Fertility control of Rattus nitidus using quinestrol:effects on reproductive organs and social behavior

Fertility control has been identified by studies in the laboratory and the field as a more appropriate and long-term control strategy for rodent pests than lethal control.In this study,we investigated the effects of quinestrol on mass of reproductive organs and on social behaviors in female and male Himalayan field rats(Rattus nitidus).A total of 16 adult females and 16 adult males were randomly assigned to 4 groups.One male and one female group were fed rice with 0.005%quinestrol by weight for 7 days,and another 2 groups were fed rice only.After 7 days,rats were assigned to 10 min dyadic encounters between groups,and investigation,aggression,defense and attack latency were quantified.All animals were killed on day 10,and reproductive organs were dissected and weighed.Dyadic encounter data showed that there were obvious changes in social behaviors of quinestrol-treated rats.Quinestrol significantly inhibited the investigative behavior of quinestrol-treated males toward control females in Rattus nitidus,but seldom affected investigation between control males and quinestrol-treated females.Aggression of control females toward quinestrol-treated males was higher than that of quinestrol-treated females,and defense of quinestrol-treated males toward control females was more remarkable than that of control males.Quinestrol remarkably decreased wet masses of epididymis and spermotophore in males and ovaries in females,but had no effect on wet masses of testes and uteri after quinestrol treatment.These results indicate that the anti-fertility effects of quinestrol on R.nitidus are attributed to not only suppressing reproductive organs but also impacting social behaviors associated with territory defense and mate choice.

Growth of tandem long-mat rice seedlings using controlled release fertilizers:Mechanical transplantation can be more economical and high yielding

The traditional soil-based rice seedling production methods for mechanical transplanting are resource-intensive,time consuming and laborious.The improvement and optimization of nutrient management in soil-less nursery raising methods like tandem long-mat seedlings(TLMS)are necessary for the resource-efficient cultivation of rice.In the present study,a controlled-release fertilizer(CRF)-polymer-coated compound fertilizer with 3 months release period(PCCF-3M)was applied as seedling fertilizer(SF),and five different dosages of SF(SF-0,SF-10,SF-20,SF-30,and SF-40)were compared with an organic substrate as the control(CK).Among all SF treatments,the best results were obtained with the application of 20 g/tray of SF(SF-20),as the seedling quality and machine transplanting quality were comparable to those of CK.In contrast,the lower dosages(SF-0 and SF-10)resulted in low nitrogen content and reduced shoot growth,while the higher dosages(SF-30 and SF-40)resulted in toxicity(increased malondialdehyde accumulation)and inhibited the root growth.Similarly,SF-20 increased panicle number(5.6-7.0%)and yield(4.3-5.3%)compared with CK,which might be related to the remaining SF entangled in the roots supporting the tiller growth of rice seedlings in the field.Moreover,SF-20 reduced the seedling block weight(53.1%)and cost of seedling production(23.5%)but increased the gross margin,indicating that it was easy to handle and economical.Taken together,our results indicate that SF-20 is a cost-effective way to promote the growth and transplanting efficiency of rice seedlings.To our knowledge,this study is the first to determine the optimum dosage of CRF for the soil-less production of rice seedlings.

Effects of Different Proportions of Controlled Release Urea and Ordinary Urea on Peanut Yield

[Objectives]To study the effects of different proportions of controlled release urea and ordinary urea on peanut yield.[Methods]A total of 5 treatments were set up according to different proportions of controlled release urea and ordinary urea,randomly arranged in blocks and repeated 3 times.[Results]The test results of field districts showed that different proportions of controlled release urea and conventional urea had different effects on peanut yield.On the basis of applying 50 kg/666.7 m^(2)of calcium superphosphate and 17 kg/666.7 m^(2)of potassium sulfate,13.34 kg/666.7 m^(2)of pure nitrogen was applied.The optimal ratio of controlled release urea to ordinary urea was 75:25,followed by 50:50.The output was 379.83 and 371.83 kg/666.7 m^(2),separately increased by 6.74%and 4.50%compared to the application of ordinary urea.[Conclusions]The combined application of controlled release urea and ordinary urea in peanuts can significantly increase peanut yield compared to just applying ordinary urea.

