Growth and nutrient uptake of peach seedlings with varying magnesium concentrations at low pH 1

Soils of the peach growing region of the Southeastern Coastal Plain are highly leached and excessively acid, with inherently low concentrations of subsoil magnesium (Mg). A greenhouse experiment was conducted to determine the effects of varying Mg concentrations at low pH on growth and Mg uptake of three peach seedling cultivars commonly used as rootstock in the region. Seedlings of ‘Lovell’, ‘Elberta’, [Prunus persica (L.) Batsch] and ‘Nemaguard’ [Prunus persica (L.) Batsch X Prunus davidiana Carriere] were grown for 36 days in nutrient solution containing 9, 21, 42, 84, 167, 333, and 667 μM Mg. Magnesium concentration in solution did not increase lateral length, number of laterals, trunk cross‐sectional area, or root volume. All terminal growth responses were cultivar related. Magnesium concentration in the leaves, stems, and roots were increased either by quadratic or cubic relationship with solution Mg concentration while Mg uptake rate was increased linearly with solution Mg concentration with all three seedling cultivar. Uptake rates of calcium, manganese, and zinc, and tissue concentrations of phosphorus, manganese, and zinc decreased with increasing Mg concentrations in nutrient solution. Predicted Mg uptake rates by‐regression analysis revealed a cubic uptake isotherm for Nemaguard and a quadratic isotherm for Elberta. Predicted tissue Mg concentration followed similar patterns of accumulation for leaves and stems, but root Mg concentration followed a cubic uptake isotherm for all three seedlings. The linear Mg uptake at low pH may be an important physiological characteristic that enables Lovell seedlings to outperform either Elberta or Nemaguard when used as a rootstock in the southeastern soils.     

Varietal traits limiting the grain yield of tropical maize

Tropical maize varieties were grown at a tropical lowland location in various -seasons and at a highland location in Mexico to study the general growth pattern of tropical maize. The following results were obtained.

1. The tropical maize variety grown at the lowland location in summer was characterized by (a) a high growth rate and a short growth duration, (b) a small leaf area duration during maturing, (c) a sizable loss of dry weight at late maturity, (d) a low harvest index, and (e) a small number of kernels formed per unit field area. Although these characters may be interrelated, the predominant cause of the former two appear to be environmental and that of the latter three, genetic.

2. The grain yield of tropical maize grown at the lowland location in summer was low mostly because of a small number of kernels and maybe also because of short leaf area duration. The senescence of leaves after silking was rapid and the growth duration was short under high temperatures.

3. Although the number of kernels was small, grain yield was higher at the highland than at the lowland location, and also was higher in the winter than in the summer plantings at the lowland location. At the highland location or in winter, the longer growth duration and the longer leaf area duration compensated for the smaller crop growth rate and resulted in a larger dry matter production after silking and a higher grain yield. Larger kernel size also contributed to the higher yield of highland maize.     

Potassium Substitution by Sodium in Root Medium Influencing Growth Behavior and Potassium Efficiency in Cotton Genotypes

ABSTRACT

Potassium (K) deficiency affects cotton (Gossypium hirsutum L.) growth. Sodium (Na) can substitute K for some non-specific functions in plants. Four cotton genotypes were evaluated for their growth rates and K use efficiency grown at various K:Na. The cotton genotypes and treatments had significant (p < 0.01) effect on biomass production, growth rate related parameters, K use efficiency, and K: Na ratio. Maximum total dry matter (2.57 g plant^-1) was accumulated by ‘NIBGE-2’ and minimum (1.91 g plant^?1) was by ‘FH-1000’. Maximum K:Na ratio in shoot was obtained by ‘MNH-786’ and minimum was by ‘NIBGE-2’when 1/3rd K was replaced with Na. Genotypes and various treatments significantly (p < 0.05) influenced specific utilization rate (SUR) and K transport rate (KTR). There was a significant relationship (R² = 0.84, n = 60) between shoot dry matter and K: Na ratio in shoot. Overall, the growth was better when K and Na were added in ratio of 3:1.     

