The risk of drought reduction in the early period of maize growth is greater than that in the later period of drought. The period and seasonal drought prone period will be beneficial to avoid drought. The first period of corn is sown every 15 days from mid May, and five periods are sowing every year. With the normal sowing date in mid June, the maize yield has no significant change, the yield of corn grain decreases and the yield is 23.3%-52.6%; the stem and leaf dry weight during the different sowing period The difference was not significant. Over 90% of the roots of Maize at different sowing stage were distributed in the 0-30 cm soil layer, and there was no obvious stratification and no significant difference in root mass density. The forward shift of sowing date may avoid the late crop drought, but the change of sowing time did not improve the root distribution and no obvious effect of drought avoidance. Over adjusting sowing time to slow the effect of seasonal drought,.3. relative to conventional tillage, short term deep tillage, no tillage and compaction improved the water status of 0-40 cm soil layer, increased the field water content 3%-5% and effective water content 22%-50%, and mainly affected the 0-20 cm soil layer. Compared with conventional tillage, the short term deep tillage increased the corn grain yield by 25.8%, 15 cm The total root mass density of Maize in x 40 cm soil was 21%, and the short term no tillage and compaction decreased 16.7% and 21.6% respectively. The total root mass density of maize decreased by 21% and 50.5% respectively. The short term deep ploughing reduced the root ratio of 0-10 cm surface corn by 10%, and the ratio of 30-40 cm depth to 43%; the short period of no tillage and compaction increased 10.5% and 6.2%, respectively. 0 cm depth root ratio is 10.5% and 54.5%. in this area, the seasonal drought occurs mostly in the 0-30 cm soil layer, and the soil water in the lower layer is abundant, only raising the surface soil available water to alleviate the seasonal drought is limited, while the short-term deep tillage promotes root ligation and absorbs deep water. The effect of Tillage on red soil drought was better than that of other tillage measures (.4.) compared with long term no tillage no fertilizer (CK), long-term no tillage fertilizer (NPK), organic manure (chicken manure, OM) and fertilizer combined with straw mulching and returning field (NPK+S) significantly increased soil organic matter content and soil nitrogen, phosphorus and potassium content; slightly increased (less than 7%) 0-40 cm soil field water holding capacity, effective containing Water and water absorption rate were mainly affected by 0-20 cm soil layer; NPK and OM decreased the surface unsaturated water conductivity by 50.7% and 67.7%, and NPK+S increased by 128%. NPK, OM and NPK+S decreased the evaporation loss rate of the first stage of the surface soil 23.7%, 36.8% and 50% respectively, and increased the leaf area 37.6%, 45.1% and 46.9%, and the root mass density 47.7%, 133%, respectively, 133%, respectively, 133%. The percentage of root dry weight, root depth and deep root system distribution from high to low in each growth period of 103.4%. maize was NPK+SOMNPKCK, and root 90% distributed in the soil layer above 20 cm. Compared with CK, three kinds of fertilization all increased maize yield and water utilization ratio 3-4 times, but increased the CWSI1.1-5.2 times of Maize during continuous drought. Long term no tillage fertilization was used. Although the root growth was promoted, a large number of roots were distributed in the 20 cm surface soil, and the application of fertilization significantly increased the leaf area, resulting in rapid water loss, high crop CWSI, soil drought and crop water stress in the.5. subtropical red soil region. 5 water conservation measures of CK and B, SM, PAM, +PAM (SPAM) and +PAM (BPAM) in Bahia were used to study the response of rain erosion surface structure to dry season drought. The results showed that the difference between CK and B, PAM, and measures was 0-30. Within 5%, the difference with SM and SPAM measures is 7.4% and 8.2%. is different from 5 kinds of water conservation measures. After rainfall, crop control (CK) significantly reduces the porosity and average pore size of WSA0.25 and 0-30 mm soil layer of 0-20 cm soil, and significantly (P0.01) increasing the crust coverage rate.CK measures, the WSA0.25 of soil is the soil WSA0.25 content of the 5 kinds of soil conservation measures. Soil porosity is the 79%-97%. of 5 kinds of water conservation measures. We use the drought intensity I and the drought degree D to quantify the soil water loss rate and soil drought condition. The correlation analysis shows that the drought intensity I is significantly positively correlated with the size of the crust and the crust coverage, and has a significant negative correlation with WSA0.25. The degree of drought D is significantly positively correlated with the crust coverage, and WSA0.25 and 0-15 mm. The porosity was significantly negative correlation, and the effect of soil 0-15 mm porosity on I and D was the greatest. The average I value and the final D value for 20 days of continuous drought were 5 kinds of water conservation measures, 1.2-2.5 times and 1.1-1.4 times respectively. The water erosion changed the surface structure, although it had little influence on the soil water storage, but significantly increased the water loss rate and drought degree in the surface soil. Rain erosion changes the surface structure to increase the surface water loss rate is one of the reasons for the formation of seasonal drought..6. straw mulch is widely used as a water conservation measure. This experiment has studied the response of soil crop system to soil water and heat by setting three straw mulching and nitrogen application levels. The results show that straw mulch is slightly increased by 0-30 cm soil. Soil moisture content (less than 5%), the maximum cooling of soil 0-5 cm soil layer at 3.3 C -6 C, maximum temperature 0.7 C -2.5 C, its cooling effect is greater than the effect of increasing temperature. Nitrogen application can increase corn yield, nitrogen plus cover increase yield more. No nitrogen application of high coverage corn grain yield significantly decreased, no nitrogen application of nitrogen cover 10000 kg/hm2 corn seed reduction to 21%. coverage The total soil NO3--N content was reduced and the content of NH4+-N was increased. Nitrogen application in the whole soil increased the content of soil NO3--N and reduced the content of NH4+-N. The total nitrogen uptake and nitrogen application increased by 16.9% and 23.6%., and Nitrogen productivity increased. Nitrogen productivity under low nitrogen level and nitrogen level under high nitrogen level were increased. Yield. The effect of straw mulching is limited by nitrogen level, covering and applying nitrogen to complement each other. It is beneficial to improve the water heat condition in the field, and to improve the crop yield and water use rate.7. on the basis of clarifying the seasonal drought characteristics of the seasonal drought in the subtropical red soil region, and through different sowing dates, tillage, fertilization and water conservation measures, to seasonal droughts. The causes and countermeasures are discussed. The results show that the root distribution and surface water loss in the subtropical red soil are the two reasons for the seasonal drought in this area. In order to promote root ligation and reduce the surface water loss, we suggest that the crops be ploughed as deep as possible in summer, early sowing and early fertilization, and the best cultivation depth is better than 30 cm in the middle of June. After sowing, organic fertilizer and chemical fertilizer should be used as basal fertilizer for deep application of soil.

【学位授予单位】：华中农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S423

【参考文献】