Effects of slow or controlled release fertilizer types and fertilization modes on yield and quality of rice

There is limited information about the influence of slow or controlled release fertilizer（S/CRF） on rice yield and quality. In this study, japonica rice cultivar Nanjing 9108 was used to study the effects of three different S/CRFs（polymer-coated urea（PCU）, sulfur-coated urea（SCU）, and urea formaldehyde（UF）） and two fertilization modes（both S/CRF and common urea（CU） as basal fertilizer, S/CRF as basal and CU as tillering fertilizer） on rice yield and quality. CU only was applied separately as control（CK）. Results showed that, rice grain yield, chalky kernel rate, chalky area, overall chalkiness, and the content of gliadin, glutenin, and protein, all showed the trends of UF〉PCU〉SCU within the same fertilization mode, and showed the trends of S/CRF as basal and CU as tillering fertilizer〉both S/CRF and CU as basal fertilizer within the same type of S/CRF. In contrast, the contents of amylose, amylopectin, and starch, as well as taste value, and peak and hot viscosity showed trends of SCU〉PCU〉UF, and the trends of both S/CRF and CU as basal fertilizer〉S/CRF as basal and CU as tillering fertilizer. Among S/CRF treatments and fertilization modes, taste values of cooked rice were positively correlated with amylose, amylopectin, and starch contents, as well as gel consistency, peak viscosity, hot viscosity, and cool viscosity, while negatively correlated with globulin, gliadin, glutenin, and protein contents. The types of S/CRF and fertilization modes are important for improving rice yield and quality. Compared to CK, higher yield and similar quality of rice was achieved with UF as basal and CU as tillering fertilizer, and similar yield with improved appearance and eating and cooking quality of rice was achieved with either both UF and CU as basal fertilizer, or PCU as basal and CU as tillering fertilizer.

Synthesis and Performance of Polyurethane Coated Urea as Slow/controlled Release Fertilizer

Polyurethane coated urea slow/controlled release fertilizer was prepared based on urea granules, isocyanate, polyols and paraffin. Isocyanate reacted with polyols to synthesize the polyurethane skin layer on urea granules surface. Paraffin serves as a lubricant during syntheses of polyurethane skin layers. The structure and nutrient release characteristics of the polyurethane skin layers were investigated by FTIR, SEM and TG. Urea nitrogen slow-release behavior of the polyurethane coated urea was tested. The experimental results indicated that compact and dense polyurethane skin layers with a thickness of 10-15 lam were formed on urea surface, the urea nitrogen slow-release time can reach 40-50 days. Paraffin proves to play a key role in inhibiting water to penetrate into urea, but excessive addition would decrease the polyurethane crosslinking density.

Release Characteristics of Different N Forms in an Uncoated Slow/Controlled Release Compound Fertilizer

This study examined the release characteristics of different N forms in an uncoated slow/controlled-release compound fertilizer （UCRF） and the N uptake and N-use efficiency by rice plants. Water dissolution, soil leaching, and pot experiments were employed. The dynamics of N release from the UCRF could be quantitatively described by three equations： the first-order kinetics equation [N1=N0 （1-e^-kt）], Elovich equation （N1=a ＋ blnt）, and parabola equation （N1=a ＋ bt^0.5）, with the best fitting by the first-order kinetics equation for different N （r= 0.9569^＊＊-0.9999^＊＊）. The release potentials （No values estimated by the first-order kinetics equation） of different N in the UCRF decreased in the order of total N 〉 DON 〉 urea-N 〉 NH4^＋-N 〉 NO3^-N in water, and total N 〉 NH4^＋-N 〉 DON 〉 urea-N 〉 NO3^--N in soil, respectively, being in accordance with cumulative amounts of N release. The constants of N release rate （k values and b values） for different N forms were in decreasing order of total N 〉 DON 〉 NH4^＋-N 〉 NO3^--N in water, whereas the k values were urea- N 〉DON 〉 NH4^＋-N 〉 total N 〉 NO3^--N, and the b values were total N 〉 NH4^＋-N 〉 DON 〉 NO3^--N 〉 urea-N in soil. Compared with a common compound fertilizer, the N-use efficiency, N-agronomy efficiency, and N-physiological efficiency of the UCRF were increased by 11.4%, 8.32 kg kg^-1, and 5.17 kg kg^-1, respectively. The ratios of different N to total N in the UCRF showed significant correlation with N uptake by rice plants. The findings showed that the first-order kinetics equation [Nt=N0 （l-e^kt）] could be used to describe the release characteristics of different N forms in the fertilizer. The UCRF containing different N forms was more effective in facilitating N uptake by rice compared with the common compound fertilizer containing single urea-N form.

