Case study on nitrogen and phosphorus emissions from paddy field in Taihu region

The agricultural non-point source pollution by nitrogen (N) and phosphorus (P) loss from typical paddy soil (whitish soil, Bai Tu in Chinese) in the Taihu Lake region was investigated through a case study. Results shown that the net load of nutrients from white soil is 34.1 kg ha(-1) for total nitrogen (TN), distributed as 19.4 kg ha(-1), in the rice season and 14.7 kg ha(-1) in the wheat season, and for total phosphorus (TP) 1.75 kg ha(-1), distributed as 1.16 kg ha(-1) in the rice season and 0.58 kg ha(-1) in the wheat season. The major chemical species of N loss is different in the two seasons. NH4-N is main the form in the rice season (53% of TN). NO3-N is the main form in wheat season (46% of TN). Particle-P is the main form in both seasons, (about 56% of TP). The nutrient loss varied with time of the year. The main loss of nutrients happened in the 10 days after planting, 64% of TN and 42% of TP loss, respectively. Rainfall and fertilizer application are the key factors which influence nitrogen and phosphorus loss from arable land, especially rainfall events shortly after fertilizer application. So it is very important to improve the field management of the nutrients and water during the early days of planting.     

Field Studies on 32P Movement and P Leaching from Flooded Paddy Soils in the Region of Taihu Lake, China

Field experiments were done in two sites, Yixing and Changshu, Jiangsu province, China, to study P movement and leaching in flooded paddy soils. P movement in soil was investigated by using the KH₂ ³²PO₄ tracker method, and the amount of P leached from the soil layer in different depths was estimated by measuring P concentrations in the soil solution and saturated hydraulic conductivities in field. Determination was done about one month after P application. There was 46% and 42% of total ³²P retained in the 0–5cm layer of soil in the Yixing site and in the Changshu site respectively. The ³²P retained in the 25–30 cm layer was only about 1–2% of the total ³²P added. Furthermore, 8.01% of ³²P in the soil of Yixing site and 16.8% of ³²P in the soil of Changshu site was lost from the layer 0–30cm soil. The seasonal amounts of P leached from the top soil layer and from bottom layer are about 4.5–5.8% and 1.6–2.1% of the total P application, respectively. Changes of total P concentrations in soil solutions during rice growth showed that the fertilizer P applied before flooding of the paddy fields suffered a flash leaching loss and a slow leaching loss. We concluded that the fertilizer P could quickly move in the flooded paddy rice field and parts of it can enter into surface water and ground water. Unless the P application is well managed the risk of P loss and consequently environmental pollution exist.     

Changes of Soil Microbiological Properties Caused by Land Use Changing From Rice–Wheat Rotation to Vegetable Cultivation

A survey was done recently in Jiaxing city of Zhejiang Province in the Yangtze River Delta to compare the differences of soil microbiological properties among paddy soils with different land use including continuous open-field vegetable cultivation (OFVC), plastic-greenhouse vegetable cultivation (PGVC) and traditional rice–wheat rotation (RWR). The soil types included are percolating, permeable and waterlogged paddy soils. The results indicate that the microbial flora was markedly changed as the land use changed for all the three soil types. In continuous vegetable cultivation soils, especially in PGVC soils, the bacteria amounts decreased dramatically, but the fungal and actinomyce amounts increased as compared with RWR soils. The dehydrogenase activities decreased significantly in vegetable soils, especially in PGVC soils as compared with RWR soils. The microbial biomass C and the total phospholipid contents (TPL) in vegetable cultivation soil greatly decreased as compared with RWR soils. Biolog analysis indicated that the kinds of carbon sources that could be metabolized by native microbes in PGVC soils greatly decreased as compared with OFVC soils and RWR soils, revealing that microbial diversity had decreased since land use change. The activities of some soil enzymes including urease, invertase and phosphase were all lower in OFVC soils than those in RWR soils, and those in PGVC soils were the lowest. The degradation of microbiological activities in continuous vegetable cultivation soils, especially in PGVC soils, as compared with RWR soils might have been caused by soil acidification and accumulation of salts due to overuse of both organic and inorganic fertilizers in vegetable cultivation.     

