广东大豆地方种质磷效率特性研究Ⅰ.大豆基因型磷效率特性差异及其与土壤有效磷含量的关系

在低磷红壤上,对原产广东省的大豆基因型磷效率与其来源地土壤有效磷含量的关系进行研究。结果表明：植株磷素吸收量相对值不仅可以反映大地低磷红一长适应性,而且可以反映大豆基因型磷效率特性,ＲＶＰＰＵ是较大的大豆基因型。     

低磷胁迫下溶液培养大豆生长和磷素营养特性及其与土培下磷效率特性的关系

采用无磷 (P0 )和低磷 (P1 )溶液培养方法 ,对 1 9份经田间和盆栽土培试验中磷效率特性表现不同的大豆基因型进行研究 ,探讨低磷溶液培养条件下大豆基因型生长和磷素营养特性及其与土培条件下磷效率特性的关系。结果表明 ,在低磷溶液培养下 ,不同大豆基因型吸收溶液中可溶性磷的能力存在差异 ,吸收的磷量可达到自身固有磷量的 5 %～ 80 %左右。土培条件下磷效率比值相对值较小 (即在酸性红壤耕地上适应性较好 )的基因型 ,在低磷溶液培养下 ,不同基因型吸收溶液中可溶性磷的能力有强有弱 ;而磷效率比值相对值较大 (即在酸性红壤耕地上适应性较差 )的基因型 ,亦有相似的表现。低磷处理的不同大豆基因型植株鲜重净增量为无磷处理的 17.79%～99.09% ,植株干重净增量为 15.64 %～11.6 67%。无磷处理的植株干、鲜生物量 ,地上部干、鲜量 ,磷效率比值和低磷处理的磷效率比值以及种子重与土培条件下大豆基因型磷效率比值相对值呈显著、极显著正相关。     

酸性红壤中磷高效大豆新种质的磷营养特性

采用一系列磷高效大豆新种质及对照材料,在华南酸性红壤地区3种不同磷水平的代表性土壤上,分春、夏两季研究了不同大豆品种的磷营养特性,探讨了不同大豆品种（系）在不同磷水平土壤上的最佳施磷量及其经济效益。结果表明, 1）土壤有效磷含量是影响酸性红壤地区大豆生产的重要因素,无论从地上部生物量、磷吸收量还是产量来看,所有供试品种均表现出高磷>中磷>低磷土壤的趋势。2）施磷对低肥力土壤上大豆产量的影响较大,对中等肥力土壤影响较小,而对高肥力土壤,施磷肥反而造成大豆减产; 过量施用磷肥会造成大豆对磷的“奢侈吸收”。3）大豆的磷营养特性具有显著的基因型差异,因而需要不同磷养分管理方式。4个磷高效大豆新种质在低肥力土壤上仅需施用少量磷肥,在中、高肥力土壤上不需施磷即可满足生长需要。经济效益分析结果表明,磷高效品种无论在低肥力还是在中、高肥力土壤上,其纯收入均远高于本地和国家大豆区域试验对照品种。     

活化钙镁磷肥对不同磷效率基因型冬小麦生长及磷效率的影响

用土培方法研究了两种磷肥 (枸溶性钙镁磷肥CMP和水溶性磷肥过磷酸钙SSP)和两种非水溶性磷肥活化剂(无机矿物活化剂IA和有机活化剂OA)在石灰性土壤中对不同磷效率小麦苗期生长和基因型差异以及磷效率的影响。结果表明 ,SSP和CMP对不同磷效率基因型小麦生长的影响无显著差异 ,但对植株磷效率的影响效果明显不同。SSP可提高植株的磷吸收效率 ,CMP对提高植株的磷利用效率更有效。不同磷效率小麦生长的基因型差异在所有磷肥处理中均表现 ,但在CMP处理中的差异最大 ,不同溶解性磷肥品种可作为小麦磷效率基因型的鉴定材料。两种非水溶性磷肥活化剂对钙镁磷肥均有效 ,但作用大小和方向因小麦基因型不同而异 ,OA有利于磷高效基因型小麦的生长 ,IA对磷低效基因型小麦的生长则更加有利 ,其效果甚至超过水溶性磷肥。经IA处理的CMP能明显提高小麦植株的磷含量和吸磷量 ,并能显著增加土壤的有效磷含量     

