趙建華, 孫建好, 李偉綺

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玉米播期對(duì)大豆/玉米間作產(chǎn)量及種間競(jìng)爭(zhēng)力的影響*

趙建華, 孫建好, 李偉綺

(甘肅省農(nóng)業(yè)科學(xué)院土壤肥料與節(jié)水農(nóng)業(yè)研究所 蘭州 730070)

在間作系統(tǒng)中, 間作作物間合理的共生期可有效提高間作系統(tǒng)作物對(duì)時(shí)空資源的高效利用。而間作作物播期直接影響間作作物間共生期的長(zhǎng)短, 由此導(dǎo)致的時(shí)空生態(tài)位分離會(huì)直接影響到作物生產(chǎn)力和種間相互作用。為明確大豆/玉米間作系統(tǒng)中玉米播期對(duì)間作作物產(chǎn)量、系統(tǒng)生產(chǎn)力及間作作物間資源競(jìng)爭(zhēng)力的影響, 本研究設(shè)置3個(gè)玉米播期處理——M1(4月24日與大豆同時(shí)播種, 與大豆共生期165 d)、M2(5月4日播種, 與大豆共生期150 d)、M3(5月14日播種, 與大豆共生期140 d), 通過對(duì)單間作條件下作物產(chǎn)量、干物質(zhì)累積的測(cè)定, 研究了玉米不同播期下大豆/玉米間作系統(tǒng)作物產(chǎn)量、系統(tǒng)生產(chǎn)力、共生期內(nèi)種間競(jìng)爭(zhēng)力變化。結(jié)果表明: 3個(gè)播期處理不影響間作產(chǎn)量?jī)?yōu)勢(shì), 土地當(dāng)量比(land equivalent ratio, LER)均大于1; 但隨播期延遲, LER變小, M1處理LER最大, 達(dá)1.37。玉米播期變化對(duì)間作大豆產(chǎn)量無顯著影響; 隨玉米播期延遲, 間作玉米產(chǎn)量下降, 間作系統(tǒng)生產(chǎn)力隨之下降。玉米播期對(duì)間作大豆產(chǎn)量構(gòu)成無顯著影響; 隨玉米播期延遲, 間作玉米的百粒重隨之減小, M3的百粒重(26.1 g)僅為M1(36.6 g)的71%。玉米播期延遲抑制了大豆玉米共生后期玉米資源競(jìng)爭(zhēng)力的恢復(fù), 在大豆和玉米共生前期, 大豆的資源競(jìng)爭(zhēng)力強(qiáng)于玉米, 而共生后期(9月至收獲), 玉米的資源競(jìng)爭(zhēng)力顯著提升; M3處理大豆相對(duì)于玉米的資源競(jìng)爭(zhēng)力(aggressivity,sm)始終高于M1和M2, 玉米相對(duì)擁擠指數(shù)隨播期延遲而降低, 表現(xiàn)為M1>M2>M3, 而競(jìng)爭(zhēng)比率為M3>M2>M1。因此, 就本研究而言, 甘肅河西灌區(qū)大豆/玉米間作系統(tǒng)中4月24日大豆和玉米同時(shí)播種是此系統(tǒng)間作作物的適宜播期, 兩作物同時(shí)播種可有效穩(wěn)定間作作物產(chǎn)量及系統(tǒng)生產(chǎn)力, 間作玉米播種延遲會(huì)導(dǎo)致間作系統(tǒng)生產(chǎn)力下降。

大豆/玉米間作; 玉米播期; 共生期; 產(chǎn)量; 種間競(jìng)爭(zhēng)力; 生態(tài)位

間套作由于較單作有明顯的產(chǎn)量?jī)?yōu)勢(shì), 高效利用土地和農(nóng)業(yè)資源, 穩(wěn)定系統(tǒng)生產(chǎn)力[1], 控制病蟲草害[2-4]等特點(diǎn), 而受到廣泛的關(guān)注, 尤其像豆科/禾本科間作, 如蠶豆(L)/玉米(L)[5]、豌豆(L)/玉米[6]、大豆[(Linn.) Merr.]/玉米[7]等, 由于其高產(chǎn)、資源高效利用而被甘肅河西灌區(qū)農(nóng)民普遍接受。

