Subsoil compaction effects on crops in Punjab, Pakistan:II. Root growth and nutrient uptake of wheat and sorghum

Crop yields can be reduced by soil compaction due to increased resistance to root growth, and decrease in water and nutrient use efficiencies. A field experiment was conducted during 1997–1998 and 1998–1999 on a sandy clay loam (fine-loamy, mixed, hyperthermic Typic Haplargids, USDA; Luvic Yermosol, FAO) to study subsoil compaction effects on root growth, nutrient uptake and chemical composition of wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor L. Moench). Soil compaction was artificially created once at the start of the study. The 0.00–0.15 m soil was manually removed with a spade. The exposed layer was compacted with a mechanical compactor from 1.65 Mg m⁻³ (control plot) to a bulk density of 1.93 Mg m⁻³ (compacted plot). The topsoil was then again replaced above the compacted subsoil and levelled. Both compacted and control plots were hoed manually and levelled. Root length density, measured at flowering stage, decreased markedly with compaction during 1997–1998 but there was little effect during 1998–1999. The reduction in nutrient uptake by wheat due to compaction of the subsoil was 12–35% for N, 17–27% for P and up to 24% for K. The reduction in nutrient uptake in sorghum due to subsoil compaction was 23% for N, 16% for P, and 12% for K. Subsoil compaction increased N content in wheat grains in 1997–1998, but there was no effect on P and K contents of grains and N and P content of wheat straw or sorghum stover. During 1997–1998, K content of wheat straw was statistically higher in control treatment compared with compacted treatment. In 1998, P-content of sorghum leaves was higher in compacted treatment than uncompacted control. Root length density of wheat below 0.15 m depth was significantly reduced and was significantly and negatively correlated with soil bulk density. Therefore, appropriate measures such as periodic chiselling, controlled traffic, conservation tillage, and incorporating of crops with deep tap root system in rotation cycle is necessary to minimize the risks of subsoil compaction.     

Root growth,nutrient uptake and use efficiency by roots of tropical legume cover crops as influenced by phosphorus fertilization

The root is an important organ which supplies water and nutrients to growing plants. Data related to root growth and nutrient uptake by tropical legume cover crops are limited. The objective of this study was to evaluate root growth of tropical legume cover crops and nutrient uptake and use efficiency under different phosphorus (P) levels. The P levels used were 0 (low), 100 (medium) and 200 (high) mg kg^?1 of soil and 5 cover crops were evaluated. Root dry weight, maximum root length, specific root length were significantly influenced by P and cover crop treatments. Maximum values of these root growth parameters were achieved with the addition of 100 mg P kg^?1 soil. The P X cover crops interaction for all the macro and micronutrients, except manganese (Mn) was significant, indicating variation in uptake pattern of these nutrients by cover crops with the variation in P rates. Overall, uptake pattern of macronutrients was in the order of nitrogen>calcium>potassium>magnesium>phosphorus (N > Ca > K > Mg > P) and micronutrient uptake pattern was in the order of iron>manganese>zinc>copper (Fe > Mn > Zn > Cu). Cover crops which produced maximum root dry weight also accumulated higher amount of nutrients, including N compared to cover crops which produced lower root dry weight. Higher uptake of N compared to other nutrients by cover crops indicated that use of cover crops in the cropping systems can reduce loss of nitrate (NO₃^?) from soil-plant systems. Increase in root length and root dry weight with the addition of P can improve nutrient uptake from the soil and less loss of macro and micronutrients from the soil-plant systems.     

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。     

Yearly variation of root distribution with depth in relation to nutrient uptake and corn yield

Abstract

Root length and root distribution in the soil profile is important in determining the amount of nutrients and water taken up by the plant. Data about year to year variation of corn (Zea mays L.) root growth and its relation to nutrient uptake are limited. An evaluation of the importance of root system size and distribution on P and K uptake and corn yield was made from samples taken annually from a long‐term fertility experiment on Raub silt loam, fine silty, mixed, mesic Aquic Argiudolls. Root density varied with soil depth among years, whereas P and K fertilizer treatment had no measureable influence on total root length. Ear leaf P concentration was highly correlated with the amount of roots in the 0 to 15 cm layer which contained most of the available P. Since P was not appreciably limiting corn yield, no significant relation was found between yield and P content of the ear leaf. Yields on K deficient plots were positively correlated with root density in the topsoil. Correlations of root densities in the deeper soil layers with both yield and ear leaf nutrient concentration became increasingly smaller with depth in the soil profile. The results indicate that root length plus root distribution in the soil may influence year to year variation in yield particularily on soils having low available nutrient levels. This variation in root growth may be responsible for differences among years in the response of crops to applied P and/or K.     

