Coordinated responses of leaf and nodule traits contribute to the accumulation of N in relay intercropped soybean

Maize(Zea mays L.)-soybean(Glycine max L.Merr.)relay intercropping provides a way to enhance land productivity.However,the late-planted soybean suffers from shading by the maize.After maize harvest,how the recovery growth influences the leaf and nodule traits remains unclear.A three-year field experiment was conducted to evaluate the effects of genotypes,i.e.,supernodulating(nts1007),Nandou 12(ND12),and Guixia 3(GX3),and crop configurations,i.e.,the interspecific row spacing of 45(I45),60(I60),75 cm(I75),and sole soybean(SS),on soybean recovery growth and N fixation.The results showed that intercropping reduced the soybean total leaf area(LA)by reducing both the leaf number(LN)and unit leaflet area(LUA),and it reduced the nodule dry weight(NW)by reducing both the nodule number(NN)and nodule diameter(ND)compared with the SS.The correlation and principal component analysis(PCA)indicated a co-variability of the leaf and nodule traits in response to the genotype and crop configuration interactions.During the recovery growth stages,the compensatory growth promoted soybean growth to reduce the gaps of leaf and nodule traits between intercropping and SS.The relative growth rates of ureide(RGR_U)and nitrogen(RGR_N)accumulation were higher in intercropping than in SS.Intercropping achieved more significant sucrose and starch contents compared with SS.ND12 and GX3 showed more robust compensatory growth than nts1007 in intercropping.Although the recovery growth of relay intercropping soybean improved biomass and nitrogen accumulation,ND12 gained a more significant partial land equivalent ratio(pLER)than GX3.The I60 treatment achieved more robust compensation effects on biomass and N accumulation than the other configurations.Meanwhile,I60 showed a higher nodule sucrose content and greater shoot ureide and N accumulation than SS.Finally,intercropping ND12 with maize using an interspecific row spacing of 60 cm was optimal for both yield advantage and N accumulation.

Effects of maize-soybean relay intercropping on crop nutrient uptake and soil bacterial community

Maize-soybean relay intercropping is an effective approach to improve the crop yield and nutrient use efficiency,which is widely practiced by farmers in southwest of China.To elucidate the characteristics of different planting patterns on crop nutrient uptake,soil chemical properties,and soil bacteria community in maize-soybean relay intercropping systems,we conducted a field experiment in 2015–2016 with single factor treatments,including monoculture maize(MM),monoculture soybean(MS),maize-soybean relay intercropping(IMS),and fallow(CK).The results showed that the N uptake of maize grain increased in IMS compared with MM.Compared with MS,the yield and uptake of N,P,and K of soybean grain were increased by 25.5,24.4,9.6,and 22.4%in IMS,respectively,while the N and K uptakes in soybean straw were decreased in IMS.The soil total nitrogen,available phosphorus,and soil organic matter contents were significantly higher in IMS than those of the corresponding monocultures and CK.Moreover,the soil protease,soil urease,and soil nitrate reductase activities in IMS were higher than those of the corresponding monocultures and CK.The phyla Proteobacteria,Acidobacteria,Chloroflexi,and Actinobacteria dominated in all treatments.Shannon’s index in IMS was higher than that of the corresponding monocultures and CK.The phylum Proteobacteria proportion was positively correlated with maize soil organic matter and soybean soil total nitrogen content,respectively.These results indicated that the belowground interactions increased the crop nutrient(N and P)uptake and soil bacterial community diversity,both of which contributed to improved soil nutrient management for legume-cereal relay intercropping systems.