基本的生物學(xué)原理認(rèn)為, 當(dāng)兩個(gè)作物生長(zhǎng)在一起時(shí), 種間競(jìng)爭(zhēng)作用和促進(jìn)作用總是相伴存在的[8]。間套作正是為資源需求特性不同的作物提供了時(shí)間和空間上的生態(tài)位分離, 促成了種間相互作用對(duì)相關(guān)資源的高效利用[9-11]。種間競(jìng)爭(zhēng)作用是間作優(yōu)勢(shì)發(fā)揮的重要決定因素, 如齊萬海等[12]通過根系分隔試驗(yàn)分析了小麥(L.)/玉米間作中競(jìng)爭(zhēng)力與產(chǎn)量的關(guān)系, 認(rèn)為提升小麥的競(jìng)爭(zhēng)優(yōu)勢(shì)是提高小麥/玉米間作群體整體產(chǎn)量的關(guān)鍵。因此, 在間作系統(tǒng)中, 合理的種間配置以滿足組分作物對(duì)時(shí)空資源的高效利用是間作優(yōu)勢(shì)發(fā)揮的關(guān)鍵。譬如, 不同帶型的間作群體通風(fēng)、透光等條件存在差異, 競(jìng)爭(zhēng)與互補(bǔ)程度不同, 對(duì)空間水肥等資源的利用也不同, 因而增產(chǎn)效應(yīng)也不同[13]。不同作物與玉米間作, 由于其共生期的差異, 對(duì)于玉米的生長(zhǎng)及產(chǎn)量必然造成差異[14]。這些表明通過改變間作作物空間布局, 間作作物組合搭配等均改變間作群體種間互作效應(yīng),從而影響間作產(chǎn)量?jī)?yōu)勢(shì); 而間作作物播期變化也是影響間作系統(tǒng)生產(chǎn)力的重要因素, 其實(shí)質(zhì)上是改變了間作作物共生期, 從而導(dǎo)致間作作物間時(shí)空生態(tài)位分離[15-16]。例如, 雍太文等[17]針對(duì)玉米大豆套作的研究發(fā)現(xiàn), 玉米適當(dāng)晚播有利于玉米產(chǎn)量提高; 徐婷等[18]通過兩年的田間試驗(yàn), 研究了在玉米大豆套作模式下, 從6月15日大豆適期播種, 每隔10 d一個(gè)處理, 研究大豆晚播對(duì)大豆產(chǎn)量的影響, 發(fā)現(xiàn)大豆適當(dāng)晚播有利于大豆產(chǎn)量提高。李志賢等[19]研究甜玉米間作大豆表明, 甜玉米比大豆晚播55 d和40 d, 甜玉米的輻射利用率較單作分別提高29%和降低24%。Francis等[20]研究大豆間作玉米指出, 玉米比大豆早播5 d和10 d, 玉米的產(chǎn)量與相同播期的單作相比降低幅度更大。可見, 作物適宜播期選擇是間作作物種間競(jìng)爭(zhēng)力優(yōu)化, 間套作產(chǎn)量?jī)?yōu)勢(shì)發(fā)揮的關(guān)鍵。以上研究大多基于大豆和玉米套作體系, 研究重點(diǎn)多側(cè)重于作物播期調(diào)控對(duì)作物產(chǎn)量、間套作系統(tǒng)生產(chǎn)力方面, 而在甘肅河西灌區(qū), 由于其生態(tài)氣候條件, 大豆與玉米基本形成了同種同收的間作模式, 大豆和玉米過長(zhǎng)的共生期內(nèi), 通過作物播期調(diào)控調(diào)節(jié)共生期種間競(jìng)爭(zhēng)成為該體系作物生產(chǎn)力提升的關(guān)鍵。因此, 為探明河西灌區(qū)大豆/玉米間作模式生產(chǎn)力提升的玉米最佳播期, 本研究通過設(shè)置間作玉米不同播期處理, 研究不同玉米播期對(duì)大豆/玉米間作系統(tǒng)作物產(chǎn)量、系統(tǒng)生產(chǎn)力以及對(duì)間作大豆和玉米種間競(jìng)爭(zhēng)力的影響, 旨在尋求大豆玉米間作系統(tǒng)中玉米的適播期, 為河西灌區(qū)大豆/玉米間作系統(tǒng)玉米播期選擇提供理論借鑒。

1 材料與方法

1.1 試驗(yàn)區(qū)概況

試驗(yàn)于2013年在甘肅省農(nóng)業(yè)科學(xué)院張掖節(jié)水農(nóng)業(yè)試驗(yàn)站進(jìn)行, 試驗(yàn)站地處甘肅省河西走廊中部的張掖市(100°26′E, 38°56′N), 海拔1 570 m, 平均年日照時(shí)數(shù)3 085 h, 晝夜溫差13.00~16.07 ℃, 年平均氣溫7 ℃, ≥0 ℃積溫3 388 ℃, ≥10 ℃積溫2 896 ℃, 無霜期153 d。0~200 cm平均土壤容重為1.376 g·cm-3, 年平均蒸發(fā)量2 075 mm, 年降水量不足130 mm, 干旱指數(shù)達(dá)10.3, 屬于典型的無灌溉就無農(nóng)業(yè)的干旱灌溉地區(qū), 具有西北綠洲灌溉農(nóng)業(yè)區(qū)的典型特征。地下水埋深68~73 m, 地下水位年變幅1.0 m左右。試驗(yàn)地屬灌漠土, 有機(jī)質(zhì)17.9 g·kg-1, 速效氮128.8 mg·kg-1, 速效磷24.7 mg·kg-1, 速效鉀82.0 mg·kg-1, pH 8.2。