Study on the Rapid Method to Predict Longevity of Controlled Release Fertilizer Coated by Water Soluble Resin

The study discussed the rapid method to test and predict the longevity of controlled release fertilizers （CRFs） coated by water soluble resin by using the short-term leaching under higher temperature. Pure water dissolving incubation and higher temperature leaching were used to study the patterns of the nutrient release of the CRFs. The correlation analysis between the days at 25℃ and the hours at 80℃ of Trincote 1 and Trincote 2 for the same cumulative release rates were conducted. Patterns of cumulative nutrient release curve followed one factor quadratic regression equation at each given temperatures, and each of relative coefficient was bigger than 0.995. As the temperature increased, nutrients release of the CRFs increased. The longevity of resin coated CRFs were predicted by use of both the cumulative nutrients release equation at 80℃ and the regression equation of release time needed for the same cumulative release rates between 25 and 80℃. There were only 0.3-6.9% relative errors between the tested longevity and predicted one. In conclusion, the longevity of resin coated CRFs could be predicted more quickly and precisely by use of the higher temperature short-term leaching method than that of the traditional differential release rate. The longevity of resin coated CRF could be rapidly and precisely predicted in a few hours by application of the higher temperature shortterm leaching method.

Study of Dynamics of Floodwater Nitrogen and Regulation of Its Runoff Loss in Paddy Field-Based Two-Cropping Rice with Urea and Controlled Release Nitrogen Fertilizer Application

The article deals with the effects of urea and controlled release nitrogen fertilizer （CRNF） on dynamics of pH, electronic conductivity （EC）, total nitrogen （TN）, NH4^＋-N and NO3 -N in floodwater, and the regulation of runoff TN loss from paddy field-based two-cropping rice in Dongting Lake, China, and probes the best fertilization management for controlling N loss. Studies were conducted through modeling alluvial sandy loamy paddy soil （ASP） and purple calcareous clayey paddy soil （PCP） using lysimeter, following the sequence of the soil profiles identified by investigating soil profile. After application of urea in paddy field-based two-cropping rice, TN and NHa＋-N concentrations in floodwater reached peak on the 1st and the 3rd day, respectively, and then decreased rapidly over time; all the floodwater NO3--N concentrations were very low; the pH of floodwater gradually rose in case of early rice within 15 d （late rice within 3 d） after application of urea, and EC remained consistent with the dynamics of NH4^＋-N. The applied CRNF, especially 70% CRNF, led to significantly lower floodwater TN and NH4^＋ concentrations, pH, and EC values compared with urea within 15 d after application. The monitoring result for N loss due to natural rainfall runoff indicated that the amount of TN lost in runoff from paddy field- based two-cropping rice with urea application in Dongting Lake area was 7.47 kg ha^-1, which accounted for 2.49% of urea- N applied, and that with CRNF and 70% CRNF application decreased 24.5 and 27.2% compared with urea application, respectively. The two runoff events, which occurred within 20 d after application, contributed significantly to TN loss from paddy field. TN loss due to the two runoffs in urea, CRNF, and 70% CRNF treatments accounted for 72, 70, and 58% of the total TN loss due to runoff over the whole rice growth season, respectively. And the TN loss in these two CRNF treatments due to the first run-off event at the 10th day after application to early rice decreased 44.9 and 44.2% compared with urea, respectively. In conclusion, the 15-d period after application of urea was the critical time during which N loss occurred due to high floodwater N concentrations. But CRNF decreased N concentrations greatly in floodwater and runoff water during this period. As a result, it obviously reduced TN loss in runoff over the whole rice growth season.

