根瘤菌菌株NM353对小麦/蚕豆间作体系中作物生长及养分吸收的影响

采用不同根系分隔方式(小麦与蚕豆根系完全分隔、尼龙网分隔和不分隔)研究了间作蚕豆接种根瘤菌菌株NM353,在施氮和不施氮情况下,蚕豆和小麦的生长和养分吸收状况。结果表明,无论何种分隔方式和施氮与否,接种根瘤菌菌株NM353对蚕豆的生长都好于不接种;同时,间作小麦也通过根系的相互作用受益。在施氮情况下,接种与不接种处理相比,蚕豆生物量在三种分隔方式中依次增加了15%、16%和5%;吸氮量依次增加了17%、9%和12%;而根系不分隔并接种根瘤菌NM353还改善间作小麦的生长,其生物量、吸氮量比不接种时分别增加了13%和22%。因此,小麦/蚕豆间作中通过选择合适的菌株进行接种,并配合适当的氮肥施用,可以充分发挥豆科生物固氮作用,并改善与之间作的作物氮素营养。     

根系交互作用对等高绿篱—大豆间作系统N素吸收转移的影响

通过15N标记叶片和15N标记土壤的地下部分隔箱栽试验,探讨了根系交互作用对大豆/绿篱间作体系氮素吸收和转移的影响。结果表明,紫穗槐-大豆系统无隔处理大豆和紫穗槐生长被抑制,其生物量和吸氮量均低于网隔和板隔2种分隔方式;而香根草-大豆间作下,大豆与香根草的生物量和吸氮量都表现为根系无隔时最高。大豆植株体内15N丰度,香根草-大豆间作下,尼龙网分隔处理高于无隔处理,香根草则表现为无隔处理较高;紫穗槐-大豆间作下,紫穗槐和大豆体内15N丰度都表现为根系无隔处理较低。大豆和绿篱共生期内,2种绿篱都从大豆体内竞争了氮素,发生了大豆向绿篱的氮素转移。表明香根草与紫穗槐对肥料氮的竞争能力均强于大豆;紫穗槐和大豆间作表现为种间抑制作用,不利于大豆和紫穗槐生长;香根草和大豆间作表现为互补作用,营养竞争和促进同在,促进了大豆和香根草生长。     

两种间作体系中养分竞争与营养促进作用研究

应用根系分隔技术研究小麦 /蚕豆、小麦 /大豆间作中养分竞争和营养促进作用结果表明 ,与豆科根系相互作用时小麦生物量和养分吸收量均大于完全分隔和 30 μm孔径尼龙网分隔处理 ;与小麦根系相互作用时大豆生长受抑 ,生物量低和养分吸收量下降 ,而蚕豆生物量和养分吸收量未受显著影响。小麦竞争能力强于蚕豆和大豆 ,小麦 /大豆间作体系存在种间竞争作用 ,而小麦 /蚕豆间作体系存在种间促进互惠作用     

地下部分隔对间作小麦养分吸收和白粉病发生的影响

通过根系分隔的盆栽试验,探讨了地下部分隔对小麦//蚕豆间作系统中小麦的养分吸收和白粉病发生的影响。结果表明:根系不分隔小麦的生物量和N、P、K吸收量均大于尼龙网分隔处理和根系完全分隔处理。根系分隔方式还影响了小麦白粉病的发生,小麦白粉病的发病率和发病指数均表现为根系不分隔(I)尼龙网分隔(M)完全分隔(P)。表明地下部的相互作用改善了小麦的生长,提高了小麦抗白粉病的能力。     