1.2 試驗(yàn)設(shè)計(jì)

試驗(yàn)包括3種種植方式, 分別為大豆/玉米間作、大豆單作、玉米單作。玉米設(shè)3個(gè)播期處理, 分別為4月24日(M1)、5月4日(M2)和5月14日(M3); 大豆無論單間作均于4月24日播種。試驗(yàn)處理分別用IM1(間作玉米播期4月24日)、IM2(間作玉米播期5月4日)、IM3(間作玉米播期5月14日)、SM1(單作玉米播期4月24日)、SM2(單作玉米播期5月4日)、SM3(單作玉米播期5月14日)、大豆單作SS(播期4月24日)代表。玉米出苗時(shí)間分別為5月4日、5月19日和5月29日, 因此, 3個(gè)播期處理大豆與玉米的共生期分別為165 d(IM1)、150 d(IM2)和140 d(IM3)。試驗(yàn)采用隨機(jī)區(qū)組排列, 重復(fù)3次。施肥量為N 240 kg·hm-2, 其中50%基施, 50%在玉米大喇叭口期追施; P2O590 kg·hm-2, 一次性基施。

大豆/玉米間作采用4∶3行比(4行大豆, 3行玉米)種植, 帶幅215 cm, 每小區(qū)種植3個(gè)組合帶。小區(qū)面積6.45 m×6 m=38.7 m2; 間作玉米行距30 cm, 株距22 cm; 單作玉米等行距種植, 行距60 cm, 株距22 cm; 大豆無論單間作行距25 cm, 株距20 cm, 大豆與玉米的距離為40 cm。

供試大豆品種為‘中黃30’, 供試玉米品種為‘鄭單958’。種植時(shí)采用點(diǎn)播器點(diǎn)播, 出苗后間苗以保證1穴1株。大豆和玉米收獲時(shí)間均為2013年10月16日。

1.3 樣品采集及方法

作物出苗后進(jìn)行地上部生物量測(cè)定, 共采樣6次, 采樣時(shí)間分別為6月13日、7月3日、7月26日、8月15日、9月5日、10月17日。每小區(qū)選取長(zhǎng)勢(shì)一致植株4株, 采集地上部鮮樣, 鮮樣先在105 ℃下殺青1 h, 然后在80 ℃下烘干至恒重后稱重。作物成熟后, 間作小區(qū)以每小區(qū)中間種植帶為計(jì)產(chǎn)帶(避免邊行優(yōu)勢(shì))進(jìn)行實(shí)收測(cè)產(chǎn); 計(jì)產(chǎn)面積2.15 m×6 m=12.9 m2, 于單作小區(qū)中間部位選取與間作同等面積進(jìn)行收獲計(jì)產(chǎn)。同時(shí)在大豆、玉米計(jì)產(chǎn)帶以外隨機(jī)取大豆15株、玉米10株進(jìn)行產(chǎn)量構(gòu)成因素的考察, 大豆考察豆莢數(shù)、豆粒數(shù)、百粒重, 玉米考察穗粒數(shù)、百粒重等性狀。

1.4 數(shù)據(jù)處理與統(tǒng)計(jì)分析

1.4.1 數(shù)據(jù)計(jì)算

土地當(dāng)量比(land equivalent ratio)常用于衡量間作優(yōu)勢(shì)[21]:

LER=is/ss+im/sm(1)

式中:is和im分別代表間作總面積上大豆和玉米的籽粒產(chǎn)量, kg·hm-2;ss和sm分別為單作大豆和單作玉米的產(chǎn)量。當(dāng)LER>1, 表明間作有優(yōu)勢(shì), 當(dāng)LER<1為間作劣勢(shì)。

間作系統(tǒng)生產(chǎn)力(system productivity, SP, kg·hm-2)[22]為單位面積兩種間作作物籽粒產(chǎn)量的加權(quán)平均值。

SP=is×s+im×m(2)