Genetic variability in nitrogen utilization at four growth stages in soft red winter wheat

Studies were conducted to determine relationships among nitrate reductase activity (NRA), dry weight (DW), nitrogen (N) uptake, and N concentration in soft red winter wheat (Triticum aestivwn L.). Data were collected for three growing seasons from field plots grown on a silt loam and one growing season on a sandy loam. Ten cultivars were measured under field conditions with plant samples taken at Feekes Growth Stages 6, 10, 10.5, and 11.1. NRA was measured using an in vivo assay method on fully expanded leaves representing the upper most part of the canopy. Results indicated that N uptake was highest during Stages 10.5 to 11.1, although not significantly different for all cultivars. Few differences were found among cultivars for N concentration. The NRA measured under field conditions was more stable at Growth Stage 6. Path coefficients between NRA and DW, N uptake, and N concentration varied considerably depending on the growth stage, indicating that selection for N utilization using one or more of the measurements evaluated in this study should consider the stage of growth.     

Two years of a field study on sesame growth and yield,nutrient uptake by PGP bacteria application and capsule type

Abstract

A two-year field experiment was conducted to study PGP bacteria on growth and yield productivity of sesame. Factors were control, Nitroxin, Biophosphor, and an equal combination of biofertilizers along with sesame capsule type. 1000-seed weight and oil content increased in the second year, but, seed yield reduced (-12.6?g m²), which represented a negative relationship between seed weight and yield. The effect of year on No. of single and multi-cap node plant^?1 was reversed. Seed yield, chlorophyll, protein, and N increased in the multi-cap seed, whereas, 1000-seed weight and seed weight plant^?1 was decreased. Maximum yield and yield components were achieved in the second and first year, respectively, along with the multi-cap seed. Nitroxin, after the equal combination, was approximately showed the maximum enhancement of growth and yield productivity of sesame. The most seed yield (4261 k ha^?1) was performed in the first year, combined biofertilizers and multi-cap seed, whereas, the highest oil content was gained in the second year and single-cap that it was due to the higher N and P use efficiency in the first year. No. of node plant^?1 and capsule No. plant^?1 showed the most correlation with the other parameters. Seed yield was correlated with No. of node plant^?1 (r?=?0.925) and leaf dry weight (r?=?0.885). The N and P use efficiency had been higher in the first year, multi-cap, and equal combination. Nitrogen Use efficiency was higher compared to phosphorous. The uptake of N and P by sesame increased with the integrated application of different bacteria.     

Genotypic differences in growth,yield and nutrient accumulation of spring wheat cultivars in response to long-term soil fertility regimes

Determining genotypic responses to soil fertility may assist selection of cultivars that can be adapted to varied soil fertility regimes, and such selection under field conditions is still limited. A two-year field experiment was conducted in long-term field trials to investigate wheat genotype effects on early growth, yield and nutrient accumulation as affected by varied long-term soil fertility managements and nitrogen (N) fertilization. Results show that the early growth, grain yield and nutrient accumulation of spring wheat plants were strongly affected by soil fertility managements and genotypes. Early shoot and root biomass of singly grown plants and leaf canopy growth under standard growth density was associated with subsequent grain yield of plants under standard growth density across the gradient in soil fertility levels. Taifun and Thasos had stable higher yield and N and phosphorus (P) uptake across varied soil fertility regimes compared with other genotypes. Økilde, however, increased yield by 8–34% and N and P accumulation by 1–22% only when grown in the high organic manure treatment compared with other genotypes, indicating that it is more adapted to high organic fertility regimes. Therefore, the different responses and adaptations of genotypes to soil fertility regimes should be included during selection of cultivars.     

Growth,yield and nutrient uptake of taro grown under upland conditions

There is a scarcity of basic information on dry matter accumulation by various plant organs, nutrient uptake, and yield of taro [Colocasia esculenta (L.) Schott] grown under upland conditions. These data are essential for the development of technological packages, growth simulation models, and decision support systems designed to promote agrotechnology transfer of the crop in the tropics. Two taro cultivars were planted and harvested for biomass about every six weeks during the growing season. At each harvest, plants were separated into various plant parts and their dry matter and nutrient content were determined. There were no significant differences (P<0.05) in total and edible dry matter content between cultivars. However, cultivar ‘Lila’ absorbed significantly smaller amounts of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and zinc (Zn) than cultivar ‘Blanca’, suggesting that it had a higher nutrient‐use efficiency. Fresh corm yields were not significantly different and averaged 20,221 kg/ha for both cultivars.     

