張冬麗，張朋月，沈玉君，丁京濤

畜禽養(yǎng)殖糞水酸化貯存及氮素減損增效研究進(jìn)展

張冬麗，張朋月，沈玉君，丁京濤※

（1. 農(nóng)業(yè)農(nóng)村部規(guī)劃設(shè)計研究院農(nóng)村能源與環(huán)保研究所，北京 100125；2. 農(nóng)業(yè)農(nóng)村部資源循環(huán)利用技術(shù)與模式綜合性重點(diǎn)實驗室，北京 100125）

畜禽糞水酸化貯存能夠有效調(diào)控糞水貯存中微生物、環(huán)境與氮素間的作用關(guān)系，實現(xiàn)糞水氮素的減損增效，是一種具有廣泛應(yīng)用前景的關(guān)鍵技術(shù)。該研究系統(tǒng)綜述了糞水酸化貯存中氮素的遷移轉(zhuǎn)化機(jī)理，比較評價了常見酸化劑和不同酸化貯存工藝的應(yīng)用效果，分析了酸化貯存技術(shù)對糞水氮素減損增效的影響。梳理總結(jié)得到：糞水酸化存儲中氮素的遷移轉(zhuǎn)化機(jī)制主要包括有機(jī)氮礦化、銨態(tài)氮固持、無機(jī)氮轉(zhuǎn)化的抑制及硝化3個關(guān)鍵環(huán)節(jié)，可以依靠改變微生物作用和化學(xué)平衡狀態(tài)實現(xiàn)氮素的減損；與其他酸化工藝相比，長期酸化工藝具有酸化效果更加穩(wěn)定、應(yīng)用范圍較為廣泛等優(yōu)勢；糞水酸化技術(shù)能夠大幅降低NH3排放，以及部分N2O的排放，進(jìn)而提高糞肥還田后土壤肥效，但不合理的酸化貯存技術(shù)及施用方式也會降低糞水肥效，甚至引起二次污染；未來應(yīng)重點(diǎn)從氮素遷移轉(zhuǎn)化路徑的定量分析、復(fù)合酸化劑的開發(fā)、糞肥施用效果及風(fēng)險的評估應(yīng)對等方面進(jìn)行深入研究。

酸；肥效；畜禽糞水；氮素減損

0 引 言

隨著畜禽養(yǎng)殖業(yè)規(guī)模化的發(fā)展，糞水處理成為限制養(yǎng)殖場發(fā)展的重要因素[1]，相對固體糞便而言，液態(tài)糞水處理難度大，更易導(dǎo)致環(huán)境污染。據(jù)統(tǒng)計，中國畜禽養(yǎng)殖糞污年產(chǎn)生量約30.5億t，其中養(yǎng)殖過程產(chǎn)生的糞水量大、分散，更容易導(dǎo)致面源污染[2]。目前，貯存發(fā)酵被認(rèn)為是一種實現(xiàn)養(yǎng)殖糞水無害化、資源化的處理方式，能夠利用糞水中的氮、磷、鉀等元素，同時對部分有害微生物進(jìn)行滅活，既能促進(jìn)物質(zhì)循環(huán)又能提升廢棄污染物的經(jīng)濟(jì)價值[3]。然而，在傳統(tǒng)的糞水貯存發(fā)酵工藝中，容易產(chǎn)生氨氣（NH3）、硫化氫（H2S）等臭氣以及氧化亞氮（N2O）、甲烷（CH4）等溫室氣體，不僅造成糞肥產(chǎn)品肥效的降低，還會造成PM2.5濃度上升等一系列環(huán)境問題[4-6]。

近年來，隨著畜禽糞水排放規(guī)模的進(jìn)一步增大以及生態(tài)環(huán)境保護(hù)要求的持續(xù)提高，糞水酸化技術(shù)逐漸成為糞污臭氣控制研究和應(yīng)用的關(guān)鍵技術(shù)[7-9]。畜禽糞水酸化貯存技術(shù)能夠通過改變糞水pH值，實現(xiàn)系統(tǒng)中NH4+和NH3間平衡關(guān)系的調(diào)節(jié)，進(jìn)而減少糞水貯存及農(nóng)田施用中氨氣等氣體排放，提高糞水貯存中養(yǎng)分固持率[10-12]。糞水酸化貯存技術(shù)已在國外得到較多的發(fā)展和應(yīng)用，例如以濃硫酸酸化貯存糞水技術(shù)已在丹麥、瑞典等國普遍推廣，丹麥有12%～20%的糞水采用酸化處理[13-14]。