Optimized nitrogen application methods to improve nitrogen use efficiency and nodule nitrogen fixation in a maize-soybean relay intercropping system

In China, the abuse of chemical nitrogen （N） fertilizer results in decreasing N use efficiency （NUE）, wasting resources and causing serious environmental problems. Cereal-legume intercropping is widely used to enhance crop yield and improve resource use efficiency, especially in Southwest China. To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system （IMS）. Three N rates, NN （no nitrogen application）, LN （lower N application： 270 kg N ha-1）, and CN （conventional N application： 330 kg N ha-1）, and three topdressing distances of LN （LND）, e.g., 15 cm （LND1）, 30 cm （LND2） and 45 cm （LND3） from maize rows were evaluated. At the beginning seed stage （R5）, the leghemoglobin content and nitrogenase activity of LND3 were 1.86 mg plant-1 and 0.14 mL h-1 plant-1, and those of LND1 and LND2 were increased by 31.4 and 24.5%, 6.4 and 32.9% compared with LND3, respectively. The ureide content and N accumulation of soybean organs in LND1 and LND2 were higher than those of LND3. The N uptake, NUE and N agronomy efficiency （NAE） of IMS under CN were 308.3 kg ha-1, 28.5%, and 5.7 kg grain kg-1 N, respectively; however, those of LN were significantly increased by 12.4, 72.5, and 51.6% compared with CN, respectively. The total yield in LND1 and LND2 was increased by 12.3 and 8.3% compared with CN, respectively. Those results suggested that LN with distances of 15-30 cm from the topdressing strip to the maize row was optimal in maize-soybean intercropping. Lower N input with an optimized fertilization location for IMS increased N fixation and N use efficiency without decreasing grain yield.

Timing and splitting of nitrogen fertilizer supply to increase crop yield and efficiency of nitrogen utilization in a wheat–peanut relay intercropping system in China

Agronomically optimizing the timing and rates of nitrogen(N) fertilizer application can increase crop yield and decrease N loss to the environment. Wheat(Triticum aestivum L.)–peanut(Arachis hypogaea L.) relay intercropping systems are a mainstay of economic and food security in China. We performed a field experiment to investigate the effects of N fertilizer on N recovery efficiency, crop yield, and N loss rate in wheat–peanut relay intercropping systems in the Huang-Huai-Hai Plain, China during 2015–2017. The N was applied on the day before sowing, the jointing stage(G30) or the booting stage(G40) of winter wheat, and the anthesis stage(R1) of peanut in the following percentage splits: 50-50-0-0(N1), 35-35-0-30(N2), and 35-0-35-30(N3), using 300 kg N ha-1, with 0 kg N ha-1(N0) as control. ^(15)N-labeled(20.14 atom %) urea was used to trace the fate of N in microplots. The yields of wheat and peanut increased by 12.4% and 15.4% under the N2 and N3 treatments, relative to those under the N1 treatment. The ^(15)N recovery efficiencies( ^(15)NRE) were 64.9% and 58.1% for treatments N2 and N3, significantly greater than that for the N1 treatment(45.3%). The potential N loss rates for the treatments N2 and N3 were23.7% and 7.0%, significantly lower than that for treatment N1(30.1%). Withholding N supply until the booting stage(N3) did not reduce the wheat grain yield; however, it increased the N content derived from ^(15)N-labeled urea in peanuts, promoted the distribution of ^(15)N to pods, and ultimately increased pod yields in comparison with those obtained by topdressing N at jointing stage(N2). In comparison with N2, the N uptake and N recovery efficiency(NRE) of N3 was increased by 12.0% and 24.1%,respectively, while the apparent N loss decreased by 16.7%. In conclusion, applying N fertilizer with three splits and delaying topdressing fertilization until G40 of winter wheat increased total grain yields and NRE and reduced N loss. This practice could be an environment-friendly N management strategy for wheat–peanut relay intercropping systems in China.

Relay-intercropping soybean with maize maintains soil fertility and increases nitrogen recovery efficiency by reducing nitrogen input