接种菌根真菌对不同磷效率基因型大豆生长和磷吸收的影响

接种丛枝菌根真菌(AMF)能显著促进大豆生长和对磷的吸收,但不同磷效率基因型大豆对AMF接种的响应还少有报道。为探究接种AMF对不同磷效率基因型大豆生长和磷转运基因表达的影响,以磷高效大豆BX10和磷低效大豆BD2为试验材料进行盆栽试验,设置接菌和不接菌处理,对大豆干重、菌根侵染性状、氮磷养分含量、根系性状,以及菌根诱导的磷转运基因表达进行了分析。结果表明, AMF接种显著促进了大豆的磷吸收,并且接菌效果存在显著的基因型差异,接种AMF显著增加了BD2的地上部干重、磷含量以及植株总磷吸收量,但只增加了BX10的地上部磷含量和总磷吸收量,对植株地上部干重没有显著影响。无论接种与否,BD2的地上部磷含量均显著高于BX10,表明磷低效的BD2具有较高的植株体内磷转运能力。不接菌条件下,两个大豆基因型根系性状无显著差异;接种AMF后BX10的根系体积和根系平均直径均显著高于BD2。BD2的菌根生长反应(MGR)和菌根磷反应(MPR)均显著高于BX10,对菌根依赖性更高。此外,在接菌处理的BD2根系,代表菌根途径磷吸收的磷转运基因GmPT8、GmPT9和GmPT10表达均显著高于BX10;相应地,BD2的总磷吸收量也显著高于BX10。以上结果表明,接种AMF对促进磷低效大豆BD2生长和磷吸收的作用更大,这可能主要是由于BD2菌根途径的磷吸收量较高,体内磷转运效率较高。以上结果将为研究AMF接种对磷吸收的贡献提供理论依据。     

长期大气CO2浓度升高对大豆磷吸收及根际磷转化的影响

磷(P)作为第二重要的植物营养元素,能够调节作物对气候变化的适应性。东北不同地区黑土有机质含量存在着较大差异,对作物营养吸收产生较大影响。然而,长期大气CO₂浓度升高对不同有机质含量黑土大豆生长、土壤磷组分以及相关微生物机制的影响鲜有研究。本研究利用开顶式生长室(OTC)重点探究了气候变化对不同有机质黑土大豆根际土壤磷组分和相关磷转化微生物功能基因的影响。结果表明,不同有机质含量的黑土大豆磷吸收对长期大气CO₂浓度升高的响应一致,既先升高后降低。然而,大豆根际磷组分的响应存在差异性。大气CO₂浓度升高降低了高有机质黑土中大豆根际NaHCO3-Po含量,但增加了低有机质黑土中大豆根际有机磷库(NaHCO3-Po和NaOH-Po)的含量,而降低了无机磷库(NaOH-Pi)的含量。同时,大气CO₂浓度升高使高有机质黑土根际土壤基因拷贝数增加53.0%,低有机质黑土中大豆根际土壤基因拷贝数增加44.4%。因此,长期气候变化条件下,高有机质含量黑土通过有机磷矿化功能微生物来满足大豆对磷素的需求;而在低有机质含...     

