蘭艷,黃鵬,江谷馳弘,雷小波,丁春邦,李天,3*(.四川農(nóng)業(yè)大學(xué)農(nóng)學(xué)院,成都630;.四川農(nóng)業(yè)大學(xué)生命科學(xué)學(xué)院,四川雅安6504;3.四川農(nóng)業(yè)大學(xué)水利水電學(xué)院,四川雅安6504)

成都平原稻作區(qū)施氮量和栽插密度對(duì)粳稻D46產(chǎn)量及品質(zhì)的影響

蘭艷1,黃鵬1,江谷馳弘1,雷小波1,丁春邦2,李天1,3*
(1.四川農(nóng)業(yè)大學(xué)農(nóng)學(xué)院,成都611130;2.四川農(nóng)業(yè)大學(xué)生命科學(xué)學(xué)院,四川雅安625014;3.四川農(nóng)業(yè)大學(xué)水利水電學(xué)院,四川雅安625014)

摘要為探明成都平原稻作區(qū)粳稻產(chǎn)量和品質(zhì)與施氮量、栽插密度及其互作的關(guān)系,實(shí)現(xiàn)水稻高產(chǎn)優(yōu)質(zhì)生產(chǎn).以粳稻D46為供試品種,采用二因素裂區(qū)試驗(yàn)設(shè)計(jì),設(shè)置3個(gè)氮水平(N 150、225、300 kg/hm2)和3個(gè)栽插密度(20× 104、26.67×104、40×104穴/hm2),研究其對(duì)粳稻D46產(chǎn)量和品質(zhì)的影響.結(jié)果表明,施氮量和栽插密度均顯著影響粳稻D46產(chǎn)量及其構(gòu)成因素(P＜0.05).在施氮量為225 kg/hm2和栽插密度為26.67×104穴/hm2時(shí),水稻產(chǎn)量最高(7.58×103kg/hm2),顯著高于其他處理(P＜0.05).施氮量和栽插密度對(duì)稻米品質(zhì)均有不同程度的影響,其中施氮量的影響最為顯著.在施氮量＜225 kg/hm2時(shí),隨著氮肥施用量的增加,稻米的加工品質(zhì)提高,堊白率和蛋白質(zhì)含量增加,堊白度和食味品質(zhì)降低;而當(dāng)施氮量＞225 kg/hm2時(shí)稻米品質(zhì)隨氮肥用量的增加而降低.提高栽插密度不利于稻米品質(zhì)形成.本試驗(yàn)研究認(rèn)為,實(shí)現(xiàn)成都平原稻作區(qū)粳稻D46高產(chǎn)與優(yōu)質(zhì)的適宜施氮量為225 kg/hm2,栽插密度為26.67×104穴/hm2.

關(guān)鍵詞成都平原;施氮量;栽插密度;粳稻D46;產(chǎn)量;品質(zhì)

浙江大學(xué)學(xué)報(bào)(農(nóng)業(yè)與生命科學(xué)版) 42(1):63～73,2016

Journal of Zhejiang University(Agric.&Life Sci.)

http://www.journals.zju.edu.cn/agr

E-mail:zdxbnsb@zju.edu.cn

URL:http://www.cnki.net/kcms/detail/33.1247.S.20160119.1928.008.html

Effect of nitrogen application and planting density on grain yield and quality of japonica rice cultivar D46 in the planting area of Chengdu plain.Journal of Zhejiang University(Agric.&Life Sci.),2016,42(1):63-73

LAN Yan1,HUANG Peng1,JIANG Guchihong1,LEI Xiaobo1,DING Chunbang2,LI Tian1,3*(1.Agricultural College,Sichuan Agricultural University,Chengdu 611130,China;2.College of Life Sciences,Sichuan Agricultural University,Ya”an 625014,Sichuan,China;3.College of Water Conservancy and Hydropower Engineering,Sichuan Agricultural University,Ya”an 625014,Sichuan,China)

Summary Rice is one of the most important crops in the world,especially in Asia,where more than 90%of the world’s rice is grown and consumed.In recent years,with the increase of living quality,the requirement for rice improvement is not only limited to yield,but also to its quality.During rice development,genetic and environmental factors significantly affect both of the yield and quality.Among the environmental factors,fertilizer management and planting density are considered as the main factors affecting rice growth and development.Data from the previous studies on the impact of nitrogen application rate and planting density on rice yield and quality have beeninconsistent due to the differences in regional ecological conditions.Therefore,it is necessary to continue exploring the influence of nitrogen application rate and planting density on rice yield and quality.