Optimized nitrogen(N)management can increase N-use efficiency in intercropping systems.Legume-nonlegume intercropping systems can reduce N input by exploiting biological N fixation by legumes.Measurement of N utilization can help in dissecting the mechanisms underlying N uptake and utilization in legume-nonlegume intercropping systems.An experiment was performed with three planting patterns:monoculture maize(MM),monoculture soybean(SS),and maize-soybean relay intercropping(IMS),and three N application levels:zero N(NN),reduced N(RN),and conventional N(CN)to investigate crop N uptake and utilization characteristics.N recovery efficiency and 15N recovery rate of crops were higher under RN than under CN,and those under RN were higher under intercropping than under the corresponding monocultures.Compared with MM,IMS showed a lower soil N-dependent rate(SNDR)in 2012.However,the SNDR of MM rapidly declined from 86.8%in 2012 to 49.4%in 2014,whereas that of IMS declined slowly from 75.4%in 2012 to 69.4%in 2014.The interspecific N competition rate(NCRms)was higher under RN than under CN,and increased yearly.Soybean nodule dry weight and nitrogenase activities were respectively 34.2%and 12.5%higher under intercropping than in monoculture at the beginning seed stage.The amount(Ndfa)and ratio(%Ndfa)of soybean N2 fixation were significantly greater under IS than under SS.In conclusion,N fertilizer was more efficiently used under RN than under CN;in particular,the relay intercropping system promoted N fertilizer utilization in comparison with the corresponding monocultures.An intercropping system helps to maintain soil fertility because interspecific N competition promotes biological N fixation by soybean by reducing N input.Thus,a maize-soybean relay intercropping system with reduced N application is sustainable and environmentally friendly.

Effect of Limited Single Irrigation on Yield of Winter Wheat and Spring Maize Relay Intercropping

A field experiment was conducted during the 2002/2003 cropping season of winter wheat （Triticum aestivum） and spring maize （Zea mays） to evaluate the effect of limited single drip irrigation on the yield and water use of both crops under relay intercropping in a semi-arid area of northwestern China. A controlled 35 mm single irrigation, either early or late, was applied to each crop at a certain growth stage. Soil water, leaf area, final grain yield and yield components such as the thousand-grain weight, length of spike, fertile spikelet number, number of grains per spike, and grain weight per spike were measured, and water use efficiency and leaf area index were calculated for the irrigated and non-irrigated relay intercropping treatments and sole cropping controls. The results showed that yield, yield components, water use efficiency, and leaf area index in the relay intercropping treatments were affected by limited single drip irrigation during various growth stages of wheat and maize. The total yields in the relay intercropping treatment irrigated during the heading stage of wheat and the heading and anthesis stage of maize were the highest among all the treatments, followed by that irrigated during the anthesis stage of wheat and silking stage of maize; so was the water use efficiency. Significant differences occurred in most yield components between the irrigated and non-irrigated relay-intercropping treatments. The dynamics of the leaf area index in the relay-intercropped or solely cropped wheat and maize showed a type of single-peak pattern, whereas that of the relay intercropping treatments showed a type of double-peak pattern. Appropriately, limited single irrigation and controlled soil water content level could result in higher total yield, water use efficiency, and leaf area index, and improved yield components in relay intercropping. This practice saved the amount of water used for irrigation and also increased the yield. Therefore, heading stage of wheat and heading and anthesis stage of maize were suggested to be the optimum limited single irrigation time for relay-intercropped wheat and maize in the semi-arid area.

不同带宽行比对玉米/大豆带状间套作群体产量和氮素效率的影响

为明确玉米/大豆带状间套作的最优配置,大田试验条件下,以单作玉米(MM)和单作大豆(MS)为对照,设置5种不同带宽行比:2 m带宽玉豆行数比为2∶2(T1)、2.4 m带宽玉豆行数比为2∶3(T2)、2.4 m带宽玉豆行数比为2∶4(T3)、2.8 m带宽玉豆行数比为2∶3(T4)、2.8 m带宽玉豆行数比为2∶4(T5),研究不同带宽行比对玉米/大豆带状间套作群体产量和氮素利用效率的影响。结果表明,玉米籽粒产量总体上随着带宽增加呈现逐渐减少的趋势,大豆籽粒产量总体上随着带宽增加呈现逐渐增加的趋势;相同带宽条件下,随着玉米大豆行比增加,玉米籽粒产量下降,大豆籽粒产量增加;玉米和大豆的植株氮素吸收利用效率变化规律与籽粒产量基本相一致。与对照相比,T2有提高玉米和大豆的收获指数,增加氮素在玉米和大豆籽粒的分配比例、降低在茎秆的分配比例的趋势。综合产量、经济效益以及群体氮素吸收、分配和利用效率的表现,2.4 m带宽下种植2行玉米3行大豆为鄂西南山区玉米/大豆的最优间套作模式。

