Varietal Differences in Development of Maize (Zea mays L.) Seedlings on Compacted Soils

Differences among open-pollinated tropical maize ( Zea mays L.) varieties in seedling development and establishment on compacted soils were studied. Soil dry density was used as an index of compaction. Three soil compaction levels and 12 traits associated with development and establishment of maize seedlings were investigated. A control (without compaction) was also included. Varietal differences were observed for most traits measured. Genetic differences for seedling development on compacted soil were detected. Varietal differences contributed about three times the contribution of compaction to total variability in the traits. Better seedling development and performance were obtained in moderately compacted soil than in the control. Shoot length, shoot dry weight and per cent dry matter in roots were good indicators of the tolerance of maize seedlings to compaction. A physiological strategy for maize seedling establishment on compacted soil was proposed. The implications of the results for seed testing were also highlighted. It was concluded that consideration should be given to the genotype of maize destined for use in ecologies prone to high soil densities. All varieties of maize grown in an agroecological zone could be screened to identify genotypes tolerant of higher soil densities. The seeds could then be multiplied and distributed to farmers.     

Maize Yields as Affected by Short- and Long-Term Improved Fallows: A Comparative Analysis in the Asian Humid Tropics

Improved short‐ or long‐term fallows are considered suitable low external input technologies for maintaining productivity and sustainability of tropical smallholder upland cropping units, although comparisons on the benefits of this technology are not widely reported. A field study evaluated the impact of improved short (6 months) and long‐term fallow (18 months) using Crotalaria juncea and Tithonia diversifolia, in relation to a natural fallow of the same durations, on the productivity of maize (Zea mays), the most important upland cereal in tropical Asia, over a minor season. The use of improved fallows, especially Tithonia, increased maize yields over the Crotalaria or natural fallow. While the overall yields of maize after a long fallow were greater, the beneficial impact of the green manures was significantly higher in the short fallows. The causal factors for this trend, including biomass production of the improved fallows and possible impact on soils, along with the greater benefits of short‐term fallows for increasing maize yields in the tropics due to lower requirements of unproductive time are presented.     

国审玉米新品种辽单38选育报告

辽单38由辽宁省农业科学院玉米研究所选育,2003年通过国家品种审定委员会审定,组合为辽26×丹340。该品种属晚熟品种,具有产量高、活秆成熟、抗逆性强、品质优良等特点。     

玉米单交种丹玉27号(丹638)的选育及应用

玉米单交种丹玉27号(丹638)是丹东农业科学院玉米研究所于1994年以丹1324 2为母本,丹5026为父本组配而成。2000年7月经辽宁省农作物品种审定委员会审定,命名为丹玉27号;在2002年1月经内蒙古自治区农作物品种审定委员会认定通过。该品种为中熟品种,需要≥10℃积温2490℃·d,在辽宁、内蒙古、吉林生育期115～120d,在河南、河北及安徽一带生育期85～90d,产量平均比对照种本育九号增产10%以上。     

早熟玉米品种主要农艺性状与产量相关研究

运用相关及回归分析方法，研究了20个早熟玉米品种主要农艺性状与产量之间的关系，并利用回归方程估测备性状值的变化对产量的影响。结果表明，行粒数与产量关系最为密切，其次是株高、穗长。穗粗、穗位高、穗行数、千粒重对单产的提高效果不大。     

An Analysis of Seasonal Effects on Leaf Nitrate Reductase Activity and Nitrogen Accumulation in Maize (Zea mays L.)

