秸稈還田與化肥配施對(duì)漢中盆地稻麥輪作農(nóng)田土壤固碳及經(jīng)濟(jì)效益的影響

吳玉紅 郝興順,* 田霄鴻 陳 浩 張春輝 崔月貞 秦宇航

秸稈還田與化肥配施對(duì)漢中盆地稻麥輪作農(nóng)田土壤固碳及經(jīng)濟(jì)效益的影響

吳玉紅1郝興順1,*田霄鴻2陳 浩1張春輝1崔月貞1秦宇航1

1漢中市農(nóng)業(yè)科學(xué)研究所, 陜西漢中 723000;2西北農(nóng)林科技大學(xué)資源環(huán)境學(xué)院, 陜西楊凌 721000

為漢中盆地秸稈還田技術(shù)和合理化肥減量技術(shù)提供科學(xué)依據(jù), 2015—2017年小麥和水稻生長(zhǎng)季, 設(shè)置秸稈不還田+常規(guī)施肥(SN+NPK); 秸稈常規(guī)還田+常規(guī)施肥(S+NPK); 秸稈促腐還田+常規(guī)施肥(SD+NPK); 秸稈促腐還田+化肥減量15% (SD+85%NPK); 秸稈促腐還田+化肥減量30% (SD+70%NPK), 共5個(gè)處理, 研究其對(duì)土壤總有機(jī)碳(TOC)、活性有機(jī)碳(LOC)、碳儲(chǔ)量(SCS)、作物產(chǎn)量及經(jīng)濟(jì)效益的影響。結(jié)果表明與秸稈不還田配施常規(guī)施肥處理(SN+NPK)相比, 秸稈還田配施不同比例化肥處理顯著提高了稻田0~15 cm土層的TOC和LOC, 增幅分別為3.62%~25.07%和23.01%~46.79%; S+NPK和SD+NPK處理提高了0~30 cm碳儲(chǔ)量, 增幅分別為4.67%和18.20%。而SD+85%NPK和 SD+70%NPK分別降低8.31%和9.83%。S+NPK和SD+NPK處理顯著增加了小麥和水稻籽粒產(chǎn)量, 而SD+85%NPK和SD+70%NPK處理均降低了小麥和水稻產(chǎn)量, 周年產(chǎn)量2年平均增幅分別為3.47%、8.70%、?3.65%、?8.12%。與SN+NPK處理相比, S+NPK、SD+NPK、SD+85%NPK、SD+70%NPK處理周年經(jīng)濟(jì)效益2年平均增幅分別為16.91%、23.56%、6.02%、1.06%。土壤有機(jī)碳、作物產(chǎn)量和經(jīng)濟(jì)效益SD+NPK處理的最高, S+NPK 處理次之, SD+70%NPK處理最低, 與之相比, SD+85%NPK處理在小麥和水稻兩季共減少化肥80 kg hm–2, 作物周年產(chǎn)量降低不明顯, 經(jīng)濟(jì)效益略有增加。秸稈還田與常規(guī)化肥配施是提高漢中盆地稻麥輪作體系農(nóng)田固碳、產(chǎn)量及經(jīng)濟(jì)效益的最佳措施, 兩季作物全量還田條件下化肥用量減少15%是適宜該區(qū)域的綠色生產(chǎn)模式。