玉米-大豆和玉米-甘薯套作对玉米生长及氮素吸收的影响

【目的】利用根系分隔技术, 研究不同需氮特性的旋花科、 豆科作物与玉米套作后,玉米的生长特性与养分吸收差异及其增产机理。【方法】采用石英砂培盆栽试验,二因素完全随机试验设计。以玉米-大豆、 玉米-甘薯两种套作模式为研究对象,设计不分隔、 部分分隔、 完全分隔三种隔根方式。分析不同套作模式下不同隔根方式对玉米地下根系活力、 根系生物量及地上植株叶片光合特性、 籽粒产量和吸氮量的影响。【结果】1)不同种植模式对玉米生长有显著影响,不分隔处理时,与大豆套作的玉米根系活力、 籽粒重及地上植株总吸氮显著高于与甘薯套作的玉米,分别高6.25%、 8.69%和18.89%; 部分分隔或完全分隔时,两套作处理间差异不显著(P0.05)。 2)隔根方式影响玉米的物质积累及籽粒产量,表现为不分隔部分分隔完全分隔。3)不分隔有助于促进共生玉米生长,但不同套作模式的影响效果不一致;玉米-大豆套作处理下,不分隔处理的玉米根系活力、 净光合速率、 籽粒产量和总吸氮量均高于隔根处理,比完全分隔处理的分别高25.65%、 27.31%、 64.69%和71.65%;玉米-甘薯套作下增加幅度为17.59%、 19.83%、 52.38%和46.21%,分别比玉米-大豆套作处理低31.44%、 27.39%、 19.03%和35.51%。 4)相关分析表明,两种套作处理玉米地下根系干重与地上植株干物质重、 叶片光合速率及籽粒重显著正相关,相关系数分别为0.984、 0.927和0.986(P0.01);且地下根系活力与地上植株叶片净光合速率显著正相关,相关系数达0.929(P0.01)。【结论】种植模式和隔根方式显著影响了玉米的物质积累及氮素吸收。根系不分隔时,玉米－大豆套作处理下玉米的根系活力、 净光合速率、 生物量、 籽粒产量及总吸氮量显著高于玉米－甘薯套作;隔根处理导致的生物量和吸氮量下降主要是由根系活力降低引起的。与玉米-甘薯套作相比,大豆促进了玉米根系活力的提高,有效调节了玉米地上部植株光合作用及干物质积累,实现产量和氮素吸收的增加。     

春小麦大豆间作条件下作物养分吸收积累动态的研究

采用田间小区试验和微区根系分隔试验,通过间作与相应单作养分吸收动态的比较,阐明了小麦大豆间作中养分吸收的种间竞争作用和促进作用。结果表明,小麦具有更强的养分竞争能力,在两作物共生的８０多天中,间作小麦的吸氮量、吸磷量始终高于单作小麦,是其获得高产的基础。虽然间作大豆在前期养分吸收缓慢,在两作物共生期的氮磷钾吸收量均显著地低于单作大豆,但小麦收获后有明显的恢复。种间根系分隔试验结果表明,小麦大豆根系间不分隔时,小麦的吸氮量和吸磷量有明显的边行优势;用塑料膜分隔时,边行优势消失;但用尼龙网分隔时,小麦吸磷量表现出一定的边行优势,是大豆根际效应所致。     

地下部分隔对蚕豆/玉米间作氮素吸收和土壤硝态氮残留影响

利用田间试验,探讨了地下部分隔对蚕豆/玉米间作氮素吸收和土壤硝态氮残留的影响,结果表明:蚕豆/玉米间作,蚕豆不分隔条件下籽粒和秸秆吸氮量比分隔分别增加20 10%,34 43%;玉米不分隔条件下籽粒吸氮量与分隔近似,但秸秆吸氮量比分隔减少13 04%;蚕豆和玉米不分隔条件下土壤硝态氮累积量都高于分隔。蚕豆/空带间作,蚕豆不分隔籽粒吸氮量高于分隔,但土壤硝态氮累积量没有差异。空带/玉米间作,地下部分隔与否,作物吸氮量和土壤硝态氮累积量都没有差异。     

隔根与接种 FM 对红壤上玉米/大豆植株生长及氮素利用的影响

【目的】探讨接种摩西管柄囊霉 (Funneliformis mosseae,FM) 和不同隔根处理对红壤上间作植株生长、植株氮吸收量和土壤氮的影响。【方法】采用盆栽模拟试验,设不同菌根处理[不接种 (NM)、接种 (FM)]与玉米/大豆不同隔根处理 (根系不分隔、部分分隔、完全分隔)。【结果】接种 FM 的玉米、大豆根系均有一定的侵染,菌根侵染率在部分分隔处理下最低。间作根系的分隔处理对玉米和大豆的菌根依赖性产生了明显影响,大豆的菌根依赖性随间作交互作用强度的加大而增加。无论何种隔根处理,接种 FM 均显著增加了玉米植株生物量,其地上部生物量高出 NM 处理 11.7%～81.4%,根系生物量高出 NM 处理 18.8%～166.7%。根系分隔处理下,接种 FM 均显著降低了大豆生物量。同一隔根方式下,接种 FM 明显提高了玉米的植株氮吸收量和根系氮吸收效率。在不分隔处理下,接种 FM 显著增加了大豆的地上部氮吸收量,但在部分分隔和完全分隔处理下则反而有所下降;在部分分隔处理下,接种 FM 显著降低了大豆根系的氮吸收量,在不分隔和完全分隔处理下亦呈下降趋势。在部分分隔处理下,接种 FM 显著提高了大豆根系氮吸收效率,在完全分隔处理下反而有明显下降,且在 NM–不分隔处理下的大豆根系氮吸收效率最低。相关分析显示,玉米、大豆植株氮吸收量与土壤碱解氮含量呈显著负相关。【结论】接种丛枝菌根真菌 (AMF) 和隔根方式的组合能不同程度地影响玉米和大豆对氮的吸收利用及间作植株的生长,并能对土壤有效氮产生较大影响。所有的复合处理中,AMF和间作根系部分分隔处理组合对玉米和大豆生长及氮素利用的促进作用较好,并能有效降低土壤碱解氮的残留。     