Chengdu plain,the main rice cropping region in the southwest of China,has the unique light,heat and water resources.In order to promote the planting of a japonica rice variety(identified in our previous research)in this area,we investigated how nitrogen(N)application rate and planting density and their interactions affect grain yield and quality.Data from this study would provide information for japonica rice cultivation in the area for high yield and good quality.

To investigate the effect of nitrogen application rate and planting density on rice grain yield and quality characteristics,we used japonica rice cultivar D46 as the test material in this study.Split plot experiments with N application rate(N 150,225 and 300 kg/hm2)as main plot and planting density(20×104,26.67×104and 40×104seedlings/hm2)as sub-plot were carried out.The experiment was conducted on sandy loam in 2013 at the experimental farm of Sichuan Agricultural University in Wenjiang,China.

The results showed that both N application rate and planting density had significant effects on the yield of the japonica rice cultivar D46(P＜0.05).The combination of N application rate of 225 kg/hm2and planting density of 26.67×104seedlings/hm2led to the highest yield(7.58×103kg/hm2),and which was significantly higher than other treatments(P＜0.05).Dry matter accumulation tended to increase with the increase of N application rate during the whole growth period,whereas,for planting density,it reached the maximum at 26.67×104seedlings/hm2rather than at 20×104and 40×104seedlings/hm2.Furthermore,N application rate and planting density were shown to have different degrees of influence on the rice quality.The processing quality,chalky rate and protein content increased as the N application increased from 150 to 225 kg/hm2and then declined with any further increases in N supply.In contrast,increasing planting density was not conducive to improving rice quality.

Based on the results,and considering the importance of improving both rice yield and quality,the optimal combination of N application rate and planting density for japonica rice cultivar D46 in the planting area of Chengdu plain is N 225 kg/hm2and 26.67×104seedlings/hm2,respectively.

Key words Chengdu plain;nitrogen application rate;planting density;japonica rice cultivar D46;grain yield;grain quality

水稻產(chǎn)量和品質(zhì)形成主要受遺傳因子和環(huán)境因素的調(diào)控[1-6].在諸多環(huán)境因素中,種植密度和肥料運(yùn)籌是影響水稻生長(zhǎng)發(fā)育的重要因素[7 9].隨著農(nóng)業(yè)用地日益緊張和不合理施肥導(dǎo)致的面源污染加劇,以優(yōu)化栽培密度和高效利用肥料的水稻高產(chǎn)優(yōu)質(zhì)技術(shù)研究得到廣泛的關(guān)注[3,10 14].

已有研究表明,在一定范圍內(nèi)施氮量與產(chǎn)量呈拋物線關(guān)系,適當(dāng)增施氮肥量有利于植株生長(zhǎng),可以提高水稻產(chǎn)量[15];但過(guò)量氮肥施用不利于水稻營(yíng)養(yǎng)器官中的碳水化合物形成和氮素向籽粒轉(zhuǎn)移,最終導(dǎo)致產(chǎn)量降低和土壤中氮素積累[16].近年來(lái),如何提高稻米品質(zhì)成為研究的核心,其中施氮量和栽插密度對(duì)稻米品質(zhì)的影響成為研究的焦點(diǎn)[17-20].徐春梅等[19]研究認(rèn)為增施氮肥能夠提高稻米的碾磨和外觀品質(zhì)以及蛋白質(zhì)含量;而栽插密度對(duì)稻米品質(zhì)影響不明顯.謝黎虹等[21]研究認(rèn)為增大種植密度可以提高整精米率,降低RVA的消減值、回復(fù)值和米飯質(zhì)地的硬度.眾多研究一致認(rèn)為,整精米率和蛋白質(zhì)含量隨施氮量提高而增加,而堊白性狀和直鏈淀粉含量對(duì)氮肥用量的響應(yīng)則不一致[22].