稻麥輪作; 秸稈還田; 化肥減量; 土壤有機(jī)碳; 周年生產(chǎn)力

化肥在提高作物產(chǎn)量, 保障糧食安全方面做出了巨大貢獻(xiàn)[1], 但我國(guó)化肥施用過(guò)量現(xiàn)象普遍, 因而嚴(yán)重的農(nóng)業(yè)面源污染問(wèn)題日益突出[2-3]。源頭減量技術(shù)是控制農(nóng)業(yè)面源污染的根本所在, 而化肥減量是源頭減量的主要措施[4-5], 有機(jī)肥替代減量技術(shù)則是化肥減量的重要措施。漢中盆地是陜西省主要的水稻生產(chǎn)基地, 同時(shí)也是國(guó)家南水北調(diào)中線工程及引漢濟(jì)渭工程漢江的水源涵養(yǎng)地, 其水體污染狀況直接影響調(diào)水的水質(zhì), 而農(nóng)業(yè)面源污染是主要污染之一[6]。本區(qū)域化肥使用量普遍較大, 有機(jī)肥投入嚴(yán)重缺乏、秸稈利用率低等問(wèn)題較為突出[7-8]。秸稈直接還田不僅可以減少因秸稈焚燒而產(chǎn)生的環(huán)境污染,還可以提高土壤肥力, 被認(rèn)為是秸稈綜合利用中最經(jīng)濟(jì)有效的方式, 也是一種有效的農(nóng)田培肥措施[9]。在化肥零增長(zhǎng)的背景下, 對(duì)秸稈中養(yǎng)分進(jìn)行再利用從而減少化肥使用量作為控制種植業(yè)源頭面源污染的一項(xiàng)有效措施備受關(guān)注[7-11], 但受氣候條件和土壤肥力等因素的影響, 減量施肥效果可能存在著很大的區(qū)域性差異。減量技術(shù)應(yīng)兼顧作物產(chǎn)量和生態(tài)效益, 結(jié)合環(huán)境區(qū)域特征, 因地制宜, 因此更具針對(duì)性地提出化肥減量化技術(shù)對(duì)穩(wěn)定作物產(chǎn)量和減少面源污染具有重要意義。當(dāng)前針對(duì)北方旱地、南方雙季稻田、稻–油輪作體系秸稈還田與化肥減量配施對(duì)土壤有機(jī)碳、作物產(chǎn)量影響的研究較多[3,10-13], 而針對(duì)陜西南部水稻–小麥輪作系統(tǒng)中秸稈還田與化肥減量配施對(duì)土壤碳庫(kù)、作物產(chǎn)量及經(jīng)濟(jì)效益研究較為缺乏。因此, 研究適宜該地區(qū)秸稈還田替代化肥的適度減量技術(shù), 對(duì)保障農(nóng)業(yè)可持續(xù)發(fā)展及保證水源地水質(zhì)安全具有重要意義。本文探討了在秸稈還田基礎(chǔ)上減少化肥施用量的可行性, 開展了秸稈還田和化肥配施對(duì)稻麥輪作土壤有機(jī)碳、作物產(chǎn)量及經(jīng)濟(jì)效益影響研究, 旨在探索適宜漢中盆地稻麥輪作體系中培肥地力、提高產(chǎn)量、增加效益、生態(tài)安全的一種技術(shù)模式, 為漢江水源地秸稈還田效益和適度的化肥減量技術(shù)提供科學(xué)依據(jù)。

1 材料與方法

1.1 試驗(yàn)地概況

試驗(yàn)地位于陜西省勉縣漢中市農(nóng)業(yè)科學(xué)研究所試驗(yàn)示范站(33°09'38"N, 106°54'56"E), 海拔約600 m, 屬易濕潤(rùn)區(qū), 無(wú)霜期260 d, 年均氣溫14℃左右, 年均降水量800~1000 mm, ≥10℃年積溫為4480℃。供試土壤類型為黃褐土型潴育性水稻土。試驗(yàn)前土壤pH為5.19, 有機(jī)質(zhì)18.8 g kg–1、全氮1.25 g kg–1、速效磷35.3 mg kg–1、速效鉀78.9 mg kg–1。

1.2 試驗(yàn)設(shè)計(jì)

試驗(yàn)于2015—2017年間進(jìn)行, 實(shí)行冬小麥?水稻輪作。小麥季和水稻季均設(shè)置5個(gè)處理: ①秸稈不還田+常規(guī)施肥(SN+NPK); ②秸稈常規(guī)還田+常規(guī)施肥(S+NPK); ③秸稈促腐還田+常規(guī)施肥(SD+NPK); ④秸稈促腐還田+化肥減量15% (SD+85%NPK); ⑤秸稈促腐還田+化肥減量30% (SD+70%NPK)。水稻、小麥肥料均使用尿素(46%)、洋豐復(fù)合肥(14-16-15)、氯化鉀(60%)。施用山東君德牌高活性秸稈腐熟劑(枯草芽孢稈菌, 有效活菌數(shù)≥20億個(gè)g–1, 使用量30 kg hm–2)。秸稈還田方式及田間操作見(jiàn)表1。試驗(yàn)小區(qū)面積0.12 hm2, 東西長(zhǎng)80 m, 南北寬15 m, 每個(gè)處理0.36 hm2。為便于機(jī)械化作業(yè), 采用大區(qū)試驗(yàn)設(shè)計(jì), 隨機(jī)排列, 每個(gè)處理重復(fù)3次, 3個(gè)小區(qū)順序排列。

供試小麥品種為漢麥5號(hào), 分別于2015年10月15日播種, 2016年5月23日收獲, 2016年10月15日播種, 2017年5月24日收獲。小麥化肥常規(guī)用量為N 180 kg hm–2、P2O590 kg hm–2、K2O 84.6 kg hm–2?；蕼p量處理為NPK同時(shí)減少相應(yīng)的比例。所有處理中氮肥70%做底肥, 30%做追肥, 每年冬灌時(shí)追施, 磷鉀肥均做基肥。