不同大豆品种在养分吸收及产量上的比较

采用盆栽试验方法对红丰11等四个大豆品种吸收利用氮、磷、钾养分的能力进行了比较研究。结果表明,在施肥一致的条件下,不同大豆品种对养分的吸收利用能力不同,养分利用率也不同,导致产量的差异。以红丰11养分吸收量最多,表现产量最高。     

Coronatine effects on yield,nutrient uptake,and physio-biochemical attributes of soybean roots

Roots absorb water and nutrients from the soil, give mechanical support to plants, and supply hormones that affect many physiological and biochemical processes. Roots also exert control over whole-plant growth and development by synthesizing plant hormones and controlling the uptake of mineral nutrients. Coronatine (COR) is an analogue of jasmonic acid and is a chlorosis-inducing non-hostspecific phytotoxin with an alleviative effect on plant growth under stress conditions. A 2-year field study was conducted to determine the effect of COR on the physiological and biochemical attributes of the root and the seed yield of soybean (Glycine max L. Cv. Zhonghuang 13). COR was foliar-applied at 10 nM during the 7-trifoliolate leafs stage. Root dry weight was significantly increased on average by 37% with COR over the 2 years. The root nitrogen concentration increased by 19.2%, phosphorus concentration by 23.3%, and potassium concentration by 31.2% following COR application. The content of cytokinins was increased by 31.5% and 46.0%, while that of abscisic acid was decreased by 45.0% and 25.5% with COR over the 2 years. Seed yield was increased 7.0% in 2008 and 9.6% in 2009, respectively, due to COR application.     

Effect of phosphorus,nitrogen fertilization and foliar applied manganese on yield and nutrient concentration of soybean

Abstract

A greenhouse experiment was conducted on clay loam soil of pH 7.8 to evaluate the effect of P, N fertilization and foliar applied Mn on yield and nutrient concentration in leaves and seeds of soybean. A significant yield increase was obtained for each added increment of P fertilizer up to 30 kg P₂O₅/acre. At application rates of 0, 15, 30 & 45 kg P₂O₅/acre, the seed yield was subsequently 27.8, 65.8, 82.8 & 83.6% of the maximum yield obtained at the maximum calculated P level. The yield increase accounted 14.2 and 10.2% for N and Mn applications. In all treatments, in which P was combined with N, the seed yield was relatively higher than with P or N applied alone.

Phosphorus, N and Mn content in leaves and seeds were positively correlated with the applied nutrient fertilizers. At any given level of applied P and Mn, P content was significantly higher in +N than ‐N treatments. By Mn application, P content in leaves and seeds was decreased. Phosphorus and Mn applications did not influence N content in leaves and seeds.     

Root growth and N‐uptake activity of oilseed rape (Brassica napus L.) cultivars differing in nitrogen efficiency