本課題組多年來(lái)致力于粳稻品種選育和推廣種植,篩選出了米飯食味獨(dú)特,產(chǎn)量高,適宜在成都平原種植的粳稻品種D46.為進(jìn)一步加快該品種在成都平原稻作區(qū)的推廣,本試驗(yàn)在前人已研究證明施氮量和栽插密度是影響水稻產(chǎn)量和品質(zhì)形成的主要因素的基礎(chǔ)上,以施氮量和栽插密度為因素,研究其對(duì)粳稻D46品質(zhì)的影響,對(duì)在成都平原稻作區(qū)生態(tài)條件下推廣種植粳稻具有重要的現(xiàn)實(shí)生產(chǎn)意義和理論意義.

1　材料與方法

1.1供試材料

田間試驗(yàn)于2013年在四川農(nóng)業(yè)大學(xué)成都校區(qū)試驗(yàn)農(nóng)場(chǎng)進(jìn)行.試驗(yàn)田耕層土壤質(zhì)地為沙質(zhì)壤土,有機(jī)質(zhì)含量25.09 g/kg,全氮1.53 g/kg,全磷0.38g/kg,全鉀14.23 g/kg,堿解氮150.20 mg/kg,速效磷58.64 mg/kg,速效鉀108.52 mg/kg,p H 6.79.供試水稻品種為粳稻D46,該品種株型適中,產(chǎn)量高,品質(zhì)優(yōu),穩(wěn)產(chǎn),全生育期為140 d左右.

1.2試驗(yàn)設(shè)計(jì)

采用二因素裂區(qū)設(shè)計(jì),主區(qū)為栽插密度(D),設(shè)3個(gè)水平,分別為20×104穴/hm2(25 cm×20 cm,D1),26.67×104穴/hm2(25 cm×15 cm,D2)和40×104穴/hm2(25 cm×10 cm,D3);副區(qū)為施氮量,分別為無(wú)氮對(duì)照(N0)、低氮(N 150 kg/hm2,N1)、中氮(N 225 kg/hm2,N2)和高氮(N 300 kg/hm2,N3).共12個(gè)處理,每個(gè)處理3次重復(fù).每個(gè)小區(qū)面積24 m2.小區(qū)間筑埂并用塑料薄膜包裹(高35 cm,寬30 cm),以防止串水串肥,小區(qū)四周設(shè)置保護(hù)行.4月2日播種,地膜育秧,5月7日移栽,葉齡為五葉一心,每穴雙苗.

試驗(yàn)以尿素(N≥46.4%)為氮肥,作為基肥與蘗肥施入,比例為7∶3;以過(guò)磷酸鈣(含P2O512.0%)為磷肥,施用量為120 kg/hm2,全部以基肥一次性施入;以氯化鉀(含K2O 60%)為鉀肥,施用量為180 kg/hm2,作為基肥和穗肥施入,比例為1∶1.其余田間管理措施與一般大田水稻生產(chǎn)相同.

1.3測(cè)定項(xiàng)目與方法

1.3.1產(chǎn)量及其構(gòu)成因素

成熟前每小區(qū)選取30株調(diào)查有效穗數(shù);并各取具有代表性植株5株進(jìn)行考種,調(diào)查每穗粒數(shù)、結(jié)實(shí)率、千粒質(zhì)量等指標(biāo),然后分區(qū)收獲,脫粒后曬干稱量.

1.3.2干物質(zhì)質(zhì)量的測(cè)定

分別于水稻分蘗盛期、拔節(jié)期、抽穗期、灌漿中期、成熟期按平均數(shù)法對(duì)每個(gè)處理隨機(jī)選取3穴取樣,將根剪除后按葉片、莖鞘、穗(抽穗后)分開,洗凈后在105℃下殺青30 min,75℃烘干至恒量,測(cè)定各器官的干物質(zhì)質(zhì)量.

1.3.3稻米品質(zhì)的測(cè)定

各處理稻谷收獲后自然陰干、存放3個(gè)月使其理化性質(zhì)穩(wěn)定后測(cè)定其加工、外觀、蒸煮及營(yíng)養(yǎng)品質(zhì).堊白率和堊白度根據(jù)《GB/T 17891—1999》,糙米率根據(jù)《GB/T 5495—2008》,整精米率根據(jù)《GB 1350—2009》,直鏈淀粉含量依據(jù)《GB 15683—2008》,蛋白質(zhì)含量根據(jù)《NY/T 3—1982》的方法測(cè)定.