A simple and precise method for fitting a von Bertalanffy growth curve

The parameter K of the von Bertalanffy equation, as developed by Beverton and Holt (1957), is first estimated by the relation $$\log _e \left( {dL_t /dt} \right) = A - Kt$$ where dLt/dt denotes growth increments per a unit of age, t denotes age, and A is a constant. The K estimate is used to evaluate L∞; $$L_\infty = \left( {e^K \sum\limits_2^n {L_t - \sum\limits_1^{n - 1} {L_t } } } \right)/\left( {n - 1} \right)\left( {e^K - 1} \right)$$ The L∞ estimate is used to estimate t _o, and to obtain a better estimate for K; $$\log _e \left( {1 - L_t /L_\infty } \right) = - Kt + Kt_0 $$ The K estimate may be used to obtain another estimate for L∞. Solved examples show that a single iteration is sufficient to obtain fitted equations which are, on the average, as precise as equations fitted by the least squares method shown by Tomlinson and Abramson (1961). This new method can be used, with a slight modification, for the second equation given above, if growth data have unequal age intervals. The variance of K, t _o and log _e L∞ can be estimated by applying the simple methods used in the case of straight-line relationships.     

Effects of dissolved ammonium addition and host feeding with Artemia salina on photoacclimation of the hermatypic coral Stylophora pistillata

 Effects of nutrient treatments on photoacclimation of the hermatypic coral Stylophora pistillata (Esper) were studied. Studies on photoacclimation of colonies from different light regimes in the field were evaluated and used to design laboratory experiments. Coral colonies were collected in the Gulf of Eilat (Israel) from January to March 1993. Exterior branches of colonies from different depths (1 to 40 m) displayed different trends in production characteristics at reduced and very low levels of illumination. From 24 ± 3% to 12 ± 2% of incident surface photosynthetic active radiation (PAR_o), zooxanthella population density and chlorophyll a+c per 10⁶ zooxanthellae increased, a trend seen in the range of light levels optimal for coral growth (90 to 30% PAR_o). The P _max of CO₂ per 10⁶ zooxanthellae decreased, while P _max of CO₂ per 10³ polyps increased, indicating an increase in zooxanthella population density at low light levels. Proliferous zooxanthella frequency (PZF, a measure of zooxanthella division) declined significantly at light levels <18 ± 3% PAR_o. At the lowest levels of illumination (<5% PAR_o), zooxanthella population density decreased, as did the PZF; chl a+c per 10⁶ zooxanthellae was unchanged. In 28-d experiments, exterior coral branches from the upper surfaces of colonies from 3 m depth (65 ± 4% PAR_o) were incubated in aquaria under bright (80 to 90% PAR_o), reduced (20 to 30% PAR_o), and extremely low (2 to 4% PAR_o) light intensities. At each light intensity, the corals were maintained in three feeding treatments: sea water (SW); ammonium enriched SW (SW + N); SW with Artemia salina nauplii (SW + A). An increase in P _max of CO₂ per 10³ polyps was found in corals acclimated to reduced light (20 to 30% PAR_o) in nutrient-enriched SW, while in SW, where the increase in zooxanthella population density was smaller, it did not occur. Nutrient enrichments (SW + N at 2 to 4% PAR_o and SW + A at 20 to 30% PAR_o) increased zooxanthella population density, but had no effect on chl a+c per 10⁶ zooxanthellae. Acclimation for 14 d to reduced (10 to 20% PAR_o) and extremely low (1 to 3% PAR_o) light intensities shifted ¹⁴C photoassimilation into glycerol and other compounds (probably glycerides), rather than sugars. Both ammonium addition and feeding with Artemia salina nauplii resulted in an increase in photosynthetic assimilation of ¹⁴C into amino acids. We conclude that acclimation to reduced light consists of two processes: an increase in photosynthetic pigments and in zooxanthella population density. Both processes require nitrogen, the increase in zooxanthella population density needing more; this adaptation is therefore limited in nitrogen-poor sea water. Received: 19 June 1998 / Accepted: 13 June 2000     