Nitrate‐N uptake from soil depends on root growth and uptake activity. However, under field conditions N‐uptake activity is difficult to estimate from soil‐N depletion due to different loss pathways. We modified the current mesh‐bag method to estimate nitrate‐N‐uptake activity and root growth of two oilseed‐rape cultivars differing in N‐uptake efficiency. N‐efficient cultivar (cv.) ‘Apex' and N‐inefficient cv. ‘Capitol' were grown in a field experiment on a silty clayey gleyic fluvisol near Göttingen, northern Germany, and fertilized with 0 (N₀) and 227 (N₂₂₇) kg N ha^–1. In February 2002, PVC tubes with a diameter of 50 mm were installed between plant rows at 0–0.3 and 0–0.6 m soil depth with an angle of 45°. At the beginning of shooting, beginning of flowering, and at seed filling, the PVC tubes were substituted by PVC tubes (compartments) of the same diameter, but with an open window at the upper side either at a soil depth of 0–0.3 or 0.3–0.6 m allowing roots to grow into the tubes. Anion‐exchange resin at the bottom of the compartment allowed estimation of nitrate leaching. The compartments were then filled with root‐free soil which was amended with or without 90 mg N (kg soil)^–1. The newly developed roots and nitrate‐N depletion were estimated in the compartments after the installing period (21 d at shooting stage and 16 d both at flowering and grain‐filling stages). Nitrate‐N depletion was estimated from the difference between NO ‐N contents of compartments containing roots and control compartments (windows closed with a membrane) containing no roots. The amount of nitrate leached from the compartments was quantified from the resin and has been taken into consideration in the calculation of the N depletion. The amount of N depleted from the compartments significantly correlated with root‐length density. Suboptimal N application to the crop reduced total biomass and seed‐yield formation substantially (24% and 38% for ‘Apex’ and ‘Capitol’, respectively). At the shooting stage, there were no differences in root production and N depletion from the compartments by the two cultivars between N₀ and N₂₂₇. But at flowering and seed‐filling stages, higher root production and accordingly higher N depletion was observed at N₀ compared to N₂₂₇. Towards later growth stages, the newly developed roots were characterized by a reduction of root diameter and a shift towards the deeper soil layer (0.3–0.6m). At low but not at high N supply, the N‐efficient cv. ‘Apex’ exhibited higher root growth and accordingly depleted nitrate‐N more effectively than the N‐inefficient cv. ‘Capitol’, especially during the reproductive growth phase. The calculated nitrate‐N‐uptake rate per unit root length was maximal at flowering (for the low N supply) but showed no difference between the two cultivars. This indicated that the higher N‐uptake efficiency of cv. ‘Apex’ was due to higher root growth rather than higher uptake per unit of root length.     

Negative and positive contributions of arbuscular mycorrhizal fungal taxa to wheat production and nutrient uptake efficiency in organic and conventional systems in the Canadian prairie

Improving technologies and the challenge of producing more bio-products while reducing the environmental footprint of humans are shifting paradigms in agricultural research. Harnessing the microbial resources of arable soils is a new avenue to improve the efficiency of nutrient use in agriculture. The objective of this study was to define how crop management influences the contribution of resident AM fungi to nutrient efficiency and crop productivity. The AM fungal communities of 72 organically and 78 conventionally managed wheat fields of the Canadian prairie were described by 454 pyrosequencing and related to crop productivity and N and P use efficiency. Conventional management reduces soil pH and increases the fluxes of all soil nutrients except S, B, and K. Organic management increased the abundance of Claroideoglomus reads. The efficiency of N and P uptake from soil by organic wheat was 2.3 and 1.8 times higher than that of conventional systems. This high N and P uptake efficiency in organic wheat crops was mainly attributable to the low soil fertility of organic fields, as wheat biomass production was 1.44 times greater in conventional than organic systems. Overall, the amounts of N and P taken up by conventional and organic wheat crops were similar. Plant nutrient balance and the abundance of Paraglomus drove conventional wheat production, whereas organic production depended mainly on soil moisture, plant nutrient balance, and abundance of Glomus, which was associated with reduced and nutrient-inefficient wheat production. The high nutrient concentrations at maturity and the low productivity of organic wheat fit a model of limiting CO₂-assimilation. The trade-off between nutrient use efficiency and productivity in low input wheat production could be relieved by reducing the abundance of Glomus species, increasing soil moisture and early N availability, or by improving the inherent CO₂ assimilation capacity of wheat.     

土壤钾水平对不同熟性棉花光合作用及产量的影响

  目的  施钾是保障土壤钾素供应和棉花高产的必要手段,缩节胺化学封顶是调节棉花生物量分配的重要措施,合理协调两者的关系是棉花提质增产的前提,因此探究包膜含缩节胺氯化钾对土壤钾素形态及棉花生长特性的影响,可为维持土壤钾素平衡及实现棉花减肥高产提供依据。  方法  采用盆栽试验,共设7个处理,分别为一次基施包膜含缩节胺氯化钾（CRKMC,0.15 g kg⁻¹土）、减量30%包膜含缩节胺氯化钾（CRKMC70%）、控释氯化钾（CRK）、减量30%控释氯化钾（CRK70%）、分次施用普通氯化钾（KCl）、减量30%普通氯化钾（KCl70%）及空白对照（CK）。测定棉花生育期内土壤钾素含量、棉花株高、茎粗、光合特性和产量。  结果  CRKMC处理的籽棉产量最高,较CRK和KCl处理分别显著增加了13.80%和22.58%,且CRKMC70%处理棉花产量与CRK处理相比不减产。此外,CRKMC处理显著提高了棉花植株茎粗、净光合速率、SPAD值和钾素农学利用率,且蕾期后CRKMC处理的土壤速效钾、缓效钾和水溶性钾含量高于KCl处理。蕾期至盛花期,速效钾部分转化为缓效钾储存,使得缓效钾含量升高,且各控释处理效果优于普通钾肥。  结论  一次基施包膜含缩节胺氯化钾可有效保障土壤钾素供应,提高土壤固钾潜力并优化棉花生长特性,为实现棉花高产、优化用工提供技术支撑。     