“小麦/玉米/大豆”套作体系中不同作物间的相互作用及氮素的转移、吸收

在根系分隔盆栽条件下,采用15N土壤稀释标记方法,研究了“小麦/玉米/大豆”三熟套作体系不同作物间的相互作用及氮素的转移、吸收利用特性。结果表明,“小麦/玉米/大豆”套作体系促进小麦对肥料氮和土壤氮的吸收,不分隔处理的生物产量、15N总吸收量和总回收率得到显著提高,土壤残留15N丰度及总氮含量明显降低;玉米表现出套作优势（Awc<0,NCRwc<0）,不分隔处理的籽粒产量、籽粒15N吸收量、15N总回收率、土壤残留15N丰度及总氮含量较分隔处理提高17.17%、24.52%、17.63%、13.9%和10.1%;大豆表现出套作劣势,不分隔处理的15N总吸收量、籽粒15N吸收量、15N总回收率和土壤残留15N丰度降低,土壤总氮含量提高6.06%。“小麦/玉米/大豆”套作体系存在氮素的双向转移,以玉米向小麦、大豆向玉米转移为主。     

菌根对紫色土上间作玉米生长及磷素累积的影响

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)在土壤与植物系统的磷素循环中发挥着关键的作用。本文通过盆栽模拟试验研究了不同AMF接种状况[不接种(NM)、接种Glomus mosseae(GM)、接种G.etunicatum(GE)]和玉米/大豆间作体系不同根系分隔方式(不分隔、尼龙网分隔、塑料膜分隔)对间作玉米植株生长及磷素吸收累积的影响。研究结果表明:GM处理下的间作玉米根系侵染率在不同根系分隔方式之间的差异不显著,而GE处理则在塑料膜分隔处理下对玉米的侵染率最高。接种不同AMF对间作玉米促生效果不同,GM和GE处理在不同根系分隔情况下表现出各自的优势,与未接种处理相比,GM处理能使玉米生物量、株高有一定程度增加并在根系不分隔处理下玉米磷吸收较多、生长较好;GE处理能使植株生物量有一定程度增加并在尼龙网分隔处理下的玉米磷吸收较多、生长较好。间作体系不同根系分隔方式对玉米的影响也不同,其中玉米地上部生物量在根系分隔处理下普遍小于不分隔处理,但根系生物量的大小情况则刚好相反。另外,无论何种接种状况,玉米根系磷含量及吸收量均以尼龙网分隔处理显著较高。而根系磷吸收效率则以接种G.mosseae且不分隔根系处理显著高于分隔处理。所有复合处理中,以接种G.etunicatum与尼龙网分隔根系组合处理对间作玉米的生长及磷素累积的促进作用最好,若应用于滇池流域,可望有效控制坡耕地土壤磷素的迁移。     

Complementary resource use in intercropped faba bean and cabbage by increased root growth and nitrogen use in organic production