Conservation Genetics at the Species Boundary

Abstract: Conservation genetics has expanded its purview such that molecular techniques are now used routinely to prioritize populations for listing and protection and infer their historical relationships in addition to addressing more traditional questions of heterozygosity and inbreeding depression. Failure to specify whether molecular data are being used for diagnosis-related questions or for population viability questions, however, can lead either to misinterpretation of character data as adaptive information or to misinterpretation of frequency or distance data as diagnostic or historical information. Each of these misinterpretations will confound conservation programs. The character-based approach to delimiting phylogenetic species is both operationally and logically superior to "diagnostic" methods that involve distance- or frequency-based routines, which are unstable over time. Tree-based criteria for the diagnosis of conservation "units" are also inappropriate because they can depend on patterns inferred without reference to diagnostic characters. Intraspecific studies, conservation-related or otherwise, that adopt terminology and methods designed to infer nested hierarchic relationships confuse diagnosis with historical inferences by treating diagnoses as outcomes rather than as precursors to phylogeny reconstruction. A character-based diagnostic approach recognizes the analytical dichotomy between species hierarchies and population statistics and provides a framework for the understanding of each. No species concept, however, should be viewed as an absolute criterion for protecting populations, but as part of a framework from within which identification of protection and management goals can be achieved effectively and defensibly.     

Study On the Hydraulic Characteristics of Taichung Harbour in Taiwan

For this study, field measurements of current profiles, buoy trajectories and the lag of two tidal stations were performed to explore the flow characteristics of Taichung Harbour. in order to distinguish the effects of wind drift current on circulation inside Taichung Harbour, field surveys during both summer and monsoon (winter) season were completed separately. the speed of the drift current was about 3.5% that of the, wind speed, based on the field data. the horizontal dispersion coefficients were close to Bowden's (1965) formula for the tidal current. the water temperature showed a two-layer profile, with the mixing thickness about 4 to 6 metres for the upper layer. the corresponding Richardson number was about 70. the tidal lag between the two tidal stations was 9.68 minutes. All the results agree well with the theoretical results.     

慢生型花生根瘤菌16S rRNA分析

以２１株分离自四川,云南不同花生产区的慢性型花生根瘤菌和６株参比菌株为材料,进行了１６ＳｒＤＮＡＰＣＲ－ＲＦＬＰ,结果除证实了慢性型花生根瘤菌同慢生型大豆根瘤菌（Ｂｒａｄｙｒｈｉｚｏｂｉｕｍｊａｐｏｎｉｃｕｍ）高度的遗传相似性外,还发现了一些菌株同Ｂｒａｄｙｒｈｉｚｏｉｂｉｕｍｌｉａｏｎｉｎｇｅｎｓｉｓ和Ｂｒａｄｙｒｈｉｚｏｂｉｕｍｅｌｋａｎｉｉ有较高的遗传相似性,菌株Ｓｐｒ１－２的１６ＳｒＲＮＡ     

Effect of different pearling times on the quality of hull-less barley rice北大核心CSCD

Hull-less barley is a special food crop rich in various nutrients in Qinghai-Tibet Plateau. Six-pearling is often used to produce commercial hull-less barley rice in order to improve its rough taste and inferior cooking quality. This study evaluated the differences in the nutritional, cooking, sensory, and storage qualities of hull-less barley rice with different pearling times to obtain suitable processing conditions for the production of high-quality hull-less barley rice. With increasing pearling time, the contents of vitamin B6, vitamin E, dietary fiber, iron, zinc, phenols, and flavonoids significantly decreased to a large extent, protein and vitamin B3 decreased slightly, the contents of total starch and β-glucan increased significantly, and γ-aminobutyric acid (GABA) initially increased and then decreased. The peak, trough, and final viscosity of whole grain barley were 1 860.50 cP, 914.50 cP, and 2 150.00 cP, respectively, and increased after six-pearling to 4 219.00 cP, 2 628.00 cP, and 5 074.00 cP, respectively. At the same time, the water absorption and volume expansion of the pearled hull-less barley increased significantly. The hardness of pearled hull-less barley reduced from 4 708.50 g to 2 282.00 g, its adhesiveness increased from 0.00 to -7.33, and its taste and sensory quality exhibited better. The activities of α-amylase, polyphenol oxidase, lipase, and catalase in pearled hull-less barley slightly decreased. Hull-less bran flour is rich in a variety of nutritional components and could be a potential resource with great developmental value. In general, hull-less barley rice obtained from three-pearling has high nutritional value, high cooking quality, low enzyme activity, and low energy consumption; therefore, it can be used to produce high-quality barley rice. This study provides important information for high-quality pearled hull-less barley and further utilization of barley bran flour. © 2022 Science Press. All rights reserved.