施氮与种间距离下大豆/玉米带状套作作物生长特性及其对产量形成的影响

为明确施氮和种间距离下套作作物生长特性及其对产量形成的影响。本文以大豆/玉米带状套作系统为研究主体,探究不同氮水平(施氮与不施氮)与种间距离(玉豆间距30、45、60和75 cm、单作100 cm)下作物生长率、干物质积累与分配及产量差异,并对作物干物质积累过程进行拟合,综合分析作物生长规律和产量效益。结果表明:玉米生长率在抽雄期至乳熟期达最大,不施氮下以间距30 cm(MS30)最高,较玉米单作(MM100)高出34.99%。套作大豆生长率在初花期前显著低于单作(SS100),而初花期后高于SS100,以间距60cm(MS60)最高,盛花期—盛荚期在不施氮下较SS100高出78.91%。Logistic方程可较好的拟合玉米、大豆的干物质积累过程,且R2均在0.95以上。与不施氮相比,施氮推迟了玉米干物质积累高峰,提高了干物质积累量;套作大豆生育前期干物质积累慢于单作,而生育后期间距45cm(MS45)、MS60干物质积累逐渐与单作持平甚至超过单作。施氮提高了玉米籽粒干物质分配率而显著提高产量,2年间玉米产量分别提高10.05%、40.90%。随种间距离增加套作大豆产量呈先增后减趋势,以MS60最高,MS30最低,MS60两年间在不施氮与施氮下较MS30分别平均高出23.88%、31.77%。套作下土地当量比均在1.35以上,其中以施氮下MS60最大(1.89)。适宜的种间距离(间距60 cm)可实现套作下玉米和大豆协同生长,提高作物生长率、促进干物质积累与分配、提高系统产量和土地当量比。

基于最小数据集的典型黑土区不同林龄小黑杨土壤质量差异

东北作为我国重要农产品基地,其黑土有机质含量可达普通土壤的十倍。近年来由于过度的开发与利用,导致黑土质量下降,因此研究农田防护林对土壤质量的改善具有战略意义。为探讨农田防护林对黑土质量的改善效果,以不同林龄(Y1:林龄是1 a的小黑杨;Y5:林龄是5 a的小黑杨;Y6:林龄是6 a的小黑杨;Y8:林龄是8 a的小黑杨)小黑杨林下土壤为研究对象,通过测定小黑杨防护林样地的土壤理化性质,分析不同林龄小黑杨林下土壤理化性质的差异,并通过最小数据集方法对林下土壤质量进行评价。结果显示:(1)不同林龄土壤质地为:Y1:砂质土壤;Y5:壤土;Y6:粉砂质土壤;Y8:粉砂质土壤。(2)土壤透气保水性随林龄增长向良性方向演化,表层土壤容重由1.33 g/cm^(3)减小到1.17 g/cm^(3),不同土层间差异不显著,且土壤物理指标与树木生长量及其他土壤因子具有较强的相关性。(3)土壤pH随林龄减小,随土层呈波动性变化,范围在6.19—6.58之间。土壤养分随林龄呈波动性变化,垂直变化差异显著,除速效钾外均富集在表层,各土壤养分元素之间相关性较弱。(4)土壤微量元素有效态含量在不同林龄及土层均差异显著,且各元素之间相关性较强。(5)基于最小数据集的构建发现,影响不同林龄小黑杨土壤质量的最小数据集指标包括全氮、全钾、饱和持水量、速效磷、钙、锰,经总数据集验证所构建的最小数据集可体现小黑杨林下土壤质量有效信息。(6)小黑杨不同林龄土壤质量指数介于0.358—0.667,土壤质量综合得分排名为Y8>Y6>Y5>Y1。基于以上发现,小黑杨作为农田防护林对黑土区土壤质量改善效果明显,土壤保水透气性显著提升,土壤化学养分及微量元素含量部分提高,且不同林龄小黑杨对养分的循环利用效果差异显著。为实现黑土资源的合理利用,本研究建议随防护林林龄增加,更改林下套种作物以提高土壤质量及作物产量,为幼龄防护林对黑土区耕地的可持续利用提供科学依据。

