Influence of nitrogen and sulfur fertilization on quality of canola (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) under rainfed conditions

Field experiments were conducted at Cereal Crops Research Institute, Pirsabak, Nowshera, Pakistan, during winter 2003~2004 and 2004~2005 to evaluate the effect of nitrogen and sulfur levels and methods of nitrogen application on canola (Brassica napus L. cv. Bulbul-98) under rainfed conditions. Four levels of S (0, 10, 20, and 30 kg/ha) and three levels of N (40, 60, and 80 kg/ha) and a control treatment with both nutrients at zero level were included in the experiments. Sulfur levels were applied at sowing while N levels were applied by three methods (100% soil application, 90% soil 10% foliar application, and 80% soil 20% foliar application). The experiments were laid out in randomized complete block (RCB) design having four replications. Oil content increased significantly up to 20 kg S/ha but further increase in S level did not enhance oil content. Glucosinolate content increased from 13.6 to 24.6 μmol/g as S rate was increased from 0 to 30 kg/ha. Protein content increased from 22.4% to 23.2% as S rate was increased from 0 to 20 kg/ha. Oil content responded negatively to the increasing N levels. The highest N level resulted in the highest values for protein (23.5%) and glucosinolate (19.9 μmol/g) contents. Methods of N application had no significant impact on any parameters under study.     

How silicon fertilizer improves nitrogen and phosphorus nutrient availability in paddy soil?

In order to reveal the mechanism of silicon(Si) fertilizer in improving nitrogen(N) and phosphorus(P) nutrient availability in paddy soil, we designed a series of soil culture experiments by combining application of varying Si fertilizer concentrations with fixed N and P fertilizer concentrations. Following the recommendations of fertilizer manufacturers and local farmers, we applied Si in concentrations of 0, 5.2, 10.4, 15.6, and 20.8 μg/kg. At each concentration of added Si, the availability of soil N and P nutrients, soil microbial activity, numbers of ammonia-oxidizing bacteria and P-decomposing bacteria which means that the organic P is decomposed into inorganic nutrients which can be absorbed and utilized by plants, and urease and phosphatase activity first increased, and then decreased, as Si was added to the soil. These indicators reached their highest levels with a Si application rate of 15.6 μg/kg, showing values respectively 19.78%, 105.09%, 8.34%, 73.12%, 130.36%, 28.12%,and 20.15% higher than those of the controls. Appropriate Si application(10.4 to 15.6 μg/kg) could significantly increase the richness of the soil microbial community involved in cycling of N and P nutrients in the soil. When the Si application rate was15.6 μg/kg, parameters for characterizing microbial abundance such as sequence numbers, operational taxonomic unit(OTU)number, and correlation indices of microbial community richness such as Chao1 index, the adaptive coherence estimator(ACE)index, Shannon index, and Simpson index all reached maximum values, with amounts increased by 14.46%, 10.01%, 23.80%,30.54%, 0.18%, and 2.64%, respectively, compared with the control group. There is also a good correlation between N and P mineralization and addition of Si fertilizer. The correlation coefficients between the ratio of available P/total P(AP/TP) and the number of ammonia-oxidizing bacteria, AP/TP and acid phosphatase activity(AcPA), AP/TP and the Shannon index, the ratio of available N/total amount of N(AN/TN) and the number of ammoniated bacteria, and AN/TN and AcPA were 0.9290, 0.9508,0.9202, 0.9140, and 0.9366, respectively. In summary, these results revealed that enhancement of soil microbial community structure diversity and soil microbial activity by appropriate application of Si is the key ecological mechanism by which application of Si fertilizer improves N and P nutrient availability.     

