本文選題：溫度梯度 + 水氮遷移　； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：由于大面積缺水、農(nóng)田作物用水缺少合理科學(xué)的指導(dǎo)以及施肥技術(shù)水平的限制,導(dǎo)致了我國水資源大量浪費,肥料使用率普遍低下。養(yǎng)分隨水分的大量流失,不僅使得作物產(chǎn)量低下,還對環(huán)境安全構(gòu)成嚴重威脅;同時農(nóng)田灌溉水溫也是實際農(nóng)業(yè)生產(chǎn)中對耕作、灌溉和排水產(chǎn)生影響的一個重要因素,灌溉水溫不僅影響著作物的生長發(fā)育、土壤肥力以及土壤中水分和氮素的轉(zhuǎn)化遷移,還影響作物對土體內(nèi)水分和養(yǎng)分的吸收利用,及作物的生長發(fā)育和產(chǎn)量。只有同時兼顧土壤水、氮、熱三者之間的關(guān)系,進行相關(guān)調(diào)控,才能滿足作物的生長需要,提高作物產(chǎn)量。因此,開展灌水量,施肥量以及溫度梯度耦合下土壤水氮熱的分布特性試驗研究,將為揭示不同因素間的耦合效應(yīng),增強氮素和水資源利用效率,促進農(nóng)作物增產(chǎn),制定科學(xué)合理有效的灌溉施肥制度提供重要的指導(dǎo)意義。本文通過室內(nèi)土柱模擬試驗,研究在不同溫度梯度、不同灌水量及不同肥液濃度下土壤水熱變化對尿素遷移轉(zhuǎn)化規(guī)律的影響。主要結(jié)論如下:1、入滲率隨時間延長而逐漸減小。在同一入滲時段內(nèi),入滲率隨土壤灌水量、肥液濃度、溫度梯度的增加均增加。2、隨著入滲時間的增加,累積入滲量與濕潤鋒推進距離均增大。同一入滲時段內(nèi),累積入滲量與濕潤鋒推進距離隨灌水量、肥液濃度及溫度梯度的增大均增大。3、不同灌水量、不同肥液濃度以及不同溫度梯度條件下的土壤含水率均表現(xiàn)為土柱上層含水率大于下層含水率,含水率隨土層深度逐漸減小。在土層同一深度處,灌水量越大,含水率越高;溫度梯度越大,含水率變化越明顯,穩(wěn)定時含水率最小;肥液濃度則對含水率影響不明顯。隨著時間的推移,土壤含水率隨土深的分布逐漸變得均勻,含水率的變化逐漸趨于穩(wěn)定。4、土壤溫度隨著時間的不斷推移呈現(xiàn)先增后趨于穩(wěn)定的特點,隨土深的增加呈現(xiàn)不斷減小的變化規(guī)律。同一溫度梯度下,肥液濃度一定時,同一土深處,灌水量越大,土壤溫度越高,達到平衡時所用時間越短,平衡溫度越高,土壤溫度隨時間的變化過程滿足T=a+b×3裻,隨土深的變化則滿足T=a×(?)(b|c-x|)+d,均具有較高擬合度。灌水量一定時,在相同溫度梯度時,不同肥液濃度下的土壤溫度隨土深并無顯著差別,肥液濃度對土壤溫度的影響不大。肥液濃度及灌水量一定時,同一土深處,溫度梯度越大,土壤的溫度就越高,達到平衡時平衡溫度越高,土壤溫度隨時間的變化過程滿足T=a+b×3裻,隨土深的變化則滿足T=a×(?)(b|c-x|)+d,均有較高擬合度。5、灌水量、肥液濃度以及溫度梯度三者越大,尿素的轉(zhuǎn)化越快,所花費的時間越短。在土壤垂直剖面內(nèi),灌水量越大,尿素在土壤中分布越廣,其遷移速率也就越快;肥液濃度越大,在土壤同一土深處,尿素含量就越大,肥液濃度對尿素的分布無顯著影響;溫度梯度越大,在土壤同一土層深度處,尿素態(tài)氮轉(zhuǎn)化越快,剩余的尿素態(tài)氮含量越少,溫度梯度促進尿素的轉(zhuǎn)化分布。6、銨態(tài)氮在土壤中隨時間呈現(xiàn)先增多后減小的變化規(guī)律,隨土深的分布規(guī)律是先增大后減小,在不同土深位置處具有峰值,隨灌后時間的推移,銨態(tài)氮與土深之間的變化過程均可以采用方程N_1=a×e~(b|h-c|)擬合,且具有較高擬合度。灌水量越大,土壤中25cm土深位置以上剖面內(nèi),銨態(tài)氮的含量越小;25cm土深位置以下剖面內(nèi),銨態(tài)氮的含量越大,銨態(tài)氮的分布范圍越廣。肥液濃度對銨態(tài)氮在土壤剖面中的分布影響較小,但對銨態(tài)氮含量大小影響較大,肥液濃度越大,銨態(tài)氮在土壤中含量越高。溫度梯度對銨態(tài)氮具有較顯著的影響,溫度梯度越大,土壤中尿素生成銨態(tài)氮的速率就越快,銨態(tài)氮含量就越高。7、硝態(tài)氮在土壤中隨時間呈現(xiàn)逐漸增大的變化規(guī)律,在土柱剖面中隨土深的分布規(guī)律同樣是逐漸增大。硝態(tài)氮主要積累于濕潤鋒處,且在時間的推移下隨濕潤鋒向土壤下層遷移,灌水量越大,硝態(tài)氮向下運移越遠,濕潤鋒位置處硝態(tài)氮含量越大。肥液濃度對硝態(tài)氮的分布影響不顯著,主要影響其含量大小,肥液濃度越大,土壤中硝態(tài)氮含量就越高。溫度梯度促進硝態(tài)氮的形成,溫度梯度越大,土壤中硝態(tài)氮含量越高,轉(zhuǎn)化形成硝態(tài)氮的時間越短,速率越快,硝態(tài)氮在土壤剖面主要積累于土壤底層,在不同灌水量及肥液濃度條件下,硝態(tài)氮含量隨灌后時間的延長,與土深之間滿足函數(shù)(?),具有擬合度較高;不同溫度梯度下則與土深之間滿足函數(shù)(?),同樣具有較高擬合度。8、采用室內(nèi)土柱模擬試驗,定時監(jiān)測土壤水氮熱動態(tài)變化過程,運用BP神經(jīng)網(wǎng)絡(luò)算法構(gòu)建的溫度梯度條件下土壤水熱、水氮熱分布的預(yù)測模型均具有較高的精度和良好的穩(wěn)定性,可以較好的描述溫度梯度下土壤水氮熱動態(tài)分布變化情況。
[Abstract]:Due to a large area of water shortage, the lack of rational scientific guidance for the water use of farmland and the restriction of the level of fertilization technology, the water resources in China are wasted and the fertilizer use rate is generally low. The loss of nutrients with the water is a serious threat not only to the low yield of the crops, but also to the environmental safety. At the same time, the temperature of the irrigation water is also real. It is an important factor affecting farming, irrigation and drainage in agricultural production. The irrigation water temperature not only affects the growth and development of crops, soil fertility and the transformation and migration of water and nitrogen in the soil, but also affects the absorption and utilization of water and nutrients in the soil, and the growth and yield of crops. The relationship between the three kinds of soil water, nitrogen and heat can be regulated to meet the needs of crop growth and increase crop