Intercropping can improve yield and nitrogen use efficiency in organic vegetable production by pairing crops with complementary resource use. An intercrop field experiment was conducted to determine yield, root growth and nitrogen (N) dynamics using faba bean (Vicia faba L.) grown as a vegetable and pointed cabbage (Brassica oleracea var. capitata cv. conica). Both crops were grown in monocropping (MC) and intercropping systems (IC). Minirhizotrons were used to measure root growth. Yield of pointed cabbage per metre row was 28% higher under the IC system than under MC, whereas faba bean yield as fresh seeds did not differ. The land equivalent ratio was 1.06, showing that improved yield under IC resulted from efficient land resource use. Even though MC cabbage had the highest aboveground biomass, total N accumulation was higher under IC and MC faba bean systems. Both root frequency and intensity were greater under IC faba bean rows compared with MC faba bean because of the presence of cabbage roots in faba bean rows. Monocropped cabbage had the highest root intensity and the lowest amount of soil mineral N in the 0–1.5 m depth after harvest. Monocropped cabbage was efficient in assimilating N, whereas MC faba bean was efficient in exporting N as harvestable yield. The nitrogen use efficiency using the IC system (75%) was higher than growing faba bean (44%) and cabbage (65%) alone. Thus, faba bean as an intercrop in organic cabbage production systems improves land and N use efficiency by complementary root growth.     

小麦||蚕豆间作提高间作产量的优势及其氮肥响应

为探明小麦||蚕豆间作体系种间互补和竞争与产量优势的关系及其氮肥响应，为豆科禾本科间作最佳氮素管理提供指导，本研究通过为期2年（2015—2017年）的田间定位试验，在不施氮（N0）、低氮（N1，90 kg·hm^-2）、常规施氮（N2，180 kg·hm^-2）和高氮（N3，270 kg·hm^-2）4个施氮水平下，研究小麦||蚕豆间作的产量优势及其相关种间关系。结果表明，与单作相比，两年的间作小麦产量平均显著增加23.50%，单、间作蚕豆的产量均维持在4 000 kg·hm^-2左右，土地当量比均表现为N0 > N1 > N2 > N3 > 1的趋势，系统生产力平均达5 023 kg·hm^-2。与单作相比，间作小麦和蚕豆的花后干物质累积比例、干物质转移率和贡献率均不同程度增加，增幅随着施氮量增加而降低。不同施氮水平下，小麦的种间相对关系指数均表现出明显的互利效应，相对种间竞争强度在低氮水平为种内竞争，常规氮和高氮水平为种间竞争；蚕豆的种间相对关系指数则表现出竞争效应，相对种间竞争强度表现为种内竞争。较蚕豆而言，小麦的相对种间竞争力表现出不同程度的竞争优势，在种间竞争力为0.629 2时可获得最大的间作体系混合干物质量16 093 kg·hm^-2。综上，小麦||蚕豆间作降低了低氮水平下的种间竞争强度，扩大了小麦的互利效应和竞争优势，增加了间作作物的花后干物质累积比例以及干物质贡献率，表现出明显的间作产量优势。     

添加黏土及植物残体混合物对沙质土壤中呼吸作用和微生物量碳、氮有效性的影响

Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil(7% clay) was amended with a clay-rich subsoil(73% clay) at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control(sandy soil alone) with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg~(-1): mature wheat(Triticum aestivum L.) straw with a C/N ratio of 68, mature faba bean(Vicia faba L.) straw with a C/N ratio of 39, or their mixtures with different proportions(0%–100%, weight percentage) of each straw. Soil respiration was measured over days 0–45 and microbial biomass C(MBC), available N, and p H on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency(cumulative respiration per unit of MBC on day 15) was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil p H were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and p H were influenced by clay addition to the sandy soil studied.     

Influences of intercropping and nitrogen supply on flavonoid exudation in wheat roots

Abstract

Soil and hydroponic experiments were carried out to examine the influences of intercropping and nitrogen supply on flavonoid exudation in wheat roots. Both experiments comprising three cropping patterns (wheat intercropped with faba bean, monocropped wheat, and monocropped faba bean) and three N supply levels (deficient, adequate, and excessive) with three replicates in a randomized complete block design. Across two experiments, intercropping increased but N fertilization decreased flavonoids of wheat roots frequently. Intercropping variably increased secretion of naringenin from 0.5 to 1.9 folds (P?<?0.5) in wheat roots at all three N levels, but rarely increased secretion of genistein and hesperetin in wheat at the deficient N level. Intercropped wheat secreted more flavonoids than monocropped wheat at its tillering (60^th d) and flowering (95^th d) stages; after the flowering stage, however, the differences between intercropping and monocropping were not significant at any N level. Secretion of flavonoids in wheat roots decreased with increased N supply. Interspecies and N supply altered the contents and proportions of flavonoids in wheat root exudations under wheat and faba bean intercropping. These results indicate facilitative root–root interactions and provide insight into cereal promote nodule of legume in intercropping system.     