Potential production simulation and optimal nutrient management of two hybrid rice varieties in Jinhua,Zhejiang Province,China

Potential growth of two widely-grown hybrid rice varieties in the Jinhua district of Zhejiang Province, Shanyou63 for mid-rice and Xieyou46 for late rice, was simulated using a crop growth model of WOFOST. Parameters of the rice growth in WOFOST were calibrated through field experiments from 1999 to 2002 in Jinhua. The potential yield simulated with WOFOST was about 12 t/ha for Shanyou63 and 10 t/ha for Xieyou46, which are in good agreement with the highest recorded yield obtained in this area. Under farmers practice, current yield is about 7.5 t/ha for Shanyou63 and 6.5 t/ha for Xieyou46. There is a gap between the actual rice yield and the potential yield for these two hybrid rice varieties grown in this area. The attainable target yields were set to 70% to 75% of their potential yields for the two varieties. A recently developed software ＂Nutrient Decision Support System （NuDSS）＂ for irrigated rice was used to optimize nutrient management for these two rice varieties. According to NuDSS, the optimal fertilizer N requirement for the target yields was about 150 kg/ha for Shanyou63 and about 120 kg/ha for Xieyou46, which were only about 70% of the fertilizer N application under current farmers＇ practice. Comparing with farmers＇ practice, there is great potential to increase actual rice yields and to reduce fertilizer N use rates by improving rice crop management practice in Jinhua.     

Targeted yield concept and a framework of fertilizer recommendation in irrigated rice domains of subtropical India

Soil test crop response （STCR） correlation studies were carried out in Vindhyan alluvial plain during 2001 to 2004 taking IR-36 as test crop to quantify rice production in the context of the variability of soil properties and use of balanced fertilizers based on targeted yield concept. The soils were developed on gently sloping alluvial plain with different physiographic settings and notable variation in drainage condition. Soil properties show moderate variation in texture （loamy to clay）, organic carbon content （4.4 to 9.8 g/kg）, cation exchange capacity （10,2 to 22.4 cmol （p＋）/kg） and pH （5.3 to 6,4）, Soil fertility status for N is low to medium （224 to 348 kg/ha）, P is medium to high （87 to 320 kg/ha） and K ranges from medium to high （158 to 678 kg/ha）. Database regarding nutrient requirement in kg/t of grain produce （NR）, the percent contribution from the soil available nutrients [CS （%）] and the percent contribution from the applied fertilizer nutrients [CF （%）] were computed for calibrating and fbrmulating fertilizer recommendations. Validity of the yield target for 7 and 8 t/ha was tested in farmers＇ fields and yields targets varied at less than 10%. The percent achievement of targets aimed at different level was more than 90%, indicating soil test based fertilizer recommendation approach was economically viable within the agro-ecological zone with relatively uniform cropping practices and socio-economic conditions.     

Field demonstration of reduction of lead availability in soil and cabbage （Brassica Chinensis L.） contaminated by mining tailings using phosphorus fertilizers

A field demonstration of reduction of lead availability in a soil and cabbage （Brassica Chinensis L.） contaminated by mining tailings, located in Shaoxing, China was carried out to evaluate the effects of applications of phosphorus fertilizers on Pb fractionation and Pb phytoavailability in the soil. It was found that the addition of all three P fertilizers including single super phosphate （SSP）, phosphate rock （PR）, and calcium magnesium phosphate （CMP） significantly decreased the percentage of water-soluble and exchangeable （WE） soil Pb and then reduced the uptake of Pb, Cd, and Zn by the cabbage compared to the control （CK）. The results showed that the level of 300 g P/mE soil was the most cost-effective application rate of P fertilizers for reducing Pb availability at the first stage of remediation, and that at this P level, the effect of WE fraction of Pb in the soil decreased by three phosphorus fertilizers followed the order： CMP （79%）〉SSP （41%）〉PR （23%）; Effectiveness on the reduction of Pb uptake by cabbage was in the order： CMP （53%）〉SSP （41%）〉PR （30%）. Therefore our field trial demonstrated that it was effective and feasible to reduce Pb availability in soil and cabbage contaminated by mining tailings using P fertilizers in China and PR would be a most cost-effective amendment.     