在2021年8月全國畜牧總站印發(fā)的《規(guī)范畜禽糞污處理降低養(yǎng)分損失技術(shù)指導(dǎo)意見》中，糞水酸化技術(shù)已成為治理糞污氨揮發(fā)的主推技術(shù)，同時也被納入《“十四五”全國畜禽糞肥利用種養(yǎng)結(jié)合建設(shè)規(guī)劃》。但總體來看，中國對于糞水酸化貯存的研究尚處于起步階段，有待進(jìn)一步系統(tǒng)、深入研究。本文系統(tǒng)闡述了當(dāng)前畜禽養(yǎng)殖糞水酸化貯存技術(shù)研究進(jìn)展，并展望了其應(yīng)用前景，以期為中國畜禽養(yǎng)殖糞水資源化、無害化利用技術(shù)研發(fā)應(yīng)用提供理論和數(shù)據(jù)支撐。

1 糞水酸化貯存中的氮素遷移及其減損特征

1.1 糞水酸化貯存中的氮素遷移

糞水是糞便與尿液的混合物，含有豐富的氮素等養(yǎng)分（見表1）[15-18]，適宜在經(jīng)過貯存發(fā)酵后還田進(jìn)行資源化利用。然而，糞水中的尿酸、尿素以及未分解的蛋白質(zhì)等氮素載體在好氧降解、水解或礦化作用下使糞水含有大量銨態(tài)氮，極易釋放出NH3，造成氮素養(yǎng)分的損失，成為限制養(yǎng)殖糞水資源化利用的難點(diǎn)之一[19–22]。在糞水酸化貯存過程中，氮循環(huán)在很大程度上依賴復(fù)雜的化學(xué)生物作用。糞水中氮素的形態(tài)以有機(jī)氮和銨態(tài)氮為主，其總和占糞水中總氮質(zhì)量分?jǐn)?shù)的97%以上。因此，分析其氮素遷移機(jī)制，主要可以歸納為有機(jī)氮的礦化、銨態(tài)氮的固持、無機(jī)氮轉(zhuǎn)化的抑制及硝化3個關(guān)鍵環(huán)節(jié)（見圖1）。

表1 養(yǎng)殖糞水中主要物質(zhì)含量

1）有機(jī)氮的礦化。向糞水中添加酸化劑后，少量硫酸分解了糞水底泥中部分大顆粒有機(jī)物，使之懸浮于糞水中提高了糞水中有機(jī)氮的含量。在酸性條件下，糞水中的有機(jī)氮通過好氧/厭氧微生物的礦化作用向銨態(tài)氮轉(zhuǎn)化，另一部分有機(jī)氮則通過水解作用轉(zhuǎn)化為氨基酸，并在脫氨基的作用下生成銨態(tài)氮[23-24]。2）銨態(tài)氮的固持。酸化工藝作用下，硫酸等酸化劑與銨態(tài)氮結(jié)合生成能夠長期穩(wěn)定固持的銨鹽。3）無機(jī)氮轉(zhuǎn)化的抑制及硝化。有研究表明[25-27]，糞水酸化能夠有效抑制糞水中微生物活性，通過濃硫酸酸化后糞水中耗氧率、硫酸鹽還原率均明顯降低，這可能是由于酸化糞水中含有高濃度的短鏈揮發(fā)性脂肪酸，它們作為細(xì)胞膜電位的解耦劑，抑制了微生物的代謝。因此，酸化抑制了有機(jī)氮向無機(jī)氮素的轉(zhuǎn)化，微生物活性的降低使得糞水中存在一定量過剩的溶解氧，這部分溶解氧被硝化細(xì)菌利用，也使得糞水中硝態(tài)氮含量逐漸升高，亞硝態(tài)氮含量不斷降低。