供試水稻品種為中秈稻黃華占, 2016年于4月10日育秧, 5月30日機(jī)械插秧, 9月23日收獲。2017年于4月10日育秧, 6月1日機(jī)械插秧, 9月25日收獲。水稻常規(guī)施肥量為N 180 kg hm–2、P2O590 kg hm–2、K2O 105 kg hm–2?；蕼p量處理為NPK同時(shí)減少相應(yīng)的比例。所有處理中氮肥分移栽前基施、移栽后5 d和移栽后10 d追施, 比例為6︰2︰2, 磷鉀肥一次基施。

表1 小麥、水稻秸稈還田方式及田間操作

1.3 項(xiàng)目測(cè)定與方法

1.3.1 測(cè)產(chǎn) 水稻、小麥每個(gè)處理按“S”形選取5個(gè)5 m × 5 m的樣方, 單收脫粒后曬干稱量測(cè)產(chǎn)。

1.3.2 土壤容重測(cè)定 2017年水稻收獲后, 分0~15 cm和15~30 cm共2個(gè)層次采集環(huán)刀樣測(cè)定土壤容重。

1.3.3 土壤有機(jī)碳及活性有機(jī)碳測(cè)定 2017年9月水稻收獲后采集0~15 cm、15~30 cm土層的土壤樣品, 剔除植物殘?bào)w和其他雜物, 置陰涼通風(fēng)處攤晾干, 粉碎, 過(guò)0.15 mm篩備用。采用重鉻酸鉀外加熱法[14]測(cè)定土壤總有機(jī)碳(TOC); 采用333 mmol L–1KMnO4氧化-紫外分光光度計(jì)法[15]測(cè)定活性有機(jī)碳(LOC)。非活性有機(jī)碳含量為總有機(jī)碳和活性有機(jī)碳含量之差。以秸稈不還田處理的各土層碳含量作為參考, 計(jì)算碳庫(kù)管理指數(shù)[16]。

碳庫(kù)指數(shù)(CPI) = 樣品總有機(jī)碳含量/參考土壤總有機(jī)碳含量

碳庫(kù)活度(A) = 活性有機(jī)碳碳含量/非活性有機(jī)碳含量

碳庫(kù)活度指數(shù)(AI) = 樣品碳庫(kù)活度/參考土壤活度

碳庫(kù)管理指數(shù)(CPIM) = 碳庫(kù)指數(shù)×碳庫(kù)活度指數(shù)×100 = CPI×AI×100

土壤碳儲(chǔ)量 = 土壤有機(jī)碳含量×土壤容重×土層厚度

1.4 數(shù)據(jù)處理

采用Microsoft Excel 2003軟件處理數(shù)據(jù)和繪圖, 采用DPS 7.05統(tǒng)計(jì)分析軟件對(duì)數(shù)據(jù)進(jìn)行方差分析及差異顯著性檢驗(yàn)(LSD法,=0.05)。

2 結(jié)果與分析

2.1 稻麥輪作體系下秸稈還田和化肥減量配施對(duì)稻田土壤固碳的影響

由表2可以看出, 0~15 cm土層土壤總有機(jī)碳(TOC)和活性有機(jī)碳(LOC)含量明顯高于15~30 cm土層, 土壤有機(jī)碳具有明顯表聚現(xiàn)象。與秸稈不還田常規(guī)施肥處理(SN+NPK)相比, 秸稈還田配施化肥處理(S+NPK、SD+NPK、SD+85%NPK、SD+ 70%NPK)顯著增加了0~15 cm土層的總有機(jī)碳(TOC)和活性有機(jī)碳(LOC), 增幅分別為3.62%~25.07%和23.01%~46.79%, 且SD+NPK>S+NPK>SD+85%NPK> SD+70%NPK, 說(shuō)明秸稈還田對(duì)土壤活性有機(jī)碳影響更大。S+NPK和SD+NPK處理顯著增加了15~30 cm土層TOC和LOC, 而SD+85%NPK和SD+ 70%NPK處理顯著降低了15~30 cm土層TOC和LOC, SD+NPK處理下TOC和LOC增幅最大, 較SN+NPK分別提高18.51%和41.82%, 說(shuō)明秸稈促腐還田與常規(guī)化肥配施更有利于0~30 cm土層土壤有機(jī)碳的積累。