式中:s、m分別為大豆和玉米在間作系統(tǒng)中所占的面積比例, 本試驗(yàn)中s=0.58,m=0.42。

圖4(a), 4(b)分別給出了30°壓縮拐角(模型3)在I, II線上的計(jì)算壓力和實(shí)驗(yàn)結(jié)果的分布對(duì)比. 在平板干擾區(qū)內(nèi), 計(jì)算和實(shí)驗(yàn)也符合較好, 數(shù)值計(jì)算的分離范圍略小于實(shí)驗(yàn)結(jié)果. 在楔面上, 計(jì)算壓力與實(shí)驗(yàn)值的大小比較接近, 但是峰值位置有一定的差距. 雖然30°壓縮拐角模型網(wǎng)格量要遠(yuǎn)大于20°壓縮拐角模型(見表1), 但是計(jì)算精度沒有得到提高.

種間相對(duì)競(jìng)爭(zhēng)力(aggressivity,)[23]指間作體系中一種作物相對(duì)于另一種作物對(duì)水分、養(yǎng)分等與產(chǎn)量形成有關(guān)資源的競(jìng)爭(zhēng)力:

sm=ia/(sa×s)-im/(sb×m) (3)

式中:sm為大豆相對(duì)于玉米的資源競(jìng)爭(zhēng)力;ia和sa分別代表間作大豆和單作大豆生物產(chǎn)量,ib和sb分別代表間作玉米和單作玉米生物產(chǎn)量。當(dāng)sm>0, 表明大豆競(jìng)爭(zhēng)力強(qiáng)于玉米;sm<0, 玉米競(jìng)爭(zhēng)力強(qiáng)于大豆。

相對(duì)擁擠指數(shù)(relative crowding coefficient,或RCC)[24]是基于產(chǎn)量來衡量間作優(yōu)勢(shì)和間作群體中不同組分主導(dǎo)地位的指標(biāo):

Ks=Yia×Zm /[(Ysa-Yia)×Zs](4) Km=Yib×Zs /[(Ysb-Yib)×Zm]

式中:s和m分別為大豆和玉米的相對(duì)擁擠指數(shù), 兩者相比大的一方具有更強(qiáng)的競(jìng)爭(zhēng)力。

競(jìng)爭(zhēng)比率(competitive ratio, CR)[25-26]是評(píng)價(jià)間作系統(tǒng)中組分作物競(jìng)爭(zhēng)的指標(biāo):

CRsm=[ia/sa×s]/[ib/sb×m] (5)

式中: 若CRsm>1表明大豆的競(jìng)爭(zhēng)力強(qiáng)于玉米, 若CRsm<1, 則玉米競(jìng)爭(zhēng)力強(qiáng)于大豆。

1.4.2 統(tǒng)計(jì)分析

采用Microsoft Excel 2010進(jìn)行繪圖, 用SAS 8.0統(tǒng)計(jì)分析軟件進(jìn)行方差分析, 并用LSD法對(duì)各處理間的差異顯著性在5%水平上進(jìn)行檢驗(yàn)。

2 結(jié)果與分析

2.1 玉米播期對(duì)大豆玉米間作系統(tǒng)土地當(dāng)量比(LER)的影響

圖1 不同玉米播期下大豆/玉米間作系統(tǒng)的土地當(dāng)量比

IM1: 4月24日播種間作玉米; IM2: 5月4日播種間作玉米; IM3: 5月14日播種間作玉米。不同小寫字母表示不同處理在0.05水平上差異顯著。IM1: intercropped maize was sowed in 24thApril; IM2: intercropped maize was sowed in 4thMay; IM3: intercropped maize was sowed in 14thMay. Different lowercase letters indicate significant differences among different treatments at 0.05 level.

2.2 玉米播期對(duì)大豆玉米間作系統(tǒng)作物產(chǎn)量的影響

延遲玉米播期, 間作系統(tǒng)作物產(chǎn)量隨之降低(表1), 間作玉米播期變化對(duì)間作大豆產(chǎn)量無顯著影響。在玉米單作系統(tǒng)中, M3處理產(chǎn)量顯著低于M1和M2, M1與M2之間無顯著差異; 其中, M2產(chǎn)量最高, 為13 938.7 kg?hm-2; M3僅為9 705.9 kg?hm-2, 較M1和M2的玉米產(chǎn)量下降21.3%和30.3%, M2較M1玉米產(chǎn)量提高12.9%。在間作系統(tǒng)中, 間作玉米產(chǎn)量表現(xiàn)為隨玉米播期的延遲而降低, M3處理顯著低于M1和M2處理, 而M1和M2處理間無顯著差異; 對(duì)比來看, M2和M3兩處理較M1處理玉米產(chǎn)量分別下降14.1%和37.3%。間作系統(tǒng)混合產(chǎn)量和系統(tǒng)生產(chǎn)力的變化趨勢(shì)均與間作玉米產(chǎn)量變化趨勢(shì)一致, 均隨玉米播期延遲而下降, 且M3處理顯著低于M1和M2。