低磷胁迫对不同磷效率基因型烟草苗期生长及生理特征的影响

为揭示不同磷效率烟草对低磷胁迫的响应机理,以磷高效且耐低磷基因型K326和云烟105及磷低效且低磷敏感基因型G28和中烟101为试验材料,设置低磷(0.01 mmol·L^-1,LP)和正常磷(1.00 mmol·L^-1,NP)2个处理,研究不同磷效率基因型烟草苗期主要农艺性状及生理指标对低磷处理的反应。结果表明,磷高效基因型的农艺指标(株高、地上部干重、根系干重等)在2种处理中均显著高于磷低效基因型,表明磷高效基因型在LP和NP水平下均能较好生长,对磷素具有较高的吸收或利用效率;在LP下,磷高效基因型的主根长增幅较大,干重、株高等降幅较小,即磷高效品种的生长受低磷影响较小,耐低磷性较强。在生理指标方面,LP条件下磷高效基因型的3种保护酶[过氧化氢酶(CAT)、超氧化物歧化酶(SOD)、过氧化物酶(POD)]和酸性磷酸酶(ACP)活性及可溶性糖和游离脯氨酸含量的增幅较磷低效基因型大,丙二醛(MDA)含量的增幅较小,可溶性蛋白含量、根系活力的降幅较小,水培营养液的pH值降幅较大;磷高效基因型的农艺性状及生理指标的耐低磷指数均高于磷低效基因型。综上,在低磷胁迫中,磷高效基因型烟草具有较强的活性氧清除能力,可累积较多渗透调节物质以维持细胞渗透势,较好地保护细胞,增强体内ACP活性,提高对磷素的吸收利用效率,维持自身的正常生长与代谢。本研究结果为烟草磷素高效吸收利用提供了一定的理论依据。     

热带土壤中菜豆种质耐低磷特性的评价

用来源于两个不同基因库(安第斯基因库和中美基因库)的菜豆种质为材料,比较它们在两种热带土壤中对低磷的适应性,旨在对现有种质的耐低磷能力进行系统的评价,为菜豆耐低磷育种提供新的种质资源。结果表明,供试菜豆种质中在耐低磷特性方面存在着基因型差异。在低磷条件下,来源于安第斯基因库的大粒种子基因型无论是在早期营养生长,对磷吸收,还定最后种子产量均优于来源于中美基因库的中、小粒种子基因型。不同基因型在两种热带土壤上的相时表现一致,说明菜豆对低有效磷的适应不存在着土壤特异性。然而,在高磷条件下,安第斯基因型的种子产量显著低于中美基因型。所以安第斯基因型虽有一定的耐低磷能力,但因其产量潜力较低而难以被直接利用。为此,必须分别鉴定安第斯基因型中与耐低磷有关的形态或生理生化指标,并明确其遗传控制,最后通过适当的遗传育种方法将其转移到理想的个体之中。这将是今后菜豆耐低磷育种的努力方向。     

不同pH低磷土壤上水稻磷营养特性研究

通过盆栽试验,研究了不同磷效率水稻在不同pH土壤和不同磷处理水平下的磷营养特性。结果表明,低磷条件下,分蘖期耐低磷基因型850、1574和1079的磷吸收效率最高,孕穗期3个耐低磷品种磷吸收量和利用效率均较高;到成熟期1574品种的相对磷吸收量最高,达到65%,而相对磷利用效率则以1574和850品种最高。不同pH土壤上,分蘖期,各水稻品种在碱性土壤上磷吸收量和利用效率最低,相对磷吸收量和相对磷利用效率却最高;耐低磷基因型850、1574和1079的磷吸收量高于鄂晚13和敏感基因型99012。在孕穗期,各水稻品种在碱性土壤上的磷吸收量高于其它两种土壤,但相对磷利用效率却最低;耐低磷基因型850和1574在3种土壤上磷吸收量均最高,成熟期各水稻品种磷利用效率则明显高于孕穗期。可见,不同耐低磷基因型在不同pH土壤上表现出的磷营养特性不同,在耐低磷品种的筛选过程中应该考虑土壤pH因素,生产中应根据不同土壤酸度类型选择合适的品种。     