與秸稈不還田常規(guī)施肥處理(SN+NPK)相比(表3), S+NPK和SD+NPK顯著增加了0~15 cm土層的碳儲(chǔ)量和碳庫(kù)管理指數(shù), SD+85%NPK和SD+70%NPK顯著降低了0~15 cm土層碳儲(chǔ)量, 而顯著增加了碳庫(kù)管理指數(shù)。15~30 cm 土層, S+NPK和SD+NPK處理顯著增加了碳庫(kù)管理指數(shù), 而SD+85%NPK和SD+70%NPK顯著降低了碳庫(kù)管理指數(shù)。與SN+NPK相比, S+NPK和SD+NPK處理提高了0~30 cm碳儲(chǔ)量, 增幅分別為4.67%和18.20%。而SD+85%NPK和SD+70%NPK分別降低了8.31%和9.83%。說(shuō)明秸稈促腐還田與常規(guī)化肥配施更有利于碳儲(chǔ)量的增加, 秸稈促腐還田與化肥減量配施則不利于土壤碳的積累, 且在化肥減量的條件下隨著減肥比例的增加土壤碳氮比增加, 秸稈碳轉(zhuǎn)化受阻, 進(jìn)而不利于土壤碳儲(chǔ)量的增加。

2.2 秸稈還田與化肥配施對(duì)小麥和水稻產(chǎn)量的影響

如表4所示, 2年度試驗(yàn)結(jié)果基本一致。秸稈還田和秸稈促腐還田與常規(guī)施肥配施均提高了小麥、水稻的籽粒產(chǎn)量, 秸稈促腐還田與化肥減量配施則降低了小麥、水稻的籽粒產(chǎn)量, 且隨著化肥減量比例的增加, 減產(chǎn)幅度增加。SD+NPK處理增產(chǎn)幅度最大, 小麥、水稻2年平均每公頃增產(chǎn)687.9 kg和539.9 kg。周年總產(chǎn)方面, 與SN+NPK相比, S+NPK、SD+NPK2年平均增產(chǎn)3.47%和8.70%, SD+ 85%NPK、SD+70%NPK處理2年平均減產(chǎn)3.65%和8.12%, 說(shuō)明本試驗(yàn)條件下化肥減量對(duì)當(dāng)季作物產(chǎn)量的影響大于秸稈還田的效應(yīng)。秸稈還田量方面, 水稻高于小麥, 同時(shí)由于作物籽料產(chǎn)量的年度差異, 秸稈還田量也存在年度間差異, 表現(xiàn)為水稻秸稈還田量2個(gè)年度變化較小, 而小麥秸稈還田量2017年顯著高于2016年。

表2 不同秸稈還田下的土壤有機(jī)碳和活性有機(jī)碳含量

SN+NPK: 秸稈不還田+常規(guī)施肥; S+NPK: 秸稈還田+常規(guī)施肥; SD+NPK: 秸稈促腐還田+常規(guī)施肥; SD+85%NPK: 秸稈促腐還田+化肥減量15%; SD+70%NPK: 秸稈促腐還田+化肥減量30%。TOC: 土壤總有機(jī)碳; LOC: 活性有機(jī)碳。標(biāo)以不同小寫字母的值在處理間差異顯著(< 0.05)。

SN+NPK: NPK fertilization without straw return; S+NPK: NPK fertilization with straw returning; SD+NPK: NPK fertilization with decayed straw returning; SD+85%NPK: NPK fertilization rate reduction by 15% plus decayed straw returning; SD+70%NPK: NPK fertilization rates reduction by 30% plus decayed straw returning. TOC: soil total organic carbon; LOC: labile organic carbon. Values followed by different letters within the same column are significantly different at the 0.05 probability level.

表3 不同秸稈還田處理對(duì)土壤碳儲(chǔ)量及碳庫(kù)管理指數(shù)的影響

SCS: 土壤碳儲(chǔ)量; CPMI: 碳庫(kù)管理指數(shù)。標(biāo)以不同小寫字母的值在處理間差異顯著(< 0.05)?？s寫同表2。

SCS: carbon storage; CPMI: carbon pool management index. The soil bulk density of SN+NPK, S+NPK, SM+NPK, SM+85%NPK, SM+70% NPK was 1.39, 1.27, 1.31, 1.19, and 1.28 g cm–3in 0–15 cm and 1.74, 1.67, 1.73, 1.64, and 1.66 g cm–3in 15–30 cm.Values followed by different letters within the same column are significantly different at the 0.05 probability level.Abbreviations are the same as those given in Table 2.