Quantitative Evaluation on the Comprehensive Benefit of Controlled-Release Fertilizer in Typically Middle-Low Yield Rice Field

Quantitative evaluation and analysis was made to the soil nutrients,rice yield,rice and fertilizer utilization rate,and economic and ecological benefits of the slow controlled release fertilizer in typical rice fields with middle-low yield by comparing the one-time application and split applications of slow-or controlledrelease fertilizer（ CRF） with farmers fertilizer practice as the control,with the aim to explore the effect of CRF. Results showed that compared with the control,the application of CRF could meet balance nutrients required for rice growth,and the effective panicles and seed-setting rate were higher in the treatment groups of FVOL,SVOL,LADVOLwhich applied CRF. As for soil nutrients,soil pH maintained balance in FVOL,FCAI,SVOL,LADVOL. In addition,differences in soil nutrient reduction amount reached the extremely significant level between FVOLand SXNK.SVOLwhich applied CRF provided reasonable regulation of N,P and K release rate,which showed advantages over blending fertilization and farmers fertilizer practice. Comprehensive analysis found that the application of CRF could make rice tillering growth and decline leveled off,which effectively improved the quality of rice population,and it also had higher input-output ratio than that of the control and good economic benefits. In general,CRF suits to be used widely on rice crop in the regions with medium-low yield.

Control Effect of Zinc Fertilizer Application Against Apple Little Leaf

In order to provide a theoretical basis for apple cultivation techniques and to provide a reference for preparation of scientific management measures,the occurrence and damage status of apple little leaf in northern Guizhou was investigated,and fertilizer control test against the disease was also conducted.（1）Apple little leaf occurred from April to October in apple producing areas in northern Guizhou every year,with heavy incidence from April to May,light incidence from June to July,and the lightest incidence from August to October.（2） Effectiveness test showed that application of zinc sulfate fertilizer 135 g ＋ cow dung 10 kg received the best control effect,followed by zinc sulfate fertilizer 165 g ＋ cow dung 10 kg,then zinc sulfate fertilizer 105 g ＋ cow dung 10 kg and zinc sulfate fertilizer 150 g ＋ cow dung 10 kg.（3） Based on local environmental conditions,occurrence and damage situation,incidence conditions and fertilizer efficacy test,comprehensive prevention and control technology with rational supplement of zinc fertilizer could be used to control apple little leaf.

Nitrogen Release Characteristics of a Bag Controlled Release Fertilizer

Slow release fertilizers are designed to enhance crop yield and minimizing the loss of nitrogen(N)to environment.However,N release in leaching and loss in ammonia emission from bag controlled release fertilizers have not been previously evaluated under the standardized conditions in soil.Accordingly,a laboratory study was conducted to evaluate the characteristics of N release from a bag controlled fertilizer with 1,3,5 and 7 rows of hole(B-1,B-3,B-5,B-7)and a kraft bag without hole(B-W).The results showed that the amount of N leaching of B-1,B-3,B-5,B-7 and B-W were significantly lower than urea fertilizer without bag(U).The maximum N release from the fertilizers followed the order:U(83.16%)>B-7(54.61%)>B-5(54.02%)>B-W(51.51%)>B-3(48.87%)>B-1(38.60%)during the experimentation.Compared with U treatment,ammonia volatilization losses were significantly decreased by B-1,B-3,B-5,B-7 and B-W treatments.Based on N release and loss,a suitable bag with holes should be considered in practice when using the bag controlled fertilizer to meet an environment good objective.The evaluation method merits further study combined with field experiment.