不同磷水平下玉米-大豆间作对红壤无机磷组分及有效磷的影响

通过2年盆栽试验，探讨不同磷水平下玉米–大豆间作根际土壤无机磷组分、土壤有效磷含量及作物磷吸收的差异，明确土壤无机磷组分、土壤有效磷与作物磷吸收之间的相互关系。试验设置玉米单作、大豆单作、玉米–大豆间作3种种植方式以及3个P2O5施用水平(0、50、100 mg/kg，分别记作P0、P50、P100)，共9个处理。结果表明：与单作相比，2018年和2019年在P0、P50和P100水平下，间作显著提高玉米和大豆的籽粒产量，并显著提高玉米和大豆植株的磷素吸收量。与常规施磷水平(P100)下的单作处理相比，玉米–大豆间作在磷肥减少50%(P50)的条件下，并未降低玉米和大豆的磷吸收量与籽粒产量。3个磷水平下，间作提高了玉米和大豆根际土壤有效磷含量，而降低了根际土壤总无机磷以及Fe-P、Al-P、Ca-P、O-P的含量；同时适当增施磷肥显著提高了玉米和大豆根际土壤总无机磷及各无机磷组分的含量。本试验条件下，间作促进土壤中Fe-P、Al-P、Ca-P和O-P的活化(尤其是Fe-P)，是低磷胁迫下间作土壤有效磷含量与作物磷吸收量增加的重要原因。玉米–大豆间作具有节约磷肥、维持作物产量及根际土壤有...     

EFFECT OF PHOSPHORUS APPLICATION ON HIERARCHICAL LATERAL ROOT MORPHOLOGY AND PHOSPHORUS ACQUISITION IN SOYBEAN

Root growth systems are hierarchical and sensitive to nutrient availability in soil. Lateral roots are an important component of plant root morphology. Phosphorus (P) availability regulates root branching in plants such as Arabidopsis thaliana, barley (Hordeum vulgare), and rice (Oryza sativa L.). However, little information is available for soybean (Glycine max L.). A pot experiment was conducted to determine the morphological characteristics of lateral roots of different orders and P acquirement of soybean seedlings under three levels of applied P of 0, 50 and 100 mg P kg^?1 soil. Root length, an important parameter of root characteristics, differed in four orders. Lateral roots in the second and third order contributed 39.4 and 34.2% of total root length, respectively. Moreover, since most of lateral roots were fine roots (roots having a diameter 0.5 mm), fine roots had a frequency distribution of 58.5 to 61.4% in the second and third orders. Phosphorus application significantly increased dry weight, total length and number of lateral roots in the four orders with the ranking of fourth > third > second > first (P ≤ 0.05), but did not affect the average length of a lateral root. Phosphorus application reduced the frequency distribution of fine lateral roots in the first and second orders, while increased in the third and fourth orders (P ≤ 0.05). Compared with the medium P application (50 mg P kg^?1 soil), the high P application (100 mg P kg^?1 soil) inhibited lateral root growth with decreases in root dry weight, root length and root number at all orders. Phosphorus concentration and content increased with the increase in P application. The correlation between characteristics of lateral root and P status in the plants varied among root orders. The length of lateral roots from first to third order had a positive correlation with P concentration in root and shoot, and had a good relationship with P content. Lateral root numbers at the second, third and fourth orders were significantly correlated with P content while no correlation was found with the average length of a lateral root. It is proposed that the main effect of P application appears to be on the lateral root initiation rather than on lateral root elongation, and P favors the lateral root formation of the higher orders. The total length and number of lateral root at the second and third orders play a more important role in P content than those at other lateral root orders.     

不同土壤磷的固定特征及磷释放量和释放率的研究

通过加入不同浓度的P(水土比为 2 0∶1 )并利用连续提取法 ,对三种土壤P的固定特征以及磷的释放进行了研究。结果表明 ,红壤对P的固定能力高于潮土 ,而潮土高于水稻土 ,在加入P量为 2 97gkg- 1土壤的条件下 ,三种土壤对P的固定量分别为 2 84gkg- 1、2 5 3gkg- 1和 2 0 8gkg- 1。三种土壤对P的固定率则随着加入P量的增加而降低。在P的释放研究中 ,随着提取次数的增加 ,P的释放量减少 ,并在提取 8次后 ,以后各次P的释放量不发生显著变化。三种土壤中 ,水稻土P的最大释放量 (1 2 4 0 7mgkg- 1)显著高于红壤 (60 46mgkg- 1)和潮土 (1 9 74mgkg- 1) ,水稻土P的总释放量 (1 6次 )也大于红壤和潮土 ,三种土壤P的总释放量分别为 2 0 6 0 2 (1 98gkg- 1土壤P处理 )和 2 71 91mgkg- 1(2 97gkg- 1土壤P处理 )、1 0 0 48和2 60 5 3mgkg- 1、1 1 6 0 6和 1 3 1 91mgkg- 1。三种土壤P的释放率随着提取次数的增加而增加 ,并逐渐达到稳定。水稻土的释放率显著高于红壤和潮土。水稻土和潮土中 ,1 98gkg- 1土壤P处理的土壤P的释放率高于2 97gkg- 1土壤P处理的土壤 ,红壤则相反     