圖1 畜禽養(yǎng)殖糞水酸化貯存及其氮素減損增效示意圖

1.2 糞水酸化貯存的氮素減損路徑

糞水酸化貯存中氮素的損失途徑主要是NH3的產(chǎn)生和散逸。糞水為微生物提供了一種復(fù)雜的環(huán)境條件，不僅具有好氧微生物所需的環(huán)境，同時亦為厭氧微生物提供了所需的生存環(huán)境，因此，結(jié)合糞水酸化貯存中的氮素遷移機(jī)制的相關(guān)研究結(jié)論，糞水中氮素形態(tài)轉(zhuǎn)化及氮素?fù)p失的調(diào)節(jié)，主要是通過改變微生物作用和化學(xué)平衡狀態(tài)來實現(xiàn)。其分別對應(yīng)了2種氮素減損的技術(shù)路徑，一是添加酸化劑降低糞水pH值以改變糞水中NH4+與NH3的動態(tài)平衡，促進(jìn)NH4+生成，以減少糞水中溶解NH3的排放；二是通過降低糞水pH值使微生物活性下降，降低糞水中有機(jī)物的礦化作用，進(jìn)而減少NH3的產(chǎn)生及排放[28]。

1.3 糞水酸化貯存與傳統(tǒng)工藝的差異

與傳統(tǒng)糞水貯存發(fā)酵工藝相比，糞水酸化貯存能夠穩(wěn)定固持糞水中的NH4+，體現(xiàn)了氮素減損的比較優(yōu)勢[29]。在傳統(tǒng)養(yǎng)殖糞水貯存發(fā)酵工藝中，糞水一般是以自然靜置貯存為主，表層糞水以好氧發(fā)酵為主，但深層糞水則以厭氧發(fā)酵為主。而在糞水酸化貯存發(fā)酵中，酸化后的糞水所提供的效應(yīng)離子不會被降解及轉(zhuǎn)化（易分解有機(jī)物及硝酸除外），能夠穩(wěn)定的固持糞水中的NH4+，使糞水中被固持的NH4+長期的貯存于糞水中（圖2）。

圖2 糞水酸化貯存與傳統(tǒng)工藝對比示意圖

綜合已有研究[21-29]，雖然酸化糞水一定程度上抑制了糞水中微生物對含氮有機(jī)物的礦化作用，但其也使氮素固持效率有了顯著提高，進(jìn)而減少氮素?fù)p失和氨氣排放。酸化環(huán)境下一定量過剩溶解氧促進(jìn)糞水中微生物的硝化作用，使糞水中硝態(tài)氮含量升高?？偟膩砜矗峄夹g(shù)使糞水貯存中總氮、銨態(tài)氮、硝態(tài)氮含量升高，氨氣排放、亞硝態(tài)氮含量降低，故酸化糞水對提高糞水養(yǎng)分固持率，減少環(huán)境污染具有重要意義。

2 不同糞水酸化貯存工藝的比較評價

2.1 不同類型酸化劑

糞水酸化劑目前主要有3種類型[10,30]。第一種是強(qiáng)酸類，主要有濃H2SO4、HNO3和H3PO4等，其中濃H2SO4以其低廉的價格應(yīng)用最廣，強(qiáng)酸酸化劑用量少，但糞水酸化后pH穩(wěn)定性差，且酸類具腐蝕性，對設(shè)備和安全操作要求較高，其作用方式為酸與糞水中的銨水反應(yīng)生成相對更穩(wěn)定的銨鹽和水，降低了銨氮向氨氣的轉(zhuǎn)化。其中硫酸以價格便宜，用量少等優(yōu)勢可用于中國農(nóng)村糞水的酸化。但其購置、存儲、管理過程繁瑣，故建議在農(nóng)村地區(qū)推廣以磷酸為主的酸化劑。

第二種是水解呈酸性的鹽類，主要有明礬、過磷酸鈣、氯化鋁、硫酸鋁等物質(zhì)。此類酸化劑水解后一般生成堿性沉淀物與酸，酸與氨水反應(yīng)生成銨鹽和水，此類酸化劑酸化效果相對較穩(wěn)定，但投加量相對酸類酸化劑較多，其應(yīng)用經(jīng)濟(jì)效益及環(huán)境效益是該工藝的主要考量因素[9]。