yield. Therefore, the experimental study on the distribution characteristics of soil water and nitrogen heat under the coupling of irrigation amount, fertilizer amount and temperature gradient will reveal the coupling effect among different factors, enhance the utilization efficiency of nitrogen and water resources, and promote agriculture. In this paper, the effects of soil water and heat change on the migration and transformation of urea under different temperature gradient, different irrigation amount and different concentration of fertilizer are studied by indoor soil column simulation test. The main conclusions are as follows: 1, infiltration rate is gradually extended with time. In the same infiltration period, the infiltration rate increases with the amount of soil irrigation, the concentration of fertilizer and the temperature gradient increase by.2. With the increase of infiltration time, the cumulative infiltration and the distance of the wetting front increase. The increase of the cumulative infiltration and the wetting front distance is increased with the irrigation water, the increase of the concentration of fertilizer and the temperature gradient in the same infiltration period. The soil water content of large.3, under the different irrigation amount, the concentration of different fertilizer and the different temperature gradient conditions, is that the water content of the soil column is larger than the lower water content, and the water content decreases with the depth of the soil. The greater the water content is, the higher the water content is, the greater the temperature gradient, the more obvious the water content change and the water cut in the stable time. With the passage of time, the soil moisture content gradually became more uniform with the soil depth, and the change of water content gradually stabilized.4, and the soil temperature increased first and then tended to stabilize with the time. Under a temperature gradient, when the concentration of the fertilizer is certain, the greater the amount of water in the same soil, the greater the amount of water, the higher the soil temperature, the shorter the time for the balance, the higher the equilibrium temperature, the change of the soil temperature with the time of T=a+b * 3, which satisfies the T=a * (?) (?) (b|c-x|) +d with the change of soil depth. There is no significant difference in soil temperature between soil depth and soil depth at the temperature gradient. The concentration of fertilizer has little effect on soil temperature. When the concentration of fertilizer and the amount of irrigation are certain, the higher the temperature gradient is, the higher the temperature gradient, the higher the balance temperature is, the change of soil temperature satisfies T=a+b. With the soil depth change, it meets T=a * (?) (b|c-x|) +d, with higher fitting degree.5, the greater the irrigation amount, the concentration of fertilizer and the temperature gradient, the faster the urea conversion, the shorter the time it takes. In the vertical soil profile, the larger the amount of water is, the more the urea is distributed in the soil, the faster the migration rate is, the greater the concentration of the fertilizer is, the greater the concentration of the fertilizer liquid, the greater the concentration of the fertilizer, the greater the concentration of the fertilizer liquid, the greater the concentration of