稻米淀粉黏滯性使用澳大利亞Newport Scientific儀器公司生產(chǎn)的3-D型RVA儀測(cè)定,并用TCW(thermal cycle for Windows)配套軟件進(jìn)行分析.按照AACC操作規(guī)程[23],測(cè)定稻米R(shí)VA譜特性;用峰值黏度、熱漿黏度、冷膠黏度、崩解值(峰值黏度與熱漿黏度之差)、消減值(冷膠黏度與峰值黏度之差)、回復(fù)值(冷膠黏度與熱漿黏度之差)表示,單位為RVU(rapid visco units)表示.

1.4數(shù)據(jù)處理

所有數(shù)據(jù)利用SPSS 19.0統(tǒng)計(jì)軟件進(jìn)行數(shù)據(jù)分析,結(jié)果均為3次重復(fù)的平均值,利用最小顯著差數(shù)法(LSD)在P＜0.05水平上做多重比較.

2　結(jié)果

2.1施氮量和栽插密度對(duì)D46產(chǎn)量的影響

由表1可知,施氮量和栽插密度不同,粳稻D46籽粒產(chǎn)量均有差異.與對(duì)照N0(5.86×103kg/hm2)相比,N1、N2和N3處理的籽粒產(chǎn)量分別增產(chǎn)14.61%、25.01%和19.27%,達(dá)到顯著差異水平(P＜0.05).但N2和N3處理間的籽粒產(chǎn)量差異不顯著(P＞0.05),表明施氮量達(dá)到225 kg/hm2時(shí),繼續(xù)增加氮肥用量對(duì)產(chǎn)量增加不明顯.而不同密度間稻谷產(chǎn)量差異不明顯(P＞0.05).

從粳稻D46產(chǎn)量構(gòu)成因素分析(表1)可知,施氮量對(duì)有效穗數(shù)影響達(dá)到顯著水平(P＜0.05),穗數(shù)隨著施氮量的增加而增加,但在N2和N3處理間的有效穗數(shù)差異不明顯(P＞0.05),表明在田間生產(chǎn)中施氮量為225 kg/hm2時(shí)就可保證高產(chǎn)的足夠有效穗數(shù);而施氮量對(duì)每穗粒數(shù)和結(jié)實(shí)率影響均未達(dá)到顯著差異水平(P＞0.05),說(shuō)明粳稻D46的每穗粒數(shù)和結(jié)實(shí)率對(duì)氮肥響應(yīng)不敏感;施氮量對(duì)千粒質(zhì)量影響達(dá)到顯著水平(P＜0.05),千粒質(zhì)量隨著氮肥用量的增加而下降.栽插密度對(duì)粳稻D46產(chǎn)量構(gòu)成因素均達(dá)到顯著或極顯著影響(千粒質(zhì)量除外);有效穗數(shù)隨栽插密度增加而增加,但在中密度D2和高密度D3處理間差異不顯著;而每穗粒數(shù)、結(jié)實(shí)率和千粒質(zhì)量則隨著栽插密度的增加總體上呈下降的趨勢(shì).

2.2施氮量和栽插密度對(duì)D46干物質(zhì)質(zhì)量的影響

氮肥運(yùn)籌對(duì)粳稻D46主要生育期干物質(zhì)積累量的影響達(dá)極顯著水平(P＜0.01);不同栽插密度對(duì)粳稻D46主要生育期干物質(zhì)積累量的影響達(dá)顯著或極顯著水平(分蘗期除外);而兩者交互效應(yīng)對(duì)粳稻D46干物質(zhì)積累量主要體現(xiàn)在分蘗期、拔節(jié)期和灌漿期(表2).