第三種是易分解有機(jī)物，目前以葡萄糖和蔗糖研究較多[10,31]。這類物質(zhì)主要是通過向糞水中投入大量的易分解有機(jī)物，促進(jìn)微生物快速增長，待糞水中的溶解氧不足以供給微生物進(jìn)行呼吸作用時，糞水中的厭氧微生物大量繁殖，厭氧的呼吸作用將有機(jī)物分解為乳酸，通過乳酸與氨水反應(yīng)生成乳酸銨和水。在糞水貯存后期，隨著易分解有機(jī)物的厭氧降解，糞水中的有機(jī)酸會逐漸轉(zhuǎn)化為甲烷，失去酸化效果。此方法投入量較大，成本偏高，會產(chǎn)生酸性臭氣，并吸引蛾蠓等飛蟲，引發(fā)二次污染，實際應(yīng)用較少。

2.2 不同類型酸化方式

按照酸化場所，糞水酸化方式主要有養(yǎng)殖舍內(nèi)長期酸化、貯存池中長期酸化和施用時短期酸化3種方式[10,32-33]。糞水酸化施用方式對酸化存儲過程中氮素?fù)p失量影響顯著[34-35]。

1）養(yǎng)殖舍內(nèi)長期酸化是指糞水在養(yǎng)殖舍內(nèi)酸化后，隨糞溝流入酸化處理罐，再添加酸化劑，進(jìn)行酸化，同時增加曝氣并不斷攪拌以減少酸化過程中氣泡的產(chǎn)生，酸化后的糞水一部分回流至養(yǎng)殖舍，一部分進(jìn)入糞水儲罐或糞水貯藏池。此方法的優(yōu)點(diǎn)在于糞水酸化后有利于進(jìn)行固液分離，同時收集的糞水能夠在貯存及施用過程中的各個階段均能起到減少NH3的揮發(fā)作用，進(jìn)入貯存設(shè)施的糞水一般不再進(jìn)行酸化，進(jìn)入養(yǎng)殖舍收集系統(tǒng)的糞水會注入新的糞水，并再次進(jìn)入酸化系統(tǒng)酸化，如此循環(huán)可使酸化效果更穩(wěn)定，此種酸化技術(shù)目前應(yīng)用最廣；2）貯存池中長期酸化是指糞水在貯存池中進(jìn)行酸化，向貯存池中投入酸化劑并輔以不斷攪拌。此方法在酸化過程中會產(chǎn)生大量的氣泡，增加管理風(fēng)險，另外，如果貯存時間較長，為了防止氨揮發(fā)作用增強(qiáng)，需要根據(jù)情況再次酸化；3）施用時短期酸化是指在糞水農(nóng)田施用之前，向施肥罐車中添加酸化劑，通過罐車攪拌機(jī)混合均勻進(jìn)行酸化，主要降低糞水還田施用階段NH3的揮發(fā)，提高氮素利用率[36]。

3 酸化貯存對糞水氮素減損增效影響

3.1 對氨氣排放的影響

糞水酸化能夠有效抑制糞水的堿性環(huán)境以及其中的微生物活性[25]，同時滅活糞水中部分有害微生物及致病菌[17]，從而通過化學(xué)生物作用降低NH3的排放。研究表明糞水酸化可以降低15%～77%的NH3排放（見表2），其中沈玉君等[37]研究成果表明酸化牛糞水至pH值為6.0可減少糞水貯存初始階段31.3%～54.0%的氨氣排放；DAI[38]等利用硫酸（H2SO4）酸化技術(shù)，可減少豬場污水和牛糞水50%以上的NH3排放。

酸化貯存對糞水氮素減損效果與酸化劑用量和酸化劑類型等因素密切相關(guān)[39]。郜斌斌等[12,40]的研究亦表明糞水酸化可大幅降低糞水中的NH3排放，同時NH3的排放隨酸化pH的降低而不斷降低；REGUEIRO等[41]研究發(fā)現(xiàn)在糞水中添加明礬也能起到類似的的減排效果，同時也能促進(jìn)磷（P）的增溶、提效，但其作用效果弱于常見強(qiáng)酸酸化劑。然而，目前大部分酸化糞水的pH值通常會控制在5.1以上，以使糞水酸化后酸堿度能夠逐漸恢復(fù)至中性或弱堿性。主要原因是當(dāng)酸化pH值過低時，可能會導(dǎo)致糞水長期貯存后仍呈酸性，不利于后期的還田利用，也增加了酸化工藝成本[42]。