玉米播期對(duì)大豆產(chǎn)量構(gòu)成因子無顯著影響(表2)。與單作對(duì)比, 間作大豆收獲指數(shù)提高, 且IM1和IM2處理的收獲指數(shù)顯著高于SS處理; 而在單株莢數(shù), 單株粒數(shù), 百粒重方面, 單、間作之間以及播期處理之間無顯著差異。

從表3可知, 單作和間作玉米各處理間穗粒數(shù)均無顯著差異; 單作玉米體系中, 播期改變對(duì)玉米百粒重?zé)o顯著影響, 而在間作系統(tǒng)中, 隨播期延遲, 玉米百粒重減小, M3處理的百粒重僅為M1處理的71%; 間作玉米收獲指數(shù)隨播期推遲而降低但各處理間無顯著差異, 單作玉米收獲指數(shù)M3顯著低于M1和M2。

表1 玉米播期對(duì)大豆/玉米間作體系作物產(chǎn)量的影響

表中數(shù)據(jù)為平均值±標(biāo)準(zhǔn)差, 同列數(shù)據(jù)中不同小寫字母表示0.05水平上差異顯著。M1: 4月24日播種玉米; M2: 5月4日播種玉米; M3: 5月14日播種玉米。The data were means ± S.E. (=3). Values in the same column followed by different small letters were significantly different at 0.05 level. M1: maize was sowed in 24thApril; M2: maize was sowed in 4thMay; M3: maize was sowed in 14thMay.

表2 玉米播期對(duì)間作大豆產(chǎn)量構(gòu)成因素的影響

表中數(shù)據(jù)為平均值±標(biāo)準(zhǔn)差, 同列數(shù)據(jù)中不同小寫字母表示0.05水平上差異顯著。IM1: 4月24日播種間作玉米; IM2: 5月4日播種間作玉米; IM3: 5月14日播種間作玉米; SS: 單作大豆。The data were means ± S.E. (=3). Values in the same column followed by different small letters were significantly different at 0.05 level. IM1: intercropped maize was sowed in 24thApril; IM2: intercropped maize was sowed in 4thMay; IM3: intercropped maize was sowed in 14thMay; SS: soybean monoculture.

表3 玉米播期對(duì)與大豆間作的玉米產(chǎn)量構(gòu)成因素的影響

M1: 4月24日播種玉米; M2: 5月4日播種玉米; M3: 5月14日播種玉米。*表示在<0.05水平顯著, NS表示不顯著。M1: maize was sowed in 24thApril; M2: maize was sowed in 4thMay; M3: maize was sowed in 14thMay.* indicate significant difference at 0.05 level, NS indicates no significant difference.

圖2 玉米播期對(duì)間作系統(tǒng)中大豆相對(duì)于玉米的相對(duì)競(jìng)爭(zhēng)力的影響

IM1: 4月24日播種間作玉米; IM2: 5月4日播種間作玉米; IM3: 5月14日播種間作玉米。IM1: intercropped maize was sowed in 24thApril; IM2: intercropped maize was sowed in 4thMay; IM3: intercropped maize was sowed in 14thMay.

2.3 玉米播期對(duì)作物相對(duì)競(jìng)爭(zhēng)力的影響

大豆玉米共生期內(nèi), 大豆相對(duì)于玉米的資源競(jìng)爭(zhēng)力(sm)在共生前期呈波動(dòng)性, 但sm均大于0, 而在共生后期sm均逐漸變小且最終小于0(圖2)。對(duì)比來看, IM1的sm值于7月26日采樣后開始下降, 并低于同時(shí)期其他兩個(gè)處理, 說明第3次采樣后IM1處理下大豆相對(duì)于玉米的資源競(jìng)爭(zhēng)力變?nèi)? 而玉米的競(jìng)爭(zhēng)力增強(qiáng)。而兩個(gè)晚播處理相對(duì)早播處理而言在資源競(jìng)爭(zhēng)方面依舊是大豆占據(jù)主導(dǎo)。3個(gè)處理的sm值均于9月初(9月5日采樣)后開始急劇下降, 直至降到0以下; 至采樣結(jié)束各處理sm值分別為: IM1處理-1.08、IM2處理-1.10、IM3處理-0.70。