在粳稻D46生育前期(分蘗期和拔節(jié)期),干物質(zhì)積累量以高密度D3處理最大;而在其生育后期(拔節(jié)期至成熟期)則以中密度D2處理最大.這是由于隨著生育期推進(jìn),水稻生長(zhǎng)旺盛,在低密度D1處理下,穴數(shù)少導(dǎo)致干物質(zhì)積累量也少;而在高密度D3處理下,植株生長(zhǎng)擁擠,生長(zhǎng)環(huán)境變差導(dǎo)致干物質(zhì)積累量降低.而氮肥運(yùn)籌對(duì)粳稻D46各生育期干物質(zhì)積累量的影響明顯高于栽插密度運(yùn)籌,且對(duì)中后期的影響程度明顯高于生育前期,以拔節(jié)期影響最明顯.隨著氮肥施用量的增加,水稻各生育期干物質(zhì)積累量逐漸增加,以氮水平225 kg/hm2時(shí)達(dá)到最大值;再繼續(xù)增施氮肥會(huì)使水稻干物質(zhì)積累量呈現(xiàn)不同程度降低趨勢(shì).這是由于高氮處理導(dǎo)致水稻貪青徒長(zhǎng),不利于干物質(zhì)的積累和產(chǎn)量的形成.

2.3施氮量和栽插密度對(duì)D46稻米品質(zhì)的影響

2.3.1加工品質(zhì)

施氮量顯著影響粳稻D46籽粒糙米率(圖1A)和整精米率(圖1B).籽粒糙米率和整精米率均隨氮肥用量的增加而增加,以氮水平225 kg/hm2時(shí)達(dá)到最大值;再繼續(xù)增施氮肥會(huì)使水稻加工品質(zhì)呈現(xiàn)不同程度降低趨勢(shì).與未施氮(N0)處理比較,高氮(N3)、中氮(N2)和低氮(N1)處理的籽粒糙米率和整精米率分別提高了1.04%、1.95%、1.44%和1.38%、4.37%、3.94%,且差異達(dá)到顯著水平,表明增施氮肥對(duì)提高水稻加工和外觀品質(zhì)具有重要作用.不同栽插密度處理間的籽粒糙米率在D2處理下最大,D3最小,這表明增加基本苗不利于提高水稻糙米率.而稻米的整精米率隨栽插密度的增加而降低,在栽插植密度最小(D1)時(shí)整精米率最低.D1與D3間的整精米率差異均達(dá)顯著水平(P＜0.05,圖1B).

2.3.2堊白率和堊白度

與未施氮(N0)處理相比,堊白率隨施氮量的增加而增加,尤其是當(dāng)施氮量為300 kg/hm2時(shí),堊白率明顯高于其他處理,且處理間的差異達(dá)到了顯著水平(P＜0.05,圖1C).與未施氮(N0)處理相比,堊白度整體上呈現(xiàn)隨施氮量的增加而減少的趨勢(shì),以氮水平為225 kg/hm2時(shí)堊白度最低,較未施氮水平降低了18.96%(圖1D).而堊白率和堊白度均隨著栽插密度的增加而增加,在高密度D3時(shí)顯著高于D1和D2處理(P＜0.05),這表明增加栽插密度不利于提高水稻的外觀品質(zhì).

2.2.3直鏈淀粉和可溶性蛋白質(zhì)含量

圖1E和圖1F顯示施氮量和栽插密度對(duì)粳稻D46的直鏈淀粉和可溶性蛋白質(zhì)含量有一定的影響.增加氮肥施用量有利于提高粳稻D46的直鏈淀粉和可溶性蛋白質(zhì)含量,特別是在高氮處理(N3,300 kg/hm2)與低氮處理(N1,150 kg/hm2)間的直鏈淀粉含量差異達(dá)顯著水平(P＜0.05).而可溶性蛋白質(zhì)含量在中氮處理(N2,225 kg/hm2)時(shí)最高,明顯高于未施氮處理.栽插密度對(duì)直鏈淀粉和可溶性蛋白質(zhì)含量的影響較小.

2.2.4淀粉RVA譜特性

稻米的RVA譜特性是評(píng)價(jià)稻米品質(zhì)的重要指標(biāo),也是優(yōu)質(zhì)水稻品種的選育和栽培的參考指標(biāo).本研究的結(jié)果(表3)表明,施氮量極顯著地影響了粳稻D46的RVA譜特性(P＜0.01).隨著施氮量的增加,粳稻D46的峰值黏度、熱漿黏度、冷膠黏度、崩解值、回復(fù)值等特性逐漸減低,而消減值呈現(xiàn)上升趨勢(shì).可見,稻米淀粉的RVA譜特性受氮肥水平的影響并不一致,但整體上主要表現(xiàn)為負(fù)向的影響即提高氮肥用量,稻米的黏性有變差的趨勢(shì).