玉米-大豆带状套作对土壤肥力的影响

【目的】明确玉米大豆带状套作对土壤肥力、酶活性、团聚体含量的影响以及作物产量的变化。【方法】以“登海605”为供试玉米品种,以“南豆12”为供试大豆品种,设置玉米-大豆带状套作、玉米单作和大豆单作3个处理,系统研究不同处理对土壤有机质、全氮、全磷和有效磷、全钾和速效钾含量,pH、容重,脲酶、蔗糖酶、酸性磷酸酶、硝酸还原酶活性、团聚体含量和作物产量的影响。【结果】玉米-大豆带状套作显著提高了玉米和大豆带土壤的有机质、有效磷、速效钾等养分含量,其中玉米带增幅分别为18.1%、14.9%和21.8%,大豆带有机质和速效钾增幅分别为17.7%和34.9%,而有效磷增幅较小且不显著,并保持了全氮、全磷、全钾含量和pH的稳定。玉米带土壤容重显著下降3.3%,大豆带则显著增加4.7%。带状套作显著提高了土壤蔗糖酶和脲酶的活性,玉米带增幅为16.3%和20.5%,大豆带增幅为133.7%和66.2%,酸性磷酸酶和硝酸还原酶活性保持稳定。带状套作促进了大粒径团聚体的形成,套作玉米和大豆带>2 mm团聚体分别显著提高18.8%和22.2%,其他各粒级的小团聚体不同程度下降。带状套作玉米较单作千粒重、穗粒数、有效株数和产量均无显著差异。带状套作大豆有效株数、单株粒数分别较单作显著下降12.9%、26.5%,百粒重无显著差异,最终使大豆产量达到单作的60.9%。【结论】玉米-大豆套作模式提高了土壤肥力,显著增加了有机质、速效钾、有效磷等的含量,维持了土壤中全氮、全磷、全钾含量和pH的稳定,并显著提高了土壤脲酶和蔗糖酶的活性,从而有利于土壤养分转化和植物吸收利用。带状套作还促进微小团聚体向稳定的大团聚体转化,从而提高了土壤的通透性和保水保肥能力,一定程度上影响土壤的化学性质,满足了玉米和大豆生长需要。因此,玉米-大豆带状套作可以改善土壤的化学性质和物理性质,提高土壤肥力,保持与单作相当的玉米产量,并能额外收获相当于单作产量60.9%的大豆。

生姜应答间/套作的生理生化研究进展

生姜(Zingiber officinale Roscoe)是重要的药食两用作物,有较高的经济价值。生姜喜阴,生产中常采用遮阴栽培,合理的生姜间/套作可以提高光能利用率及土地利用率,增加经济效益,在现代农业生产中具有一定的推广价值。本研究综述了间/套作对生姜生长和生理生化等方面的影响,旨在为构建简易、高产、高效、可持续发展的生姜产业提供参考;提出了生姜间/套作在分子生物学机制、根际微生态协调等方面需要进一步研究的问题,并对生姜在间/套作的未来研究方向进行了展望。

荞麦不同密度套种对田间杂草控制及魔芋生长的影响

为深化生态控草技术研究,采用1次播种荞麦控草技术方案,共设置5个荞麦播种密度梯度(3.5、7.0、10.5、14.0、17.5 kg/667 m^(2))处理和1个对照(CK,不进行化学除草、不播种荞麦),于2022年在贵州魔芋主产区威宁县开展田间小区试验,探索荞麦不同密度套种对田间杂草控制及魔芋生长的影响。结果表明,荞麦套种对魔芋地杂草有较好的控制作用,随着荞麦密度增加,对杂草的株防效、鲜重防效呈增加趋势;荞麦播种密度对魔芋出苗率影响不大,各处理之间差异不显著(P>0.05);随着荞麦播种密度增加,魔芋主茎高度呈增加趋势,叶盘直径、主茎直径呈现先增后减现象;采用荞麦控草对魔芋有增产效果,增产率在4.26%~19.85%之间,荞麦播种密度为10.5 kg/667 m^(2)时魔芋产量最高,为2124.12 kg/667 m^(2),较对照增产19.85%,显著高于T1处理,极显著高于对照。