秸稈還田與化肥減量配施條件下水稻和小麥的減產(chǎn)效應(yīng)年度間表現(xiàn)為2017年低于2016年。小麥秸稈還田與化肥減量配施降低了水稻籽粒產(chǎn)量, SD+85%NPK、SD+70%NPK較S+NPK處理2016年和2017年分別減產(chǎn)3.17%、6.53%和1.43%、3.49%。水稻秸稈還田與化肥減量配施降低了小麥籽粒產(chǎn)量, 2016年和2017年SD+85%NPK和SD+70%NPK處理減產(chǎn)率分別為12.96%、18.16%和0.89%、10.81%。

2.3 秸稈還田與化肥配施對(duì)水稻–小麥周年經(jīng)濟(jì)效益的影響

2016年和2017年周年產(chǎn)值及凈收益見(jiàn)表5。與秸稈不還田相比, S+NPK、SD+NPK、SD+85%NPK、SD+70%NPK處理周年經(jīng)濟(jì)效益2年平均增幅分別為16.91%、23.56%、6.02%、1.06%。秸稈還田與常規(guī)化肥配施產(chǎn)值和效益均明顯增加, 與化肥減量配施雖然產(chǎn)值下降, 但是降低了化肥投入成本、節(jié)約了秸稈移除的勞動(dòng)力成本, 經(jīng)濟(jì)效益除2016年度SD+70%NPK處理略低于SN+NPK處理外, 其他均高于對(duì)照處理。本試驗(yàn)條件下小麥和水稻兩季作物秸稈全量促腐還田配施常量化肥經(jīng)濟(jì)效益最佳, 較兩季不還田周年經(jīng)濟(jì)效益2年平均每公頃增加5110.50元。小麥、水稻秸稈全量促腐還田與化肥減量配施雖然對(duì)作物產(chǎn)量有影響但可以降低環(huán)境污染風(fēng)險(xiǎn), 節(jié)約成本, 增加經(jīng)濟(jì)效益。SD+85%NPK、SD+70%NPK處理周年經(jīng)濟(jì)效益2年平均每公頃較S+NPK分別增收1350.18元和273.41元。

表5 稻麥輪作體系下不同秸稈還田處理對(duì)周年經(jīng)濟(jì)效益的影響

根據(jù)當(dāng)?shù)厥袌?chǎng)銷售的肥料價(jià)格純N、P2O5、K2O分別為4.3、7.7、6.7 Yuan kg–1, 小麥、水稻價(jià)格2016年和2017年分別按照1.9、3.0 Yuan kg–1和2.0、3.1 Yuan kg–1計(jì)算。SN+NPK中秸稈處理勞動(dòng)力成本指人工移除秸稈的勞動(dòng)力成本, 按照100 Yuan person–1day–1, 30人hm–2計(jì)算, 其他處理秸稈處理勞動(dòng)力成本指秸稈覆蓋均勻的勞動(dòng)力成本, 按照100 Yuan person–1day–1, 4.5人hm–2。其他成本包括兩季作物灌溉費(fèi)用(900 Yuan hm–2)、兩季作物農(nóng)藥種子成本(750 Yuan hm–2)、小麥和水稻收獲機(jī)械成本(2700 Yuan hm–2)、機(jī)械旋耕成本(2700 Yuan hm–2)、水稻插秧機(jī)械成本(1350 Yuan hm–2)?？s寫同表2。

Data were based on average market price. Fertilizer prices were 4.3, 7.7, and 6.7 Yuan kg–1for net N, P2O5, and K2O, respectively. Crop prices were 1.9 and 3.0 Yuan kg–1for wheat and rice in 2016, 2.0 and 3.1 Yuan kg–1for wheat and rice in 2017, respectively. The labor cost refers to the cost of manual removal of straw and calculated according to 100 Yuan person–1day–1and 30 persons hm–2in the SN+NPK treatment. However, the labor cost in other treatments refers to the cost of manual mulching uniformly of straw and calculated according to 100 Yuan person–1day–1and 4.5 persons hm–2. Other costs include two-season crop irrigation costs, two-season crop seed and pesticide costs, wheat and rice harvesting machinery costs, wheat and rice mechanical tillage costs and rice transplanting machinery cost which were calculated at 900, 750, 2700, 2700, and 1350 Yuan hm–2, respectively. Abbreviations are the same as those given in Table 2.