Antifertility effects of EP-1 (quinestrol and levonorgestrel) on Pacific rats (Rattus exulans)

Pest rodents pose a serious threat to island biodiversity.Fertility control could be an alternative approach to control the impact of rodents on these islands.In this study,we examined the antifertility effects of EP-1 baits containing quinestrol(E)and levonorgestrel(P)using a dose of 50 ppm E and P at three different ratios(E:P ratio=1:2,1:1,and 2:1)on Pacific rats(Rattus exulans)in the Xisha Islands,Hainan,China.Compared to the control group,all animals in EP-1 treatment groups showed significantly decreased food intake and body weight.In treated males,there were obvious abnormalities in testis structure and a significant decrease of relative seminal vesicle weight,but no significant effect on relative uterine and ovarian weights(g kg-1 body weight),or ovarian structure in females.Adding 8%sucrose to the original 50-ppm baits(E:P ratio=1:1)significantly increased bait palatability for males and females.This dose induced uterine edema and abnormalities of ovarian structure in females but had no significant negative effect on the relative testis,epididymis,and seminal vesicle weights(g kg-1 body weight)or sperm density in males.In summary,50-ppm EP-1(1:1)baits have the potential to disrupt the fertility of females,and 8%sucrose addition to the EP-1 baits(E:P ratio=1:1)could improve bait palatability.This dose disrupted the testis structure in males.Future studies are needed to improve bait acceptance and assess the antifertility effects of EP-1(1:1)on Pacific rats in captive breeding trials and underfield conditions.

Recent Advances on the Technologies to Increase Fertilizer Use Efficiency

To increase fertilizer use efficiency （FUE） and to minimize its negative impact on environment have been the focal points in the world for a long time. It is very important to increase FUE in China for its relatively low FUE and serious losses of nutrients. Recent advances of the technologies to increase FUE are reviewed in this article. These include site-specific and real-time nitrogen management, non-destructive quick test of the nitrogen status of plants, new types of slow release and controlled release fertilizers, site-specific nutrient management, and use of urease inhibitor and nitrification inhibitor to decrease nitrogen losses. Future outlook in technologies related to FUE improvement is also discussed.

Characterization of Nitrogen Uptake Pattern in Malaysian Rice MR219 at Different Growth Stages Using ^(15)N Isotope

Nitrogen （N） use efficiency is usually less than 50%, and it remains a major problem in rice cultivation. Controlled release fertilizer （CRF） technology is one of the well-known efforts to overcome this problem. The efficiency of CRF, however, is very much dependent on the timing of nutrient release. This study was conducted to determine the precise time of N uptake by rice as a guideline to develop efficient CRF. Fertilizer N uptake by rice at different growth stages was investigated by using 15N isotopic technique. Rice was planted in pots, with 15N urea as N source at the rate of 120 kg/hm2. Potassium and phosphorus were applied at the same rate of 50 kg/hm2. Standard agronomic practices were employed throughout the growing periods. Rice plants were harvested every two weeks until maturation at the 14th week and analyzed for total N and 15N content. Nitrogen derived from fertilizer was calculated. Total N uptake in plants consistently increased until the 11th week. After that, it started to plateau and finally declined. Moreover, N utilization by rice plants peaked at 50%, which occurred during the 11th week after transplanting. N derived from fertilizer in rice plants were in the range of 18.7% to 40.0% in all plant tissues. The remaining N was derived from soil. Based on this study, N release from CRF should complete by the 11th week after planting to ensure the maximum fertilizer N uptake by rice plants. Efficient CRF should contribute to higher N derived from fertilizer which also resulted in a higher total N uptake by rice plants, increasing the potential of rice to produce higher yield while at the same time of reducina loss.

Effects of Different Slow-release Fertilizers on Growth and Yield of Ratooning Rice

The effect of slow-release fertilizer application on reducing the fertilization times of ratooning rice was explored by carrying out plot experiments using different slow-release fertilizer formulas.The results showed that compared with conventional fertilization of farmers(TCK),there were no significant differences in plant heights of the first rice crop and ratoon rice crop and the number of tillers was slightly increased,by applying different ratios and types of slow-release fertilizers,indicating that reducing fertilization times did not affect rice growth.Compared with the TCK,the yields of treatments T1,T2,T3 and T4 of slow-release fertilizers increased to a certain extent.The yield of the first rice crop increased by 14.7%,16.7%,23.5% and 17.5%,respectively,the yields of the ratoon rice crop increased by 6.3%,5.8%,7.4% and 8.1%,respectively,and the yields of the two rice crops increased between 10.8% and 16.1%,indicating that reasonable combined application of slow-release nitrogen and fast-acting nitrogen fertilizer could meet the nutrient requirements of ratooning rice at different growth stages,and the application of slow-release fertilizers could reduce the fertilization times of ratooning rice.Based on the combination of rice yield and slow-release fertilizer cost in the first rice crop and ratoon rice crop,the T 3 formula was preferred,that is,urea-formaldehyde slow-release nitrogen fertilizer was used as the base and tillering fertilizer,and polyurethane-coated slow-release nitrogen fertilizer was used as the panicle-sprouting fertilizer.