Organic nitrogen components in soils from southeast China

Objective:To investigate the amounts of extractable organic nitrogen(EON),and the relationships between EON and total extractable nitrogen(TEN),especially the amino acids(AAs) adsorbed by soils,and a series of other hydrolyzed soil nitrogen indices in typical land use soil types from southeast China.Under traditional agricultural planting conditions,the functions of EON,especially AAs in the rhizosphere and in bulk soil zones were also investigated.Methods:Pot experiments were conducted using plants of pakchoi(Brassica chinensis L.) and rice(Oryza sativa L.).In the rhizosphere and bulk soil zone studies,organic nitrogen components were extracted with either distilled water,0.5 mol/L K2SO4or acid hydrolysis.Results:K2SO4-EON constituted more than 30% of TEN pools.K2SO4-extractable AAs accounted for 25% of EON pools and nearly 10% of TEN pools in rhizosphere soils.Overall,both K2SO4-EON and extractable AAs contents had positive correlations with TEN pools.Conclusions:EON represented a major component of TEN pools in garden and paddy soils under traditional planting conditions.Although only a small proportion of the EON was present in the form of water-extractable and K2SO4-extractable AAs,the release of AAs from soil exchangeable sites might be an important source of organic nitrogen(N) for plant growth.Our findings suggest that the content of most organic forms of N was significantly greater in rhizosphere than in bulk soil zone samples.However,it was also apparent that the TEN pool content was lower in rhizosphere than in bulk soil samples without added N.     

Evaluation of spatial and vertical variability of nitrogen and phosphorus in sewage-irrigated soil in Tongliao, China

The reuse of wastewater for the irrigation of farmlands is gaining popularity, and the nutrient leaching associated with wastewater irrigation is becoming a matter of concern. The variability of nitrogen and phosphorus fractions in wastewater-irrigated soil was investigated in both horizontal and vertical directions in Kongjiaxiang, Tongliao, Inner Mongolia, China. The results showed that wastewater irrigation resulted in the concentrations of available N and P being 40.36% and 66.49% higher, respectively, than those with groundwater irrigation. Different forms of N and P exhibited significantly different distribution patterns. Higher concentrations of NO3- and total available N, as well as of those of Ca-P and total available P were observed near wastewater irrigation channels. Ca-P has a spatial distribution pattern similar to that of available P. The concentrations of NO3- and NH4+ were the highest in top soil and decreased with depth. The complex interactions between nitrate leaching and nitrogen transformation processes (e.g., nitrification, denitrification, and mineralization) determined the vertical profile of NO3- . The significant amount of NH4+ loss inhibited its deep seepage. The Ca-bound compound contained more P than other inorganic fractions as a result of high Ca levels throughout the soil profile. The differences in the concentrations of Ca-bound P at different depths could be due to the upward flux or translocation of Ca from subsurface to surface soil and the sequestration of P.     

Imidacloprid in processed tea and tea liquor

Imidacloprid is a newly introduced broad-spectrum chloronicotinyl insecticide and will find its way in agricultural production, particularly in Asia. However, information on the fate of imidacloprid in crop plants is lacking. The degradation of imidaclopnd in processed CTC tea and tea liquor was investigated in the present study in which imidacloprid was applied at recommended application rate （30.0 g a.i./ha） and twice the recommended application rate （60.0 g a.i./ha） for three consecutive seasons. Imidacloprid was rapidly dissipated in processed tea following first order reaction kinetics at all application rates and had half-lives of 0.9 1-1.16 d with the residue in tea liquor found to be below detectable limit on 3rd day samples. The study revealed that imidacloprid is safe for human consumption and will not pose any residual toxicity problem.     