水分和磷对苗期玉米根系形态和磷吸收的耦合效应

水分亏缺和土壤缺磷已经成为玉米(Zea mays L.)生产的主要限制性因素,但水分和磷如何调节玉米根系形态和磷吸收尚不完全清楚。本研究采用盆栽土培试验,设置4个水分梯度[田间持水量的35%(W1)、55%(W2)、75%(W3)和100%(W4)]和2个磷处理[高磷:205 mg(P)·kg~(-1);低磷:11 mg(P)·kg~(-1)],探究水分和磷对苗期玉米根系生长和磷吸收的耦合效应。结果表明:(1)不管土壤磷供应如何,玉米苗干重、根干重、总根长和根表面积随水分供应强度的增加呈现先增加后降低的趋势,土壤有效磷含量也表现出相似的变化趋势,根质量比和平均根直径随水分供应强度的增加呈现下降的趋势,植株磷含量和磷累积量随水分供应强度的增加呈现稳定增加的趋势;(2)水分亏缺(W1)和过量供应(W4)均不利于玉米根系生长和干物质累积,水分亏缺(W1)抑制玉米对土壤磷素的获取,水分过量供应(W4)引起土壤磷素的奢侈吸收(W4),轻度的水分胁迫(W2)能够促进玉米根系的生长和干物质累积,减少对土壤磷的奢侈吸收,充足的水分供应(W3)能够促进玉米根系的生长、干物质累积和土壤磷素的吸收;(3)磷供应显著增加了玉米苗干重、根干重(W4除外)、总根长、根表面积、植株磷含量(W4除外)和磷累积量,但降低了玉米的根质量比。(4)两因素方差分析结果表明,水分对苗干重、根干重、根质量比、总根长、根表面积、平均根直径、植株磷含量、植株磷累积量和土壤有效磷含量的相对贡献分别为45.94%、36.71%、67.95%、59.63%、58.34%、81.86%、24.75%、35.66%和3.00%,磷对这些参数的相对贡献分别为34.78%、21.19%、14.84%、9.22%、9.21%、1.56%、35.54%、49.75%和94.40%,可见水分是控制玉米根系形态和干物质累积的关键因子,磷是控制玉米地上磷吸收和土壤有效磷含量的关键因子。总体来说,低磷条件下玉米根系对土壤磷的获取偏向于以根形态为主导的适应策略,高磷条件下玉米根系对土壤磷的获取偏向于以根生理吸收为主导的适应策略。水分和磷之间较好的耦合能够促进玉米根系生长、干物质累积,减少对土壤磷素的奢侈吸收。     

玉米苗期磷效率相关根系分泌物的QTL定位

为了充分利用现有的遗传信息和基因资源,揭示玉米磷营养高效的分子机制,本研究以磷高效玉米自交系082和磷低效玉米自交系掖107为亲本组配的F2世代为作图群体,采用SSR和AFLP分子标记构建了遗传连锁图,以两个时期,两个磷水平和两个地点共4种环境下的241个F2∶3家系各性状的平均值作为表型值,采用复合区间作图法定位了磷效率相关的3种根系分泌物的QTL。四种环境下检测表明,(1)检测到4个影响酸性磷酸酶活性的QTL,其中有两个QTL AP1-KXNP和AP9-KXNP被重复检测到,分别分布在第1和9二条染色体上,所在标记区间分别为bnlg1268a-umc1290a和P1M3/d-P1M3/g,在染色体上的位点分别为bin1.09和bin9.04,单个QTL解释酸性磷酸酶变异的9%～16%,2个QTL共解释酸性磷酸酶变异的25%;(2)检测到5个影响有机酸含量的QTL,其中只有1个在两种环境下被重复检测到,位于第9染色体上,标记区间为P1M3/f-P1M7/g,在染色体上的位点为bin9.03;(3)检测到5个影响H+含量的QTL,但没有一个被重复检测到。结果表明,影响酸性磷酸酶活性的两个QTL AP1-KXN...     