the fertilizer solution, the greater the concentration of the fertilizer, the greater the concentration of the fertilizer, the greater the concentration of the fertilizer liquid, In the same soil depth, the more urea content is, the concentration of fertilizer has no significant influence on the distribution of urea. The greater the temperature gradient, the faster the urea nitrogen transformation, the less the residual urea nitrogen content at the same soil depth, and the temperature gradient to promote the transformation of urea.6, and the ammonium nitrogen in the soil first increases and then decreases in the soil. The distribution law of soil depth first increases and then decreases, and has a peak value at different soil depth. The process of the change between ammonium nitrogen and soil depth can be fitted with the equation N_1=a x e~ (b|h-c|) with the change of soil depth. The greater the amount of water, the higher the depth of the soil in the soil, the ammonium nitrogen in the depth of the soil in the deep position of the soil 25cm. The smaller the content of the 25cm soil, the larger the ammonium nitrogen content and the wider distribution of ammonium nitrogen. The concentration of the ammonium nitrogen has little influence on the distribution of ammonium nitrogen in the soil profile, but it has greater influence on the ammonium nitrogen content, the greater the concentration of the fertilizer, the higher the ammonium nitrogen content in the soil. The temperature gradient is more significant to the ammonium nitrogen. The higher the temperature gradient, the faster the ammonium nitrogen of the soil in the soil, the higher the ammonium nitrogen content is.7, the nitrate nitrogen in the soil presents a gradual increase in the soil with time, and the distribution of soil depth in the soil column section is gradually increased with the soil depth. The wetting front migrated to the lower layer of the soil, the greater the amount of irrigation, the farther the nitrate nitrogen moved down, the more nitrate nitrogen in the position of the wetting front. The concentration of fertilizer had no significant influence on the distribution of nitrate nitrogen, which mainly affected the content of nitrate nitrogen, the higher the concentration of the fertilizer, the higher the nitrate content in the soil. The higher the nitrate nitrogen content in the soil, the shorter the transformation of nitrate nitrogen, the faster the rate, the nitrate nitrogen in the soil profile is mainly accumulated in the soil bottom. Under the conditions of different irrigation and fertilizer concentration, the nitrate nitrogen content is prolonged with the time of irrigation, and it has a higher fitting degree with the soil depth, and under the different temperature gradient, With the soil depth to satisfy the function (?), it also has a higher fitting degree.8, using the indoor soil column simulation test to monitor the dynamic change process of soil water and nitrogen heat, using the temperature gradient condition constructed by the BP neural network algorithm, the prediction model of the water and nitrogen heat distribution has high accuracy and good stability, and it can be better. The change of soil water and nitrogen thermal dynamic distribution under temperature gradient is described.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S158;S27

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