Anti-fertility effect of levonorgestrel and quinestrol in Brandt’s voles(Lasiopodomys brandtii)

The combination of levonorgestrel and quinestrol(EP-1)has been shown to have anti-fertility effects on several wild rodents,but the mechanism underlying these effects is poorly understood.We investigated the effects of EP-1 and each of its components,levonorgestrel(P)and quinestrol(E),on the fertility of Brandt’s voles(Lasiopodomys brandtii)by using a gastric gavage method.The doses for EP-1,E and P were 1,0.34 and 0.66 mg/kg body weight,respectively.Male voles(n=98)were treated daily for 5 or 14 days,then the testes and epididymides were collected,weighed and examined histologically at 30(D30),60(D60)or 90(D90)days after the end of treatment.Four males were allowed to mate with normal females at D90.Female voles(n=75)were treated for 3 days and a further 3 days after a 7-day interval.The uteri and ovaries were weighed and examined histologically at 15(D15),30(D30)or 75(D75)days after the end of treatment.Each of three females were mated with fertile males at D30 and D75,respectively.Our results indicated that quinestrol(E)significantly decreased the sperm numbers in the testes as well as the weight of the testes and epididymides,with both of these tissues showing obvious structural abnormalities,and significantly reduced the litter size and the pup weight for females mated with males of the E treatment group.For female voles,treatment with E,P or EP-1 resulted in no marked influence on the fertility status.These data indicate that quinestrol(E)alone has a significant anti-fertility effect on male Brandt’s voles,but is ineffective in combination with levonorgestrel(P).

Recovery of fertility in quinestrol-treated or diethylstilbestroltreated mice:Implications for rodent management

Fertility control is an alternative strategy to traditional culling for the management of rodent pests.Previous studies have demonstrated that quinestrol is a potential contraceptive for male rodents,but the recovery of fertility in quinestrol-treated rodents has not been evaluated.This study used C57BL/6J mice to evaluate the recovery rate of male fertility after the administration of quinestrol.Diethylstilbestrol(DES),a non-steroid estrogenic compound,was used for comparison.Different groups of mice were treated with 1 mg/kg quinestrol,1 mg/kg DES,or castor oil separately for 7 days.These mice were then killed on days 8,22 and 50 respectively.Our results indicated that the weight of epididymides and seminal vesicles decreased significantly on days 8 and 22 in quinestrol/DES-treated mice,with extensive histological changes in the seminiferous tubules.Sperm concentrations in the cauda epididymal fluid were significantly reduced on days 8 and 22 in both quinestrol and DES treatment groups and on day 50 for the DES,but not the quinestrol group.Further analysis revealed that DES-treated mice exhibited a higher proportion of abnormal sperm accumulation in the epididymis,indicating that the normal sperm transportation to the cauda epididymis was blocked.Our results indicate that the anti-fertility effects on male mice given quinestrol were of shorter duration than for those receiving DES at the dose of 1 mg/kg body weight.

Evolutionary mechanisms and practical significance of reproductive success and clonal diversity in unisexual vertebrate polyploids