表2 糞水酸化后氨氣排放情況

3.2 對N2O氣體排放的影響

糞水酸化貯存中，N2O主要來自氮素降解過程的反硝化階段，已有研究[37]表明，酸化會抑制糞水中有機(jī)物的降解，故理論而言酸化后的糞水在貯存中含氮有機(jī)物的降解率會下降，導(dǎo)致糞水中的銨氮生成量下降，且酸化劑的加入會降低銨氮向硝氮的轉(zhuǎn)化率，從而進(jìn)一步降低硝氮向N2O的轉(zhuǎn)化，故酸化糞水理論上也會顯著抑制糞水中N2O的排放量[43-46]。HUSTED以及WANG等學(xué)者[39-40]的研究均表明，糞水酸化會顯著降低酸化糞水貯存期間CH4、N2O等溫室氣體的排放量，雖然在糞水酸化階段排放量會顯著升高，主要是由于酸化階段攪拌擾動糞水導(dǎo)致的，并非添加酸化劑導(dǎo)致的。此外，李路路等[42,47]的研究表明酸化糞水會抑制N2O的排放，同時李路路還發(fā)現(xiàn)酸化沼液會提升2.59倍，但酸化沼液對CO2的排放量計劃無影響。綜上酸化糞水可以有效降低糞水貯存期間溫室氣體的排放。

3.3 對糞肥還田后土壤肥效的影響

國內(nèi)外已有研究發(fā)現(xiàn)，糞水酸化后還田可以提高土壤中N、P等有效態(tài)養(yǎng)分含量，對作物生長具有重要意義（見表3）。酸化糞污不僅可以降低貯存期糞污中氨氣的排放[28]，提高糞水中無機(jī)鹽成分，在酸化糞污施用到農(nóng)田后也能夠有效提高作物產(chǎn)量。FANGUEIRO等[48]通過向具有高有機(jī)質(zhì)含量的石灰性壤土和低有機(jī)質(zhì)含量的酸性砂土中施入酸化的糞污，土壤中的NH4+在施入后的30 d內(nèi)明顯大于添加未酸化糞污的處理，可以看出施入酸化處理的糞污可以使土壤中的N以NH4+的形式停留在土壤中，降低土壤中NH3揮發(fā)的損失。S?RENSEN[13,49]等的研究也表明向農(nóng)田施入酸化后的糞污能夠明顯降低土壤中NH3的揮發(fā)，同時其表明施入酸化的糞污的農(nóng)田中CH4的累積排放量也顯著下降，F(xiàn)ROST等[50]的研究表明施入酸化糞污的土壤相對施入未酸化糞污的土壤其氨揮發(fā)損失降低了85%，提高了黑麥草對NH4+的利用率，同時也明顯提升了該土壤上種植黑麥草的干物質(zhì)產(chǎn)量，同樣，也有研究[51]表明土壤表面施入酸化后的糞污能夠有效減少土壤N損失，促進(jìn)作物對N的吸收。FANGUEIRO等[52]最新研究再次表明在燕麥播種0 和8 d后的土壤表面單獨(dú)施用酸化豬糞水或與尿素聯(lián)合使用均能有效降低NH3-N的排放，尿素和酸化豬糞水聯(lián)合應(yīng)用還進(jìn)一步提高了尿素的使用效率。

表3 糞污酸化貯存及施用肥效特征

3.4 對農(nóng)田環(huán)境的影響

酸化后的糞水還田后可以提高土壤肥效，但不合理的酸化貯存技術(shù)及施用方式會降低糞水肥效，甚至引起二次污染[53-56]。主要原因是糞水中有大量以銨氮為主的鹽分，向糞水添加酸化劑會使銨鹽形態(tài)更加穩(wěn)定，雖然降低了氨氣排放，但卻增加了糞水鹽分含量，鹽含量升高是糞水酸化還田的難點(diǎn)之一。

正如COCOLO等[57]研究表明，酸化后糞水固液分離出的干物質(zhì)含量降低了10%～50%，這主要是由于糞污中部分固體物質(zhì)在酸性條件下以無機(jī)鹽的形式溶出。HJORTH等[58]發(fā)現(xiàn)糞水中的無機(jī)沉淀物在酸性條件下溶解，使可溶性磷和可溶性鈣、鎂含量增加，糞水電導(dǎo)率增加。

另外，也有研究者發(fā)現(xiàn)不科學(xué)的酸化還田技術(shù)會帶來土壤酸化問題，如FANGUEIRO等[59]將糞污酸化至pH值為5.5短期存放后進(jìn)行試驗，研究結(jié)果表明長期施用酸化后的糞污可能會導(dǎo)致土壤pH值降低。