在不同栽培密度下,粳稻D46的RVA譜特性也表現(xiàn)出一定的差異,它極顯著地影響了稻米的峰值黏度(P＜0.01),而對(duì)其余RVA譜特性指標(biāo)影響不明顯(P＞0.05).在同一施氮水平條件下,提高栽插密度,粳稻D46的峰值黏度、熱漿黏度、冷膠黏度、崩解值等特性呈現(xiàn)先增加后減少的趨勢(shì),而回復(fù)值和消減值呈上升趨勢(shì).由以上可知,稻米淀粉的RVA譜特性受栽培密度影響較大,移栽的密度過(guò)大或過(guò)小均影響稻米的黏性,從而使稻米的品質(zhì)變差.

3　討論

3.1施氮量和栽插密度對(duì)D46產(chǎn)量及干物質(zhì)積累的影響

水稻產(chǎn)量形成是一個(gè)物質(zhì)生產(chǎn)、轉(zhuǎn)運(yùn)和積累的過(guò)程;而干物質(zhì)生產(chǎn)是水稻產(chǎn)量形成的基礎(chǔ),干物質(zhì)的積累、分配和轉(zhuǎn)運(yùn)對(duì)水稻獲得高產(chǎn)具有重要意義[24-25].有研究表明,適當(dāng)?shù)牡适┯昧亢驮圆迕芏瓤梢杂行У靥岣呷~綠素含量,進(jìn)而有利于干物質(zhì)的生產(chǎn)、積累和轉(zhuǎn)運(yùn),從而有利于水稻高產(chǎn)的形成[26].本研究結(jié)果表明,在氮用量0～225 kg/hm2范圍內(nèi)增施氮肥,有效地促進(jìn)了水稻的生長(zhǎng),增加了干物質(zhì)的積累,有利于有效穗數(shù)、每穗粒數(shù)和結(jié)實(shí)率的增加;且各時(shí)期干物質(zhì)積累量與產(chǎn)量密切相關(guān)(圖2).然而在高氮肥水平下(＞225 kg/hm2),水稻貪青徒長(zhǎng),無(wú)效分蘗和低效分蘗也隨之增多而導(dǎo)致成穗率下降;且水稻各生育期的干物質(zhì)質(zhì)量和分配也降低,不利于植株干物質(zhì)向籽粒的轉(zhuǎn)運(yùn),影響產(chǎn)量構(gòu)成因素協(xié)調(diào)發(fā)展,不利于水稻高產(chǎn)的形成,還造成了氮肥的浪費(fèi)以及對(duì)環(huán)境的污染,這與徐春梅等[19]的研究結(jié)果一致.

增加栽插密度,水稻植株間生長(zhǎng)空間逐漸縮小,葉片重疊加劇,葉面積指數(shù)下降,通風(fēng)透光性降低,從而光合作用減弱[12].本實(shí)驗(yàn)條件下,低密度20×104穴/hm2栽培植株間光合作用最強(qiáng),結(jié)實(shí)率最好.然而,群體有效穗數(shù)和每穗粒數(shù)少,干物質(zhì)積累量較低,不利于水稻高產(chǎn)的形成(表1,表2);相反,在高密度40×104穴/hm2栽培下,雖有效穗數(shù)有增加,但植株緊湊,生長(zhǎng)環(huán)境惡化,且加之四川盆地高溫高濕的環(huán)境,加劇了植株間病蟲害的發(fā)生,葉片早衰現(xiàn)象嚴(yán)重,導(dǎo)致干物質(zhì)積累量在生育后期轉(zhuǎn)運(yùn)受阻;而每穗粒數(shù)和結(jié)實(shí)率也最低,不利于水稻高產(chǎn)的形成.而在中等密度26.67×104穴/hm2栽培下,植株光合作用較強(qiáng),使得干物質(zhì)積累較大,群體有效穗數(shù)較高,每穗粒數(shù)和結(jié)實(shí)率最大,因此產(chǎn)量最高.這與樊紅柱等[27]在四川盆地稻作區(qū)的研究結(jié)果基本一致.