POTASSIUM FERTILIZATION AND FRUIT PRODUCTION OF PAGE CITRUS ON A PUNSIRUS ROOTSTOCK: QUANTITATIVE AND QUALITATIVE TRAITS

Determination of optimum rates of potassium (K) for high citrus production with great qualitative traits is of both agricultural and economical significance, particularly when performing long–term experiments. A five–year field experiment was conducted in the Citrus Research Center of Tonekabon, Iran in a silty clay loam. The objectives were to: 1) to apply different rates of K fertilizer and determine the optimum rates for citrus high production, and 2) to evaluate the effects of K fertilization on the fruit quantitative and qualitative traits for the production of tasty and great quality fruits for fresh or long consumption. Fifteen–year citrus trees were fertilized with five rates of potassium at control, 750, 1500, 2250 and 3000 g tree^?1 on the basis of a completely randomized block design in five replicates. Fruit parameters were determined. Potassium significantly increased fruit yield and qualitative traits at the optimum amount of 1500 g tree^?1.     

湘南浓香型稻作烟区密集烘烤不同阶段升温速度组合研究

为提高密集烘烤烟叶品质,优化密集烘烤工艺,以湘南浓香型稻作烟区的云烟97品种烟叶为材料,研究密集烘烤不同阶段升温速度组合对烟叶化学成分、经济性状的影响及能耗成本。结果表明,上部和下部烟叶在35～38℃以3 h升温1℃,38.1～42℃以2 h升温1℃,42.1～45℃或47℃以3 h升温l℃,45.1℃或47.1～54℃以2 h升温1℃,54.1～68℃以2 h升温1℃的升温速度组合较好;中部叶在35～38℃以2 h升温1℃,38.1～42℃以1 h升温1℃,42.1～47℃以2 h升温l℃,47.1～54℃以1 h升温1℃,54.1～68℃以1 h升温1℃的升温速度组合较好。各升温速度组合有利于协调烤后烟叶化学成分,提高上等烟比例和均价,降低能耗成本。     

生物有机肥在有机水稻上的施用量研究

八福仙生物有机肥不同施用量试验结果表明,生物有机肥对水稻各项指标的提高和改善均有作用,从提高产量、改善品质和经济投入等方面综合考虑,基施生物有机肥用量宜控制在3 840.0～ 4 800.0 kg/hm2.     

时代生活文化，园林景观之魂——论传统文化在营造园林空间意境中的主导性

古典园林空间意境的产生与中国传统哲学文化密不可分,儒道佛思想主要是通过对中国文人性格和审美情趣的渗透,折射到园林风格和景观意境的审美观念中,从而对园林空间的意境营造产生影响。文章从意境的本源、风格、立意构思、布局和表现手法等方面来揭示传统文化对其产生的深刻引导作用,并提出新时代的园林设计师,在对待传统园林的继承与发展创新问题上,不应还只停留在抄袭模仿古典园林文化的表面层次上,而应当探根索源,挖掘其最原真的一面——即对时代生活文化的反映。设计师应当作为生活的阐释者,要把握时代的精神,加强对传统文化的修养,这样设计出来的作品才富有民族特色,才能经得起生活的推敲和历史的检验。     

玉米-大豆轮作及氮肥水平对玉米农艺性状及产量的影响

以郑单958为试验材料,采用裂区试验设计,研究吉林东部半山区玉米-大豆轮作、连作及4个氮肥水平(0 kg/hm²(F1)、90 kg/hm²(F2)、180 kg/hm²(F3)和270 kg/hm²(F4))对玉米农艺性状及产量的影响。结果表明,轮作处理在干物质积累、叶面积、叶面积指数及籽粒产量方面均优于连作处理,而对其他产量构成因素并未形成优势;F3、F4处理在株高、相对叶绿素含量(SPAD)、叶面积指数、产量构成及产量等指标均显著高于不施氮肥的F1处理(P<0.05),高水平氮素(F3、F4)投入对穗粗、百粒重和籽粒产量有一定促进作用,降低了秃尖长度,对行粒数及穗行数影响不明显(P>0.05);F3、F4处理较F1处理籽粒增产幅度达18.45%和16.52%。为此,在吉林东部半山区玉米轮作系统的氮肥施用量以180 kg/ hm²左右为最佳。     

我国控释氮肥应用研究现状综述

随着控释氮肥的生产量和消费量的不断增加,许多学者置身于控释氮肥应用研究之中,该文从产量及氮肥利用率、环境效应和生物学效应方面进行综述,并提出我国控释氮肥存在问题及展望。     

网师园“殿春簃”小院文人造园意境探析

立足于风景园林学科的理论发展背景,针对苏州网师园殿春簃小院的造园意境进行研究,从匾额点题、浮窗见志、曲径通幽、理水藏源、会情书斋、网师寄意6个方面进行分析,总结出殿春簃小院营造意境的方法,从而达到丰富和完善风景园林学科理论研究的目的。