高产棉田土壤碱性磷酸酶及脲酶空间变异特征分析

以10 m×10 m网格布点连续采集棉田3个生长期的土样,测定土壤碱性磷酸酶和脲酶活性,运用地统计方法建立其空间变异模型和等值线图,探讨棉田土壤在棉花生长的不同阶段,土壤碱性磷酸酶和脲酶活性在时间及空间上的变化特征。结果表明,3个时期的碱性磷酸酶和脲酶均属于中等变异性。土壤碱性磷酸酶和脲酶垂直空间变异性不同,棉花在3个生长期0～20 cm土层脲酶和碱性磷酸酶活性的变异系数均大于20～40 cm土层,而碱性磷酸酶的变异系数在垂直方向是底层大于上层。棉田土壤酶活性也存在时间变异规律,棉花生长发育至吐絮期,酶活性逐渐增加。在垂直空间分布上,3个时期土壤碱性磷酸酶和脲酶活性均随土壤深度的增加而降低。     

不同氮肥在石灰性潮土中的转化及ATS对尿素氮转化的调控效应

根据氮肥施入土壤后的转化特性进行氮肥的高效调控和管理是提高氮肥利用效率、缓解氮肥污染的重要措施。为探究不同氮肥在石灰性潮土中的转化特性差异及硫代硫酸铵（ammonium thiosulfate，ATS）作为氮肥调控剂对尿素氮转化的影响，该研究采用室内土壤培养（土壤水分含量为田间持水量的60%，温度25 ℃）试验方法，以尿素、硫酸铵、氯化铵和ATS作为供试肥料，比较4种氮肥施入石灰性潮土后的转化特性差异，并以ATS作为氮素调控剂，以单施尿素作为对照，探究尿素配施不同用量ATS对尿素氮转化的影响。结果表明，4种供试氮肥在石灰性潮土中的转化过程明显不同。尿素在石灰性潮土中的水解速率最快，硝化作用强度也最高，硫酸铵其次；氯化铵由于Cl^-的硝化抑制作用，土壤表观硝化率在7～21 d显著低于尿素和硫酸铵（P＜0.05）；ATS施入土壤后，NH₄⁺-N转化为NO₂^--N的速率最高，而NO₂^--N转化为NO₃^--N的速率最低，NH₄⁺-N在土壤中的存留时间最长，出现峰值之后也一直保持最高的含量，表观硝化率最低。将ATS作为氮素调控剂与尿素配合施用，当其用量在60 mg/kg（含S量）以上时，既表现出了明显的抑制尿素水解的作用效果，也表现出了显著的硝化抑制作用（ P <0.05），且随着ATS用量的增加，抑制效应明显增强。这对于减少氮素损失，提高氮肥利用效率具有积极意义。但供试4种氮肥施入土壤后均出现了亚硝酸盐的累积，其中ATS处理的累积量显著高于尿素、硫酸铵和氯化铵（P＜0.05），累积持续时间也最长。ATS作为氮素调控剂调控氮素转化，也出现了类似的结果，且随着ATS用量增加，亚硝酸盐在土壤中存留时间明显延长，含量和峰值明显提高，出现峰值的时间也明显延后。     

Effect of Organic and Inorganic Nutrients for Soil Quality Conservation and Yield of Rainfed Low Land Rice in Sub-tropical Plateau Region

The effect of organic sources of nutrients and inorganic fertilizers, was studied on grain yield of lowland rice and some aspect of soil quality parameters in a field experiment at Agricultural Experimental Farm of Indian Statistical Institute, Giridih, situated at eastern plateau region of India, during consecutive years 1997–2002. Chemical fertilizers and various organic matters were applied to two rice cultivars, Sabita and Subarna. The highest mean grain yield was 3.53 t ha^?1 and maximum agronomic efficiency was 60.3 % with the application of inorganic fertilizer followed by cow dung, where 3.47 t ha^?1 grain yield was recorded with an agronomic efficiency of 57.5 %. Grain yield of rice recorded under organic sources of nutrients was not significantly different from that of inorganic fertilization though there was improvement in soil quality parameters under organic sources. Soil organic carbon (0.72 %), microbial biomass‐C (279.23 μg g^?1 dry soil), urease activity with buffer (33.54 μg urea hydrolyzed g^?1 oven‐dry soil) and non‐buffer (21.97 μg urea hydrolyzed g^?1 of oven‐dry soil) methods and acid phosphatase activity (2.24 μg para‐nitrophenol released g^?1 of oven‐dry soil) analysed following the harvest of the crop were highest under cow dung manure treatment; the most efficient organic source under the experiment. Mean grain yield of rice was significantly higher in Sabita cultivar over Subarna. The regression analyses among the variables have shown that there was linear relationship among soil parameters and grain yield of rice.     