3 討論

3.1 秸稈還田及與化肥配施對(duì)稻–麥輪作土壤有機(jī)碳、活性有機(jī)碳及碳儲(chǔ)量的影響

施肥和秸稈還田是影響土壤有機(jī)碳的重要管理措施。本試驗(yàn)中秸稈還田與各個(gè)化肥處理配施較秸稈不還田單施化肥處理, 顯著提高了0~15 cm土層的總有機(jī)碳(TOC)和活性有機(jī)碳(LOC)。秸稈常規(guī)還田和秸稈促腐還田與常規(guī)化肥配施顯著增加了15~30 cm土層TOC和LOC, 而秸稈還田與化肥減量配施則顯著降低了TOC和LOC, 且隨著化肥減少量的增加降幅呈遞增趨勢(shì)。本試驗(yàn)條件下秸稈旋耕還田主要集中在0~15 cm土層, 秸稈還田對(duì)0~15 cm土層有機(jī)碳的影響大于施肥的影響。這與相關(guān)研究結(jié)果一致[17]。趙亞南等研究四川盆地施肥對(duì)稻麥輪作下紫色土有機(jī)碳的影響, 表明秸稈還田與化肥配施處理對(duì)有機(jī)碳的提升效果高于單施化肥的處理。本試驗(yàn)中土壤活性有機(jī)碳含量的變化幅度較總有機(jī)碳大, 說(shuō)明活性有機(jī)碳對(duì)秸稈還田的響應(yīng)較為敏感。本文中秸稈還田與化肥配施的處理較單施化肥處理, 顯著提高了0~15 cm土層的碳庫(kù)管理指數(shù), 15~30 cm土層秸稈還田與常規(guī)化肥配施顯著增了碳庫(kù)管理指數(shù)而秸稈還田與化肥減量配施顯著降低了碳庫(kù)管理指數(shù)。本試驗(yàn)中秸稈還田和秸稈促腐還田與常規(guī)化肥配施均提高了0~15 cm和15~30 cm土層的碳庫(kù)管理指數(shù)和碳儲(chǔ)量, 秸稈促腐還田配施化肥更能提高碳庫(kù)管理指數(shù)和碳儲(chǔ)量, 這與相關(guān)研究結(jié)論一致[19], 這可能與秸稈促腐還田增加了土壤有機(jī)碳和土壤活性有機(jī)碳有關(guān)。而秸稈促腐還田與化肥減量配施較秸稈促腐還田與常規(guī)化肥配施顯著降低了0~15 cm和15~30 cm土層的碳庫(kù)管理指數(shù)和碳儲(chǔ)量, 可能是因?yàn)榛蕼p施較常規(guī)施肥增加了C/N, 使得秸稈的腐解受到了抑制。

3.2 秸稈還田與化肥減量配施對(duì)稻–麥輪作周年生產(chǎn)力的影響

化肥零增長(zhǎng)行動(dòng)的背景下, 不同種植體系中化肥減量技術(shù)研究得到了廣泛的關(guān)注。很多研究表明[20-22], 水稻–小麥、小麥–玉米、玉米–油菜等輪作體系中, 適量減肥并沒(méi)有引起產(chǎn)量的顯著變化。本試驗(yàn)中秸稈還田與化肥減量配施均顯著降低了小麥和水稻的產(chǎn)量, 且隨著化肥減量的增加對(duì)作物產(chǎn)量的負(fù)面影響遞增。本試驗(yàn)中秸稈還田與化肥減量配施對(duì)水稻產(chǎn)量影響小于對(duì)小麥產(chǎn)量的影響, 可能是由于水田具有較好的水熱穩(wěn)定性, 基礎(chǔ)地力對(duì)水稻產(chǎn)量的貢獻(xiàn)大[23]。此外, 也可能是因?yàn)樗炯拘←溄斩掃€田和小麥季水稻秸稈還田的肥料效應(yīng)差異性, 水稻季小麥秸稈還田后高溫和淹水條件下有利于小麥秸稈的腐解和養(yǎng)分的釋放, 減弱了化肥減量對(duì)水稻生長(zhǎng)的顯著影響, 而小麥生長(zhǎng)在冬季, 氣溫低且干旱, 水稻秸稈腐解及養(yǎng)分釋放較慢, 不能顯著降低減肥對(duì)小麥生長(zhǎng)的影響, 這一研究結(jié)論與趙亞南等[3]研究的稻油輪作減量施肥對(duì)水稻油菜生長(zhǎng)影響的結(jié)論一致。