大豆-玉米带状复合种植技术探讨

大豆-玉米带状复合种植技术作为近年来国家重点示范推广的稳粮扩油项目,已在全国16个省份得到推广应用。简介大豆-玉米带状复合种植技术和种植模式,分析与传统的大豆-玉米间套作模式的差异,并从品种、栽培、施肥、用水、控草等环节提出技术要求,从除草剂施用、病虫害防控等方面提出注意事项。

种间距对不同结瘤特性套作大豆根瘤生长及固氮潜力的影响

为充分挖掘套作大豆的固氮潜力,本试验以玉米/大豆带状套作系统为对象,研究了不同玉豆间距(30 cm、45 cm、60 cm和75 cm)下不同结瘤特性大豆品种(贡选1号、桂夏3号和南豆25号)的根瘤生长及固氮潜力差异。结果表明,与单作相比,带状套作可延缓大豆根瘤数目和鲜重峰值出现的时间:玉豆间距60 cm处理下,各品种大豆根瘤数目和鲜重显著高于其他间距处理,并在达到峰值期后高于单作大豆;品种间表现为:南豆25号>桂夏3号>贡选1号。带状套作相对于单作会降低始粒期(R5)前大豆根瘤的单株固氮潜力,但玉豆间距60 cm处理下,R5期贡选1号、桂夏3号和南豆25号的单株固氮潜力2年平均较单作提高8.53%、16.40%和13.70%。不同大豆品种根瘤侵染细胞内含物积累过程差异较大,相较单作,玉豆间距60cm处理下,R5期类菌体数量增多,其中聚-β-羟基丁酸盐颗粒(PHB)增加,以南豆25号表现最优。因此,带状套作下适宜的种间距(玉豆间距60cm)可增加R5期大豆根瘤数目和鲜重,提高大豆根瘤类菌体和PHB的数量,增强大豆根瘤的固氮潜力,以强结瘤品种南豆25号效果最好。

玉米行向配置对带状套作大豆光合特性、叶片结构及产量的影响

玉米-大豆带状复合种植技术具有提高土地利用率,扩大大豆生产面积,提高大豆产量的作用,而田间配置直接影响大豆生长发育和产量形成。本研究通过分析玉米-大豆带状套作模式行向配置对大豆形态、光合生理参数及产量的影响,确定南方区域玉米-大豆带状套作模式的最优行向。试验采用单因素随机区组设计,玉米大豆行比为2∶2,带宽2 m,设置6个处理:玉米西北-东南行向净作(CKm)、大豆西北-东南行向净作(CKs)和4种行向的玉米-大豆带状套作[东-西(A1)、南-北(A2)、西北-东南(A3)、东北-西南(A4)],分析套作大豆光环境、株高、叶面积指数、光合色素、光合参数、叶片结构特性、粒叶比及产量等对复合种植系统行向的响应。结果表明,东-西行向和西北-东南行向处理的大豆前期受荫蔽程度显著低于南-北行向和东北-西南行向处理(P<0.05);东-西行向种植,套作大豆受光量最大。与净作大豆西北-东南行向处理相比,带状套作各处理大豆叶面积指数、地上部生物量、光合色素含量、净光合速率、叶片生产能力、叶片厚度、气孔密度显著降低,整体趋势为东-西行向>西北-东南行向>南-北行向>东北-西南行向处理。东-西行向处理各生育时期大豆叶面积指数、地上部生物量、光合色素含量、净光合速率以及大豆叶片厚度、气孔密度、气孔长度和气孔开度均显著高于其他带状套作处理。在产量和效益方面,东-西行向处理的大豆产量和整株粒叶比、1~5节位粒叶比及3~4节位粒叶比分别为1932.66 kg∙hm^(-2)和1074.25 g∙m^(-2)、498.50 g∙m^(-2)及207.59 g∙m^(-2),高于其他带状套作处理(P<0.05)。与玉米净作处理相比,南-北行向、西北-东南行向和东北-西南行向处理玉米实际产量显著降低,而东-西行向处理玉米产量增加1.67%。东-西行向处理下玉米产量贡献率最高(79.44%),土地当量比为1.66。在中国南方地区,东-西行向种植能显著发挥玉米-大豆套作复合种植模式的优势。