HJORTH等[58]也發(fā)現(xiàn)類似現(xiàn)象，使用濃硫酸作為酸化劑會使土壤pH值降低。對于酸化糞水還田引起的鹽分過高問題，現(xiàn)有研究尚未提供系統(tǒng)解決方案[60-61]。而對于土壤酸化問題，部分學(xué)者研究提出延長糞水貯存時間等緩解路徑。如丁京濤等[62-64]發(fā)現(xiàn)隨著儲存時間的推移，還田前的糞污將呈中性乃至堿性，不足以對農(nóng)田pH及其土壤肥效產(chǎn)生影響。因此科學(xué)的糞水酸化還田技術(shù)可有效減少糞水酸化對土壤的副作用。同時，結(jié)合中國農(nóng)村環(huán)境和農(nóng)田自然稟賦情況以及糞水酸化存儲技術(shù)特征，分析認(rèn)為中國農(nóng)村地區(qū)應(yīng)采取養(yǎng)殖舍內(nèi)長期酸化的酸化工藝，待酸化糞水存儲足夠長時間后還田利用。

4 結(jié)論與展望

糞水酸化貯存技術(shù)是一種成本低、操作簡單的糞水資源化利用技術(shù)，能夠有效減少糞水貯存及農(nóng)田施用過程N(yùn)H3的揮發(fā)損失，提高糞水肥效，同時糞水酸化貯存還田可有效減少養(yǎng)分流失，對促進(jìn)中國種養(yǎng)循環(huán)、發(fā)展生態(tài)農(nóng)業(yè)具有重要的意義。目前，歐美等發(fā)達(dá)國家對糞水酸化貯存及施用技術(shù)的研究較多，在國內(nèi)仍處于初始探究階段，相關(guān)機(jī)理與技術(shù)研究存在許多不足。尤其是糞水酸化存儲過程中NH3和N2O排放規(guī)律尚不清楚，糞水酸化存儲過程N(yùn)H3和溫室氣體產(chǎn)排微生物驅(qū)動機(jī)制和協(xié)同減排的系統(tǒng)研究相對缺乏，科學(xué)經(jīng)濟(jì)的酸化技術(shù)工藝、應(yīng)用標(biāo)準(zhǔn)研究依然不足。

因此，針對現(xiàn)有研究中存在的不足，未來應(yīng)重點(diǎn)從以下幾方面深入研究：1）采用同位素示蹤等新型生化手段，結(jié)合定量PCR技術(shù)，探明糞水存儲過程中含氮?dú)怏w的產(chǎn)排規(guī)律，摸清糞水存儲過程中的氮素遷移轉(zhuǎn)化路徑；2）以復(fù)合酸化劑等作為研發(fā)重點(diǎn)，系統(tǒng)研究不同酸化劑、酸化方式對糞水的酸化效果，篩選出成本低、效果好的酸化劑，明確不同酸化劑、pH、貯存時間、貯存方式對糞水養(yǎng)分含量的影響效果及作用機(jī)制，進(jìn)而確定科學(xué)合理的酸化技術(shù)工藝；3）研究酸化后糞水的農(nóng)田施用效果及環(huán)境風(fēng)險，分析酸化糞水施用后對土壤理化性質(zhì)、土壤生物群落及酶活性、農(nóng)作物生長及產(chǎn)量、養(yǎng)分淋溶損失、氨氣及溫室氣體排放等變化特性，制定糞水酸化還田技術(shù)標(biāo)準(zhǔn)，規(guī)范糞水還田方式與施用量，減少環(huán)境風(fēng)險；4）在明確酸化機(jī)理及工藝參數(shù)的基礎(chǔ)上，開展適用于中小型養(yǎng)殖場的糞水酸化貯存裝備研發(fā)，同時要充分考慮相關(guān)酸化設(shè)備與設(shè)施的耐腐蝕性能，強(qiáng)化國內(nèi)酸化貯存技術(shù)的推廣應(yīng)用。

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Progress in the mechanism for the promotion of nitrogen loss reduction during the acidification storage of animal slurry

ZHANG Dongli, ZHANG Pengyue, SHEN Yujun, DING Jingtao※

(1.,,100125,; 2.,,100125,)

