本文選題：干旱程度 + 根系分布　； 參考：《華中農(nóng)業(yè)大學(xué)》2017年博士論文

【摘要】：干旱是造成農(nóng)業(yè)損失最嚴(yán)重的自然災(zāi)害之一,即使在濕潤(rùn)多雨的亞熱帶紅壤區(qū)也頻發(fā)季節(jié)性干旱。人們對(duì)季節(jié)性干旱的發(fā)生機(jī)制及其調(diào)控進(jìn)行了深入研究和實(shí)踐,然而,多是單一研究土壤或作物對(duì)季節(jié)性干旱響應(yīng),缺乏對(duì)土壤-作物系統(tǒng)對(duì)季節(jié)性干旱響應(yīng)及緩解季節(jié)性干旱對(duì)策的系統(tǒng)探討。本研究在充分認(rèn)識(shí)亞熱帶紅壤區(qū)季節(jié)性干旱時(shí)空特征的基礎(chǔ)上,通過(guò)設(shè)置不同的作物種植時(shí)期、耕作措施,探索從時(shí)間和空間上減緩季節(jié)性干旱的途徑。通過(guò)設(shè)置不同的施肥措施和秸稈覆蓋等水保措施,分析土壤水分、作物生長(zhǎng)及根系分布、土壤結(jié)構(gòu)變化與季節(jié)性干旱的關(guān)系;從土壤、作物、施肥、田間管理多方面探討對(duì)土壤-作物系統(tǒng)對(duì)季節(jié)性干旱的響應(yīng)及季節(jié)性干旱的發(fā)生機(jī)制,得到如下主要結(jié)論:1.亞熱帶紅壤區(qū)季節(jié)性干旱具有鮮明的時(shí)空特征。該區(qū)每年7~10月蒸發(fā)量大于降雨量,7~8月份蒸發(fā)量是降雨量的2.1倍,兩者相差達(dá)265.8 mm,此時(shí)段最易發(fā)生干旱。林地、草地、裸地和農(nóng)田四種土地利用方式中,農(nóng)田7~8月份處于作物需水旺盛期,且根系多分布在0-30 cm土層。因此,每年7~8月農(nóng)田0-30 cm土層易發(fā)生季節(jié)性干旱,且連續(xù)干旱超過(guò)12天不利于玉米生長(zhǎng),玉米生長(zhǎng)前期遇旱減產(chǎn)風(fēng)險(xiǎn)大于后期遇旱。調(diào)整播期或促進(jìn)根系下扎可能會(huì)減少季節(jié)性干旱危害。2.錯(cuò)開(kāi)作物需水旺盛期或關(guān)鍵期與季節(jié)性干旱易發(fā)時(shí)段將有利于避旱。連續(xù)兩年從5月中旬開(kāi)始每15天播種一期玉米,每年播種五期。以正常播期6月中旬為參照,播期前移,玉米產(chǎn)量無(wú)顯著變化;播期后移,玉米籽粒產(chǎn)量顯著下降,減產(chǎn)達(dá)23.3%-52.6%;不同播期間莖葉干重差異不顯著。不同播期玉米成熟期的根系90%以上均分布在0-30 cm土層,且無(wú)明顯分層,根質(zhì)量密度也無(wú)顯著差異。播期前移可能會(huì)避開(kāi)作物后期遇旱,但是改變播期并沒(méi)有改善根系分布,也沒(méi)有明顯的避旱效果,播期后移作物反而減產(chǎn)。通過(guò)調(diào)整播期來(lái)減緩季節(jié)性干旱的效果不佳。3.相對(duì)于常規(guī)耕作,短期的深耕、免耕和壓實(shí)均改善0-40 cm土層水分狀況,提高田間持水量3%-5%和有效水含量22%-50%,且主要影響0-20 cm土層。與常規(guī)耕作相比,短期的深耕提高玉米籽粒產(chǎn)量25.8%,15 cm×40 cm土體玉米總根質(zhì)量密度21%;短期的免耕和壓實(shí)則分別減產(chǎn)16.7%和21.6%,分別降低玉米總根質(zhì)量密度21%和50.5%;短期的深耕降低了0-10 cm表層玉米根系比例約10%,提高30-40 cm深度根系比例43%;短期的免耕和壓實(shí)分別提高10.5%和6.2%,降低30-40 cm深度根系比例10.5%和54.5%。該區(qū)季節(jié)性干旱多發(fā)于0-30 cm土層,下層土壤含水量充足,僅提高表層土壤有效水對(duì)緩解季節(jié)性干旱作用有限;而短期的深耕促進(jìn)根系下扎,吸收深層水分。針對(duì)時(shí)空特征鮮明的亞熱帶紅壤季節(jié)性干旱,短期深耕緩解紅壤干旱效果優(yōu)于其它耕作措施。4.與長(zhǎng)期免耕不施肥相比(CK),長(zhǎng)期免耕施用化肥(NPK)、有機(jī)肥(雞糞,OM)和化肥配合秸稈覆蓋還田(NPK+S)顯著提高土壤有機(jī)質(zhì)含量和土壤氮磷鉀含量;輕微提高(小于7%)0-40 cm土層田間持水量、有效含水量和吸水速率,且主要影響0-20 cm土層;NPK和OM分別降低地表非飽和導(dǎo)水率50.7%和67.7%,NPK+S則提高128.0%;NPK、OM和NPK+S分別降低表層土壤第一階段蒸發(fā)失水速率23.7%、36.8%和50.0%,分別提高夏玉米葉面積37.6%、45.1%和46.9%和根質(zhì)量密度47.7%、133.0%和103.4%。