Canadian University Professors’Perceptions of the Challenges and Support to Engage in Research

Research has been an important responsibility for university professors. Although there has been an increased demand for research, few studies have been conducted directly with university professors to obtain their perceptions of the challenges the increased focus on research have presented. This study employed a qualitative methodology to inquire into the change of work life bought about by the increased demand for research, and the strategies professors have adopted to balance their teaching, research and service. It also inquired into the barriers to conducting research, and effective support strategies. Some barriers and support identified in this study were in accordance with what previous studies have identified. Perhaps because the professors interviewed were all tenured, they noted that the increased demand for research had not significantly changed their work life. Strategies they used to help them meet the demands for research included, but were not limited to, integrating their teaching and research, and collaborating with others on research projects. Barriers to research included bureaucratic constraints, newness to research, lack of time, and lack of funding.     

Competitive adsorption of Cd, Cu, Hg and Pb by agricultural soils of the Changjiang and Zhujiang deltas in China

Soils can often be contaminated simultaneously by more than one heavy metal. The sorption-desorption behavior of a metal in a soil will be affected by the presence of other metals. Therefore, selective retention and competitive adsorption of the soils to heavy metals can affect their availability and movement through the soils. In this study, the simultaneous competitive adsorption of four heavy metals (Cd, Cu, Hg, and Pb) on ten agricultural soils collected from the Changjiang and Zhujiang deltas, China was assessed. The results showed that the competition affected the behavior of heavy metal cations in such a way that the soils adsorbed less Cd and Hg, and more Pb and Cu with increasing total metal concentrations, regardless of the molar concen- tration applied. As the applied concentrations increased, Pb and Cu adsorption increased, while Cd and Hg adsorption decreased. The adsorption sequence most found was Pb>Cu>Hg>Cd. The maximum adsorption capacity for the heavy metal cations was calculated, and affected markedly by soil properties. The results suggest that Hg and Cd have higher mobility associated to the lower adsorption and that Pb and Cu present the opposite behavior. Significant correlations were found between the maximum adsorption capacity of the metals and pH value and exchangeable acid, suggesting that soil pH and exchangeable acid were key factors controlling the solubility and mobility of the metals in the agricultural soils.     

Fertilization increases paddy soil organic carbon density

Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC.     

莆田市常太枇杷园土壤肥力与果树营养状况测定

莆田市常太镇枇杷园土壤肥力和叶片营养状况分析结果表明:枇杷园土壤偏酸,全N、Mg供给不足,B供给严重不足。有效P含量不高,K、Ca、Cu、Fe、Mn、Zn土壤供给充足,并有偏高趋势。枇杷叶片N、P、K、B、Mg质量分数未达到适宜指标,Cu、Mn、Zn、Fe含量偏高,与施用含重金属农药有关。据此提出了合理施药、培肥的农艺措施,为生态果园的建立提供理论依据。     

Studies on nutrient uptake of rice and characteristics of soil microorganisms in a long-term fertilization experiments for irrigated rice

The ecosystem characteristics of soil microorganism and the nutrient uptake of irrigated rice were investigated in a split-block experiment with different fertilization treatments, including control (no fertilizer application), PK, NK, NP, NPK fertilization, in the main block, and conventional rice and hybrid rice comparison, in the sub block. Average data of five treatments in five years indicated that the indigenous N supply (INS) capacity     

不同氦、磷、钾营养条件下白肋烟生长发育过程中有关化学物质的变化动态

采用定期取样杀青烘干化验分析的方法，探索在不同N，P，K营养条件下白肋烟生长发育过程中的糖、氮、烟碱等化学物质变化规律，结果表明：总糖、还原糖随生长期推进呈增加趋势，而总氮、蛋白质呈下降趋势；随施N量增加各生长期的总氮、蛋白质、烟碱增加，而旺长、成熟期总糖和伸根、旺长前期、成熟期的还原糖下降；随施P量增加各生长期的总氮和伸根、旺长前期、成熟期的蛋白质、烟碱增加，而旺长期的总糖、旺长前期的还原糖和旺长后期的蛋白质、烟碱下降；随施K量增加各生长期的总氮、烟碱、蛋白质下降；N，K对总糖和还原糖，N，P对烟碱、总氛、蛋白质影响较大．     