Wheat response to N2 fixed by faba bean (Vicia faba L.) as affected by sulfur fertilization and rhizobial inoculation in semi‐arid Northern Ethiopia

Nitrogen fixation in faba bean (Vicia faba cv. Mesay) as affected by sulfur (S) fertilization (30 kg S ha^–1) and inoculation under the semi‐arid conditions of Ethiopia was studied using the ¹⁵N‐isotope dilution method. The effect of faba bean–fixed nitrogen (N) on yield of the subsequent wheat crop (Triticum aestivum L.) was also assessed. Sulfur fertilization and inoculation significantly (p < 0.05) affected nodulation at late flowering stage for both 2004 and 2005 cropping seasons. The nodule number and nodule fresh weighs were increased by 53% and 95%, relative to the control. Similarly, both treatments (S fertilization and inoculants) significantly improved biomass and grain yield of faba bean on average by 2.2 and 1.2 Mg ha^–1. This corresponds to 37% and 50% increases, respectively, relative to the control. Total N and S uptake of grains was significantly higher by 59.6 and 3.3 kg ha^–1, which are 76% and 66% increases, respectively. Sulfur and inoculation enhanced the percentage of N derived from the atmosphere in the whole plant of faba bean from 51% to 73%. This corresponds to N₂ fixation varying from 49 to 147 kg N ha^–1. The percentage of N derived from fertilizer (%Ndff) and soil (%Ndfs) of faba bean varied from 4.3% to 2.8 %, and from 45.1% to 24.0%, corresponding to the average values of 5.1 and 47.9 kg N ha^–1. Similarly, the %Ndff and %Ndfs of the reference crop, barley, varied from 8.5 % to 10.8% and from 91.5% to 89.2%, with average N yields of 9.2 and 84.3 kg N ha^–1. Soil N balance after faba bean ranged from 13 to 52 kg N ha^–1. Beneficial effects of faba bean on yield of a wheat crop grown after faba bean were highly significant, increasing the average grain and N yields of this crop by 1.11 Mg ha^–1 and 30 kg ha^–1, relative to the yield of wheat grown after the reference crop, barley. Thus, it can be concluded that faba bean can be grown as an alternative crop to fallow, benefiting farmers economically and increasing the soil fertility.     

小麦蚕豆间作体系氮素吸收累积动态及其种间氮素竞争关系

  【目的】  通过研究小麦//蚕豆间作地上部的氮含量和吸收量，明确不同氮水平下小麦//蚕豆间作的氮吸收累积特征，解析间作小麦和蚕豆种间氮素竞争关系。  【方法】  田间试验采用两因素随机区组试验设计，设置3个种植模式 (单作小麦，单作蚕豆及小麦//蚕豆间作) 及4个氮水平 (N0，N1，N2，N3)，其中小麦的4个施氮量依次为0、90、180、270 kg/hm2，蚕豆的4个施氮量依次为0、45、90、135 kg/hm2。测定了单间作小麦和蚕豆的产量、地上部氮累积含量，利用Logistic模型模拟小麦蚕豆的氮吸收关键参数及氮吸收动态，分析了间作小麦和蚕豆的氮素竞争关系。  【结果】  小麦//蚕豆间作整体平均提高小麦产量33.4% (除N3外)、降低蚕豆产量20.7%，N0和N1水平下，间作具有显著产量优势。通过Logistic模型分析发现，间作条件下小麦的氮吸收高峰比蚕豆晚12～19天。4个氮水平下，间作主要提高了小麦最大氮累积量 (A)、最大氮吸收速率 (R_max) 和初始氮吸收速率 (r)，却降低了蚕豆的A、达到最大氮吸收速率所需的时间 (T_max) 和R_max。在营养生长阶段，小麦的氮素竞争力低于蚕豆，施氮可提高小麦的氮素吸收量。从施氮水平和种植模式共同作用角度分析，N0、N1和N2水平下，间作分别提高小麦的R_max 34.1%、44.6%和21.0%。因此，当小麦达到氮吸收高峰后，间作分别提高小麦氮吸收速率和氮素累积量15.1%～48.4%和9.2%～28.9%，却降低蚕豆氮吸收速率和氮素累积量7.3%～28.4%和7.9%～14.0%。此时，间作小麦氮素竞争力大于蚕豆，在N1水平下小麦的氮素竞争力最强。  【结论】  小麦//蚕豆间作提高了小麦的初始及最大氮素吸收速率 (r和R_max)，提高了小麦生殖生长阶段的氮素吸收和累积，是间作小麦产量优势的基础。优化氮肥投入量，可调控小麦和蚕豆的种间竞争及互补关系，是小麦//蚕豆间作体系产量优势形成、氮素高效吸收利用的关键。     