玉米各生育期根干重、根深度、深層根系分布比例從高到低依次是NPK+SOMNPKCK,且根系90%均分布在20 cm以上土層。與CK相比,三種施肥均提高玉米產(chǎn)量和水分利用率3-4倍,但是在發(fā)生持續(xù)干旱時(shí),均增大玉米CWSI1.1-5.2倍。長(zhǎng)期免耕施肥雖然促進(jìn)了根系生長(zhǎng),但是大量根系分布在20 cm表層土壤,加之施肥顯著增大葉面積,導(dǎo)致在發(fā)生持續(xù)干旱時(shí),表層土壤失水快,作物CWSI高,加劇表層土壤干旱和作物水分脅迫。5.亞熱帶紅壤區(qū)前期水蝕后期干旱。本研究通過(guò)在作物間設(shè)置無(wú)水保措施的作物對(duì)照(CK)和百喜草帶(B)、秸稈覆蓋(SM)、聚丙烯酰胺表施(PAM)、稻草覆蓋+PAM(SPAM)、百喜草帶+PAM(BPAM)5種水保措施,研究雨蝕地表結(jié)構(gòu)變化對(duì)旱季性干旱的響應(yīng),結(jié)果表明,夏玉米生育期0-30 cm土壤儲(chǔ)水量CK與B、PAM和BPAM措施差異在5%以?xún)?nèi),與SM和SPAM措施差異為7.4%和8.2%。與5種水保措施不同,降雨后作物對(duì)照(CK)顯著(p0.05)降低0-20 cm土壤的WSA0.25和0-30 mm土層孔隙率及平均孔徑,顯著(p0.01)增加結(jié)皮覆蓋率。CK措施下土壤的WSA0.25是5種水保措施土壤WSA0.25含量的63%-88%,土壤孔隙率是5種水保措施的79%-97%。我們用干旱強(qiáng)度I和干旱程度D量化土壤失水速率和土壤干旱狀況。相關(guān)分析表明,干旱強(qiáng)度I與結(jié)皮大小、結(jié)皮覆蓋率顯著正相關(guān),與WSA0.25顯著負(fù)相關(guān)。干旱程度D與結(jié)皮覆蓋率顯著正相關(guān),與WSA0.25和0-15 mm孔隙率顯著負(fù)相關(guān),且土壤0-15 mm孔隙率對(duì)I和D的影響最大。CK措施連續(xù)干旱20天的平均I值和最后D值分別是5種水保措施1.2-2.5倍和1.1-1.4倍。水蝕改變地表結(jié)構(gòu),雖然對(duì)土壤儲(chǔ)水量影響很小,但是顯著提高了表層土壤失水速率和干旱程度。雨蝕改變地表結(jié)構(gòu)提高地表失水速率是季節(jié)性干旱形成的原因之一。6.秸稈覆蓋作為一種水保措施被廣泛運(yùn)用。本試驗(yàn)通過(guò)設(shè)置三個(gè)秸稈覆蓋和施氮水平研究土壤-作物系統(tǒng)對(duì)土壤水熱狀況的響應(yīng),結(jié)果表明,秸稈覆蓋輕微提高0-30 cm土壤含水量(小于5%),對(duì)土壤0-5 cm土層最大降溫3.3℃-6℃,最大增溫0.7℃-2.5℃,其降溫效果大于增溫效果。施氮提高玉米產(chǎn)量,施氮加覆蓋增產(chǎn)更多。不施氮時(shí)高覆蓋量玉米籽粒產(chǎn)量顯著降低,不施氮時(shí)覆蓋10000 kg/hm2玉米籽粒減產(chǎn)達(dá)21%。覆蓋總體降低土壤NO3--N含量,提高NH4+-N含量;施氮總體提高土壤NO3--N含量,降低NH4+-N含量。覆蓋和施氮總體分別提高玉米吸氮量超過(guò)16.9%和23.6%。覆蓋時(shí)增施氮肥,氮素生產(chǎn)率提高。低氮水平下覆蓋降低氮素生產(chǎn)率,高氮水平下覆蓋提高氮素生產(chǎn)率。秸稈覆蓋的作用受氮水平限制,覆蓋和施氮相互彌補(bǔ),既有利于改善田間水熱狀況,又有利于提高作物產(chǎn)量和水分利用率。7.在闡明亞熱帶紅壤區(qū)季節(jié)性干旱時(shí)空特征的基礎(chǔ)上,通過(guò)不同播期、耕作、施肥和水保措施,對(duì)季節(jié)性干旱發(fā)生的原因及對(duì)策進(jìn)行了探討,結(jié)果表明:亞熱帶紅壤農(nóng)田根系分布和地表失水是該區(qū)季節(jié)性干旱發(fā)生的兩個(gè)原因。為促進(jìn)根系下扎和減少地表失水,我們建議每年夏季作物盡量深松耕、早播種、早施肥,耕作深度最好超過(guò)30 cm,避免6月中旬以后播種,同時(shí)有機(jī)肥配合化肥作為基肥深施土壤;盡量保持全年秸稈覆蓋。
[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.

【學(xué)位授予單位】：華中農(nóng)業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：S423

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相關(guān)碩士學(xué)位論文 前1條

1 高躍;基于HYDRUS模型的紅壤坡耕地水分動(dòng)態(tài)研究[D];華中農(nóng)業(yè)大學(xué);2013年

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