磷素水平对大豆氮素积累及产量的影响

利用砂培方法和15N示踪技术研究了磷素水平对大豆氮素积累、根瘤固氮和产量的影响。结果表明:大豆植株氮素积累、根瘤固氮和产量均随磷素营养水平的提高而呈单峰曲线变化,营养液磷素浓度31mg/L左右时达到峰值,当营养液磷素浓度达11mg/L时,再提高磷素浓度对大豆根瘤固氮率无明显促进作用;而对于大豆植株氮素积累、根瘤固氮量和产量,只有当营养液磷素浓度达到21mg/L时,再提高磷素浓度才无明显促进所用,表明满足根瘤固氮的磷素营养水平较产量形成的水平要求低。     

施磷量对不同磷效率小麦氮、磷、钾积累与分配的影响

在土培盆栽条件下,以磷高效小麦(CD1158-7、省A3宜03-4)和磷低效小麦(渝02321)为材料,研究了不施磷、施磷(P)10、20和30mg/kg对小麦不同生育时期生物量、籽粒产量及氮、磷、钾的积累与分配的影响。结果表明:(1)随施磷量的减少,不同磷效率品种小麦籽粒产量和生物量均减少;同一施磷处理,磷高效品种籽粒产量和生物产量高于磷低效基因型。不施磷、施磷10mg/kg,高效品种CD1158-7、省A3宜03-4的籽粒产量为低效品种渝02321 的1.84 倍和1.74倍、1.64倍和1.27倍。(2)低磷处理,磷高效品种小麦植株能够积累较多的氮素;扬花期之前,磷高效品种氮素积累量占小麦全生育期积累量的比例高于低效品种。拔节期、孕穗期氮素分配比例为叶>茎>根,扬花期为叶>茎>穗>根,而成熟期为籽粒、颖壳>茎>叶>根。拔节期和孕穗期磷高效品种根的氮素分配比例高于低效品种,而扬花期和成熟期磷高效品种穗(籽粒)氮素分配比例较高。(3)小麦植株磷素积累量主要集中在拔节期以后的生育时期,占全生育期的82.32%~94.23%。低磷处理,高效品种在拔节期和孕穗期磷素积累量高于低效品种,孕穗期尤为突出。扬花期之前,不施磷处理下,磷高效品种根的磷素分配比例较高。(4)不同施磷处理下,拔节期、孕穗期及扬花期,磷高效品种小麦的钾积累量高于低效品种。不同器官钾素分配比例拔节期和孕穗期均为叶>茎>根,扬花期为茎>叶>穗>根,成熟期为茎>叶>籽粒、颖壳>根。磷高效品种在颖壳和籽粒的钾素分配比例高于低效品种。     

PHOSPHORUS UPTAKE AND USE EFFICIENCY IN FIELD CROPS

Phosphorus (P) is required by crop plants for many physiological and biochemical functions. Knowledge of phosphorus uptake and its use by crop plants is essential for adequate management of this essential nutrient. A field experiment was conducted during four consecutive years to determine P uptake and use efficiency by upland rice, dry bean, corn and soybean grown in rotation on a Brazilian Oxisol. Plant samples were taken at different growth stages during the growth cycle of each crop for phosphorus analysis. Phosphorus concentration (content per unit dry matter) significantly decreased in a quadratic fashion with the advancement of plant age in four crop species. Phosphorus concentration was higher in legumes compared to cereals. Phosphorus uptake in shoot, however, significantly increased in an exponential quadratic fashion with the advancement of plant age of crop species. At harvest, P uptake was higher in grain compared to shoot, indicating importance of this element in improving crop yields. Phosphorus use efficiency (grain or straw yield per unit P uptake) was higher in cereals compared to legumes. The P use efficiency for grain production was 465 kg kg^?1 for upland rice, 492 kg kg^?1 for corn, 229 kg kg^?1 for dry bean and 280 kg kg^?1 for soybean. The higher P use efficiency in cereals was associated with higher yield of cereals compared to legume species.     