施氮量和栽插密度的交互作用也會(huì)對(duì)產(chǎn)量、產(chǎn)量構(gòu)成因素及干物質(zhì)形成產(chǎn)生不同的影響,只有協(xié)調(diào)產(chǎn)量構(gòu)成因素之間的關(guān)系,才能實(shí)現(xiàn)優(yōu)質(zhì)高產(chǎn)[19].在本試驗(yàn)中,施氮量和栽插密度的增加,水稻分蘗和群體穴數(shù)增加,從而使得群體有效穗數(shù)增加,然而大量分蘗又不能有效成穗,使得成穗率降低,這限制了產(chǎn)量的增加.在施氮量N2(225 kg/hm2)處理下,每穗粒數(shù)最大,且每穗粒數(shù)隨栽插密度增加而下降;結(jié)實(shí)率隨施氮量增加而增加,且在密度D2(26.67×104穴/hm2)處理下最大;而千粒質(zhì)量隨施氮量的增加而不斷減小,受密度的影響則不明顯.綜上所述,在施氮量225 kg/hm2與栽插密度26.67× 104穴/hm2的組合(D2N2)下產(chǎn)量和干物質(zhì)積累量最大,是實(shí)現(xiàn)高產(chǎn)栽培的最優(yōu)組合.

3.2施氮量和栽插密度對(duì)D46品質(zhì)的影響

稻米品質(zhì)形成與水稻生長(zhǎng)發(fā)育過(guò)程密切相關(guān),是多種物質(zhì)共同完成了一系列積累、轉(zhuǎn)化等過(guò)程而形成的[28].本試驗(yàn)研究結(jié)果表明,在施氮量0～225 kg/hm2的范圍內(nèi)增施氮肥,干物質(zhì)積累量增加,糙米率和整精米率增加;而在高施氮量300 kg/hm2處理下,干物質(zhì)積累分配下降,灌漿受阻,不飽滿籽粒增多,糙米率和整精米率下降.在栽培密度上,中密度(26.67×104穴/hm2)比低密度和高密度栽培下糙米率和整精米率都較高.可見,在施氮量225 kg/hm2和栽插密度為26.67×104穴/hm2的組合下,稻米的加工品質(zhì)最好.

堊白率和堊白度體現(xiàn)了稻米的外觀品質(zhì).在本試驗(yàn)中,栽培密度由20.00×104穴/hm2提高至40.00×104穴/hm2時(shí),水稻植株間緊湊、葉片重疊加劇、通風(fēng)透氣性下降,植株光合作用減弱,使堊白率和堊白度增加.這與已有報(bào)道關(guān)于氮肥用量對(duì)稻米堊白性質(zhì)影響的結(jié)果不一致.有研究認(rèn)為施氮量與堊白呈負(fù)相關(guān)[29];而許仁良等[30]的研究指出氮肥用量與堊白呈正相關(guān);也有研究者發(fā)現(xiàn)稻米堊白性質(zhì)不受施氮量的影響[31].在本研究中,堊白率隨施氮量增加而增加.這是由于增施氮肥雖促進(jìn)植株的生長(zhǎng),但成穗率降低,晚生分蘗增多,穗部的干物質(zhì)和氮素分配減少,淀粉體排列疏松使得堊白率增加[17,19,22];此外,施氮量的增加會(huì)導(dǎo)致水稻光合作用增強(qiáng),物質(zhì)的積累和轉(zhuǎn)運(yùn)增強(qiáng),使堊白面積減小,從而降低了堊白度;但在高施氮量300 kg/hm2處理下,物質(zhì)的積累和轉(zhuǎn)運(yùn)受阻,堊白面積增大,從而使堊白度有所增加(圖1D),這與程效義等[32]的研究結(jié)果基本一致.