大豆玉米共生期內(nèi), 大豆的相對(duì)擁擠指數(shù)(s)各處理間無明顯差異, 且s值均小于0.5, 后期IM2處理相對(duì)較高。9月5日采樣之前, 玉米的相對(duì)擁擠指數(shù)(m)各處理間無明顯差異, 且均小于同期的s; 而9月5日采樣后,m急劇上升并超過s, 其中IM1和IM2處理的m上升迅速, 說明此時(shí)玉米對(duì)于資源的競(jìng)爭(zhēng)占據(jù)優(yōu)勢(shì), 至共生期結(jié)束,m排序?yàn)? 4月24日播種處理(1.67)>5月4日播種處理(1.52)>5月14日播種處理(0.45)(圖3)。

采樣時(shí)期競(jìng)爭(zhēng)比率(CR)變化趨勢(shì)與作物相對(duì)競(jìng)爭(zhēng)力變化趨勢(shì)一致。由圖4可知, 各處理在9月5日采樣之前CR值呈波動(dòng)性, 且CR值均大于1, 在7月之前, IM3處理CR值高于IM1和IM2; 7月至8月, IM1和IM2處理的CR值高于IM3; 而從8月至采樣結(jié)束, 表現(xiàn)為IM3處理高于IM2和IM1?？梢钥闯鲈绮ヌ幚碛衩赘?jìng)爭(zhēng)力占據(jù)優(yōu)勢(shì)的時(shí)間要早于晚播的兩個(gè)處理。

圖3 玉米播期對(duì)間作系統(tǒng)間作期間大豆(a)和玉米(b)相對(duì)擁擠指數(shù)的影響

IM1: 4月24日播種間作玉米; IM2: 5月4日播種間作玉米; IM3: 5月14日播種間作玉米。IM1: intercropped maize was sowed in 24thApril; IM2: intercropped maize was sowed in 4thMay; IM3: intercropped maize was sowed in 14thMay.

圖4 不同玉米播期下間作系統(tǒng)中大豆相對(duì)于玉米的競(jìng)爭(zhēng)比率動(dòng)態(tài)變化

IM1: 4月24日播種間作玉米; IM2: 5月4日播種間作玉米; IM3: 5月14日播種間作玉米。IM1: intercropped maize was sowed in 24thApril; IM2: intercropped maize was sowed in 4thMay; IM3: intercropped maize was sowed in 14thMay.

3 討論與結(jié)論

播期是影響作物產(chǎn)量的主要因素之一[27-28], 在間作系統(tǒng)中作物播期改變也會(huì)顯著改變間作作物產(chǎn)量[29]; Ifenkwe等[30]研究發(fā)現(xiàn), 玉米馬鈴薯(L.)間作, 玉米播期推遲, 玉米產(chǎn)量顯著減小; 卞新民等[31]研究表明大豆玉米間作系統(tǒng)大豆播期推遲, 大豆產(chǎn)量明顯下降。楊燕竹等[32]研究發(fā)現(xiàn), 大豆/玉米間作, 隨玉米播期延遲, 大豆產(chǎn)量及系統(tǒng)混合產(chǎn)量均隨之降低。本研究中, 隨間作玉米播期推遲, 玉米產(chǎn)量和間作系統(tǒng)生產(chǎn)力也隨之下降, 而大豆和玉米同期播種時(shí), 間作作物產(chǎn)量均最高, 體系生產(chǎn)力也最高, 變化趨勢(shì)與前人研究一致。因此, 本研究條件下, 玉米播期延遲對(duì)大豆/玉米間作系統(tǒng)作物產(chǎn)量的影響趨勢(shì)為間作玉米越晚播, 玉米的產(chǎn)量越低, 間作系統(tǒng)生產(chǎn)力也越低, 究其原因可能是晚播玉米受早播大豆在資源競(jìng)爭(zhēng)上的抑制, 后期作物產(chǎn)量形成受到影響。

播期能夠調(diào)控間套作群體對(duì)光、氣、水、熱等氣候資源的利用率和競(jìng)爭(zhēng)矛盾, 適宜的播期可改善作物產(chǎn)量構(gòu)成因子, 促進(jìn)作物增產(chǎn)增收[33]。Ijoyah等[34]研究玉米間作秋葵[(L.) Moench], 玉米晚播會(huì)造成玉米穗長(zhǎng)、穗粗、穗重顯著減小。雍太文等[17]研究大豆播前玉米4個(gè)播期套作大豆發(fā)現(xiàn), 玉米早播比晚播提高大豆中層莢數(shù)、粒數(shù)、粒重。在本研究中, 玉米播期延遲是在大豆已經(jīng)播種的情形下, 大豆產(chǎn)量構(gòu)成因子并沒有受晚播玉米的顯著影響, 而晚播玉米籽粒百粒重相對(duì)于大豆同期播種處理顯著減小, 其原因可能是晚播玉米在生長(zhǎng)前期受到大豆生長(zhǎng)的抑制, 導(dǎo)致后期產(chǎn)量形成弱于早播玉米。

