氮素营养水平对小麦后移栽棉氮代谢的影响

对不同氮素营养水平下的小麦后移栽棉叶片硝酸还原酶活性、棉株含氮量及叶片氨基酸含量等进行了测定。结果表明，除８月１９日外，叶片硝酸还原酶活性与施氮量呈极显著正相关（ｒ＝０．９６９３～０．９８８１）；地上部各器官的含氮率和绝对含氮量均随施氮量的增加而提高，且不同器官间呈同步增减的趋势，因而氮素分配比例的变化不大；提高氮素营养水平可显著增加小麦后移栽棉的叶片氨基酸总量和游离氨的含量（ｒ＝０．５３１６和０．５６０５），在１７种氨基酸中，谷氨酸、脯氨酸等７种氨基酸的含量与施氮量呈显著的正相关（ｒ＝０．５２５６～０．６０７４）。虽然施氮量越高，棉株的氮素代谢越旺盛，但小麦后移栽棉的适宜施氮量约为２０５ｋｇ／ｈｍ２。     

硝酸钙在底泥修复中的作用机理及

受污染底泥的修复已经成为水环境修复中的重要组成部分，在底泥中注入硝酸钙则是近十多年来发展起来的一种污染底泥原位处理技术。全面分析了硝酸钙在底泥修复中去除有机物、抑制磷的释放以及消除水体黑臭现象的机理，并介绍了这一技术在国内外的研究和应用状况。研究成果表明：在底泥中注入硝酸钙的技术已从实验室和中试研究阶段发展到了实际的工程动作阶段，并且在有机物PAHS的降解和硫化物的去除方面已经得到了很好的效果。     

蔬菜的硝酸盐污染及防控措施

由于不合理的种植手段,造成了蔬菜的硝酸盐污染,影响蔬菜的品质,威胁人类的身体健康和生命安全。通过重视施用有机肥、合理施用氮肥、注意施肥时期和施肥种类、在不同季节使用正确栽培设施、使用硝化抑制剂(氮肥增效剂)等技术手段,可以明显减少硝酸盐在蔬菜中的残留,对发展绿色无公害蔬菜生产和提高人民生活水平有着十分重要的意义。     

硝酸盐对硅胶表面噻虫嗪的光敏化降解的初步研究

以硅胶模拟土壤颗粒,研究了噻虫嗪在硅胶表面的光解作用。通过正交实验,研究了萃取剂种类、萃取剂用量、萃取时间,以及噻虫嗪在硅胶上的负载量等因素对萃取效果的影响,确定了最佳萃取条件。通过对照NO-3存在与否2种情况下噻虫嗪的光解情况,考察了NO3-对噻虫嗪光解作用的影响。结果表明,在氙灯照射下,噻虫嗪的半衰期与硝酸钾的负载量有关,随着硝酸钾含量的增加,噻虫嗪的半衰期有明显降低,速率常数相应增大,硝酸盐对噻虫嗪的光解有促进作用。随着光照强度的增大,噻虫嗪的半衰期也相应缩短。     

Nitrate and bromide contents of glasshouse radish as affected by soil content and global radiation

Abstract

Samples (208) of radish (Raphanus sativus L.) foliage and root were collected from commercial glasshouses. Simultaneously corresponding soil samples were taken. Both plant and soil samples were analysed for nitrate and bromide.

The nitrate contents of foliage and root are affected by global radiation and by nitrate content of the soil. An interaction between the two factors was found; It indicated that soil nitrate content had a considerable effect in summer, but much less so in winter under poor light conditions, when the level of nitrate in the crop is high regardless of the nitrogen status of the soil. To study the effect of radiation on nitrate content of radish in summer it was found best to consider the cumulative amount of radiation during 10 days before harvest; in winter, a period of 20–30 days was more suitable.

The bromide content of foliage and root (highest values being resp. 390 and 73 mg Br per kg fresh product) was correlated with the concentration of bromide in the 1:2 volume soil extract. An increase of 1 mmol NO₃ per 1 soil extract lowered the Br content of fresh radish roots by 5.8 mg Br per kg.     