INFLUENCE OF DIFFERENT RATES OF PHOSPHORUS ON GROWTH,YIELD AND PHOSPHORUS USE EFFICIENCY IN TWO WHEAT CULTIVARS

To study the influence of different rates of phosphorus (P) on growth and yield of wheat, experiments were conducted at NIAB, Faisalabad, Pakistan under natural conditions. Results indicated that the P requirement of wheat at early growth was higher and adequate available P in the growth medium helped to attain relatively higher growth rate and resulted in higher grain yield. The two wheat cultivars when subjected to different rates of P application showed that the cultivar ‘MH-97’ was more responsive than ‘Pasban-90’ that attributed to its higher P translocation efficiency from roots to tops. The two cultivars also showed differential yield response when grown under field condition. At optimum nitrogen (N): P ratio of 1.5:1, the cultivar ‘MH-97’ gave 31.5% while cultivar ‘Pasban-90’ gave a maximum response of 25.9% over their respective N alone application. Contrarily, at the wider NP ratio of 3:1, yield response of cultivar ‘MH-97’ was 26.5% while that of cultivar ‘Pasban-90’ was only to the extent of 2.2%, thereby indicating a much wider difference in their yield response pattern. Thus, choosing an appropriate cultivar for a particular rate of fertilizer application would be more rewarding in terms of yield and profitability.     

大豆品种耐低磷和对磷肥效应的遗传差异

大豆不同品种对低磷胁迫和磷肥效应有显著的遗传差异。低磷胁迫下,苗期植株叶片酸性磷酸酶活性（APA）和叶面积与品种的子粒产量呈极显著相关;APA、叶面积、干物质量和氮积累量与生物学产量呈显著或极显著相关。但在施磷条件下,它们之间则无相关关系。这表明APA、叶面积、干物质量和氨积累量可作为耐低磷基因型的筛选指标。试验表明,耐低磷能力弱的品种对磷肥反应更为敏感。在低磷和施磷条件下产量均较高的品种也是存在的,它们对不同的磷素营养环境有着广泛的适应性,进一步挖掘这类基因型很有意义。     

EFFICIENCY OF RHIZOBIUM INOCULATION AND P FERTILIZATION IN ENHANCING NODULATION,SEED YIELD,AND PHOSPHORUS USE EFFICIENCY BY FIELD GROWN SOYBEAN UNDER HILLY REGION OF RAWALAKOT AZAD JAMMU AND KASHMIR,PAKISTAN