西南地区玉米-大豆带状套作成本及综合效益分析

为了探究玉米-大豆带状套作模式在西南地区的推广价值,采用比较分析法和主成分分析法,对4种种植模式,即玉米-大豆带状套作(SRI)、玉米-大豆单行套作(RI)、单作玉米(MM)和单作大豆(MSB)的产量、产值、成本、成本构成及综合效益进行了分析。与单作相比,SRI模式显著提高土地复种指数,提高了土地利用率,具有良好的产出效果,不同地区SRI模式的平均纯收益为13422.17元/hm^(2),较RI、MM和MSB模式分别高24.15%、32.86%和554.98%;SRI总成本为13252.70元/hm^(2),较MM和MSB模式分别高31.99%和100.72%,较RI模式低1.87%。总成本中用工费用所占的比例最高,较MM和MSB模式分别增加21.51%和76.28%,较RI模式低2.85%;就综合效益而言,川南-仁寿、川中-乐至和川西-雅安地区的SRI模式综合效益排名均位于各地区第一,川南和川中丘陵地区的综合效益最好,其次为川西盆周山区。玉米-大豆带状套作模式是西南地区提高经济效益和综合效益较为理想的种植模式,其在丘陵地区的推广价值要高于盆周山区。

小麦边际效应与种植方式规范化的研究

采用田间小区、池栽和大田生产试验三种方法,通过对不同带型小麦边际效应的研究,理论模拟了间套条件下小麦产量的变化规律,提出了间套优势的概念和对小麦种植方式进行优化评价的思路。即间套优势(RIS)=相对产量/相对占地面积,它是边行优势大小和边行优势在总产量中所占比例的综合反映,利用RIS是否大于1可作为间套种植是否合理的依据。通过理论分析和实践验证,"20+40cm"(畦麦行距25cm,小麦小行距即沟宽20cm,大行距即垄宽50cm)小麦种植模式具有间套通用性强、适应性广、夏秋双高产的特点,对于实现小麦间套种植方式的规范化和机械化,可能具有重要意义。

玉米-大豆带状套作对大豆根瘤性状和固氮能力的影响

【目的】研究玉米-大豆带状套作系统中大豆生物量积累、根瘤特性、固氮酶活性和植株酰脲含量与固氮能力间的关系,明晰套作根系固氮能力的变化规律,为筛选适宜玉米-大豆带状套作的大豆品种提供理论依据。【方法】以强结瘤大豆NTS1007及其亲本BRAGG和本地耐荫大豆南豆12三个结瘤特性不同的大豆品种(系)为试验材料,在大田试验条件下,采用传统挖掘法挖根考察根瘤生长特性,并对玉豆带状套作下的大豆地上部与地下部生物量积累、根瘤固氮酶活性和植株酰脲含量进行测定和分析。【结果】与单作相比,玉豆带状套作下大豆植株生物量显著下降,地下部(33.15%)较地上部(20.84%)下降更为明显,根瘤生物量受地上部和地下部的共同调控(R2=0.613、0.916);大豆根瘤数目、单株瘤重和酰脲含量均显著下降,根瘤数目与地下部生物量呈显著正相关(R2=0.813);单位重量和单株固氮酶活性均显著下降,在达到峰值后下降速度均小于单作;单株固氮酶活性增长速率最快的时间滞后于单作。不同结瘤特性大豆对玉豆带状套作的响应不同,玉豆带状套作下NTS1007单株根瘤数目最多,但与单作相比其降幅最大(52.42%),BRAGG地下部和地上部生物量、根瘤重量下降幅度最大(37.73%、31.28%、43.25%),南豆12的根瘤数目、地上部和地下部生物量、根冠比的降幅均为最小(40.12%、10.17%、19.83%、10.41%);玉豆带状套作下NTS1007的单株固氮酶活性和单位重量酰脲含量降幅最大(64.41%、21.72%),BRAGG的单位重量固氮酶活性降幅最大(24.16%),南豆12的单位重量和单株固氮酶活性、单株酰脲含量均表现为最高,且降幅最小(10.01%、45.81%、17.88%)。【结论】玉豆带状套作显著降低了大豆地上部、地下部生物量和根冠比,减少了单株根瘤数目,降低了单位重量根瘤和单株固氮酶活性,抑制了大豆固氮能力的发挥。但生殖生长后期固氮能力下降速度低于单作,这有利于套作大豆籽粒蛋白质的积累。不同结瘤特性大豆对套作的响应不同,强结瘤大豆NTS1007的地上部干物质积累和地下根瘤形成对套作环境反应敏感,南豆12则对玉豆带状套作表现出了良好的适应性。