梁濤等[24]研究四川盆地稻田基礎(chǔ)地力對(duì)產(chǎn)量的響應(yīng)表明, 隨著基礎(chǔ)地力的提升, 土壤對(duì)產(chǎn)量的貢獻(xiàn)越來(lái)越大, 肥料對(duì)產(chǎn)量的影響越來(lái)越小。因此化肥減量基礎(chǔ)是建立在高的基礎(chǔ)肥力的基礎(chǔ)之上, 化肥減量的適宜比例與土壤基礎(chǔ)地力、作物類型有較大的關(guān)系。本試驗(yàn)中秸稈還田與化肥減量配施均降低了小麥和水稻的產(chǎn)量, 但是隨著秸稈還田年限的增加, 作物減產(chǎn)效應(yīng)有下降趨勢(shì), 可能是因?yàn)殡S著小麥和水稻秸稈逐年歸還進(jìn)入土壤, 土壤匯碳功能增強(qiáng)從而提升了土壤基礎(chǔ)地力, 化肥減量對(duì)作物產(chǎn)量的影響作用減小。添加秸稈腐熟劑是促進(jìn)秸稈腐解的重要措施之一[25]。已有研究證實(shí), 秸稈促腐還田可以加速秸稈腐解進(jìn)程、增加作物產(chǎn)量[26-27]。本試驗(yàn)中秸稈還田施用腐熟劑配施常規(guī)化肥與常規(guī)秸稈還田配施化肥相比, 對(duì)小麥和水稻產(chǎn)量的增加并未表現(xiàn)出較強(qiáng)的優(yōu)勢(shì), 可能是因?yàn)榻斩挻俑€田初期腐熟劑中功能微生物促進(jìn)土壤微生物大量快速繁殖, 產(chǎn)生了與作物競(jìng)爭(zhēng)養(yǎng)分的現(xiàn)象, 對(duì)作物生長(zhǎng)初期產(chǎn)生一定影響, 但隨著秸稈腐解, 促腐條件下秸稈中養(yǎng)分釋放及土壤養(yǎng)分有效性提升優(yōu)于常規(guī)秸稈還田處理, 相比而言秸稈促腐還田更有利于促進(jìn)作物中后期的生長(zhǎng), 可見(jiàn), 秸稈腐熟劑和化肥配施的最佳用量需進(jìn)一步研究, 以便秸稈促腐還田技術(shù)的推廣應(yīng)用。

3.3 秸稈還田量和化肥減量比例對(duì)作物產(chǎn)量的影響

秸稈還田可替代下季作物化學(xué)養(yǎng)分的比例受秸稈還田量、秸稈種類等因素影響較大[28]。秸稈碳源的輸入有利于促進(jìn)土壤微生物繁殖, 土壤微生物參與土壤C、N、P等元素循環(huán)過(guò)程中可能造成微生物與作物競(jìng)爭(zhēng)養(yǎng)分, 本試驗(yàn)中水稻秸稈還田量高于小麥秸稈還田量, 微生物與小麥競(jìng)爭(zhēng)養(yǎng)分更加激烈, 而化肥減量條件下養(yǎng)分競(jìng)爭(zhēng)則愈加激烈。不同類型秸稈可替代下季作物化肥減量的比例也存在差異, 宋大利等[24]認(rèn)為長(zhǎng)江中下游稻麥輪作體系中隨著秸稈還田量的增加, 可以替代下季作物的化學(xué)養(yǎng)分施用量比例也隨之增大, 水稻秸稈全量還田(6891.2 kg hm–2)理論上可以替代小麥34.0% (N)和34.7% (P2O5)化學(xué)養(yǎng)分施用量, 2/3水稻秸稈還田就可以完全替代小麥化肥鉀的施用量, 小麥秸稈全量還田 (5392.2 kg hm–2)可以替代水稻19.7% (N)、12.0% (P2O5)和54.2% (K2O)的化學(xué)養(yǎng)分施用量。而本試驗(yàn)中水稻秸稈全量還田條件下NPK養(yǎng)分替代比例15%、30%時(shí), 水稻秸稈2年平均還田量為8943.9 kg hm–2和8695.5 kg hm–2, 均高于6891.2 kg hm–2, 但小麥產(chǎn)量?jī)赡昶骄謩e下降6.93%和14.49%。小麥秸稈全量還田條件下NPK養(yǎng)分替代比例為15%和30%時(shí), 小麥秸稈2年平均還田量分別為4477.9 kg hm–2、4892.3 kg hm–2, 均低于5392.2 kg hm–2, 水稻產(chǎn)量2年平均分別下降2.30%和5.01%?？梢?jiàn)秸稈還田量和可替代下季作物化學(xué)養(yǎng)分施用量比例理論值與生產(chǎn)實(shí)際差異較大, 本試驗(yàn)中秸稈還田量為全量還田, 化肥替代比例只涉及了15%和30%, 因此適宜本區(qū)域的秸稈還田量和不同化肥減量比例的最優(yōu)組合有待進(jìn)一步深入研究。