Unisexual reproduction is generally relevant to polyploidy, and unisexual vertebrates are often considered an evolutionary “dead end” due to the accumulation of deleterious mutations and absence of genetic diversity. However, some unisexual polyploids have developed strategies to avoid genomic decay, and thus provide ideal models to unveil unexplored evolutionary mechanisms, from the reproductive success to clonal diversity creation. This article reviews the evolutionary mechanisms for overcoming meiotic barrier and generating genetic diversity in unisexual vertebrates, and summarizes recent research advancements in the polyploid Carassius complex. Gynogenetic gibel carp(Carassius gibelio) is a unique amphitriploid that has undergone a recurrent autotriploidy and has overcome the bottleneck of triploid sterility via gynogenesis. Recently, an efficient strategy in which ploidy changes, including from amphitriploid to amphitetraploid, then from amphitetraploid to novel amphitriploid, drive unisexual-sexual-unisexual reproduction transition and clonal diversity has been revealed.Based on this new discovery, multigenomic reconstruction biotechnology has been used to breed a novel strain with superior growth and stronger disease resistance. Moreover, a unique reproduction mode that combines both abilities of ameiotic oogenesis and sperm-egg fusion,termed as ameio-fusiongensis, has been discovered, and it provides an efficient approach to synthesize sterile allopolyploids. In order to avoid ecological risks upon escape and protect the sustainable property rights of the aquaculture seed industry, a controllable fertility biotechnology approach for precise breeding is being developed by integrating sterile allopolyploid synthesis and gene-editing techniques.This review provides novel insights into the origin and evolution of unisexual vertebrates and into the attempts being made to exploit new breeding biotechnologies in aquaculture.

Anti-fertility effect of levonorgestrel and/or quinestrol on striped field mouse(Apodemus agrarius):evidence from both laboratory and field experiments

The effect of combined levonorgestrel(P)and quinestrol(E)on the fertility of stripedfield mouse(Apodemus agrarius)has not been evaluated.We performed a series of experiments in both the laboratory andfield to assess the effect of P and/or E on the fertility of A.agrarius.In the laboratory,to test the time-dependent anti-fertility ef-fects of P and E,as well as their mixtures,90 male stripedfield mice were randomly assigned to 6 treatment groups(n=60),and a control group(n=30).Mice in 3 treatment groups were administered 1 of the 3 compounds(1 mg�kg–1[body weight]EP-1,0.34 mg�kg–1 E,0.66 mg�kg–1 P)for 3 successive days(another half for 7 suc-cessive days)via oral gavage;mice were then sacrificed 15 and 45 days after initiating the gavage treatment.Ourfindings indicated that E and EP-1 treatment,but not P or control treatment,significantly decreased the sperm count in the caudal epididymis,as well as the weight of the testes,epididymides,and seminal vesicles.Additionally,fer-tile female mice mated with E-and EP-1-treated males produced smaller pups.These data indicate that E and EP-1 can induce infertility in male A.agrarius.In thefield,the population density of A.agrarius was significantly influ-enced by EP-1,and the rodent density in the treatment group was lower than that in the control group.Overall,our results indicate that EP-1 is an effective contraceptive in A.agrarius,a dominant rodent species in the farmland.

Design of variable-rate liquid fertilization control system and its stability analysis

Variable-rate technology(VRT)has been paid more attentions by farmers in an attempt to match inputs to local growing conditions efficiently.Farmers in every country are highly encouraged to adopt this practice rather than uniform-rate application(URA).However,the standard methods and design used to quantify application accuracy for VRT remain lacking.Therefore,a variable-rate liquid fertilization control system was designed to meet accurate fertilization demand.The designed control system could enable the real-time proportion and mixture of three kinds of liquid fertilizers,namely,N,P and K,in accordance with decision support subsystem.The task controller reads related information and sends such data to the control system,which is responsible for fertilization operation.The controller could realize liquid fertilizer adjusting through the electromagnetic flow control valves.A high-precision flow meter could measure the fertilization amount,which is sent as feedback to the controller to form a closed-loop control system based on the improved proportional-integral-derivative(PID)control algorithm that could enhance the stability and accuracy of precision variable-rate liquid fertilization control systems.Comparisons between the actual and planned application rates indicated good performance for both static and field experimental trials.Mathematical models and transfer functions for some functional modules were then constructed by classical theories to derive a system characteristic equation.To verify the static and dynamic performances,the control system was simulated using the Simulink module on Matlab.Results showed that the variable-rate fertilization was in accordance with the planned data and that the signal trace effect was good.The error was less than 5%for fertilization amount and fertilizer proportion,respectively,and the control response time was 6 s.