Effects of Carbofuran on Availability of Macronutrients and Growth of Tomato Plants in Natural Soils and Soils Amended with Inorganic Fertilizers and Vermicompost

The effects of lower field rate (LFR), field rate (FR), and higher field rate (HFR) applications of carbofuran on ammonium (NH₄)-nitrogen (N), nitrate (NO₃)-N, available phosphorus (P), and available potassium (K) contents in natural soils and those amended with inorganic fertilizers and vermicompost on the growth of tomato plants were studied. The NH₄-N, NO₃-N, available P, and available K contents increased up to FR but the most significant increase in was observed at LFR of carbofuran application. At HFR there was a significant reduction in nutrient availability. With passage of time all these parameters increase up to 30 days; thereafter, a decrease was observed up to the end of the experiment in both unamended and amended soils. The greater plant growth was observed at LFR of carbofuran application and at HFR the plants exhibited phytotoxicity in the form of marginal leaf scorching in both systems. The morphological growth parameters of tomato plants were positively correlated with nutrients availability.     

Analysis of NO3 interception of the parasitic angiosperm Orobanche spp. using a positron-emitting tracer imaging system and 13NO− 3: A new method for the visualization and quantitative analysis of the NO3 interception ratio

Abstract

The root parasitic plants Orobanche spp. (broomrapes) seriously affect agricultural production. A visualization and quantitative analytical method for the interception of nutrients was established using a positron-emitting tracer imaging system and ¹³NO^? ₃. By using this analytical method that involves volume normalization with ¹⁸F^? images, the nitrogen nutrient interception ratio of the Orobanche spp. was calculated to be 73.6 ± 3.9% in a host–parasite system of red clover (Trifolium pratense L.).     

Inorganic N analysis of soil extracts by automated and distillation procedures

Abstract

A comparison was made of automated procedures and steam distillation for analysis of NH₄ ⁺ and NO₃ ^‐ in KCl extracts of soils. Automated analysis of NH₄ ⁺ utilized the phenate‐hypochlorite reaction. Nitrate was analyzed by E. coli reduction of NO₃ ^‐ to NO₂‐which was then determined colorimetrically by reaction with sulfanilamide and napthylethylenediamine diHCl. Soil extracts were made with 1 M and 2 M KCl. Extracting with 1 M KCl was as effective as 2 M KCl. Extracts in 1 M KCl did not interfere with E. coli reduction of NO₃‐, but 2 M KCl did. The automated procedures when compared to distillation gave similar if not better precision and reduced variation particularly at low N concentrations. The automated procedure tended to give higher values at higher NO₃‐concentrations. Reduced time required for the analyses provided an additional advantage for the automated procedures.     

Shoot nitrate reductase activities of field‐layer species in different forest types. II

Analysis of in vivo shoot nitrate reductase activity (NRA) of the grass Deschampsia flexuosa (L.) Trin. has been proposed as a method of indicating the availability of nitrate in northern temperate forest soils. We report the seasonal variation in NRA and the influence of temperature on the NRA assay. Studies were performed in the field or on natural populations on topsoil monoliths in a greenhouse.

The induced in vivo NRA as measured at 28°C was higher in plants grown at lower than at higher temperatures within the range 4–20°C, although the induction was faster at higher temperatures. When the assay was performed at various temperatures, enzyme activity was much lower at lower temperatures. The accumulation of organic nitrogen in shoots showed that reduction actually increased with temperature. Transfer of monoliths from high to low temperature led to an increase of in vivo NRA within a day, whereas the decline caused by the reverse began after six days. Variations in temperature accounted for between 0 and 80% of the seasonal variation in NRA in the field, depending on the influence of the variability in nitrate supply.

Maximally induced NRA after application of nitrate was mostly higher in a clearfelling than in a closed forest. In the forest, there was a close correlation between current and maximally induced NRA. One interpretation of this result is that low availability of nitrogen may have been a cause of the lower maximally induced NRA there. This is supported by results from other studies.

We conclude that variations in temperature and availability of nitrogen, particularly nitrate, are largely responsible for seasonal variations in NRA. The influence of temperature can be adjusted for.     

Corn (Zea mays L.) Grain and Stover Yield as Affected by Soil Residual Mineral Nitrogen

Evaluation of nitrogen (N) dynamic in soil using regression equations is important for proper determination of N fertilization. A 3-year field experiment was conducted to (1) develop the best-fitted regression model relating corn grain and stover yield to soil residual ammonium (NH₄)-N and nitrate (NO₃)-N for corn yield prediction and (2) evaluate how such a model can be beneficial to the health of ecosystem by predicting the appropriate rates of N fertilization for corn production. Soil NH₄-N and NO₃-N were determined at corn harvest at the depths of 0–30 and 30–60 cm. Nitrogen fertilizer rates and soil mineral N accounted for a maximum of 93% variation in corn grain yield. Soil mineral N enhanced corn yield more than N fertilizer. Totals of 63.1 and 14.1 kg/ha of soil residual NO₃-N and NH₄-N were found in the 0- to 60-cm depth, indicating the importance of performing soil N tests.