間作系統(tǒng)中同時(shí)存在種間競(jìng)爭(zhēng)和種內(nèi)競(jìng)爭(zhēng), 由于生態(tài)位的相對(duì)分散, 種間競(jìng)爭(zhēng)應(yīng)小于種內(nèi)競(jìng)爭(zhēng), 這也有利于間作提高復(fù)合群體的綜合產(chǎn)量[35]。而間作作物播期的調(diào)節(jié)加劇或減弱了作物間的競(jìng)爭(zhēng)作用, 播期的合理搭配可優(yōu)化“時(shí)空效應(yīng)”和“補(bǔ)償效應(yīng)”[32]。本研究中, 玉米播期改變引起的大豆和玉米共生期的變化, 從而引起共生期內(nèi)大豆和玉米種間競(jìng)爭(zhēng)的差異; 間作作物的相對(duì)競(jìng)爭(zhēng)力、相對(duì)擁擠指數(shù)和競(jìng)爭(zhēng)比率為普遍采用的反映間作作物種間競(jìng)爭(zhēng)能力的指標(biāo)。本研究中共生前期, 大豆相對(duì)于玉米的資源競(jìng)爭(zhēng)力各處理雖呈現(xiàn)波動(dòng)變化, 但始終大于0, 大豆相對(duì)擁擠指數(shù)>玉米相對(duì)擁擠指數(shù), 競(jìng)爭(zhēng)比率大于1, 說明共生前期大豆競(jìng)爭(zhēng)力占有優(yōu)勢(shì)。這也與雍太文等[36]的研究, 大豆玉米帶狀種植方式下, 玉米的資源競(jìng)爭(zhēng)力弱于大豆的結(jié)果相一致。播期變化產(chǎn)生的間作物種間產(chǎn)量的差異主要是由于間作物種間競(jìng)爭(zhēng)力的分異引起的[37-38]。本研究中大豆和玉米共生后期(9月至10月), 大豆相對(duì)于玉米的競(jìng)爭(zhēng)力及競(jìng)爭(zhēng)比率開始急劇下降, 玉米的相對(duì)擁擠指數(shù)上升, 說明共生后期玉米對(duì)資源的競(jìng)爭(zhēng)力強(qiáng)于大豆。然而晚播處理玉米競(jìng)爭(zhēng)力增強(qiáng)還是弱于早期播種處理, 同樣的趨勢(shì)表現(xiàn)在玉米的相對(duì)擁擠指數(shù)上, 玉米相對(duì)擁擠指數(shù)后期急劇上升, 然而上升速度M1處理始終快于M2處理和M3處理。晚播處理的競(jìng)爭(zhēng)比率值始終高于早播處理, 這些均表明間作玉米晚播造成了后期玉米競(jìng)爭(zhēng)力的恢復(fù)受到抑制。因此, 合理的播期配置使間作物種間競(jìng)爭(zhēng)力最優(yōu)化是提高間作系統(tǒng)生產(chǎn)力的前提。

本研究通過改變間作玉米播期探討了間作玉米播期對(duì)大豆、玉米產(chǎn)量及大豆/玉米間作系統(tǒng)生產(chǎn)力和作物間競(jìng)爭(zhēng)力的影響, 研究結(jié)果表明在河西灌區(qū)大豆/玉米間作系統(tǒng)中, 隨間作玉米播期的推遲, 間作系統(tǒng)土地當(dāng)量比減小, 系統(tǒng)生產(chǎn)力下降, 間作玉米產(chǎn)量下降; 玉米播期的延遲對(duì)大豆產(chǎn)量及產(chǎn)量構(gòu)成因子無顯著影響, 而間作玉米百粒重隨播期延遲顯著降低; 引起間作系統(tǒng)玉米產(chǎn)量降低的主要因素是播期延遲抑制了共生后期玉米資源競(jìng)爭(zhēng)力的恢復(fù), 在共生前期, 大豆相對(duì)于玉米的資源競(jìng)爭(zhēng)力大于0, 大豆相對(duì)擁擠指數(shù)>玉米相對(duì)擁擠指數(shù), 競(jìng)爭(zhēng)比率大于1, 大豆對(duì)資源的競(jìng)爭(zhēng)占有優(yōu)勢(shì), 共生后期, 雖然玉米的相對(duì)擁擠指數(shù)明顯升高, 但是表現(xiàn)為晚播處理的恢復(fù)不如早播處理。因此, 對(duì)于甘肅河西灌區(qū)大豆/玉米間作種植系統(tǒng)而言, 大豆和玉米同期播種會(huì)穩(wěn)產(chǎn), 玉米晚播反而減產(chǎn), 此研究結(jié)果為甘肅河西灌區(qū)大豆/玉米間作種植中作物適宜播期選擇提供了理論指導(dǎo)。