不同供磷水平对旱作条件下水稻生长、根系形态和 养分吸收的影响

通过盆栽试验,比较分析了磷素对旱作条件下不同水稻品种苗期生长、根系形态及磷素吸收利用效率的影响。结果表明,施用磷肥促进水稻地上部和根系的生长,低磷胁迫显著增大了植物的根冠比,且品种间差异明显,丛矮2在低磷水平和高磷水平下的根冠比比值为1.982,而黄华占相应的比值为1.096;随供磷浓度的增加,水稻植株含磷量增加而磷素生理利用率降低,在3种磷水平下,3345的磷素吸收效率均高于其他4个品种,磷素生理利用率却低于其他4个品种。根系形态参数与磷素吸收、利用效率的相关性分析表明:根系总长对水稻植株吸磷量影响最大。总之,适当地施用磷肥能更好地协调根系与地上部的关系,促进根系的生长和根系对磷素的吸收。     

Interrelationships between growth and nutrient uptake in alfalfa and corn

Nutrient requirements o£ plants during their various phases of growth are affected by several internal and external factors. The changes in rate of uptake by root with age are an important factor to meet the increasing plant demand for nutrients. Nutrient culture experiments were carried out under controlled greenhouse conditions with corn (Zea Mays L.) and alfalfa (Medicago sativa L.) to investigate the relationship of stage of growth to changes in plant parameters and nutrient uptake properties. With advancement of age. both plant species increased their ambient growth medium pH towards neutrality. With increasing age in alfalfa there was very little change in observed S:R ratio and root growth rate. On the other hand in corn plants the S:R ratio increased and growth rate for root and shoot decreased with age. Alfalfa contained higher concentrations of N, K, Na, and Ca than corn; while ion concentrations in both crops decreased with plant age. At all stages of growth, alfalfa absorbed less nutrients than corn. The rates of nutrient influx, I_n in both the crops showed various degrees of correlation with age and rate of shoot growth. In corn. I_n for ions reached a maximum at 25 days growth; whereas, in alfalfa, I_n reached maximum at 30 days of growth. The differences in influx rates for different ions in the two species are probably due to the difference in development of shoot and root parameters and shoot demand for the ions.     

土壤紧实胁迫对黄瓜生长、产量及养分吸收的影响

用容重分别为1.2、1.4和1.6.g/cm3的土壤进行盆栽试验,研究了土壤紧实度对黄瓜生长、产量及养分吸收的影响。结果表明,当土壤紧实度增大时,黄瓜秧苗的株高在定植后的15.d后受到显著抑制;第4叶的叶宽和叶长在定植后9～17.d内增加;茎粗则是在稍紧的土壤中(R.1.4)最大,过紧的土壤中(R.1.6)最小;根系伸长生长受阻,干物质质量及活力显著下降,根冠比降低;生物学产量、经济产量、经济系数的变化情况及植株对氮、磷、钾吸收量的变化与茎粗的变化趋势相同。在本试验条件下,容重为1.2.g/cm3的土壤利于株高及根系的生长,容重1.4g/cm3的土壤则利于茎粗、根系养分的吸收及产量的增加。     

Phenology,flowering and yield performance of 13 diverse strawberry cultivars grown under Nordic field conditions

As part of an overall assessment of the commercial suitability of strawberry cultivars for the Nordic environment, we studied 13 diverse cultivars in an experimental field in South East Norway. Early-maturing cultivars were characterized by early initiation of floral primordia and early flowering and fruit maturation. High temperatures in July and early August delayed floral initiation in the early cultivars, resulting in more synchronous initiation of early and late cultivars. The recent Norwegian cultivar ‘Nobel’, which has an everbearing parent, differed from the other cultivars by early initiation also at elevated summer temperature. Inadequate yield and berry size were identified as important causes for outdating of older cultivars, such as ‘Senga Sengana’ and ‘Glima’. Overall, the high-yielding and large-fruited ‘Sonata’ was judged as the best fresh consumption cultivar in Norway, and market trends indicate that it will continue to expand its market share at the expense of ‘Korona’, mainly because of inadequate fruit firmness and shelf life of the latter. Adequate yields and berry quality justify the use of the late maturing ‘Florence’ for prolongation of the fresh market season. The results are discussed together with practical experiences and market preferences in an attempt to provide overall cultivar recommendations for Norway.