Nodulation and root growth increase in lower soil layers of water‐limited faba bean intercropped with wheat

Below‐ground niche complementarity in legume–cereal intercrops may improve resource use efficiency and root adaptability to environmental constraints. However, the effect of water limitation on legume rooting and nodulation patterns in intercropping is poorly understood. To advance our knowledge of mechanisms involved in water‐limitation response, faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were grown as mono‐ and intercrops in soil‐filled plexiglass rhizoboxes under water sufficiency (80% of water‐holding capacity) and water limitation (30% of water‐holding capacity). We examined whether intercropping facilitates below‐ground niche complementarity under water limitation via interspecific root stratification coupled with modified nodulation patterns. While no significant treatment effects were measured in intercropped wheat growth parameters, water limitation induced a decrease in shoot and root biomass of monocropped wheat. Likewise, shoot biomass and height, and root length of monocropped faba bean significantly decreased under water limitation. Conversely, water limitation stimulated root biomass of intercropped faba bean in the lower soil layer (15–30 cm soil depth). Similarly, total nodule number of faba bean roots as well as nodule number in the lower soil layer increased under intercropping regardless of water availability. Under water limitation, intercropping also led to a significant increased nodule biomass (48%) in the lower soil layer as compared to monocropping. The enhanced nodulation in the lower soil layer and the associated increase in root and shoot growth provides evidence for a shift in niche occupancy when intercropped with wheat, which improves water‐limited faba bean performance.     

Effects of Nitrogen and Phosphorus Fertilizers and Intercropping on Uptake of Nitrogen and Phosphorus by Wheat,Maize, and Faba Bean

Abstract

One‐third of all the cultivated land area is used for multiple cropping and half of the total grain yield is produced with multiple cropping in China. There have been numerous studies on nutrient acquisition by crops in legume/non‐legume intercropping systems, but few on nutrient uptake in cereal/cereal intercropping. This paper describes a field experiment in which integrated wheat/maize and maize/faba bean systems were compared with sole wheat and sole faba bean cropping to assess the effects of intercropping on nutrient uptake by wheat, maize, and faba bean under various application rates of nitrogen (N) and phosphorous (P) fertilizers. Results show that both N and P fertilizers and intercropping enhanced N uptake by wheat, while only P fertilizer and intercropping increased P acquisition by wheat. The advantage of N uptake by border rows of wheat intercropped with maize declined with increasing N fertilizer application rate, but that of P acquisition was not affected by P fertilizer. The amounts of both N and P taken up by maize intercropped with faba bean were much higher than those by maize intercropped with wheat throughout the period of intercropping. Both fertilization and intercropping did not influence the N and P uptake by faba bean.     

Grain legume pre-crops and their residues affect the growth, P uptake and size of P pools in the rhizosphere of the following wheat

Legumes have been shown to increase P uptake of the following cereal, but the underlying mechanisms are unclear. The aim of this study was to compare the effect of legume pre-crops and their residues on the growth, P uptake and size of soil P pools in the rhizosphere of the following wheat. Three grain legumes (faba bean, chickpea and white lupin) were grown until maturity in loamy sand soil with low P availability to which 80?mg P kg^?1 was supplied. This pre-crop soil was then amended with legume residues or left un-amended and planted with wheat. The growth, P uptake and concentrations of P pools in the rhizosphere of the following wheat were measured 6?weeks after sowing. In a separate experiment, residue decomposition was measured over 42?days by determining soil CO₂ release as well as available N and P. Decomposition rates were highest for chickpea residues and lowest for wheat residues. P release was greatest from white lupin residues and N release was greatest from faba bean residues, while wheat residues resulted in net N and P immobilisation. The growth of the following wheat was greater in legume pre-crop soil without residue than in soils with residue addition, while the reverse was true for plant P concentration. Among the legumes, faba bean had the strongest effect on growth, P uptake and concentrations of the rhizosphere P pools of the following wheat. Regardless of the pre-crop and residue treatment, wheat depleted the less labile pools residual P as well as NaOH-Pi and Po, with a stronger depletion of the organic pool. We conclude that although P in the added residues may become available during decomposition, the presence of the residues in the soil had a negative effect on the growth of the following wheat. Further, pre-crops or their residues had little effect on the size of P pools in the rhizosphere of wheat.