A field experiment was conducted in continuity of our previous study to assess the effect of Rhizobium inoculation (RI) and phosphorus fertilization (P) on growth, yield, nodulation, and P use efficiency of soybean. Different treatments were i) Rhizobium strains (0, S₃₇₇, S₃₇₉, and the mixture of S₃₇₇+S₃₇₉ i.e. S₀, S₁, S₂, S₃); ii) phosphorus fertilizer (0, 50, 100 kg ha^?1 i.e. P₀, P₁, P₂). Soybean variety NARC-1 was as used as a testing crop. Results indicated that root and shoot growth increased by RI treatments whether used alone or in combination with P. Rhizobium inoculation increased plant height up to 12% while P did not show significant effect. Increases in soot dry weight, root length and root dry weight due to RI and P was 57 and 22%, 42 and 7%, 55 and 25%, respectively, over the control treatment. Number of nodules increased from 73 in the control to a maximum of 151 in S₂ while the number increased from 90 in the control to 147 in P₂. Combine application of strains and P increased nodules number from 65 at S₀P₀ to a maximum of 183 at S₂P₂. Similar response was also observed for nodules mass. Soybean seed yields ranged between 1710 and 2335 kg ha^?1 against 1635 kg ha^?1 in the control indicating a maximum of 43% increase over control. Concentration of N and P in plants and their uptake was significantly increased by RI and P. RI also increased the N and protein content of soybean seed. Apparent recovery efficiency (ARE) of applied P was 10?12% and the agronomic, agrophysiological, recovery, utilization efficiencies, and harvest index of P decreased with increasing P rates. Nodule number significantly correlated with the DM yield (r² = 0.78) and seed yield (r² = 0.63) while P uptake significantly correlated with root length (r² = 0.48) and root mass i.e. dry weight (r² = 0.65). Also a significant correlation existed between N uptake and DM yield (r² = 0.98) and N uptake and seed yield (r² = 0.65), P uptake and DM yield (r² = 0.73), and P uptake and seed yield (r² = 0.83). The results of present study indicated a substantial growth and yield potential of soybean under the hilly region and increase in yield and N₂ fixing potential (nodulation) can be achieved by applying Rhizobium inoculation with P fertilization.     

黄壤性水稻土的磷素特征及供磷能力的相关研究

第四纪红色粘土母质发育起来的黄壤性水稻土,二十多年来大量施用磷肥,磷在耕层富集.耕层全磷含量平均0.048%,有效磷含量平均11.6ppm,分别比底土层高1.7倍和7.5倍,比荒地表层高2.1倍和28.4倍.黄壤性水稻土无机磷形态为混合分布型,Al-P、Fe-P、Ca-P、O-P分别占无机磷总量的5.9%,30.6%,28.7%和34.8%.小麦、水稻分蘖期测定的A值与产量和植株吸磷量相关,能表示土壤磷素有效性的高低.A值与土壤Fe-P和Ca-P相关,表明这两种磷酸盐是稻麦的主要磷源.Olsen法可作为测定黄壤性水稻士有效磷含量的标准方法.     

VARIATION IN PHOSPHORUS EFFICIENCY AMONG BRASSICA CULTIVARS I: INTERNAL UTILIZATION AND PHOSPHORUS REMOBILIZATION

Plants have adapted a number of mechanisms to cope with widespread phosphorus (P) deficiency in arable lands. Crop species and even cultivars differ widely in one or more of these adaptive mechanisms hence, in P efficiency. Identification of these mechanisms is pre-requisite for long term breeding programs. Two independent experiments were conducted to study the possible mechanisms of P efficiency in Brassica cultivars. Eight Brassica cultivars (‘B.S.A.’, ‘Toria’, ‘Toria Selection’, ‘Brown Raya’, ‘Peela Raya’, ‘Dunkeld’, ‘Rainbow’, and ‘CON-1’) were selected on the basis of differences in growth under P deficiency from preliminary experiment. In the first experiment, cultivars were grown for 40 days in sand supplied either with sparingly soluble phosphate rock (PR) or soluble mono-ammonium phosphate (MAP). Cultivars differed significantly (P<0.05) for biomass production, P contents and P use efficiency. Low P availability in PR treatment resulted in significantly lower dry weights and P contents than those grown with MAP. The cultivars ‘Rainbow’, ‘Brown Raya’ and ‘Dunkeld’ accumulated more biomass (3.2 g/pot) and P contents (3.0 mg/pot) than other cultivars when grown with PR. Root dry weight was significantly correlated with shoot dry weight, shoot P content and total P content (r > 0.65) indicating significance of improved root growth for P acquisition. While in the second experiment cultivars were grown with adequate P for 30 days and then P was withdrawn from the nutrient solution by replacing fresh P free nutrient solution for 10 days. Induced P deficiency increased P contents in young leaves by two folds indicating remobilization of P from older leaves and shoot. Nonetheless cultivars varied for remobilization but differences in P remobilization could not explain the differences in P utilization efficiency among cultivars. Hence further experimentation to study root morphology, P uptake, and organic acid exudation by these cultivars in relation to P deficiency is recommended.