已有研究表明,直鏈淀粉含量和淀粉RVA譜特性與稻米的蒸煮食味品質(zhì)具有密切聯(lián)系,對(duì)判斷稻米蒸煮食味品質(zhì)的優(yōu)劣具有重要參考價(jià)值[18,20 21,24].王玉文等[33]研究指出淀粉RVA譜特性的消減值＜0時(shí),崩解值越大、消減值越低或消減值＞0時(shí),崩解值越小、消減值越大,稻米的黏度就越大,口感越好.本試驗(yàn)研究表明,氮肥用量對(duì)淀粉RVA譜特性的影響最大,各處理間差異達(dá)顯著水平;而栽插密度對(duì)淀粉RVA譜特性的影響較小,各處理間差異不顯著.同時(shí),本研究中粳稻D46淀粉RVA譜特性中的消減值均為負(fù)值(表3),表明增加崩解值和減小消減值可以提高稻米的口感.而崩解值和消減值受施氮量的影響較大,氮肥用量增加,崩解值減小、消減值增加,稻米的口感降低,表明減少施氮量有助于稻米蒸煮食味品質(zhì)的提高.栽插密度對(duì)粳稻D46淀粉RVA譜特性的影響較小.在中低密度栽培(＜26.67×104穴/hm2)時(shí)稻米的口感優(yōu)于高密度栽培(＞40.00×104穴/hm2),這與葉全寶等[24]對(duì)粳稻“常優(yōu)1號(hào)”和“武運(yùn)粳7號(hào)”的研究結(jié)果基本一致.有研究表明,稻米直鏈淀粉含量與淀粉RVA譜特性之間存在一定的關(guān)系[34-35].在本試驗(yàn)中,直鏈淀粉含量與崩解值呈極顯著負(fù)相關(guān)(-0.809),而與消減值呈極顯著正相關(guān)(0.769).結(jié)果(表4)表明,直鏈淀粉含量降低,崩解值增大、消減值減小,米飯適口性好,稻米的蒸煮食味品質(zhì)提高,這與隋炯明等[34]的研究結(jié)果基本一致.

本試驗(yàn)研究表明,稻米可溶性蛋白質(zhì)含量主要受施氮量的影響比較明顯,而受栽插密度的影響不明顯.施氮量在0～225 kg/hm2范圍內(nèi)增加時(shí),植株氮素積累量和轉(zhuǎn)運(yùn)增強(qiáng),故蛋白質(zhì)含量增加;而在高氮300 kg/hm2水平條件下,植株氮素積累量增加,但轉(zhuǎn)運(yùn)卻有所下降.因此,氮素向籽粒的轉(zhuǎn)運(yùn)受阻導(dǎo)致蛋白質(zhì)含量降低.可見,適宜的氮肥用量才有利于提高稻米可溶性蛋白質(zhì)含量,提高其營(yíng)養(yǎng)品質(zhì).

4　結(jié)論

在本試驗(yàn)條件下,施氮量和栽插密度對(duì)產(chǎn)量、產(chǎn)量構(gòu)成因素及干物質(zhì)積累量有顯著影響,且存在明顯交互效應(yīng),產(chǎn)量提高主要是通過(guò)增加有效穗數(shù)實(shí)現(xiàn)的.在施氮量＜225 kg/hm2時(shí),增加栽插密度可顯著提高水稻籽粒產(chǎn)量;而在施氮量＞225 kg/hm2時(shí),繼續(xù)增施氮肥不能提高水稻產(chǎn)量和干物質(zhì)積累量,這表明通過(guò)增施氮肥來(lái)提高水稻產(chǎn)量是不現(xiàn)實(shí)的.而施氮量和栽插密度對(duì)粳稻D46品質(zhì)有不同程度的影響,其中以施氮量的影響最為顯著.在低氮肥條件下,隨著施氮量的增加,稻米的加工品質(zhì)、外觀品質(zhì)、食味品質(zhì)均趨好;而當(dāng)?shù)视昧浚?25 kg/hm2時(shí)稻米品質(zhì)有所降低;提高栽插密度對(duì)稻米品質(zhì)形成無(wú)利.以上所述,成都平原稻作區(qū)粳稻D46高產(chǎn)與優(yōu)質(zhì)的適宜施氮量為225 kg/hm2,栽插密度為26.67×104穴/hm2.

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收稿日期(Received):2015-07-29;接受日期(Accepted):2015-10-27;網(wǎng)絡(luò)出版日期(Published online):2016-01-19

*通信作者(

Corresponding author):李天(http://orcid.org/0000-0003-1255-4804),Tel:+86-835-2882176,E-mail:lit@sicau.edu.cn第一作者聯(lián)系方式:蘭艷(http://orcid.org/0000-0001-6398-3487),E-mail:lanyansicau@163.com

基金項(xiàng)目:四川省科技廳科技支撐計(jì)劃項(xiàng)目(2014NZ0103).

DOI:10.3785/j.issn.1008-9209.2015.07.291

中圖分類號(hào)S 511

文獻(xiàn)標(biāo)志碼A