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.     

Effects of different levels of soil salinity on yield attributes,accumulation of nitrogen,and micronutrients in Brassica spp.

The present study was conducted to assess the effect of soil salinity on yield attributes as well as nutrient accumulation in different plant parts of seven Brassica cultivars from two different species raised in pot culture experiment with two levels of salinity treatments along with control corresponding to soil electrical conductivity (EC) values of 1.65 (S₀), 4.50 (S₁) and 6.76 (S₂) dS m^?1. The experiment was consisted of twelve replications in a completely randomized design. Imposition of salinity stress affected various yield attributing characters including plant height, which ultimately led to severe yield reduction. However, tolerant cultivars, CS 52 and CS 54 performed better under salt treatment showing lesser yield loss. Salinity stress reduced the nitrogen (N) content in leaves of the Brassica plants, which reflected in decreased seed protein content. Reduced accumulation of iron (Fe), manganese (Mn) and zinc (Zn) was observed in leaf, stem and root at flowering and post-flowering stages, while CS 52 and CS 54 showed less reduction than susceptible cultivars under salinity stress.     

富硒花生品种筛选及外源调控花生富硒生产技术研究

本研究通过田间试验,测定不同花生品种的自然富硒能力及对外源硒的利用指数,然后通过施用外源硒,研究不同调控措施对花生籽粒硒含量及外源硒利用率的影响,为富硒花生生产提供技术参考。研究结果表明:自然条件下,12个花生品种春花生籽粒的硒含量在0.041～0.180 mg/kg,秋花生籽粒的硒含量在0.039～0.066 mg/kg,外源硒的利用指数为2.3～3.7。施用外源硒肥均能显著提高花生籽粒硒含量,含硒肥料基施、淋施和叶面喷施情况下,花生籽粒对外源硒的利用率分别为0.056%～0.064%、0.23%～0.25%和3.74%～4.99%。可见,不同花生品种间硒的富集能力和对外源硒利用能力均有差异,而叶面喷施的硒肥施用方式下花生对外源硒的利用率最高。     

Effect of soil pH and N fertilization oh uptake and fractions of Ca and Mg in two barley cultivars

Abstract

A study has been made of the amounts of Ca and Mg removed from dry matter of young barley plants by sequential extraction with water, M NaCl, 0.4 M acetic acid and 0.6 M HCl. Two contrasting cultivars were examined and other factors included the effects of the soil pH in which the plants were grown and the form of N‐fertilizer used. The distribution of total Ca and Mg and the different fractions between young and old tissues was also examined.

Water and NaCl between them removed the bulk of the Ca and Mg (between 80 and 90%) and broadly, where uptake of total Ca or Mg increased with increase in soil pH, there was little change in the percentage of either cation appearing in the fractions, indicating a constant removal by the extractants, irrespective of content.

Only about a third of the total Ca was found in the upper half of the plants, against over 60% in the case of Mg and the same distribution was found for the percentages of the water‐soluble and the exchangeable fractions.

Small differences between cultivars and between N forms in respect of fractions and their distribution in the plant were found, but these did not affect the overall general pattern.     

川西低山丘陵区植茶土壤团聚体矿质氮分布特征

研究植茶对土壤团聚体全氮和矿质氮的影响可为茶园土壤合理施用氮肥提供理论依据.通过野外调查和室内分析,研究不同茶树品种(福鼎大白、川茶3号、川农黄芽早和川沐217)对土壤团聚体中全氮和矿质氮含量的影响.结果 表明:(1)各植茶品种土壤团聚体含量随粒径减小呈先减小后增大的变化趋势,＞2 mm粒径团聚体含量显著高于其他粒径团...     

INFLUENCE OF CORN (ZEA MAYS L.) CULTIVAR DEVELOPMENT ON RESIDUE PRODUCTION

The amount and composition of crop residues added to soil in agroecosystems can influence decomposition processes and soil organic matter levels. This study aimed to evaluate residues (quantity and quality) of different corn cultivars commonly used in Brazilian cropping systems. The experiment was conducted for two seasons (2005/2006 and 2006/2007) in Rolândia, Paraná State, Brazil. Ten corn cultivars that represent five degrees of breeding development (i.e., landrace, commercial variety, double cross, triple cross, and single cross hybrids) were evaluated. At harvest, carbon (C) and nitrogen (N) of non-yield residue and grain were determined. Except for grain C, other measures (grain N concentration, residue C and N concentration, and C:N ratio) varied among cultivars. In general, the hybrids had higher residue C and lower residue N concentrations than the landraces and commercial varieties. Findings suggest that breeding selection may have altered residue production and composition, which may influence soil C dynamics.     