玉米-豆科作物带状间套作对养分吸收利用及产量优势的影响

为明确玉米大豆套作、玉米花生间作养分吸收利用对产量优势贡献的差异。本研究开展了2年大田试验,通过比较间套作与相应单作成熟期植株氮磷钾养分吸收量和利用效率,综合分析了玉米大豆套作、玉米花生间作中养分吸收和利用效率的变化。结果表明:玉米大豆套作土地当量比(land equivalent ratio,LER)为1.16~1.72,具有套作产量优势,玉米花生间作LER为0.89~1.13,无明显间作产量优势。玉米大豆套作体系中,植株氮、磷、钾养分吸收总量比相应单作提高32.60%~54.22%、27.35%~34.64%和17.74%~24.42%,氮素利用效率低于相应单作21.99%~42.07%。氮、磷、钾吸收效率对LER的贡献分别为0.34~0.62、0.31~0.46和0.22~0.32,利用效率的贡献分别为–0.11~–0.35、–0.03~–0.31和–0.11~0.22。玉米花生间作体系中,氮、磷、钾养分吸收总量分别高出相应单作–7.86%~31.58%、23.09%~46.52%和1.60%~55.48%,氮素利用效率高出相应单作7.55~26.60。氮、磷、钾吸收效率对LER的贡献分别为0~0.22、0.05~0.27和–0.11~0.32,利用效率的贡献分别为–0.25~0.19、–0.32~0.11和–0.47~0.32。因此,玉米大豆套作优势在营养方面的基础主要来自于相对于单作养分吸收总量的增加,而玉米花生间作无明显间作优势主要因为养分吸收对产量优势的贡献较小。

氮肥和种植密度对带状种植小麦抗倒能力的影响及边际效应

西南地区小麦以套作为主,因有效穗不足而使产量受到严重制约。本研究旨在提出该地区套作小麦高产栽培的适宜密度和氮肥施用量,提高小麦生育后期的抗倒伏能力,确保有效穗和最终产量。2009—2010和2010—2011连续两年度,选用主推品种川麦42,在纯氮120kghm-2和180kghm-22个施氮水平下,按60、120、180、240和300万株hm-2密度进行带状种植,对小麦群体发展、茎秆形态特征和倒伏机械特性进行了行间差异分析。结果表明,边行、次边行和中间行均随种植密度的增加茎蘖数和有效穗增多,但单株干物重及其在穗中的分配比例下降,茎秆质量降低。群体发展和个体质量在拔节后表现出显著的边行优势,成穗率、有效穗、单茎干物重、节间粗度、茎壁厚度、节间充实度和机械强度均以边行最优;同时密度对边行优势有显著影响,在180万株hm-2密度下,边行的有效穗基本达到饱和;密度继续增加时次边行和中间行的有效穗显著增加,并伴随株高和重心高度增加、单茎干物重降低、干物质分配在穗中的比例减小、节间充实度和茎秆机械强度急剧下降、倒伏时期提前、倒伏指数和倒伏程度增加。增加施氮量有提高中间行茎秆机械强度和降低倒伏指数、增强茎秆抗倒伏能力的趋势,但总体表现不显著。因此认为,120～180万株hm-2种植密度有利于套作小麦个体和群体质量的协调,是南方丘陵旱地带状种植小麦抗倒高产的适宜种植密度。