The important enzyme in nitrogen (N) assimilation, nitrate reductase (NR), is an inducible enzyme influenced by many external (light, temperature, etc.) and internal (genotype) factors. The efficiency of the N assimilation system may vary with genotype and season. In the present study, the effects of season on NR activity in relation to N accumulation in maize plants were investigated. Six different cultivars of maize, namely Ganga-11, Deccan-103, Hi-starch (hybrids), Arun, Manjari and Vijay (composites), were sown during the monsoon (88-day crop duration) and in winter (150-day crop duration). In vivo NR activity in the last fully expanded leaf (LFEL), and the N contents of the whole plant and the LFEL were estimated at seven phenological growth stages. Three different states of N metabolism in maize, namely (i) low NR activity per unit leaf area per unit time coinciding with high accumulation of N, (ii) high NR activity coinciding with low N accumulation, and (iii) low NR activity coinciding with low N accumulation, were noted. These results clearly demonstrate that the relationships between N uptake and accumulation parameters change with the season and crop growth stage and are subject to a genotypic influence. Thus it is necessary to evaluate genotypes under similar environments to select a genotype with high N use efficiency. As these relationships are growth dependent, care must be taken to evaluate them at a particular phenological stage rather than on the basis of days after sowing.     

Einfluß der Erosion auf die Standortproduktivität im Silomaisanbau

Influence of erosion on productivity of maize ( Zea mays L.) cultivation
Accelerated erosion was monitored in Eastern Schleswig-Holstein (F.R.G.) during the last decades. The objective of this study was to compare agricultural productivity of upper, middle and base slope segments to the respective soil parameters, reflecting results of long-term erosion.
Five soil catenas were surveyed. Each catena was divided into three segments representing an eroded area (upper segment), an area with an equilibrium between erosion, accumulation and soil development (middle segment) and an area with accumulation (base slope segment).
In 1986 soil qualities, growth characters and yield components of maize were analysed for each slope segment. At eroded slope segments vegetation cover and yield were significantly lower than at middle and base slope segments. Middle slope segments (equilibrium between erosion, accumulation and soil development) snowed balanced soil quality parameters and high maize yields with a desired combination of yield components.     

Resin-Extractable Phosphorus, Vanadium, Calcium and Magnesium as Factors in Maize (Zea mays L.) Yield

Resin extraction of soil permits evaluation of ratios of readily extracted elements and correlation of concentrations obtained with crop yield. This information provides guidance on potential genotype selection and fertility management. Two hybrids of maize ( Zea mays L.), designated 2292 and 3895, were grown annually in rotational succession on a 3.2-ha site with soybean ( Glycine max L.) and wheat ( Triticum aestivum L.). Soil samples (0–15 cm) were extracted with ion-exchange resins and extracts were analysed with inductively coupled plasma. Data were regressed against crop yield using stepwise multiple correlation methods. Each hybrid was sensitive to unique combinations of extracted chemistries. Both hybrids of maize were sensitive to the resin-extractable V : (V + P) molar ratio and potential losses of ≥ 20 % were indicated as the ratio approached 0.2. A positive response to the Mg : (Mg + Ca) resin-extractable ratio was noted for maize hybrid 2292 in each of three successive years. Changes of yield potentials associated with the Mg : (Mg + Ca) ratio for hybrid 2292 ranged from none to ≥ 20 % as the ratio ranged from 0.2 to about 0.8. The results indicate that, in the presence of large extractable concentrations of competing or inhibitory ions, different approaches to nutrient management in the form of fertilizer nutrient analysis, application, and genotype selection are needed to overcome effects of competing ions.     

玉米轮选系产量配合力和抗病性研究

研究了东农群体—１的第一轮选出的自交系和组成该群体的较好原始亲本的产量配合力和抗大斑病能力．结果表明，轮选系的一般配合力效应和抗大斑病能力均优于较好原始亲本，且差异达到０．０５的显著水平．也证明了用轮回选择法提高玉米自交系的配合力和抗病能力很有效。     

定西县“秸秆畜牧业”开发之我见

定西县是全国出名的干旱贫困县，至今人均占有粮食３０２．８ｋｇ，依赖饲料粮的增加来发展畜牧业是不现实的。唯一出路是靠农作物秸秆资源，采用科技手段提高其营养价值，即开发“秸秆畜牧业”，实现全县脱贫致富。文章重点就小麦秸氨化处理及玉米秸青贮调制可经济效益之对比，探讨全县开发“秸秆畜牧业”并非空中楼阁，一纸空变。