Acidification storage of animal slurry is one of the key technologies to effectively regulate the relationship between microorganisms, environment, and nitrogen for the high reduction of nitrogen loss and efficiency in animal slurry. This review aims to systematically investigate the nitrogen migration and transformation during the acidified storage of animal slurry in recent years. Three acidifiers were used, including the strong acid, hydrolyzed acidic salt, and easily decomposed organic matter. Three types of acidizing storage were then selected, namely long-term, medium, and long-term acidizing in the storage pool and short-term acidizing in the application. Finally, the economic cost and application effectiveness were comparatively evaluated in this case. More importantly, a systematic analysis was performed on the reduction of nitrogen losses and enhancement of fertilizer effectiveness, according to the technical route in the acidification storage. Furthermore, future research directions were addressed to identify the shortcomings of existing technologies for the acidified storage of animal slurry. Specifically, the nitrogen migration and transformation in the acidification storage process of animal slurry were divided into organic nitrogen mineralization, ammonium nitrogen fixation, inhibition of inorganic nitrogen conversion, and nitrification. Two reasons were attributed to reducing the nitrogen loss in the acidification storage of animal slurry. The addition of acidifiers was one way to change the dynamic balance of NH4+and NH3by lowering the pH of animal slurry, in order to promote the formation of NH4+while reducing the emission of dissolved NH3in animal slurry. The microbial activity decreased with the decreasing pH and mineralization of organic matter in animal slurry, thus reducing the production and emission of NH3. The acidification storage of animal slurry reduced the NH3emissions by 15%-77%. The degradation rate of nitrogenous organic compounds decreased with the addition of acidifiers, leading to the lower production of ammonium nitrogen. And the conversion rate of ammonium nitrogen to nitrate nitrogen was also reduced, thus further reducing the conversion of nitrate nitrogen to N2O. To sum up, the nitrogen losses were reduced to alter the microbial action and chemical equilibrium state. In addition, the long-term acidizing process presented more stable acidizing and a wider application range during the application, compared with the medium and long-term acidizing in the storage pool and the short-term acidizing. The acidification storage of animal slurry can be expected to stabilize and retain NH4+in the animal slurry. Therefore, acidification and returning to the field can improve the content of effective nutrients (such as N and P) in the soil for the high efficiency of soil fertility. However, the low efficiency of manure fertility and the secondary pollution can also be found in the unreasonable acidification storage and application in practice. It is a high demand for the quantitative analysis of nitrogen migration and transformation pathways in the process of fecal water storage, the complex acidifiers, and the post-acidification animal slurry in agricultural fields. The assessment and response to environmental risks can be launched for the research and development of acidification storage equipment in the future.

acids; fertilizer efficiency; animal slurry; nitrogen loss reduction

2022-11-05

2022-03-30

農(nóng)業(yè)農(nóng)村部規(guī)劃設(shè)計研究院自主研發(fā)項目：廢棄物肥料化利用創(chuàng)新團(tuán)隊（CXTD-2021-11）；青年拔尖人才支持計劃（SQ2022QB00354）；典型畜禽養(yǎng)殖場不同類型糞水資源價值與安全性綜合評估技術(shù)（21327304D）

張冬麗，博士，工程師，研究方向為農(nóng)業(yè)廢棄物資源化利用技術(shù)研發(fā)。Email：dongliustb@126.com

丁京濤，高級工程師，研究方向為農(nóng)業(yè)廢棄物資源化利用與環(huán)境保護(hù)技術(shù)研發(fā)。Email：dingjingtao@163.com

10.11975/j.issn.1002-6819.202211070

S21；X713

A

1002-6819(2023)-08-0012-08

張冬麗，張朋月，沈玉君，等. 畜禽養(yǎng)殖糞水酸化貯存及氮素減損增效研究進(jìn)展[J]. 農(nóng)業(yè)工程學(xué)報，2023，39(8)：12-19. doi：10.11975/j.issn.1002-6819.202211070 http://www.tcsae.org

ZHANG Dongli, ZHANG Pengyue, SHEN Yujun, et al. Progress in the mechanism for the promotion of nitrogen loss reduction during the acidification storage of animal slurry[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2023, 39(8): 12-19. (in Chinese with English abstract) doi：10.11975/j.issn.1002-6819.202211070 http://www.tcsae.org