Evaluation of landrace topcross hybrids of pearl millet for arid zone environments

Pearl millet (Pennisetum glaucum (L.) R. Br.) cultivars for marginal, arid environments need to combine the adaptation to stress conditions of indigenous landraces with an improved yield potential and disease resistance, to allow them to both perform well in farmers fields and to meet the requirements for cultivar release. This paper evaluates landrace-based topcross hybrids (adapted landraces crossed on high-yielding male-sterile lines), as a quick and efficient way of achieving this objective. Topcross hybrids showed a consistent increase in biomass production across all test environments, including the harsh arid zone environments. Depending upon the plant type of the male-sterile used to make the hybrid, this was expressed as increased grain yield only, or increased grain and fodder yields. The downy mildew (Sclerospora graminicola) reaction of the topcross hybrids was determined by the reaction of the male-sterile line used, with the resistant male-sterile producing resistant topcross hybrids and vice-versa. Topcrossing adapted landraces on high-yielding male-sterile lines thus provides an opportunity to improve disease resistance and grain and/or fodder yields, with no apparent loss of adaptation to the marginal environments in which the landraces have evolved.ICRISAT Journal Article no. 1575     

苏南稻田4种冬绿肥养分特性及对翻压前土壤无机氮的影响

为充分利用苏南冬闲稻田发展适宜绿肥作物种植,在大田试验条件下,研究了毛叶苕子（Vicia villosa Roth）、 光叶苕子（Vicia villosa var.）、 紫云英（Astragalus sinicus L.）和肥田萝卜（Raphanus sativus L.）4种绿肥作物的生长、 营养特性,比较分析了绿肥作物翻压前不同处理间耕层土壤无机氮含量与构成的差异。结果表明,在绿肥作物翻压期,4种绿肥作物均达到较高生物量和养分累积量,鲜重、 干重分别为24.8 30.7 t/hm2和3.6 4.2 t/hm2,不同绿肥作物间无显著差异。 4种绿肥作物的吸氮量为69.8 136.4 kg/hm2,毛叶苕子最高,肥田萝卜最低。吸磷量为7.1~11.3 kg/hm2,肥田萝卜最高,紫云英最低。吸钾量为117.6~151.3 kg/hm2,毛叶苕子最高,光叶苕子最低。与对照冬闲相比,种植绿肥作物不同程度地降低了耕层土壤无机氮含量（平均降低38.9 kg/hm2）,其中硝态氮含量下降明显,铵态氮含量均较对照土壤有增加趋势（平均提高6.5 kg/hm2）,毛叶苕子和光叶苕子处理铵态氮含量增加显著。4种绿肥作物均适合苏南冬闲稻田种植,能潜在降低无机氮的损失风险和为后季水稻作物生长提供养分。     

IDENTIFICATION OF GROUNDNUT (ARACHIS HYPOGAEA L.) CULTIVARS TOLERANT OF SOIL SALINITY

Field screening of 83 groundnut cultivars was undertaken for two seasons to assess their tolerance of salinity based on plant mortality and yield attributes. During the dry season, soil salinity of 4 dS m^?1 at sowing and 6–7 dS m^?1 21–98 days after sowing (DAS) caused high mortality without seed formation in any cultivars, however, at salinity 4.5 dS m^?1 during sowing and 3.5–3.0 dS m^?1 15–80 DAS during wet season, 61 cultivars produced seed. The cultivars ‘VRI 3’, ‘UF 70–103’, ‘TKG 19A’, ‘S 206’, ‘Tirupati 4’, ‘M 522’, ‘Punjab 1’, ‘BG 3’, ‘Somnath’ and ‘ICGV 86590’, with high plant stand during both the seasons and over 75 g m^?2 seed yield during wet season, were identified salinity tolerant. However, 15 cultivars with more than 50 g m^?2 seed yield were moderately tolerant and 28 cultivars with less than 25 g m^?2 seed yield were sensitive to salinity.     

ROOT ZONE TEMPERATURE INFLUENCES ZINC REQUIREMENT OF MAIZE CULTIVARS ON A CALCAREOUS LOAM SOIL

The zinc (Zn) requirement of a maize (Zea mays L.) hybrid (‘FHY-396’) and an indigenous variety (‘EV-7004’) was measured at low (22.4 ± 5°C) and high (28.8 ± 5°C) root-zone temperatures (RZT). Four Zn rates (0, 3, 9 and 27 mg kg^?1 soil) were applied to a calcareous loam soil in pots for the glasshouse study. Shoot and root dry matter yields were significantly more at the higher RZT. Regardless the RZT, maximum relative shoot dry matter yield in hybrid and variety was produced, respectively, at 9 and 3 mg Zn kg^?1 soil. Zinc concentration in roots and shoots of both the cultivars increased with Zn rates and it was significantly more at the higher RZT. Cultivars differed in critical Zn concentration (C_ZnC) required for maximum shoot dry matter yield. The C_ZnC ranged from 25 to 39 μg Zn g^?1 plant tissue for optimum growth of both the cultivars at low and high RZT.