4 結(jié)論

秸稈還田與化肥配施均能夠顯著提高0~15 cm土層土壤有機(jī)碳和活性有機(jī)碳, 且對(duì)土壤活性有機(jī)碳促進(jìn)作用更明顯。秸稈還田和秸稈促腐還田與常量化肥配施增加了0~30 cm土層碳儲(chǔ)量, 同時(shí)提高了小麥和水稻的產(chǎn)量及經(jīng)濟(jì)效益。秸稈還田與化肥減量配施0~30 cm土層碳儲(chǔ)量有下降趨勢(shì), 小麥和水稻產(chǎn)量下降但經(jīng)濟(jì)效益增加。稻麥體系條件下兩季作物秸稈促腐還田配施常量化肥產(chǎn)值與效益最佳, 兩季作物秸稈常規(guī)還田配施常量化肥次之, 而兩季作物秸稈促腐還田條件下化肥減量15%對(duì)小麥水稻產(chǎn)量沒(méi)有顯著影響, 不僅可以維持作物穩(wěn)產(chǎn), 節(jié)約成本, 提高經(jīng)濟(jì)效益, 又可以降低環(huán)境污染風(fēng)險(xiǎn), 同時(shí)具有農(nóng)學(xué)、環(huán)境及經(jīng)濟(jì)的三重效應(yīng)。因此, 秸稈還田與化肥配施是提高漢中盆地稻麥輪作體系農(nóng)田固碳、產(chǎn)量及經(jīng)濟(jì)效益的最佳措施, 而兩季作物秸稈全量還田條件下化肥減量15%是適宜該區(qū)域的化肥減量技術(shù)和綠色生產(chǎn)模式。

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Effect of straw returning combined with NPK fertilization on soil carbon sequestration and economic benefits under rice–wheat rotation in Hanzhong basin

WU Yu-Hong1, HAO Xing-Shun1,*, TIAN Xiao-Hong2, CHEN Hao1, ZHANG Chun-Hui1, CUI Yue-Zhen1, and QIN Yu-Hang1

1Hanzhong Agricultural Research Institute, Hanzhong 723000, Shaanxi, China;2College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, Shaanxi, China

A two-year field experiment was conducted to investigate the response of soil carbon sequestration, crop yield and economic benefit to rates of NPK application and straw returning under rice–wheat rotation from 2015 to 2017. The experiment included five treatments: application of NPK without straw returning (SN+NPK), application of NPK with straw returning (S+NPK), application of NPK with decayed straw returning (SD+NPK), application of NPK with 15% reduction plus decayed straw returning (SD+85%NPK) and application of NPK with 15% reduction plus decayed straw returning (SD+70%NPK). Compared with SN+NPK, total organic carbon (TOC) and active organic carbon (LOC) in 0–15 cm depth increased by 3.62%–25.07% and 23.01%–46.79% in the treatments of straw returning plus different returned NPK application, respectively. Both S+NPK and SD+NPK treatments increased organic carbon storage (SCS) in 0–30 cm soil layer by 4.67% and 18.20%, but SD+85%NPK and SD+70%NPK decreased the SCS by 8.31% and 9.83%, respectively. Compared with SN+NPK, both S+NPK and SD+NPK increased grain yields for wheat and rice. However, SD+85%NPK and SD+70%NPK treatments significantly reduced grain yields for wheat and rice. Compared with SN+NPK treatment, the increase in annual average yield was 3.47% for S+NPK, 8.70% for SD+NPK, –3.65% for SD+85%NPK, and –8.12% for SD+70%NPK, while the increase of annual net profit in two years was 16.91%, 23.56%, 6.02%, and 1.06%, respectively. Soil organic carbon, crop yield and efficiency were the highest in the SD+NPK treatment, but lowest in SD+70%NPK. Compared with SD+70%NPK treatment, SD+85%NPK did not affect the annual average yield, but slightly increased the annual net profit due to a cost reduction caused by less fertilizer application with a total reduction of 80 kg ha–1. In conclusion, the combination of straw returning with NPK fertilization is an effective farming practice to improve soil carbon sequestration, crop yield and economic benefits in Hanzhong basin. Considering the environment and economic effects, decayed straw returning with 15% reduction in NPK application is more suitable to achieve the fertilizer reduction and green production.

rice–wheat rotation; straw return; fertilizer reduction; soil organic carbon; annual productivity

本研究由陜西省科技統(tǒng)籌創(chuàng)新工程計(jì)劃項(xiàng)目(2015KTCL02-21)和陜西省農(nóng)業(yè)科技創(chuàng)新轉(zhuǎn)化項(xiàng)目(NYKJ-2018-HZ01)資助。

This study was supported by the Innovation Project of Science and Technology of Shaanxi Province (2015KTCL02-211) and the Agricultural Science and Technology Innovation and Transformation Project of Shaanxi Province (NYKJ-2018-HZ01).

10.3724/SP.J.1006.2020.92013

郝興順, E-mail: 372770515@qq.com, Tel: 0916-2231123

E-mail: 382755569@qq.com

2019-03-19;

2019-09-26;

2019-10-15.

URL:http://kns.cnki.net/kcms/detail/11.1809.S.20191015.1208.002.html