Root zone microbial populations, urease activities, and purification efficiency for a constructed wetland

In order to investigate the effects of microorganisms and their urease activities in macrophytic root zones on pollutant removal, four small-scale plots (SSPs) of vertical/reverse-vertical flow wetlands were set up to determine: a) the relationship between the abundance of microorganisms in the root zones and water purification efficiency; and b) the relationship between urease activities in the root zones and pollutant removal in a constructed wetland system. Total numbers of the microbial population (bacteria, fungi, and actinomyces) along with urease activities in the macrophytic root zones were determined. In addition, the relationships between microbial populations and urease activities as well as the wastewater purification efficiencies of total phosphorus (TP), total Kjeldahl nitrogen (TKN), biochemical oxygen demand in 5 days (BOD₅), and chemical oxygen demand (COD) were also analyzed. The results showed that there was a highly significant positive correlation (r = 0.9772, P < 0.01) between the number of bacteria in the root zones and BOD₅ removal efficiency and a significant negative correlation (r = -0.9092, P < 0.05) between the number of fungi and the removal efficiency of TKN. Meanwhile, there was a significant positive correlation (r = 0.8830, P < 0.05) between urease activities in the root zones and the removal efficiency of TKN. Thus, during wastewater treatment in a constructed wetland system, microorganism and urease activities in the root zones were very important factors.     

Effect of biosolid amendment on enzyme activities in earthworm (Lumbricus terrestris) casts

We studied the effect of amendment of sewage sludge biosolids on enzyme activity in soil and earthworm (Lumbricus terrestris) casts. Enzyme activities and contents of nutrients and organic matter of surrounding soil were compared with the corresponding properties of earthworm casts. This short time experiment was conducted at 20 ± 0.5 °C in the laboratory, simulating field conditions of biosolid treatments. In general, all of doses of biosolid treatments influenced the enzyme activity and contents of nutrients and organic matter of earthworm casts and surrounding soil. Enzyme activity such as urease (UA), alkaline phosphatase (APA), and arylsulfatase (ASA) and the contents of organic matter and nutrients N and P in earthworm casts and surrounding soil increased with increasing biosolid application. Without biosolid additions, enzyme activities in cast of L. terrestris exceeded those in the soil. In contrast, when biosolid was added, DHA in casts was lower than the soil. Activities of UA and APA were consistently higher in L. terrestris casts than in soil of all biosolid treatments. Biosolid amendments generally increased ASA at low doses, but at higher doses, ASA decreased. In general, organic matter and contents of N and P were higher in surface casts of L. terrestris and soils than in the control soil. Activities of UA, APA, the contents of organic carbon and nutrients N and P in soil and casts showed positive correlations. On the contrary, ASA and DHA were negatively correlated with the contents of organic matter and nutrients.     

植物营养元素—Ni

本文从Ni的生理功能 ,Ni与酶活性 ,植物对Ni的吸收与运转 ,植物缺Ni的症状 ,Ni的毒害作用与植物对Ni的耐性等 6个方面论述了Ni对植物生长发育的重要性与必要性。     

The effect of different nitrogen sources on the symbiotic interaction between Sorghum bicolor and Glomus intraradices: Expression of plant and fungal genes involved in nitrogen assimilation

In the arbuscular mycorrhizal (AM) symbiosis, plants take up part of the nitrogen (N) through a mycorrhizal pathway. In this study, we assessed the effect of different N sources on the expression of genes coding for enzymes and transporters of the mycorrhizal N uptake pathway, using Sorghum bicolor and Glomus intraradices as a model. Some of the genes investigated were differentially regulated in the intraradical and in the extraradical mycelium depending on the N source. In AM roots, some fungal and plant genes were co-regulated, suggesting an interdependence of both partners in the mycorrhizal N uptake pathway. Mycorrhizal N transfer may have a preference for glycine (plant growth and N uptake stimulation).     

阿特拉津对两种不同施肥条件土壤脲酶的影响

采用田间小区试验方法，研究了阿特拉津对2种不同施肥处理中土壤脲酶活力的影响。结果表明，低浓度阿特拉津在处理初期，对土壤脲酶有一定刺激作用，随后表现为抑制作用；而高浓度的在整个处理期间对脲酶都表现为明显的抑制作用，而且抑制程度与阿特拉津浓度呈正相关。：不同施肥条件下，土壤脲酶活力受高浓度阿特拉津影响有明显差异，长期单施NPK肥，土壤脲酶活力较低，脲酶受抑制明显；而NPK与有机肥长期配合施用，脲酶活力高，脲酶受抑制程度轻。     

不同施肥水平对茎瘤芥土壤脲酶活性的影响

采用田间试验和化学分析等方法,研究了不同施肥水平下茎瘤芥土壤脲酶活性阶段变化特点,结果表明,茎瘤芥生长对土壤脲酶有明显的促进作用,随生长天数的增加,脲酶活性不断上升。随施肥水平的提高,土壤脲酶活性上升。茎瘤芥的产量与生长中后期土壤脲酶活性具有显著的正相关关系。土壤脲酶活性高低反映出茎瘤芥生长和土壤代谢状况,可作为茎瘤芥土壤生态和肥力水平的一个良好指标。     

化学农药对土壤脲酶的影响

通过对拟除虫草酯类、有机磷类、有机氯类、氨基甲酸酯类、酰胺类几种农药对土壤脲酶活性的影响进行了试验，分析了不同农药用量，不同尿素用量影响下对脲酶活性的作用。试验结果表明，九种农茏在不同情况下对脲酶活性均有不同程度的影响作用，也证明了本地区特有的农业环境条件下，化学农药可能会影响和破坏农业生态环境。