瓜蒌中矿物质元素分布及与土壤环境的相关性

为了解瓜蒌中矿物质元素的分布及与土壤的相关性,以瓜蒌及其生长土壤为实验材料,采用光谱法初步测定了瓜萎果核、果皮、茎叶以及其生长土壤中的Cu、Zn、Mn、Fe、Ca、Mg、K、Na元素含量.结果为瓜蒌中富含人体必需的矿质元素,果实各组织及其与土壤中元素之间存在相关关系(P＜0.05,P＜0.01),果实组织对土壤中元素具有一定的富集能力,尤其是茎叶对Ca、Mg、K的富集系数分别为1.23、0.98和2.93.果实中矿物质元素存在组织分布特点和区域分布差异,多数元素差异具有显著性(P＜0.05),变异系数最大为49.4％.种植环境对瓜蒌品质存在较大的影响,进一步研究瓜萎矿物质元素与环境的关系对提高品质和药效具有重要意义.     

肥料与石膏配施对滨海盐土有效磷的影响

通过盆栽试验,研究了肥料与石膏配施条件下滨海盐土有效磷变化特征,结果表明,(1)不同肥料与石膏配施条件下,滨海盐土有效磷含量以有机无机复混肥(F2)处理较高,而以单施石膏2g/kg(F0B2)处理较低。(2)磷肥施用可显著提高滨海盐土有效磷含量,供试肥料品种间滨海盐土有效磷含量以有机无机复混肥处理(F2)、无机复混肥(F1)处理最高,其次为生物有机无机复混肥(F4)和生物有机肥(F3),以空白对照(F0)最低。(3)随石膏用量增加,土壤有效磷呈显著降低趋势。(4)滨海盐土有效磷含量存在明显动态变化特征,肥料施用后有效磷总体上呈现先增加后降低趋势,最终回复到施肥前水平。(5)从土壤有效磷角度考虑,滨海盐土肥料农业施用以有机无机复混肥(F2)较为适宜。     

施肥对油菜氮、磷、钾营养及其产量的影响

在田间试验条件下研究了施肥对“秦油二号”杂交油菜氮、磷、钾营养及其产量的影响,结果表明:单施氮肥,增加植株氮、磷、钾吸收强度和植株含氮浓度,但对植株磷、钾浓度无明显影响。氮磷配施既能显著提高植株氮、磷、钾吸收强度,也能增加植株氮、磷、钾浓度。在施用氮、磷肥料基础上配施氯化钾肥,降低了植株氮、磷吸收强度和氮浓度。施肥使油菜氮,磷营养吸收高峰推迟。吸氮高峰期在油菜苔期,吸磷高峰期在油菜花角期。在本试验条件下,氮肥与磷肥配合施用油菜产量和经济效益最高,比单施氮肥增产23.2％,比氮磷钾配施增产11.4％,每亩增收三十无以上。     

长期施用含硫化肥对水稻土化学性质和水稻吸收微量元素的影响

已持续26年的湖南祁阳红壤站长期肥料试验分三个处理:NH4C1 KCl KH2PO4;尿素 KCl 过磷酸钙;(NH4)2SO4 K2SO4 过磷酸钙.其土壤、水稻植株样品被用来研究长期施用含硫化肥对水稻土酸化、SO42--S在土壤中累积、土壤-水稻系统微量元素含量和水稻产量的影响.结果表明:大量(667 kg S hm-2yr-1)施用含硫化肥15年后已导致水稻土表层土壤pH明显下降.不施硫处理SO42--S逐年下降,而施硫处理SO42--S有明显累积.施用含硫化肥24年后(1998),土壤有效Cu、B、Mn及全Ca含量有增加趋势,全Fe有减少趋势,对有效Mo、Zn及总Mg似乎没有影响.长期施用含硫化肥已显著减少水稻(特别是晚稻)吸收Fe、Mo、B、Mg、Cl,并导致水稻(特别是晚稻)产量显著下降.可见,长期施用含硫化肥可能影响水稻土性质进而影响水稻生长.