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Effect of maize sowing date on yield and interspecific competition in soybean/maize intercropping system*

ZHAO Jianhua, SUN Jianhao, LI Weiqi

(Institute of Soil Fertilizer and Water-Saving Agriculture, Gansu Academy of Agricultural Sciences, Lanzhou 730070, China)

A reasonable co-growth period between intercrop species can effectively improve the use efficiency of soil resources in time-space fabric. However, sowing date of intercrop plants directly determines the length of co-growth period of intercrop plants. This can directly affect intercropped plant productivity and interspecific interaction due to niche differentiation over time. Thus, a study was carried out to determine the effect of sowing date of intercropped maize on yield, productivity and interspecific competitiveness of crops of soybean/maize intercropping system. A total of three sowing dates of maize were set up, which were 24thApril (M1, co-growth period of maize and soybean was 165 days), 4thMay (M2, co-growth period of maize and soybean was 150 days) and 14thMay (M3, co-growth period of maize and soybean was 140 days). Then yield and dry matter accumulation of crops were investigated in both intercropping and sole systems, and system productivity and interspecific competitiveness also analyzed. The result showed that yield of soybean/maize intercropping was not affected by maize sowing date. Land equivalent ratio (LER) of all intercropping systems was greater than 1. However, LER value decreased with delay of sowing date of intercropped maize. The largest LER was for M1 (1.37) treatment. There were no significant differences in yields and yield components of intercropped soybeans with different maize sowing dates. Yield of intercropped maize and productivity of intercropping system decreased with delay of sowing date of intercropped maize. The 100-grain weight of intercropped maize decreased with delay of sowing date, 100-grain weight of M3 (26.1 g) was 71% that of M1 (36.6 g) treatment. The competitive ability of intercropped maize decreased during later co-growth period due to delay in sowing date. During early co-growth period, the competitive ability of soybean for growth resources was stronger than that of maize. However, in later co-growth period (from September to harvest), the competitive ability of maize significantly increased and was greater than that of soybean. However, the aggressiveness of soybean relative to maize (sm) under M3 was significantly higher than those under M1 and M2. Meanwhile, relative crowding coefficient of maize also was higher than that of soybean. This decreased with delay in sowing date of intercropped maize in the order of M1 > M2 > M3 and with competitive ratio values of M1 > M2 > M3. Therefore, the most reasonable sowing date of maize in soybean/maize intercropping system in Hexi Corridor of Gansu Province was on 24thApril. Here, yield of intercropped plants and the productivity of intercropping systems were maintained. The delayed sowing dates of maize decreased yield and productivity of intercropping system.

Soybean/maize intercropping system; Sowing time of maize; Co-growth period; Yield; Interspecific competition; Niche

, ZHAO Jianhua, E-mail: zhaojianhuatt@163.com

Jan. 31, 2018;

Jun. 3, 2018

S181

A

1671-3990(2018)11-1634-09

10.13930/j.cnki.cjea.180132

2018-01-31

2018-06-03

* This research was supported by the National Key Research and Development Project of China (2017YFD0201808-02), the Special Fund for Agro-scientific Research in the Public Interest of China (201103003-09) and the Youth Foundation of Gansu Academy of Agricultural Sciences (2016GAAS33).

* 國家重點(diǎn)研發(fā)計(jì)劃項(xiàng)目(2017YFD0201808-02)、國家公益性行業(yè)農(nóng)業(yè)專項(xiàng)(201103003-09)和甘肅省農(nóng)業(yè)科學(xué)院青年基金項(xiàng)目(2016GAAS33)資助

趙建華, 主要從事生物多樣性與資源高效利用方面的研究。E-mail: zhaojianhuatt@163.com

趙建華, 孫建好, 李偉綺. 玉米播期對(duì)大豆/玉米間作產(chǎn)量及種間競(jìng)爭(zhēng)力的影響[J]. 中國生態(tài)農(nóng)業(yè)學(xué)報(bào), 2018, 26(11): 1634-1642

ZHAO J H, SUN J H, LI W Q. Effect of maize sowing date on yield and interspecific competition in soybean/maize intercropping system[J]. Chinese Journal of Eco-Agriculture, 2018, 26(11): 1634-1642